Massive Science - Butt Month

Meet the warty comb jelly, the only animal with a disappearing anus

Anna Rogers — Wed, 29 Sep 2021 22:59:29 EST

Ed: Welcome to Butt Month. In the month of September, Massive will be publishing articles on the evolution, science, and technology surrounding the butt. If it touches the butt, we’ll be covering it. Why Butt Month? Why not. For previous butt stories, see the Butt Month page.

Staring at a comb jelly, it's not very obvious which end is mouth and which is butt.

A quick search of "comb jelly" shows how many of us get it wrong. We often depict comb jellies butt up (like the image for this article), though they tend to swim and rest mouth up. Comb jellies look so much like a marine bedsheet ghosts, it's understandable we'd assume the domed part is the mouth side instead of the butt.

If you keep watching a comb jelly, you may be able to tell which end is the butt, because you'll see it eat and you'll also see it poop. However, unless you have a microscope trained on the jelly's rear end, you wouldn't necessarily be aware of a vanishing act you just witnessed. A few years ago, researchers discovered that the warty comb jelly (Mnemiopsis leidyi) has a disappearing anus. Every time a warty comb jelly needs to poop, the outer skin and the digestive system fuse to form an opening. Then after the poop is completed, that nexus vanishes without a trace.

Making and unmaking an anus sounds like such an ordeal, you might imagine comb jellies poop rarely. However, comb jellies are constant consumers, and thus frequent poopers. Exactly how often the comb jelly poops scales with its body size. In a large adult comb jelly, the transient anus appears and disappears about every hour. The tiniest of comb jellies, only a fifth of a centimeter long, form and then reabsorb their anuses every 10 minutes. Still, even these tiny comb jellies spend most of their time without an anus. This vanishing act is fast. Appearing, pooping, and disappearing takes the anus just a few minutes.

The transient nature of the comb jelly anus was discovered in 2019 by Sidney L. Tamm at the Marine Biological Laboratory. However, we've known since 1850 that comb jellies have an anus, unlike many similar looking but not closely related species. Comb jellies are their own group separate from jellyfish, who have no anuses and thus poop out their mouths. An anus was in fact one of the key differences that led invertebrate zoologist Libbie Hyman to reclassify comb jellies as distinct from jellyfish in 1940, well before genome sequencing confirmed their evolutionary distance.

Prior to the discovery of the transient anus, we didn't just think comb jellies had anuses, but that they might have two. A comb jelly has a pair of structures on its rear end known as anal lobes. Both of these anal lobes swell prior to pooping, but one swells more than the other. The anus always appears on the more swollen side, while the less swollen side remains anus-less. All of the poop then moves towards the more swollen side to be ejected out of the new anus. For an individual comb jelly, it's also always the same side that gets more swollen, giving them a sort of butt "handedness". Stranger still, this "handedness" is the only feature that breaks the comb jelly's radial symmetry.

Other symmetrical warty comb jellies swimming at the Boston Aquarium

Via Wikispecies

Comb jellies are the only creatures so far known to have transient anuses. Though if any organism was going to have one, it's not too surprising it's the comb jelly. Comb jellies are anatomical trailblazers. They have a nervous system and muscles, but theses systems have very different biology from all other animals. Comb jelly genetics even indicate that their neurons and muscles evolved entirely separately. So why wouldn't comb jellies have their own way to have a butt?

Comb jellies are also some of the most plastic organisms we know of. Cut a comb jelly in half and it can completely rebuild its body in just four days, not even leaving a scar behind. If being sliced in half is just an off week, creating and reabsorbing an anus dozens of times per day may not be such a big deal.

Though comb jellies are alone in having disappearing anuses, the invertebrate world is full of strange butts. The face mite, an arachnid that is exactly what it sounds like, has lost its butt. In its fleeting 16 day life, it feasts but never poops once. Some scorpions join the face mites as butt-less arachnids. Scorpions can drop their tails to escape being eaten, but woefully sacrifice their anuses in the process.

Among the other weird butts scuttling around the ocean, there are species that breathe through their anuses, including sea cucumbers, whose anuses are also homes for fish. The ocean’s other strange symbiotic butt, or butts rather, belongs to the worm Ramisyllis multicaudata, which lives inside a sea sponge. With its head buried deep down in its host, the hundreds of butts of the worm’s branching body poke out like a reverse hydra.

The disappearing anus is just one of many recent developments in our understanding of comb jelly biology. Marine biologists have studied wild comb jellies for centuries, but recently scientists have succeeded in growing comb jellies in the lab. Comb jellies are well on their way to becoming an exciting new research organism. Because they do everything so differently, studying comb jelly biology could help find creative solutions to human biological problems. And as comb jellies pop up in more labs around the world, we might also learn a little more about what it means to have a disappearing butt.

Anna Rogers studies

Molecular Biology

at
UC Berkeley
.

A glowing butt might help some pitvipers attract their dinner

Deanna MacNeil — Tue, 21 Sep 2021 22:01:03 EST

Ed: Welcome to Butt Month. In the month of September, Massive will be publishing articles on the evolution, science, and technology surrounding the butt. If it touches the butt, we’ll be covering it. Why Butt Month? Why not. For previous butt stories, see the Butt Month page.

Nature loves to glow.

Biofluorescence occurs when waves of light are absorbed by an organism'stissue, and re-emitted as light of a different wavelength/color. It occurs across the natural world, but the function of this trait is not always obvious. Although different patterns of fluorescence have been seen in reptiles, it is not clear how widespread biofluorescence is amongst them, or why some reptiles have even evolved to glow at all.

And what about snakes? Biofluorescence has been identified in at least five types of snakes across different taxa, and of varying size, coloration, ecology, behavior and relatedness. Given the variety of snakes known to possess this trait, searching for new instances of biofluorescence is likely to provide insight into how snakes use their glowing tissues.

A recent cursory search for UV-induced visible fluorescence in a private collection of captive reptiles revealed tail biofluorescence for the first time in Trimeresurus hageni (commonly known as Hagen's pitviper), and prompted a broader search for glowing tails in other snake taxa. While biofluorescence has been seen in the body scales of snakes and lizards previously, these pitvipers are the first reported land-living vertebrates with biofluorescence restricted to a specific appendage.

Researchers examined captive snakes from the Audubon Zoo's herpetology department in New Orleans and from a private reptile collection, along with field, frozen, and fluid-preserved specimens from the wild and captivity. The researchers used a special UV light technique in a low light environment to see the biofluorescent glow with the naked human eye, and special cameras to photograph the phenomenon.

This study provides a compelling hypothesis for why some snakes evolved biofluorescent tails

With these tools, they looked at the tails of 28 pitviper species across ten genera, and discovered tail fluorescence for the first time in 22 of them. Between species and age groups, the color of the fluorescent glow varied from white to blue and bluish-green to greenish-yellow, and was observed in both wild and captive snakes. The researchers saw that two types of tail tissue glowed: the scales and the rattle. The snakes' butts were glowing.

This study provides a compelling hypothesis for why some snakes evolved biofluorescent tails. Over 80 percent of the snake species with biofluorescent tails observed in this study are known to have noticeable tail coloration, and all of these species belong to genera that contain snakes known or suspected to perform caudal luring, a form of mimicry where an organism uses its tail as a lure to attract prey.

The study uncovered 22 species of pitviper with glowing butts

Photo by Zachary Young on Unsplash

Caudal luring is a specialized hunting technique used by many different snake species, including pitvipers, who move their conspicuously colored tails in a manner that imitates a worm or worm-like larval insect to attract prey that eat such insects. Given that most of the pitviper species with newly observed fluorescent tail scalation are known or suspected caudal lurers, the researchers behind this study suspect that tail biofluorescence may facilitate or enhance caudal luring. In particular, the glowing tail scales might make a snake's tail more eye-catching and visually attractive to certain prey under certain light conditions.

Biofluorescence relies on external light sources to provide the right amount of energy for tissue to glow. In this case, the glow of the pitviper tails is dependent on UV light. The tail fluorescence may only be detectable in specific environments, such as heavily shaded forests or between dusk and dawn when visible light is low due to interference from other wavelengths of light during the day in open environments. This might explain why this trait in these pitvipers has gone unnoticed by humans. It also means that only certain prey that have the ability to see the glow under natural conditions would be attracted by biofluorescent caudal luring. Snakes mainly use caudal luring to attract frogs, toads, and lizards, some of which have exceptional visionin low light environments and even use biofluorescence themselves for communication. There is also a precedent for lizards, frogs, and toads preying on bioflurouescent insects, like some caterpillars. Pitvipers with biofluorescent tails could be mimicking these glowing insects during caudal luring.

This study is observational, and behavioral studies will be needed to assess if and exactly how the biofluorescence contributes to caudal luring for these snakes. For example, it remains unknown which prey are able to see the UV-induced biofluorescent tails of these pitvipers under natural lighting conditions.

While caudal luring is a likely explanation for the tail-specific biofluorescence observed in these pitvipers, there are also other possible explanations that will need further investigation. For instance, UV-induced biofluorescence could be involved in anti-predator displays, like those used bythe woodland brown butterflyto deceive bird predators under low light conditions. In other reptiles, like the hawksbill sea turtle, it's been suggested that UV-induced biofluorescence could be used for camouflage.

Regardless of how these pitvipers use their glowing tails, this discovery is an eye-opener for what we might be missing with our human vision, and highlights the importance of considering how the natural world looks to the non-human eye when examining specialized behaviors.

Deanna MacNeil studies
Cell Biology
.

Strong butt muscles are the key to sprinting at an elite level

Margaux Lopez — Tue, 14 Sep 2021 23:11:28 EST

Ed: Welcome to Butt Month. In the month of September, Massive will be publishing articles on the evolution, science, and technology surrounding the butt. If it touches the butt, we’ll be covering it. Why Butt Month? Why not. For previous butt stories, see the Butt Month page.

By multiple measures, track events are some of the most popular of the Summer Olympics. Without complicated rules or penalties or fourth downs that somehow magically revert back to third downs, it’s the simplest of sports: who crosses the finish line first? The men’s 100-meter sprint is the only race that crowns the “fastest man on earth.” Watching fierce competitions between men and women with bulging muscles at peak athleticism is inspiring. But which of those muscles actually matter the most when it comes to a sprinter winning gold? It is commonly believed that the hamstrings are the most important muscle to develop for speed, but new research points to your butt as the real way to leave everyone else behind.

The mechanics and muscles of sprinting have been open research questions for decades, with the general consensus pointing towards the hamstring muscles as the primary power source for elite sprinters. Bigger, stronger hamstrings have been related to faster sprint times, and the hamstring muscle in particular has been shown to strongly activate when running. Moreover, mathematical simulations of a person sprinting seem to show that the hamstrings are especially important for generating forward motion. Some scientists even argue that the prevalence of hamstring injuries in sprinters means that they must be the primary muscle group involved.

The running gait is generally divided into two phases: the stance phase, when the foot is in contact with the ground, and the swing phase, when the foot is fully off the ground and swinging forward through the air. Each part of the gait involves extra effort from different muscles. When the foot reaches forward at the end of the swing phase and then contacts the ground during the first part of the stance phase, the muscles are working primarily to decelerate the body and then prepare for the next push-off. The butt muscles are most active during this part of the gait, along with the calf muscles. The quadriceps, at the front of the thigh, come in primarily during the middle of the stance phase, generating push-off power while the abdominal muscles and the muscles along the sides of the leg provide stabilization. The hamstrings have a few different jobs — while they are active during the foot strike and the first part of the stance phase, they are actually more important for the swing phase, pulling the leg forward quickly through the air to prepare to strike the ground again. Since the hamstring is working hard and is also the most stretched out right at the end of the swing phase, this is when hamstring injuries tend to happen.

A diagram showing the steps involved in a running gait

Via Wikimedia

It’s true that bigger hamstrings generally correlate to faster sprint times. However, most research that examined hamstring muscles mostly compared them to the quadriceps and calf muscles and did not include the butt muscles as part of the study. To remedy that, researchers from Loughborough University in the UK recently shifted focus to the butt. They liked what they saw.

The study focuses on the differences in muscle volume and strength between elite sprinters, sub-elite sprinters, and non-sprinters, although only male participants were studied. Using magnetic resonance imaging (MRI), the researchers measured the volume of 23 individual lower limb muscles. The goal was to relate muscle size to personal best sprint times for a 100-meter race, and to see which muscles could be most significantly affecting sprint speed for these male runners.

Overall, while the differences in cross-sectional muscle area between the control group and the sub-elite group was consistent across almost all of the muscles tested, the differences between the elite and the sub-elite group of male sprinters were concentrated in specific areas. Three particular muscles were found to be consistently larger (in both absolute volume and size relative to body weight) in the elite sprinters vs the sub-elite sprinters: the gluteus maximus (largest butt muscle), the tensor fasciae latae right next to the glute, and the sartorius muscle that stretches along the outside of your leg from the hip to the knee. This research implies that once a sprinter is getting close to the elite level, targeted training of the butt and hip flexor could help increase speed. The three muscles that make up the hamstring were also slightly bigger in elite sprinters than in sub-elite sprinters, but those differences were not nearly as pronounced as the much larger butts.

The back of the left thigh of a human, with major muscle groups indicated, including the tensor fasciae latae close to the hip bone

Via Wikimedia

In a second study from Ritsumeikan University in Japan, researchers used MRI technology to compare the size of ten different muscle groups in the legs and lower body between sprinters and non-sprinters, again only using male participants. While it makes sense that all muscles were larger in the sprinters versus the non-sprinters, the gluteus maximus (the largest butt muscle) as well as the psoas major (the muscle that connects the trunk to the lower limbs) showed the biggest difference both in absolute size as well as size relative to body weight. Moreover, a larger gluteus maximus strongly correlated with faster sprint times among the sprinters, while the size of the hamstring muscle did not. One particular strength of this study was the sample size — it included 56 sprinters and 40 non-sprinters, one of the largest studies to date using MRI scans for this type of research.

The authors of the study go as far as to argue that the hamstring “may not be an important muscle for achieving superior sprint performance.” Based on this and the previous research, that’s likely true if you’re already an elite-level sprinter — it may be a good idea to put more focus on glute-specific strengthening exercises. However, if you’re not already competing at the international or even national level and just want to get faster for a weekly pickup soccer game, racing your sibling down the street, or just outrunning your shadow, general leg strength is likely more important than targeted exercises, as seen in the vast difference in overall muscle volume between non-sprinters and sprinters in the study.

There is a striking lack of research on the same topic for female sprinters. While running mechanics are similar between males and females, there are some small differences that emerge most clearly at elite levels, where the fastest male sprinters generally produce faster times than the fastest female sprinters. From a biomechanics perspective, the most efficient running configuration is to have the hips stacked on top of the knees, which are stacked on top of the ankles. Women tend to have wider hips than men, which interferes with this alignment and makes the running gait less efficient. On average, women also have slightly different rotation angles of the knee and hip joints while running, which isn't necessarily slower but does imply that different muscles may be involved compared to a man's running gait.

The front of the right thigh of a human, with major muscle groups indicated, including the sartorius on the inside of the leg towards the groin

Via Wikimedia

Only a single research article was found on muscle volume or strength as it relates to sprint speed for female sprinters. The researchers studied both male and female high school athletes and compared the cross-sectional area of just the psoas major and gluteus maximus muscles between sprinters, distance runners, and untrained students of similar ages. The study reports that the gluteus maximus was larger in male sprinters than in male distance runners, but the same difference was not seen between female sprinters and female distance runners. In addition, faster female sprinters had a significantly larger psoas major compared to slower sprinters but not a larger gluteus maximus, while in male sprinters it was the other way around.

While the subjects of this study are relatively young and not at the elite sprinting level, the results are believable since the mechanics of the sprinting motion itself can be slightly different between males and females due to small structural differences. Further research is needed to see whether this result holds at the elite level.

Overall, when it comes to speed, researchers agree that increasing overall lower body strength is a must. Hamstring strength in particular has historically been the focus, but for those that want an edge over their opponents, the gluteus maximus is the real key. Butts win championships.

Margaux Lopez studies
Astronomy
at
Vera C. Rubin Observatory
.

Which came first, the butt or the mouth? New research gives an answer

Lila Westreich — Wed, 08 Sep 2021 00:08:28 EST

Ed: Welcome to Butt Month. In the month of September, Massive will be publishing articles on the evolution, science, and technology surrounding the butt. If it touches the butt, we’ll be covering it. Why Butt Month? Why not. For previous butt stories, see the Butt Month page.

Like many people, you may have spent hours pondering the question of which came first, the anus or the mouth? OK, maybe it's not top-of-mind for some, but the science behind the origins of our ends has been the grounds of a long-lasting debate.

There are still creatures with prehistoric digestive systems consisting of only a single opening, where food enters and poop exits, typically rudimentary species with long evolutionary histories. Jellyfish, for example, take food in to a single hole, digest it, and then expel the waste through the same hole. But, thankfully, our distant ancestors swapped out that blueprint for a different approach to digestion.

Most mammals have one major tract for solids going "in," and one for "out"; One for eating, a mouth, and another for defecation, typically considered the anus. In the path between those two points, it's broken down and digested in the stomach, then passed through the colon. Unidirectional gastrointestinal tracts are an extremely efficient system that allows animals to keep eating even while they're digesting.

Some scientists believe that, in evolutionary history, the mouth developed first, based on how embryos develop in the womb. Others dispute this theory, arguing that the anus developed first based on embryo development in different animals. Recently, a paper published in Nature reviewed these theories to get to the bottom of it.

There's a concept in evolutionary history called Haeckel's Biogenetic Law, developed in 1866 by Ernst Haeckel. Haeckel believed that an embryo's developmental stages provide information about the adult stages of that organism's ancestors. If an embryo looks different at different stages of development, those differences correspond to how the ancestors of the species looked at adult stages. Human embryos at early stages look nothing like their adult counterparts, with quirks left over from evolution such as embryonic tails that are reabsorbed into surrounding tissues before birth. It follows that an embryo's journey through the stages of development in the womb show us a chronological replay of their evolutionary forms.

Bilateral symmetry seen in the small emperor moth, Saturnia pavonia, with two pairs of wings with symmetrically placed eyes

Jean-Pierre Hamon via Wikimedia

Then, in 1908, biologist Karl Grobben used Haeckel's idea to study the question. Grobben suggested that Bilateria — animals with bilateral symmetry where the left and right side are mirror images of each other — should be divided into two groups based on the evolution of their ins and outs. The first group had originally developed a mouth from their first opening, also known as "mouth first." The second group developed an anus first and was known as "mouth second." Following Haeckel's law, Grobben set out to prove that he could confirm one of these theories by examining embryonic development stage histories for each animal species.

Grobben formed his theories based on the development of the blastopore, the very early developmental form of any mouth or anus. It's the precursor to eating and breathing through one hole and either defecating through the same hole or other structures in the body. It's also the precursor to the more common structure of two distinct openings at either end of the body, as in humans and most mammals, where food goes in one way and goes out the other.

Some animals, such as jellyfish, take a single "bite" of food, digest it, then shoot waste back out the same hole...

The final form of the blastopore vary across all living creatures. For example, starfish form an anus, but earthworms form a mouth from the same opening. A 2016 paper published in Nature Ecology & Evolution compared the development of the blastopore in two different brachiopods — shelled creatures that open at a hinge, like many clams — to understand how the blastopore first develops into a mouth or anus based on how the embryo is organized during development.

A number of different processes are at play as embryos develop, each leading to the final structures in the bodies of adult mammals. The timing of these developments influences one another, in the same ways the development of a mouth can lead to a digestive tract and waste production system. Creatures with a different entry and exit point have more time to digest and get more nutrients out of each meal. Some animals, such as jellyfish, take a single "bite" of food, digest it, then shoot waste back out the same hole. Animals with anuses, like you or your dog, can down multiple meals without worrying about the excrement coming out the same side. That process means our digestion can be slower and more effective at removing nutrients from our food.

Researchers in the Nature study attempted to review all plausible theories by examining the blastopore, tissues, nerves and bands, and other pieces that make up the development of early human embryos. The three major theories they examined, for the evolution of mouths and anuses in bilaterians (which includes humans), were as follows:

The blastopore becomes the mouth, and the anus develops secondarily.

The blastopore becomes the anus, and the mouth develops secondarily.

The blastopore divides into the mouth and the anus through the fusion and separation of a tubular gut.

They found that the evidence supports the third scenario, in which the blastopore elongates and closes laterally at both ends, giving rise to the mouth and the anus simultaneously (or as simultaneous as embryonic development can get). The tubular gut, a long skinny tube connecting the mouth and anus slowly spreading until all that remained were the two openings we use almost every day — and then came all the stuff in between.

Anal openings first appeared around 550 million years ago, around the time of the first worm-like creatures. In the time since, some animals of lost their anus or gained a new one. While we may never truly know which came first for every living creature, this study lends evidence to the prevailing theory of the start of your butt and your gut from just one distinct channel. Thanks to your tubular gut, you have both holes available at your disposal.

Lila Westreich studies
Pollinator Ecology
at
University of Washington
.

A breathing tube through the butt could be an alternative to mechanical ventilators

Simon Spichak — Tue, 31 Aug 2021 22:22:33 EST

Ed: Welcome to Butt Month. In the month of September, Massive will be publishing articles on the evolution, science, and technology surrounding the butt. If it touches the butt, we’ll be covering it. Why Butt Month? Why not. For previous butt stories, see the Butt Month page.

To survive in extreme low-oxygen conditions deep in the ocean, fish and other creatures have developed remarkable adaptations. For example, sea spiders, loaches, and catfish evolved the ability to breathe through their butts. And they might not be the only butt breathers out there.

A recent study in the journal Med now suggests that mammals, humans included, may be able to breathe through their rear ends as well. Mice, rats, and pigs could all stave off the devastating effects of oxygen deprivation if given an oxygen enema. But could this new method provide temporary oxygen while a patient awaits a ventilator?

Can Mammals Breathe Through Their Butt?

While we often consider the butt as the exit for waste in our body, it is also an entryway with lifesaving potential. After all, humans and plenty of other mammals can absorb medications rectally. That's because there's a lot of blood vessels in the area, allowing medicine easy entry.

But medicine is specially designed to maximize absorption in the body. Oxygen doesn't have nearly as easy a path towards entry into the bloodstream through the rectum because of the mucus membrane mammals have on the intestines. There are also important anatomical differences between our intestines and those of fish that already harness this ability. Animals that can breathe through their butts, like loaches, had a much thinner epithelium in their guts and a lot less mucus. During the course of early development, a butt-breathing genetic pathway is turned on that helps dictate the structure of the intestine. When it's all said and done, the posterior end of the intestine is equipped with all the structures necessary for respiration (and gas exchange).

Would this mucus prevent oxygenation in mice? In the first experiment, researchers used a model of oxygen deprivation in mice, preventing them from breathing through their lungs. The control group didn't receive any intestinal ventilation, one group received oxygen through an anal catheter, and the final group had the mucus layer on their intestines "scrubbed" before receiving anal ventilation.

Remarkably, the mice supplied oxygen through their anus had elevated oxygen levels in their blood. The final group that also had their intestinal mucus scrubbed fared even better, surviving the longest in the low-oxygen conditions — five times as long as the control group. This experiment proved that there is potential for mammals to breathe through their butt, however, the mucus layer covering the intestinal epithelial cells makes it more difficult.

In a clinical setting, scrubbing the mucus off of a person's intestines isn't really feasible, and doesn't sound like a pleasant experience. But using a method akin to an enema may work, by infusing safe, oxygenated liquid through the butt. This liquid, called perfluorodecalin, could safely store and deliver oxygen via an enema. Due to the properties of this liquid, it doesn't need to scrub the mucus off of the intestines, meaning less discomfort and abrasion. Oxygen diffuses into the bloodstream while carbon dioxide diffuses out. Since it holds a lot of oxygen and carbon dioxide very easily, it is also delivered safely to the lungs, and is already in clinical use.

In their next experiment, mice were placed in chambers with only 10 percent oxygen. While this isn't lethal, it is enough to induce the physiological effects of a lack of oxygen, hypoxia. The mice that received oxygen-loaded PFD rectally normalized their oxygenation back to normal levels.

In rats and pigs, the researchers repeated these experiments finding that two days of the protocol didn't lead to any significant adverse effects. Importantly, the diffusion and distribution of many different drugs are tested in pigs due to similarities in physiology. While the authors couldn't figure out how exactly the oxygen passes into the intestine, they showed enough efficacy to permit more studies trials in animals and in humans. According to the press release, the research team is working with Japan Agency for Medical Research and Development to conduct more experiments and potentially head to a human trial. This could increase the ventilation capacity of hospitals during future outbreaks of respiratory diseases.

Can Rectal Ventilation Mitigate a Ventilator Shortage?

During COVID-19, many hospitals find themselves short on ventilators. During the pandemic, many will require the use of a ventilator for an average of 15 days, while a few people will need significantly more time. Ventilators aren't something that a person can use for one day and then get discharged. The first wave of people requiring ventilators will receive them immediately. However, someone whose lungs fail the next day may need to survive for two weeks without one.

In an interview with The Scientist, corresponding author Takanori Takebe, Assistant Professor, UC Department of Pediatrics and a Professor at the Institute of Research, Tokyo Medical and Dental University, Japan, explained how his father was hospitalized with acute respiratory distress syndrome due to a chronic lung condition. He saw first-hand how difficult and damaging mechanical ventilation can be on the body.

While these ventilators are the gold standard for treating acute respiratory distress syndrome, occurring through COVID-19 infection, it isn't always available. In the intervening period, there is a need for more techniques and strategies to deliver oxygen and stave off hypoxia and death. If rectal ventilation can work in humans, it will provide a way for doctors to keep some of these people in a stable condition while they await a ventilator. Additionally, since there are no patents or complex mechanical components to rectal ventilation set up, it could be cost-effective to implement.

But humans aren't pigs, or rats, or mice. Lots of incredible research and findings do not translate to humans. One problem remains unaddressed however how will patients or even animals receiving rectal ventilation poop? Can the enema be adjusted to facilitate bowel movements or could this tank the technology? Takebe will be working hard to test this method in more animal models and potentially a human clinical trial soon.

However, a company called Respirogen Inc. may beat him and his colleagues to it. Respirogen Inc. has registered a clinical trial to assess the safety of this method in healthy humans. Six healthy volunteers will experience induced hypoxia, by breathing in a mixture of gases with low oxygen content. In this study, these volunteers will then receive oxygen rectally to monitor whether this method can successfully increase oxygen levels and stave off symptoms of hypoxia. However, Respirogen Inc. will be using standard enemas and colonoscopy-cleansing procedures to reduce the chances someone will need to poop during the trial.

"In human use for treatment of hypoxia, cleansing of the colon will take place by standard enema or colonoscopy prep procedures, which are well understood and accepted," Respirogen CEO Bob Scribner explained over email. "The use of an oxygen bolus delivery allows the procedure to be suspended and restarted as needed to accommodate a patient’s need to void." Their technology uses an oxygen bolus, essentially a gas bubble, that is delivered into the butt, and could be stopped temporarily in case of a fecal emergency.

With at least two different groups working toward this goal, we may finally be able to say with some certainty, whether humans can effectively breathe through their butt. What sounds like a ridiculous question may end up saving people that aren't immediately able to access a ventilator.

Simon Spichak studies
Neuroscience
.

How the pelvis, and not bipedalism, gave humans their narrow hips

Darcy Shapiro — Tue, 06 Jul 2021 21:56:05 EST

Giving birth is generally a difficult process for humans, often requiring long hours of labor and help from other people, but this doesn't seem to be the case for our closest living relatives, the African apes. The obvious explanation is that we give birth to relatively large, big-brained babies through a pretty narrow pelvic opening, while the opposite is true for our ape cousins. But why we ended up in this painful evolutionary predicament is still an open question, one that anthropologists recently teamed up with an engineer to try to answer. It turns out, we might've been focusing on the wrong reason for that narrow pelvis all along.

For decades, the conventional wisdom among anthropologists was that the anatomy of the female pelvis is an evolutionary compromise between the demands of our unique style of locomotion, bipedalism, and the demands of giving birth to big babies. A narrower pelvis was thought to make walking and running more energy-efficient, while a wider pelvis would allow for a larger birth canal. This trade-off is often called the "obstetrical dilemma."

The supposed dilemma has been challenged recently, in part because the fields of paleoanthropology and human evolutionary biology are becoming more diverse, with a greater variety of lived experiences being brought to bear on key questions about our evolution. Anthropologists have now experimentally demonstrated that a person's sex doesn't make a difference to their running or walking efficiency and that effective bipedal locomotion isn't impaired by a wider pelvis, for example. Additionally, human birth canals aren't uniform in size and shape around the world; if this trade-off was so critical, we would expect less variability.

Big headed babies and a narrow pelvis mean Homo sapiens have a particularly difficult time giving birth

Christian Bowen on Unsplash

So, if locomotion isn't the main pressure driving selection for a narrow pelvis, what is? A paper published this year in PNAS suggests that pelvic floor function might actually be behind it, instead.

The pelvic floor is the set of muscles and connective tissue that forms the base of the pelvic canal; if the bones of your pelvis are the sides of a bowl, the pelvic floor is its bottom. The pelvic floor plays a really important role in supporting our internal organs and the weight of a large fetus and maintaining continence (your ability to control your bowels and bladder).

Becker1999 on Wikimedia Commons

The size and shape of a person's bony pelvis dictates the size and shape of their pelvic floor, and there seems to be a bit of a Goldilocks situation happening here – it can't be too big or too small. The pelvic floor needs to be strong enough to support the weight placed on it and deal with changes in pressure within the abdomen caused by normal activities like coughing, while also being stretchy enough to allow for birth. The size and thickness of the pelvic floor is where the trade-off between strength and stretchiness happens.

This study serves as a reminder that there's a lot more to our evolutionary history than bones alone can tell us

The new study came to this conclusion by testing the "pelvic floor hypothesis" using a series of mathematical models informed by experimental data from MRIs. The modeling technique allowed the researchers to vary the size and thickness of a hypothetical pelvic floor, and measure how much stretch and stress it experienced at different sizes and thicknesses. They found that the pelvic floor bent out of shape more, and the tissue experienced greater stresses and stretches, as its size increased. Increasing the thickness of the pelvic floor only partially compensated for this and came with its own downsides, like the fact that a thicker pelvic floor would require much higher abdominal pressure for giving birth and possibly also for pooping.

Human infants have much larger skulls, and must pass through a much narrower pelvis, than other apes or hominids.

ArchaeoMouse on Wikimedia Commons

These results support the "pelvic floor hypothesis" and complicate the previous idea that the main evolutionary trade-off driving human pelvic evolution was between a narrower pelvis for efficient locomotion and a wider pelvis for a more spacious birth canal. Instead, it looks like a major pressure driving selection for a narrower pelvis was actually the task of suspending a sufficiently supportive pelvic floor – one still allows for birth, but prevents rupture and prolapse.

Ultimately, this study serves as a reminder that there's a lot more to our evolutionary history than bones alone can tell us, and that it will only continue to come into greater focus when people with new, different perspectives can weigh in on the stories previous researchers have told about our shared human past.

Darcy Shapiro studies
Evolutionary Anthropology
at
Rutgers University
.

Escaping through a predator's butt is a common strategy for prey

Sahana Sitaraman — Mon, 28 Sep 2020 23:48:53 EST

Ed: Welcome to Butt Month. Every Tuesday in September, Massive will publish an article on the evolution, science, and technology surrounding the butt. If it touches the butt, we’ll be covering it. Why Butt Month? Why not.

What would happen if you were swallowed whole? Trapped in the pitch black confines of the stomach, with acid squirting from all directions, pushed down and churned by gut muscles, you might be completely digested. But some animals deceive fate, escape towards the light at the end of the intestinal tunnel, and burst out to freedom from the butt.

Consider the land snail. A common and popular prey, it's hopelessly incapable of escaping attacks. Instead, it has developed other defenses like cryptic coloration, withdrawal into its shell, and irritating smell and taste to prevent predation. But its most fascinating survival tactic is coming out alive from the butt of predatory birds.

In 2012, Shinichiro Wada reported that the land snail Tornatellides boeningi, found in the Hahajima Island in the western Pacific, could survive being swallowed by the Japanese white-eye bulbul and the brown-eared bulbul. Both predators were fed adult snails approximately 2.5mm in shell height. Once the birds had their fill, they rewarded the researcher with a load of data. Wada observed that around 15% of the fed snails passed through the gut alive, were active after their grand escape and survived for at least 1 week after the experiment. Some even gave birth to baby snails after emerging alive from the birds’ intestines.

A Tornatellides land snail

Norine W. Yeung

The tiny proportions of T. boeningi seem to play an important role in the smooth passage of the animal through the gut. Sifting through the poop of other birds on the island showed that remains of larger snail species were always seriously damaged. That small size allowed the shell to remain intact despite the many crushing and cracking parts in a bird’s digestive tract. The whole shell, along with the copious amounts of mucus produced by the snail, could have helped keep the stomach acids from reaching the snail's body. But that’s not all animals need to survive.

How does the snail breathe in there? Some species of mud snails can survive in waters with little to no dissolved oxygen for nine days or even more. They store gas bubbles in a small cavity, air from which is used in times when oxygen availability is low.

At face value, the act of passing through the gut doesn't seem pleasant. But it comes with perks. Wada and team show that snails might use this journey for their dispersal across the island. They also suggest that passing through the gut may be a cue to give birth in T. boeningi, which may enhance the probability of colonization success at the site of deposition. It's similar to how berry seeds use ingestion by birds to their benefit.

As prey evolve newer ways to shield themselves, predators also evolve strategies to counter their moves

Aquatic mollusks also show great proficiency in butting out of painful situations. Randy Brown, a scientist at the US Fish and Wildlife Service in Fairbanks, Alaska, collected wild, freshwater fish and saw that pea clams and valve snails are abundant in their feces, surviving the passage through the fishes' guts. Many emerged clams opened their shells and extended a foot, and snails emerged from their shells and began moving about. Valve snails have a chalky disk, which they use to seal their shell shut when withdrawn inside.

As prey evolve newer ways to shield themselves, predators also evolve strategies to counter their moves. The spinynose sculpin fish, Asemichthys taylori, has a solution to tear down the hard exterior of a mollusk. In 1988, Stephen Norton at UC Santa Barbara reported that these fish use their teeth to “punch” holes in the shells of their prey, making them more digestible. Norton observed that more 40% of the unpunched mollusks emerged alive from the fish intestines, but none of the punched individuals survived. What was truly fascinating was that the fish could adjust its punching behavior. When given limpets, a prey which has a protective shell but no covering over the shell's exit, fish never resorted to punching. All swallowed limpets, despite being unpunched, did not survive, because the digestive juices could enter beneath the shell. This shows that the fish reserved their energy for punching only when it was absolutely essential.

A spinynose sculpin (Asemichthys taylori)

Kevin Lee via ResearchGate

Copepods, tiny crustaceans found in fresh and marine waters, are also heavily preyed on by many fish species. Many can out-swim predators, but females carrying heavy egg sacs do not have that advantage. But that doesn’t stop them from passing on their genes. Even if the female is eaten and digested, the eggs survive the harsh environment of the fish digestive tract and hatch to produce copepod larvae. Copepods even produce two different kinds of eggs: subitaneous, which hatch soon after spawning, and resting, which have a durable outer shell, designed to survive for long periods. Surprisingly, both types emerge alive out of fish butts. Many copepods which do not produce resting eggs could use this strategy to disperse their larvae using fish as agents.

Many insects also make a back door exit, using their predators for their dispersal needs. Megastigmus wasp females lay eggs into the seeds of rose plant, which develop into larvae and eat up the soft interiors of the seed. These larvae remain alive even when the rose seeds are consumed and defecated by mockingbirds. Feeble fliers, Megastigmus wasps depend on surviving the gut environment of birds so they can reach and colonize different geographical locations. The hard coating of the seed protects the insects from being digested. Once excreted, the adults chew open the coat and emerge.

Nematode worms hitchhike on many of their predators to reach far and wide places. In 2015, Carola Peterson and colleagues reported frequent occurrence of living Caenorhabditis elegans worms in the intestines of slugs, even when the slugs were taken from places not suitable for the worm. This led them to speculate that the worms were picked up somewhere else and persisted in slug guts for some time. They tested their theory by feeding fluorescent worms to slugs and looking at the number of worms present in the feces at different times. Still living worms began emerging within a scant 12 hours. Most emerged worms also reproduced later.

A transparent view of several C. elegans worms

Via Wikimedia

When faced with stress, C. elegans adopt a resting state called "dauer." Peterson observed that most of the worms in the intestine were dauers, which suggests they might be better equipped to survive being eaten and come out the other end alive. Certain characteristics of dauer larvae help make more sense of these observations. These larvae can survive losing 98% of their water by dramatically increasing the quantity of a sugar called "trehalose" in their body. Trehalose helps maintain cell membrane structure and integrity in such conditions. A spike in trehalose levels in dauer larva could give it the means to survive the acidic, low water environment of the slug insides if it got gobbled up.

But what if I told you that sometimes dauer larvae seem to want to get eaten? These worms usually only move two dimensionally, crawling away their whole life, until they turn dauer. Dauer larvae start to lift off the ground, hoist their body vertically, and do a sort of dance. This behavior, called nictation, is thought to increase their chances of being preyed on by animals. Sort of like a giant arrow pointing to the worm. Worms do this only when their food source depletes or they face difficult climates, so as to get transported to a more favorable arena. They take charge of the intestinal reigns and orchestrate their own butt escapes.

Sahana Sitaraman studies
Neuroscience and Behavior
at
National Centre for Biological Sciences, India
.

Anuses can have teeth, farts can be weapons, butts can be homes: an interview with a farts expert

Max G. Levy — Mon, 21 Sep 2020 22:57:57 EST

Ed: Welcome to Butt Month. Every Tuesday in September, Massive will publish an article on the evolution, science, and technology surrounding the butt. If it touches the butt, we’ll be covering it. Why Butt Month? Why not.

You’re probably here for the same reason I am: because farts are amazing. A single pffff, poot, or squeak, can plug nostrils, crack smiles, and break tensions. I want to talk about farts.

Dani Rabaiotti is a zoologist based in London who wrote a best-selling book on farts in 2017 called Does it Fart? She and her co-author, ecologist Nick Caruso, along with illustrator Ethan Kocak, followed a trail of animal communication science that is criminally undercovered. In this Q&A, she shares her most memorable farts (a seal's, not her's), why cat farts are so bad, the unsolved mysteries of butt-borne defense tactics, and so much more.

This interview has been edited for length and clarity.

Max Levy: So, what's a butt?

Dani Rabaiotti: So there are actually quite a lot of definitions for what a butt is. Because obviously we have a butt and it’s made up of an anus and also like a fleshy part, buttocks. But not every animal has a bum – we’re pretty much one of the only animals that have buttocks. So it's very broad depending on what you're referring to. But, also, not even every animal has an anus. Plenty of animals have what's called a cloaca – that's the Latin word for "sewer" and it's where everything goes: you've got defecation, you've got urination, and also mating with the cloaca. Some examples of animals that have that are birds, reptiles, amphibians – they’ve all just got one hole.

So the definition of a butt is quite hard. I usually just refer to any end of an animal that's opposite its head as a butt. That's the very scientific definition that I go by.

There's just all sorts of weird and wonderful butt anatomies...ornamented, pretty gross, or just like basically completely nondescript unnoticeable butts as well

So physiologically, you're saying that butts vary a lot. Is there one that comes to mind that's really remarkably different from the rest?

There’s just so much variation between animals, like some species of sea cucumbers can have teeth in their butt. [They have teeth in their butt] because there's an animal called pearlfish that lives inside sea cucumber butts, and they want to try and keep them out because they eat their gonads and their respiratory tree, which is pretty unpleasant.

So they've evolved all these sorts of defenses. And then obviously you've got animals that use their butts to attract a mate. Some species of baboons, for example have bright blue bums. You've got people who sit down a lot because we walk on two legs so you know, we've ended up evolving buttocks. There's just all sorts of weird and wonderful butt anatomies out there. You know: ornamented, pretty gross, or just like basically completely nondescript unnoticeable butts as well.

Is there an aspect of either the anatomy or the evolution of the human butt that was really surprising to you as you've been researching?

For me, I don’t really think the human butt is super remarkable. The main thing is that we’ve got a big fleshy bum. And you know we've seen that they're more celebrated in recent years, which is great but that's just part and parcel of the fact that we walk onto those legs and we sit on it. It would be really uncomfortable if we were super bony. I think, but I'm not entirely, sure if researchers out there like human evolution researchers have it pinned down a hundred percent why exactly we have the anatomy we do. But the nice thing is that we don’t just have one hole – I’m grateful for that.

Does all of this variation make farts and butts hard to study?

As someone who wrote a whole book about farts, it was a challenge for both of us. So myself and my co-author Nick, when we were trying to define what a fart is, [we found that] the medical definition was gas produced in digestion that is expelled from the anus. We were like, "But we’re talking about animals, not every animal has an anus." So then we're like: what's an anus? Well, it's a butt. Then you have to think about, like... what is a butt. A lot of it kind of comes down to what would people think of as a butt. Obviously if people see a bird, they think the tail end is the butt even though it doesn't have an anus or butt cheeks. So we kind of had to be a bit liberal with that.

You mentioned gases play an important role in how you’re defining butts and farts, but I remember how cows burp more methane than they fart. Is that something also that happens in humans?

So we don’t produce that much methane because we don’t eat that much plant material. The reason cows produce so much is because they eat grass. And as they extract the nutrients from that, because they're so good at [digesting grass]. A lot of the cellulose gets broken down and that produces a lot of methane. Whereas when we eat plant material we're not super great at breaking it down so we don't produce anywhere near the quantities of methane that, say, a cow would.

Animals aren’t embarrassed of their farts like people are

Does that mean that carnivores are less voluminous farters?

Less gas, but also different gas. So with carnivores, they eat a lot of meat and it's got a lot of sulfurous properties, as do other things like asparagus. And that's what makes farts smell really bad, like you know that rotten egg smell? That’s where that comes from. Any animal that's eating meat is always gonna produce more of that because the food it's eating has more sulfur in it.

One of the animals in the book, the fossa, stuck out because you described the farts as fierce. What did you mean by fierce?

There's quite a few animals in there that I can attest to experiencing their farts first hand, but sadly the fossa are pretty rare, even in captivity, so I haven’t experienced it myself. But that was from the zookeeper’s mouth on that one.

Do any stand out as like really remarkable?

Definitely the worst smelling are seals and sea lions. And all the zoo keepers said this as well. I spent some time in South Georgia which is just off the coast of Antarctica, and it's just covered in fur seals and elephant seals. And we woke up one morning to just like this absolutely horrific smell in the tent. Just like rotten fish mixed with rotten eggs. Just absolutely grim.

A Northern elephant seal

Via Wikimedia

Oh my goodness.

One seal had its tail under the porch of the tent so right away, yeah, it was horrendous. But all the zoo keepers said that hands down worst animal farts – the worst – is definitely seals and sea lions.

Is it because of their digestion?

Yeah. Well I think anything that just eats fish and crabs. It smells pretty bad going in so it’s not going to come out smelling nicer. And the smell isn't always from the gas, sometimes it's also from the feces itself. So I imagine like seal poo smells terrible, that's gonna be adding to it as well. So yeah, just really grim.

Do other animals react visibly to a fart that happens next to them?

Animals aren’t embarrassed of their farts like people are, but we have definitely had quite a few reports of animals getting scared by their own farts – particularly ferrets. We’ve had a lot of reports of ferrets getting scared by their own farts.

Are any farts actually toxic?

I'd say the two that spring to mind are, well, obviously cows, horses, and other species that are ruminants like sheep and goats. They’re producing a lot of methane. So obviously it's not really toxic, but it is really bad for climate change. So that's not great.

And then also there’s a species called a beaded lacewing which is a type of insect. When it farts it produces what's called allomone – it's a chemical that only affects one species. So the larvae of that species eat termites and they fart the allomone out onto the termites which paralyzes them and then they eat them. That's very toxic.

A beaded lacewing

Katja Schulz via Flickr

It's by design because they're not that much bigger than their prey. So, like, they wouldn't have any other way of incapacitating them. And they actually kind of disguise themselves in the termite mound so they don't get detected. It just needs the prey paralyzed, and it can just kind of get on eating it without getting attacked.

So there are a lot of open questions in farts? Are there people actively like seeking answers to those mysteries? Or is that? Is there not really a final frontier for fart?

I would say that most fart and poo research is generally looking at other questions. And the answers about fart and poo specifically generally come up along the way. Like, for example, it could be a research paper about communication, it could be a research paper about diet. And then there are just happy coincidences that people find out as they're looking at other things. I don't think there's a huge part of research funding out there for research about the properties of animal farts or the properties of animal poo. Unless it’s looking at what the animal is eating or that sort of stuff.

I guess that’s probably good…

No it’s bad! I want a fart and poo research lab, that’s the dream!

Oh, do you?

Yeah, I think I'll always keep an eye on this kind of literature because you know how I wrote the book on it. I'm always expected to have my knowledge up to date. But the good thing is that there’s a good network of people who've read the book now and that means that if anything comes out in this area, any new research, everyone tags me in it. So I don't have to search too much.

Yeah so I was wondering, do people just text you and message you anytime something fart related comes up?

Oh yeah, 100 percent. Even if it’s like “planet farts,” it gets sent to me. I mean, I love it, it’s great.

It is funny how a big part of searching for life on other planets is looking for gases from possible species that are digesting, in a way.

Yeah, like I think that's it's really cool. And I guess most organisms you're looking for in space are more similar to the microorganisms we'd find in our gut rather than us. But it's very cool that this kind of gas production can reveal so much about a species' digestion, about the way it lives. Yeah, I think it's really interesting.

Did you notice any specific trends?

I think that it just kind of struck me how under-researched some of it was. It was quite surprising that there was things I wanted to know about animal farts or animal poo, or even some common myths that I couldn't actually debunk or say for certain whether they were true or not...

And I'd say definitely the most under-researched animal [for farts] are invertebrates. Anything that's not cute and fluffy was much, much harder to find out about.

Somebody follow this thrush around while it farts

coniferconifer via Flickr

So are there any misconceptions you’re still trying to resolve?

There's quite a lot of myths and legends surrounding honey badgers and mongooses and other kinds of mustelids: how they subdue bees when they eat them. And we had heard quite a lot about a few different animals that would fart on another animal to subdue it. People also say this about a species of thrush in the US, that farts on the ground to subdue worms. And I'm 99% sure that they are not true. But it was really hard for me to definitively say this is not true, because no one goes and tests. So I'd like to see more people going and validating these reports because the honey badgers farting on bees was in a field guide and the thrush farting on the worms was in a really, really, really old scientific observation. I think those ones I definitely would like to put to rest for good, if possible. So if anyone could make some up-to-date observations, on those that would be fantastic.

Anything else you want people to know?

I just want to say that animals have some amazing uses for their butts. And other animals have some amazing uses for other animals' butts, like living in them, or using them as a defense (so many animals have white tails which they put in the air as a warning sign to others).

I just think the diversity of what animals use their butts for is absolutely incredible. Butts are completely underrated and no one should ever shy away from doing research that involves butts because there's just a whole wide world out there of animal communication that revolves around butts.

And it seems to get people really interested in science.

Yeah definitely. People will want to read a book about butts or about farts. And then surprise: they’re learning.

Rabaioitti and Caruso’s book, Does it Fart? is available here.

Their newest book, True or Poo? is available here.

Max G. Levy studies
Science and Health Journalism and Chemical Engineering
.

How safe is the DNA in your poop from unwanted snooping?

Jennifer Tsang — Mon, 14 Sep 2020 23:48:42 EST

Ed: Welcome to Butt Month. Every Tuesday in September, Massive will publish an article on the evolution, science, and technology surrounding the butt. If it touches the butt, we'll be covering it. Why Butt Month? Why not.

Five years ago, scientists from the University of Wisconsin-Milwaukee and the Marine Biological Laboratory reported that they could predict obesity levels of a city from the sewage microbiome with 81 to 89 percent accuracy. They also found that the microbiomes of the humans living in a city are represented in that city's sewage.

The microbiome, the collection of microbes that live in the human gut, is thought to be linked to health. But the connections between gut microbiome and health are often made using individual samples. In the sewers, it’s a different story and whats found there can tell the lives of an entire population from just one sample. These scientists found that on average, 15 percent of the DNA from sewage samples came from human microbiomes. From the 200 samples originating from 71 U.S. cities, they noticed that there are about 60 types of bacteria common between the cities. Their abundance, and the abundance of less common microbes varied from city to city, giving each place a unique signature.

Studies like this are simple in principle. Everyone pees and poops. We excrete metabolites, vitamins, microbes, and even our own cells. This information makes its way into a wastewater treatment plant, creating a community-wide stool or urine sample. Wastewater epidemiologists can leverage our waste to detect disease outbreaks, drug use, and more. So what exactly can we detect and how is this information protected?

One study predicted obesity levels from sewers with 81 to 89 percent accuracy

Wikimedia CC 2.0

Disease monitoring

Sewers can offer almost real-time outbreak data, or in some cases, they report an outbreak even before we know it's here.

The latest example of this is COVID-19, where scientists all over the world have found genetic material from SARS-CoV-2, the virus behind the disease, in sewage. In Italy, traces of the virus were found in two cities in December. The first reported case there didn’t come until around the beginning of February. In Paris, researchers could track the rise and fall of SARS-CoV-2 infections using sewage. And in Australia, researchers used the number of viral RNA copies they found in sewage to estimate the number of infected individuals in the population.

Universities and colleges have begun to monitor SARS-CoV-2 RNA in their pipes. Kendra Maas, a facility scientist at the University of Connecticut Microbial Analysis, Resources, and Services core facility, spent the last several months preparing her university for SARS-CoV-2 sewage monitoring. “I know of about 15 universities that are currently sampling. Probably 30-50 are talking about it,” she said in early August. The University of Arizona possibly prevented an outbreak on campus when they found a positive wastewater sample from a dorm. Upon further examination, they found two students who tested positive despite showing no symptoms.

The University of Arizona possibly prevented an outbreak on campus when they found a positive wastewater sample from a dorm

But, long before COVID-19, scientists have monitored wastewater for diseases. Poliovirus can be shed in fecal matter and cell-culture based methods of disease tracking were used to track it as far back as the 1940s. In 2013, routine wastewater surveillance detected poliovirus in Israel when no cases of the acute flaccid paralysis associated with polio have been reported. That same year, sewage monitoring also gave early signs of hepatitis A and norovirus outbreaks in Sweden.

Sewage and lifestyle

However, using sewage to monitor a community’s lifestyle and general health may seem, to many, more intrusive than monitoring disease outbreaks. At the University of Queensland, scientists were able to predict socioeconomic information using wastewater. This group of researchers used biomarkers from wastewater to predict 37 characteristics from the Australian Census including median age, education, and employment. And remember the example linking sewer microbiomes to obesity? Wastewater samples are not as difficult to work with as some other environmental samples, Maas says. Presumably, you could detect any microbial DNA or RNA sequences as long as the samples are prepared properly.

In the case of drug use, some see it as a community-wide drug test. Surveilling illegal drug use through the sewers is already in practice in several cities in China which has led to the arrest of a drug manufacturer, with plans to expand to police arrest of drug users. China is not the only country to monitor drug use in wastewater. Belgium, Spain, the Netherlands, and Germany are among the countries that have been using water-based drug monitoring. In 2018, a collaboration between BioBot Analytics, a Cambridge-based start-up, and the city of Cary, North Carolina began monitoring wastewater for opioid use, the first real-time drug surveillance in the US. But unlike China, these countries are using it for epidemiological research, rather than for setting policies or policing. Daniel Burgard, a chemistry professor at the University of Puget Sound, told Business Insider, "It does bring up an interesting question of when a person’s waste is no longer their property."

Privacy concerns and anonymizing data

Whether the data points are DNA or metabolites, it’s not surprising that there are concerns about this data getting into the “wrong hands” (government, employers, insurance companies, etc.).

With on-campus sampling for COVID-19 at universities, “there isn’t a privacy concern because there is zero chance of linking it back to a particular person just through wastewater,” Maas says. There, the data is aggregated from thousands of people.

"There isn’t a privacy concern because there is zero chance of linking it back to a particular person just through wastewater,” Maas says

Markus Spiske from Pexels

But things can be different for other studies. Even if it does not trace back to a single individual, wastewater data can trace to specific populations. For example, if sampling occurs further upstream in the pipes, then the samples can begin to identify specific neighborhoods or racial groups and lead to stigmas and stereotypes in areas with higher drug use or health issues.

The Sewage Analysis CORe group Europe put together a set of guidelines addressing ethical research practices for sewage epidemiology noting that there’s historically been little oversight by research ethics committees as wastewater data is not collected on individuals. Some of their mitigation strategies include aggregating samples from multiple sites, and removing names and locations of sampling sites.

But there are other steps towards ethical and anonymous wastewater-based epidemiology data collection – many that hinge on the researchers and the peer review process. Before researchers conduct a site-specific study, they should evaluate the site’s history in ethical practices. And, during the publication and peer review process, researchers can limit the possibility of identifying vulnerable groups by thinking about what can be extrapolated from published papers. Instead of reporting population size, the researcher should instead report population rates (ex: x per 100,000 people), for example.

Wastewater based epidemiology has the potential to gauge the health of our cities, but before reaping the benefits, scientists should also weigh and address the concerns. Sewer data used for research to understand population trends is much different from using the data for policy or punishment. In the era where data is everything, we can amass a large and diverse amount of information and it’s possible to come into a future where wastewater-based data becomes more mainstream.

Jennifer Tsang studies
Microbiology
.

Conservation dogs can track individual beavers by the scent of their anal secretions

Jazmin Murphy — Mon, 07 Sep 2020 23:04:48 EST

Ed: Welcome to Butt Month. Every Tuesday in September, Massive will publish an article on the evolution, science, and technology surrounding the butt. If it touches the butt, we'll be covering it. Why Butt Month? Why not.

Conservation dogs have been trained to locate animals both dead and alive. Given that dogs' sense of smell is approximately 10,000 to 100,000 stronger than ours, they are excellent partners for tracking animals in the wild.

With the help of three "scent detection dogs" named Tapas, Chilli, and Shib, researchers have shown that with persistent training, this olfactory advantage could dramatically improve conservation canine handlers' work. How? By improving upon their ability to identify animals by tracking their individual butts.

The story of "conservation dogs" goes back in the 1890s, after one of New Zealand's first-ever recognized conservationists, Richard Treacy Henry, trained a few pups to assist in the relocation efforts of two flightless birds, the kiwi, or tokoeka and the kakapo. Though conservation dogs detect animals using many kinds of scents and excretions, recently, these identifying substances have become increasingly butt-focused.

No other bodily secretions had been shown to provide the same level of identifying information that scat does. That is until Frank Rosell, David Kniha, and Milan Haviar looked into the matter, in work published in BioOne Complete. The research team at the University of South-Eastern Norway tested the dogs on something new: the anal gland secretions (AGS) of the Eurasian beaver.

Mel Nigro

The Eurasian beaver once spanned nearly the entire Eurasian continent. At the start of the 20th century, however, their populations were down to approximately 1200 individuals. Fortunately, they've since been reintroduced throughout Europe, and now are recognized by the IUCN as "Least Concern" with 1.04 million animals and counting. Still, they are a keystone species that requires regular monitoring and protection.

Since these beavers communicate primarily through scents, they've invested quite a bit of evolutionary development into their anal glands. In fact, the anal glands are not the only butt-local organ that beavers use to make themselves known to their neighbors. They use two, each of which is located between the base of the tail and the pelvis: castor sacs, which produce a brown mucous called "castoreum," and anal glads, the "true" glands which produce AGS. AGS is a "thick gray paste" in female butts and a "yellowish oily fluid" in males. AGS contains a great deal of information about an individual beaver, including species and subspecies, sex, identity, kinship/family role, age, and social status.

Outstanding Scent Detection Using Beaver Butt Juice

The team collected 75 AGS samples from live-trapped beavers. To extract the samples, the scientists needed to manually induce the beaver’s expulsion of AGS.

Eurasian beavers excrete both castoreum and AGS on small mounds of mud on riverbanks. These locations mark their territory and are easily detectable by neighboring visitors and human researchers alike. Still, these samples could not simply be collected from the mounds, since Tapas, Chilli, and Shib needed to train with the pure fluids.

The first step was to empty the animal’s rectum to clear out any odors that would distract the dogs from the AGS. Next, the team rinsed each beaver's cloaca – an extra step to ensure the bottom was free of non-AGS particles. Finally, through manual control of the papillae, the team safely removed the AGS for training and testing.

Tapas, the conservation dog

Courtesy of Frank Rosell

Tapas, Chilli, and Shib were presented with a lineup of AGS samples, accompanied by distraction scents (these were either a blank vial, coffee grounds, tobacco, or herbal tea), and were expected to identify the target among the blank or other scents. The pups first smelled the focal AGS on its own when given the command, “Smell!” After memorizing the scent, they would then go select the match in the lineup with the command, “Search!” The lineup held both the target and the distractions.

Finally, upon finding the target, Tapas, Chilli, and Shib would lie down and point to the sample with their nose or paw.

After the 9-month training period was complete, the dogs’ sniffers – and the identifying potential of AGS – were put to the test: Six vials in total were lined up, including four AGS samples, one distraction scent, and one blank. Tapas, Chilli, and Shib were each subjected to ten trials. The results were stunning. Each dog showed themselves to be beyond capable of finding the precise beaver by their anal excretions alone.

Their successes were measured in a few ways: sensitivity (the number of times the dog correctly identified the target anal gland), specificity (how often the dog correctly indicated a distraction), and accuracy (the collective term for both sensitivity and specificity). Overall, Tapas, Chilli, and Shib scored an 88.9% accuracy, 66.7% sensitivity, and 93.3% specificity.

Chili, the conservation dog

Courtesy of Frank Rosell

Not only are these findings a clear demonstration of scent detection dogs’ ability to extract highly specific information from AGS, but it also points to the incredible reliability of the Eurasian beaver’s hind-centric olfactory communication system.

How AGS Scent-Matching May Change K9 Conservation

Although this is a remarkable discovery, it does have some shortcomings. First, the study had a small sample size, given that there were only three dogs tested. Secondly, as acknowledged in the publication, the researchers did not conduct a test where the target AGS was not present. This could have misrepresented the error rate of the dogs since the focal beaver might not always be present in the search area.

Aimee Hurt, Co-founder and Director of Special Projects for Working Dogs for Conservation (WD4C), recognizes the necessity of both DNA analysis and individual-specific scent detection in dog-assisted conservation work. Hurt said via email: "Dogs matching individuals by scent in the conservation realm has been reported in scientific literature a few times since 2007, and yet the go-to tool remains sending samples to the lab for DNA analysis. This is most commonly how our teams work, where dogs are trained to find as many samples as possible from a given species, and then the lab determines which animal the sample comes from if that's a relevant question for the objectives of that study.”

This hyper-specific identification ability presents a promising advantage in K9 conservation work. For instance, one common problem in monitoring efforts is lost or malfunctioning tracking devices. If wildlife managers needed to track a specific individual, scent detection dogs could temporarily replace the faulty equipment. Also, many species are highly sensitive to standard practices like live-trapping. A hands-off monitoring approach using dog-assisted scent tracking could relieve some of this pressure.

When asked about the circumstances in which conservation dogs would need to perform scent-matching in this way, Hurt explained that “individual identification is only one example of the ways we can capitalize on dogs' ability to discriminate scents and put that ability into indoor, controlled, lab-like settings.”

According to Kniha, "Identifying a specific animal is technically being done by detection dogs whenever they search for a specific animal. Identifying specific species or subspecies can be very useful for...distinguishing species that are very difficult to tell apart." His hopes for future application of this work are high. "I sure hope it will inspire more people to explore the potential abilities of dogs, which I believe are much greater than what we already know."

Canine conservation work has approached a new horizon. Building off past discoveries of dogs’ ability to scent-match individuals based on scat samples, Rosell and his fellow researchers, along with the awe-inspiring Tapas, Chilli, and Shib, have demonstrated that a wealth of highly valuable information is stored in the butts of Eurasian beavers. The extent to which this information can be used relies on the sniffer's power and the availability of anal secretions.

Jazmin Murphy studies
Ecology and Science Journalism
.

How did human butts evolve to look that way?

Darcy Shapiro — Mon, 31 Aug 2020 22:38:31 EST

Ed: Welcome to Butt Month. Every Tuesday in September, Massive will publish an article on the evolution, science, and technology surrounding the butt. If it touches the butt, we'll be covering it. Why Butt Month? Why not.

What makes humans different from other animals? Ask any ten people and you're likely to get ten different answers, ranging from our relatively large brains, to our incredible use of language and symbols, to our ability to dramatically modify the world around us.

But if you asked me, I'd say that it's our butts.

Take a look around the animal kingdom. Even our closest living relatives among the great apes (chimpanzees, bonobos, and gorillas), don't have proportionally as big butts as humans do. The main reason for this probably comes down to our unique style of locomotion. We're the only mammals alive today whose primary way of getting around is walking on two legs. And becoming upright bipeds has had some important consequences for our derrières.

Mel Nigro

The anatomical structure that we generally think of as a "butt" is made up of adipose tissue (fat) sitting on top of our gluteal muscles, which are attached to the bony pelvis. Ultimately, it's the shape of our pelvis that dictates the shape of our butts, and that set of bones has undergone some major changes over the last six-or-so million years.

The pelvis is made up of three parts: two innominates (or "hip bones") and the sacrum. Each innominate is also made up of three bones (the ilium, ischium, and pubis) that fuse together during growth and development. And it's the ilium that's the real difference-maker between us and our ape relatives. A chimpanzee's ilium is relatively tall and flat, with the flat sides facing forwards and backwards. Our ilia, on the other hand, are short and curved around more to the sides, making our pelvis bowl-shaped. These size and shape differences are linked to the evolution of bipedalism and the reorganization of our gluteal muscles that make upright walking possible.

The three gluteal muscles are gluteus maximus, gluteus medius, and gluteus minimus ("gluteus" derives from the Latin for "butt", so that's "biggest butt," "medium butt," and "smallest butt"). Our gluteus maximus (especially the upper part) is very large compared to that of other primates. It extends the thigh and moves it backwards, and gives us power when we run or climb stairs. And it's what gives our behind most of its shape. In other apes, though, the so-called "lesser gluteals" (gluteus medius and minimus) do a lot of this work, so the gluteus maximus doesn't have to be a major player. Hence, no booty.

What our lesser gluteals are doing instead is helping our hips not drop to the side when we stand on one leg (as we do every time we take a step forward). It's the curved shape of our ilia that allows them to do that, by changing where those muscles are and, thus, their function. Our lesser gluteals provide stability rather than power.

Even gorilla butts can't compare

Nicholas Brown / Flickr CC 2.0

We can trace this change in ilium shape and inferred gluteal function throughout our evolutionary history, from the 4.4 million year old early human relative Ardipithecus ramidus (maybe — this fossil's pelvis was in pretty bad shape when it was discovered), to australopithecines like Lucy, and to Homo erectus. The ilium has generally gotten shorter, broader, and more curved over time, which means our butt has been on a multi-million year journey to becoming the lyric inspiring piece of anatomy that it is today.

It's the shape of our pelvis that dictates the shape of our butts, and that set of bones has undergone some major changes over the last six-or-so million years

The last thing that helps make human butts unique is the fat — which might also have something to do with us becoming bipeds. Humans have relatively large brains that use a lot of energy. Our bodies store energy as fat, and we have a relatively high percentage of it for a non-aquatic mammal. This has led anthropologists to suggest that our body fat helps buffer our metabolically-expensive brains against lean times. This seems to be something that we are able to do because walking on the ground is both an energetically efficient way to get around. It also avoids the downsides of spending our lives in trees — having to support all of our weight on tree branches and exist at the mercy of gravity requires a lot of energy. (Orangutans seem to do pretty well at this — but they have the strength, flexibility, and limb proportions to make it work, not to mention opposable big toes).

While all of these changes sound pretty great, our peculiarly human arrangement of muscle and fat on our backsides comes with at least one major butt-related downside: a messier pooping situation than many other primates have. Picture a quadruped, like a chimp — its trunk and legs meet up and form an angle, with the butt at the corner and its anus pointing more outward. And that opening isn't trapped between large buttcheeks. For us, there's no angle — it's just a straight line. By standing up, we've rotated the anus to point more downward, then added additional padding around it. Hence, messier pooping. Thanks, evolution.

Darcy Shapiro studies
Evolutionary Anthropology
at
Rutgers University
.

Cats communicate with the help of bacteria living in their butts

Lauren Sara McKee — Sun, 01 Dec 2019 23:41:00 EST

It’s becoming ever clearer that we live in a microbial world. By now, we are well aware that microbes play important roles in digestion, training the immune system, and protection from pathogens. Although many studies have been done in model organisms like mice, some researchers are now asking similar questions about the microbiota of other animals in the hopes that this could help us take better care of our furry friends.

KittyBiome, a crowd-funded research platform, was started because, as vets and pet owners know, domestic cats suffer from a lot of digestive issues. And because we simply don’t know enough about cat digestion, it’s hard for vets to recommend diets or even medication that can help in the long term. Scientist Jonathan Eisen has said that the idea for KittyBiome came out of discussions at the University of California (UC) Davis Citizen Microbiology meeting, and was developed by microbial ecologist Holly Ganz. Now, their group is showing just how much the microbiome does for cats.

Photo by Andrew Umansky on Unsplash

The group at UC Davis was keen to research the cat gut microbiome, and they decided to pursue an unconventional route to fund their research, using Kickstarter to seek help from the general public. Ganz is one of the authors of a report on how crowdfunding research can fill in funding gaps when resources from organisations like the National Institutes of Health (NIH) are hard to come by.

KittyBiome reached their funding goal, and involved their citizen scientist backers in the program by asking them to send cat poop samples for sequencing. The team set out with the goal of studying the guts of at least 1000 cats, to see how much variation there is between different cats; researchers want to compare cats living in houses, cats in shelters, and feral cats, as well as cats with different health conditions.

“A lot of cats and kittens with chronic diarrhea are euthanized, and if we could come up with something to help counteract this, we could be saving lives.”

Ganz, the lead scientist on the KittyBiome project, has said that she is fascinated by the microbes found in cat guts and their anal glands and how these microbes might be linked to social behavior. Ganz hopes to use the research program to make real improvements to animal welfare: “A lot of cats and kittens with chronic diarrhea are euthanized, and if we could come up with something to help counteract this, we could be saving lives.”

Research under the KittyBiome umbrella has often been directed by the types of samples sent to the scientists by pet owners and animal healthcare professionals, leading to pretty diverse investigations into feline physiology. For some of the first KittyBiome-funded experiments, veterinarian Leah Isaacson expressed the anal sacs of a male Bengal cat as part of a regular health check-up. The cat's secretions were sent to researchers at UC Davis.

Photo by Paul Hanaoka on Unsplash

The scientists used genetic analyses to identify the bacterial species present in anal sac secretions. They found that the microbial community in this organ is far less diverse than the feline digestive systems that have been investigated, where hundreds of species across dozens of genera have been found. In the Bengal cat study, 98% of the bacteria in the anal sac came from just six genera. Just three types of bacteria that were abundant in the genetic profile of the secretions could also be grown in lab cultures – Bacteroides fragilis, Tessaracoccus sp. UCD-MLA, and Finegoldia magna.

This is a strong indication that at least some of the stinky molecules in cat spray are produced by bacteria.

Researchers tested these bacteria for their ability to produce smelly molecules called volatile organic compounds (VOCs). They compared the VOCs produced by the bacteria with those found in the original cat swabs: out of 67 molecules produced by the lab-grown bacteria, 51 were also found in the cat secretions. This is a strong indication that at least some of the stinky molecules in cat spray are produced by bacteria.

This agrees with a previous study in hyenas showing that bacteria play a role in animal odors and generally supports a theory known as the Fermentation Hypothesis — that "symbiotic microorganisms living in association with animals contribute to odor profiles used in chemical communication and that variation in these chemical signals reflects variation in the microbial community." This hypothesis is also supported by research showing that animals on antibiotics produce fewer smelly compounds in their secretions.

Fermentation is a microbial process that can happen when there is no oxygen present. It allows microbes to take energy from organic substances like sugar, and produces new small molecules that the microbes secrete as waste, like when yeast makes alcohol (ethanol) during beer production. Fermentation also happens in our guts all the time. Around 10 % of the energy we use every day comes directly from short organic acids that our gut bacteria make by fermenting food molecules we otherwise can’t digest.

The VOCs in cat spray are similar types of organic acid, called short chain fatty acids, many of which are known for their outrageous stench. If the Fermentation Hypothesis is correct, most such fatty acids in mammals would have a microbial origin. It may even be possible that the anal sac organ – which provides an oxygen-free environment for fermenting bacteria – has been retained in cats specifically to provide those bacteria a home.

These smelly substances are thought help cats identify each other as individuals and as group members. Therefore, by producing these smelly substances, bacteria living inside animals may be impacting group behavior and how animals recognize each other.

However, before any definitive conclusions can be established, these findings will need to be replicated in multiple cats, not just a single cat. Another important question is whether cats that live together in a house or shelter develop a more similar anal sac microbiota than cats who live apart or are feral. If so, would that mean that their scent markings become more similar over time? It would be fascinating to know the effect on group dynamics and recognition between animals, and how this particular bacterial community might be impacting the behavior of the host animals.

Photo by Jonas Vincent on Unsplash

So what’s next for KittyBiome? Their long-term goals are to understand the effects of diet and behavior on cat health, to hopefully develop diet plans and perhaps pre- or probiotic products that pet owners can give to their feline companions. They are collaborating with Cat Tracker, a company that provides owners with GPS trackers for their cats, and connects those data with info about how cats live and behave, what they eat, and so on. The KittyBiome researchers want to try to correlate microbiome data with behavioral observations like distance traveled and the consumption of scavenged or hunted food. They are also analyzing samples sent in by owners who feed their cats a raw pet food sold in San Francisco, to investigate the impact of an uncooked diet.

Lauren Sara McKee studies
Microbiology, Biochemistry, and Biotechnology
at
KTH Royal Institute of Technology
.

Ancient dog bones tell us what was on the menu for both dogs and humans

Jaime Chambers — Mon, 02 Sep 2019 22:17:03 EST

If you’ve ever slipped your Labrador a handful of popcorn, or found that she helped herself to the trash while you were away, you know the human-dog relationship is strongly connected with food. Those wary eyes at Neolithic campsites had much in common with the wistful ones following every bite of your dinner. Dogs have been living alongside us for at least 12,000 years, eating many of the same things we do — both given or scavenged.

In general, ancient diets can provide a valuable window into the past, revealing how food webs and ecosystems changed as we migrated around the globe. But human evidence isn't always available. When it isn’t possible to crack open human bones for clues, archaeologists have sometimes turned to dogs — assuming that whatever people were eating, the pups were too.

...a team of researchers used this strategy in a contemporary Indigenous community in two Nicaraguan villages, and found, by and large, dogs and humans dine from the same menu.

The idea of using dog remains to decipher what humans ate has been around since the late 1970s. Known as the “canine surrogacy approach,” (CSA) it offers a clever backdoor to understanding how humans hunted, foraged, and cultivated their way around the world. Plants and animals leave different chemical traces in the hair, bone, and teeth of the living things that eat them, readable as isotopic “signatures.” "Stable isotope analysis" offers a powerful tool for capturing these records within the body, essentially taking snapshots of individual diets and panoramas of food webs. This approach measures the proportions of carbon, nitrogen, sulfur, and other elements important in biology and traces that signature to the food eaten in the past (they are "stable" because this experiment analyzes non-radioactive elements that don't break down over time, like carbon-14 measured in radiocarbon dating). But it isn’t always possible to use human remains — due to lack of preservation, lack of access, and ethical concerns regarding the destructive nature of the process.

Since the 1970s, archaeologists have applied this idea with varying levels of success, finding dog diets both mirroring and diverging from that of humans. But, the approach has its critics. When it comes to isotope values, archaeologists disagree about how close is close enough for dogs to serve as substitutes for human beings. For example, carbon isotope ratios can reflect consumption of different types of plants; similarly, the more animal products someone consumes, the higher their nitrogen isotope ratios generally are. Even a three percent difference in these isotope values between individuals can mean they occupy different levels in the food chain. But until recently, no one had broadly applied the CSA to a living population to test it.

This photo has nothing to do with the article they're just very good dogs.

Photo by Matt Nelson on Unsplash

But in 2018, a team of researchers used this strategy in a contemporary Indigenous community in two Nicaraguan villages, and found, by and large, dogs and humans dine from the same menu. The scientists compared dog and human diets, and discovered that dogs mirrored human diets at the community level, over the villages as a whole. But at the individual level, dogs didn't necessarily reflect the diets of their owners. This demonstrates what the canine surrogacy approach can be good for (showing the spectrum of what a community ate), and what it might not be good for (finding out what a certain household ate).

Because the scientists looked at a living population, this team was able to simplify the comparison of dogs and humans: pairing the isotope findings with actual observations of what both species ate. But the strength of this test also illuminates exactly why the CSA can be so complicated in an archaeological context. For example, dogs may eat a lot of things humans don't – not just bone and poop, but also low-status or taboo foods. In a living population we can observe culturally founded eating patterns that people abide by and their dogs do not — but in the archaeological record, this can be more difficult. Even in this study, people from wealthier households and dogs from poorer households both showed high carbon values — although likely for different reasons. Villagers with more resources ate processed food containing corn byproducts with higher carbon values than other plants, and poorer dogs scavenged livestock feces or bone, which has a higher carbon value than meat.

Just really a terrific dog.

Photo by Tadeusz Lakota on Unsplash

Of course, this is just one study with a limited population size. Confirming the ability to use dogs as proxies for humans is difficult because of the complex nature of that relationship, which varies widely across time and space. Studies in other cultural contexts are needed, but these findings are the first step in that direction.

While dogs do not necessarily mirror the diets of their individual owners, their potential to reflect the spectrum of what a human community eats is still significant. If dog populations generally share the same menu as the people they live alongside, canines might be the key to unlocking new data on ancient diets — and therefore revealing how we feasted our way from the past to the Anthropocene present.

Jaime Chambers studies
Anthropology
at
Washington State University
.

What can ancient dog poop reveal about an ecosystem?

Allison Fritts-Penniman — Thu, 05 Jul 2018 09:00:45 EST

Imagine a North America before humans. A river winds its way through the wetlands and floodplains of what is now central California. A frog croaks, a goose honks, and a sabertooth salmon leaps upstream. A dog poops, then runs off with its pack mates.

Fast forward to the present day. That dog poop is now a fossil specimen from the Mehrten formation, a rock outcrop rich with fossils from 5.3 to 6.4 million years ago. A recent study by Xiaoming Wang, curator of vertebrate paleontology at the Natural History Museum of Los Angeles County (NHMLA), and colleagues shows us just how much we can learn from fossil poop – or “coprolites” in scientific lingo.

We can never observe directly what extinct species were eating, so we turn to poop for clues

The study, published in eLife, revealed not just the species of dog responsible for the poop, but also what this fossil dog ate, because it contained bone fragments. Finding undigested food in a poop fossil is the ultimate ground-truth for paleoecology, the study of ecosystems that existed millions of years ago. We can never observe directly what extinct species were eating, so we turn to poop for clues.

There's bones in the feces fossils

But what dogs were around five million years ago? To answer this, the authors turned to another study they recently published in the Journal of Vertebrate Paleontology, describing the fossil dogs of this rock formation. From four species of fossil dog, they narrowed it down to the most likely, the bone-cracking dog Borophagous parvus, based on its size, the size of the poop, and how common B. parvus was in this rock formation. B. parvus, known from fossils in California and Arizona, was a medium-sized dog, estimated to weigh around 50 pounds. The genus Borophagus went extinct two million years ago, with no surviving descendants. (Modern dogs belong to the same family, Canidae, but descended from a different branch of the family.)

“I have studied these animals much of my adult life, but I had never seen their poop, so you can imagine how excited I was,” says Wang. “Fossilized poop is by far rarer than bones. I’m used to thinking about teeth and how these animals chewed, and how bones are built to resist cracking under the pressure of their jaws. But the poop is more visceral and requires imagination about the other end. The information these coprolites contain is a nice confirmation of what we have long-suspected: that they are bone-eaters. We just didn’t have the physical evidence of it, but now we do.”

Physical evidence of it

Courtesy of the Natural History Museum of Los Angeles County

They had more than just proof that the dogs ate bone; they had some pieces of bone that were big enough to learn more about their prey. Scientists had a guess for what size animals these dogs ate, and were excited to finally confirm it. Paleoecologist Mairin Balisi, coauthor of both papers, explains, “Scientists had deduced that not only did they crack bone, they cracked bone of animals bigger than themselves. This is important, because if you prey on animals bigger than yourself versus smaller than yourself, those are two very different niches.”

The “niche” is the role that an animal plays in an ecosystem. For each potential role, there are tradeoffs. As Balisi puts it, “larger prey requires more effort to find, chase down or ambush, and finally kill … On the other hand, larger prey, once you have it – that’s a lot of meat right there.” The theory is, if an animal is capable of hunting larger prey, they should, because it maximizes their energy spent.

Balisi used the largest of the poop bone fragments to determine the relative size of Borophagus’ prey, and thus the niche that Borophagus occupied. It was a piece of rib likely belonging to an ungulate, such as a deer.

“I had never calculated the body size of a prey species from a single rib fragment, so I had to devise a method. This involved visiting the NHMLA Mammalogy Collections, which house the skeletal remains of large land mammals that we still have today – including ribs to which I could compare the rib fragment in the fossil poop.”

Borophagus goes metal

Public domain / Smithsonian Museum

The researchers determined that the rib most likely came from an animal that weighed from 75-220 pounds. Borophagus parvus is estimated to be at most 53 pounds, so these bone-cracking dogs definitely ate animals larger than themselves, and could crush and eat their bones, which no other predators in this ecosystem have been shown to do. This gives scientists a snapshot into the food web during that time, which is the ultimate goal of paleoecology.

The legacy of bone-eaters

Now that scientists know for sure there was a bone-eater in the ecosystem, they can speculate as to how that ecological role affected the rest of the ecosystem, and how things changed when that role was lost. With a bone-eater in the midst, bones were being broken down quickly, and the material that bone was made of was either incorporated into the predator’s body or was pooped out as ready-to-use nutrients. After the genus Borophagus went extinct two million years ago, that bone-eating role was never fully taken on by another large predator in North America. Bones were left to decompose by other, slower, means. They may have provided the base for a new micro-ecosystem of decomposers, which could then lead to the evolution of a different type of plant and animal community using those nutrients.

Around the same time that the genus Borophagous went extinct, Earth was plunged into an Ice Age. Paleoecologists want to know: how does the loss of a major ecological niche interact with such drastic climate change?

No one was there to pick it up

Courtesy of the Natural History Museum of Los Angeles County

We don’t have all the answers yet, but these questions lead us to the dangerous territory of the present. Earth’s climate is undergoing significant change. At the same time, the extinction of large predators is already having a negative impact on modern day ecosystems, even when it’s just a local extinction. Without top predators, other animals become more abundant and wreak havoc on their own prey species. This can ultimately lead to the collapse of an ecosystem.

If fossil dog poop teaches us anything, it’s that we should appreciate species for the role that they play, and the function they serve. We can choose which species we hunt, and which we protect, in a way that protects all of the functions that are necessary to keep an ecosystem afloat. We can monitor climate change, and make sure we incorporate these changes into our projections for the future. We have the power to prevent catastrophe.

Allison Fritts-Penniman studies
Ecology and Evolutionary Biology
.