On April 23rd, 2018 we learned about

Crocodiles can change their skin coloration based on environmental color cues

Few predators would antagonize an adult saltwater crocodile (Crocodylus porosus). Weighing close to a thousand pounds, these huge reptiles have little to fear in their local ecosystems. Their hatchlings, on the other hand, are usually around 2.5 ounces at birth, and need to be a bit more wary about becoming someone’s lunch. To stay safe, these tiny crocs, as well as other members of the Crocodylidae family, have developed the ability to better hide themselves by changing the color of their skin. Through a series of experiments, researchers have been able to isolate the exact mechanisms that allow these scaly predators to obscure themselves according to environmental conditions.

Shading skin according to what they see

The color changes in question are noticeable to the naked eye, assuming you’re comfortable staying in proximity to a crocodile for 60 to 90 minutes. While no crocodile was observed creating new patterning or bright shifts in hue like a chameleon, they could shift their skin from lighter to darker shades of their normal coloration. Members of the Crocodylus genus, like saltwater crocodiles, would make their tails, backs, and heads turn darker in darker environments, while members of the Gavialidae family did the opposite, lightening their backs when placed in dark environments.

In the context of this study, dark environments consisted of black or white tubs of water. It was easy to see the crocodiles change color according to their surroundings, but researchers needed to make sure that this was really triggered by what each animal was seeing, rather than other conditions like body temperature or stress levels. One way to do this was to place a crocodile in one color tub, blindfold it, then move it to the opposite lighting conditions. In those cases, the crocodiles’ coloring didn’t change according to the new environment- they kept the color that matched the last environment that their eyes were able to see. This was fairly conclusive, particularly after factors like temperature and stress hormones were found to be consistent between light and dark tubs. Finally, tests with red lights, which crocodiles don’t see as well as colors like blue, showed that if the crocodile didn’t visually perceive the difference, their skin didn’t react either.

Pinching and stretching pigments

Of course, visual stimulation can only be part of the story. Researchers also examined the crocodiles’ skin to see how it could change color once the animal noticed it was in a dark or light environment. They found that an α-melanocyte-stimulating hormone was released in the body, which triggered changes in cells’ melanosomes. When a crocodile needed to darken, the pigment in the melanosome would spread out, increasing the percentage of each cell that would absorb light. When a crocodile lightened, the same melanosomes would contract into tight packets, leaving more surface area without pigment to absorb light. This expansion and contraction is all that’s needed to achieve the relatively quick but reversible color change seen across multiple species’ skin.

Estimating when this abilities evolved

The species of crocodile that change colors revealed some information about when this ability likely evolved. Alligators, for instance, don’t change colors, which suggests that this ability had not developed when that family split from Crocodylidae 80 million years ago. Outside the genus Crocodylus, two African members of Crocodylidae showed little to no color-shifting ability, which then suggests that this trait evolved after that branch in the family tree occurred 30-40 million years ago. However, Crocodylus diversified a lot around 12 to 17 million years ago, so researchers assume that this trait was likely established by then in order for it to turn up in species that have since become separated from each other.

My third-grader asked: Do adult crocodiles do this too, or is it just the babies? Why do some of them turn the opposite color? Are they sure the pigment isn’t to help prevent sunburns?

The tests were done with baby crocodiles, possibly because they’re a lot easier to move between tubs of water. However, adults would benefit from dynamic coloration, as hiding from prey would aid in the ambush-style hunting crocodiles typically rely on.

The benefits of Gavialidae crocodiles’ reversed coloration wasn’t directly tested in this study. Researchers speculate that it acts like a form of countershading, similar to the way a shark’s white belly makes it harder to see when viewed as a silhouette from below. If true, this further supports the notion that adult crocodiles make use of these abilities to help them surprise their prey.

The sunburn question was likely sparked by Claude, the albino alligator living at San Francisco’s California Academy of Sciences. As an albino, Claude had no pigment it his skin, putting him at greater risk from ultraviolet light damage (and predation! and being spotted by prey!) While it might seem handy to be able to activate built-in sunscreen on command, it’s hard to see how that would benefit an animal more than good protection all the time. Since these animals mostly live in equatorial regions, they wouldn’t really have a pressure to decrease their ultraviolet light protection at any point, making the perception to hormone to melanosomes system needless complicated. Temperature control would seem like a better tool for a cold-blooded reptile to have, but the study directly controlled for temperature changes, and found that it didn’t influence the crocodile’s coloration.

Source: Crocodiles Alter Skin Color in Response to Environmental Color Conditions by Mark Merchant, Amber Hale, Jen Brueggen, Curt Harbsmeier & Colette Adams, Scientific Reports, volume 8

On April 17th, 2018 we learned about

Describing, and disabling, a carnivorous plant’s version of consciousness

“Wait, how do plants know things? Do they know things? They can’t, right?”

My third-grader’s brow furrowed as she ran scenarios over in her head. Plants aren’t the same as animals. They don’t have muscles to move with. They don’t have eyes like we do, and no brain to do any thinking. Nonetheless, they are known to follow the Sun, open and close flowers, and even react to the sound of predators eating their neighbors’ leaves. How was any of this possible without the anatomical gear we depend on to do any of those jobs?

It’s a tough question, and we don’t know all those answers yet. The sound sensory in particular is quite odd, but fortunately, some very reactive plants have helped botanists figure out how a plant can sense and respond to stimuli without nerve cells and a brain to do so. Because carnivorous plants like the Venus flytrap (Dionaea muscipula) and sundew plants (Drosera) have to actively trap their prey, they need to operate in a time-frame that matches the critters they want to catch. To do that, the plants are relying on so-called trigger hairs that essentially give the plant a way to “sense” when something has touched it.

As the titular fly lands on the attractively-scented “lobe” at the end of a leaf, it’s likely to bump into one or more trigger hairs. Unlike your nerve cells, those hairs don’t report back to any brain to trigger further activity. Instead, they create an action potential, which is an electrical charge that builds up in the trigger cell, eventually reaching a threshold where it gets discharged to the next cell, and the next, and the next. Eventually, this signal reaches the plant’s version of a muscle cell, which either expands or contracts to change the water pressure along the joint of the mouth-shaped lobe, causing it to close shut on the bug. With further stimulation of those trigger hairs, the flytrap will start to excrete digestive enzymes to it can actually eat its prey.

Turning off the trigger hairs

Even though trigger hairs aren’t exact matches for animal nerve cells, they’re close enough that they can be used to study the effects of the general anesthetics we use on animals. Even though those drugs are used every day to numb and temporarily paralyze people in surgery, we don’t know exactly how they do it. By using them on reactive plants like Venus flytraps and the “shy plant” Mimosa pudica, researchers are getting closer to understanding the exact cellular mechanisms that make modern surgery possible.

The answer seems to go back to the idea of action potentials, and how they get started in the first place. In both the plants trigger cells and animal nerves, a charge is built up on the outside of the cell membrane or wall. In the membrane are openings called ion channels that open and close when specific molecules are present to unlock them, a bit like a key opening a gate. Charged molecules, ions, can then move into the cell, helping it accumulate a larger charge, until eventually it triggers the release of an electrical charge to kick off another cell.

Paralyzing the plants

When carnivorous plants were subjected to anesthetics like diethyl ether, their trigger cells became unresponsive. The shy plant didn’t curl its leaves. Flytraps didn’t close after being poked. More importantly, no charge was detected at the plants’ trigger cells, indicating that the ion channels weren’t opening, heading off any action potential before it started. A second test with the roots of a mustard plant, Arabidopsis thaliana, found that the lipids, or fat proteins, in the cell membrane were being disrupted, helping researchers narrow their focus even further.

This wasn’t done to numb Venus flytraps, of course. They seem to be quite good at regulating their own activity already; they only close if multiple hairs have been touched, don’t usually close down on their pollinators, and reserve digestive enzymes for when they really have lunch in their clutches. Instead, this work may help us understand and then design better anesthetics for humans and other animals, taking some of the trial and error out of how we temporarily stop each other from sensing the world around us.

Source: We can make plants pass out—with the same drugs that mysteriously knock us out by Beth Mole, Ars Technica

On April 4th, 2018 we learned about

Staying warm in a hot spring lowers Japanese macaques’ stress hormones

Humans have enjoyed bathing in Japanese hot springs, or onsen, since at least 712 AD. The other local primates, macaque monkeys (Macaca fuscata), took a bit longer to catch on, waiting until 1963 to take a dip in the geothermally warmed waters. That first female apparently told her friends though, because the hotel where she took her bath was shortly swarmed with other bathing macaques. Rather than potty train every furry guest, certain springs were designated as exclusive to the macaques, eventually leading the founding of the Jigokudani Monkey Park in Nagano. The hot springs have only grown in popularity since that first bath, but researchers have only recently been able to confirm why the monkeys have adopted this unusual behavior.

To a human bather, the motivation for the bathing monkeys may seem obvious. Judging by the somewhat serene looks on the macaques’ faces, it’s safe to assume that they enjoy their visits to the onsen for the same reasons we do- the warm water is relaxing and pleasant. The fact that the monkeys are more likely to use the hot springs in the winter further supports the idea that they’re just interested in warming up when the weather gets cold. However, only one-third of the female monkeys living in the park seem to bathe, suggesting that this behavior may have a bit more nuance to it than a desire for hot water.

Measuring stress hormones in the monkeys’ scat

While the macaques are now adept at mimicking human bathing in the onsen, they’re not about to answer questions about their motivations. So researchers looked to their lack of hygiene for answers, testing the poop of various individuals for levels of stress hormones like faecal glucocorticoid (fGC). As expected, the warm water helped the monkeys maintain their body temperature, lowering stress levels. Less obviously, dominant females were found to demand more access to the warm pools, but also raise their stress levels more in various conflicts with other monkeys. So every bather benefited, but dominant females felt more of a swing between their stressed and relaxed moments.

So it’s not a huge surprise that our fellow primates enjoy a warm bath in cold weather, but it’s important for wildlife managers to understand. These monkeys have not only adopted behavior modeled by humans, but they’ve also grown accustomed to being fed barley over the winters in the park, partially to keep them in the area for the pleasure of tourists. These are some significant changes in behaviors, which may prove to have implications in the macaques’ health and reproduction. At this point, only 50 or so monkeys are actually bathing on a regular basis, but it’s worth understanding what that means to the macaques if humans are actively protecting this change in their ecology.

Source: Spa therapy helps Japan's snow monkeys cope with the cold, Science Daily

On March 25th, 2018 we learned about

Emotions influence circulation, and therefore coloration, in our faces, helping express how we feel

A perfect poker face may be physiologically impossible. No matter how well someone might try to hide their emotions behind a clenched jaw and vacant stare, they probably won’t be able to control their cardiovascular system well enough to stop changes in blood flow just below their skin. While these shifts aren’t necessarily as dramatic as the pink cheeks many of us get when feeling nervous or embarrassed, they are clear enough to help people read each other’s emotions with up to 75 percent accuracy.

Researchers from Ohio State University found that emotional states changed people’s circulation in their nose, eyebrows, cheeks and chin, and set out to test how much those changes were noticed by onlookers. The slight shifts in color, like a blue-yellow cast around a disgusted person’s lips, are subtle enough that most of us have never consciously noticed them. So computers were used to analyze images and find the patterns that turned up as a person experienced sadness, anger, happiness and more.

Reading emotions without facial expressions

Once those patterns were found, they were used to manipulate photos of people making neutral facial expressions. Those photos were then examined by test participants to see if they could correctly identify what emotion was coloring the otherwise blank expression. Some emotional color-schemes were harder to identify than others, but people definitely detected the correct emotion the more often than not. For example, angry colors were correctly identified 65 percent of the time, while happier hues were spotted 70 percent of the time.

A second phase of testing approached things from the opposite direction. Instead of identifying emotions on blank faces, participants were asked to assess photos were the emotional coloration was purposely mismatched to the expression being made by the face’s muscles. For instance, a rosy chin normally associated with a big smile was digitally added to a photo of someone otherwise expressing despair. Test participants couldn’t put their finger on what was wrong, but they did note that something was “off” with this round of photos, indicating that our brains do look for this kind of information, even if we’re not aware of it.

Communicating with color

These results make sense considering how social and visually oriented human beings are. We spend a lot of time trying to read each other’s faces to form bonds, get signs of danger and more. Even if we don’t take our shifting hues to the extremes of a stressed chameleon, we certainly wouldn’t be the first animal to adjust skin temperatures according to emotional states. Of course, before we pat ourselves on the back for this subtle form of communication, it’s worth noting that the entity that could most accurately read the emotional states expressed by skin coloration was a computer. Once it was trained on what to look for, image analysis was able to identify a happily-colored face with 90 percent accuracy.

Source: Happy or sad, the colour of your face reveals how you feel by Haroon Siddique, The Guardian

On March 1st, 2018 we learned about

Investigating how our brains determine when our bodies should have a drink

Your skin may seem dry, your mouth may be parched, but the experience of thirst is all in your brain. To be more precise, it’s in your ‘thirst center,’ a bundle of brain cells found in your hypothalamus. These neurons are tasked with the job of telling an animal when to get a drink, and just as importantly, when to stop sipping. Weirdly, that second command takes place well before the rest of the body can benefit from any new fluids, which has made untangling the exact functionality of this system a surprising tricky problem.

When the body wants water

The thirst center isn’t making us go for a drink at random. The hypothalamus takes in information about a lot of our physiology, including blood pressure, sodium concentration and more. When these systems are out of balance and more water is needed, one response is to create more of the hormone vasopressin in the pituitary gland, which then makes the kidneys try to reclaim water from any available urine. The second, but probably preferable response is to have the thirst center have us look for a drink.

As obvious as that response may seem, it’s taken years for researchers to isolate which cells were actually in charge of feeling thirsty. To identify exact which parts of the brain were tied to thirst, researchers turned to optogenetics, a technique that uses engineered neurons to be activated by light via implanted fiber optics. In this case, mice had their brain cells monitored and stimulated until they either became thirsty, or artificially had their thirst quenched without needing a drink.

In this process, it became clear that the amount of water an animal drinks is entirely up to the brain. Water won’t do a body much good until 10 to 15 minutes after it’s been ingested, whereas mice’s thirst center stopped them from drinking after only a minute each time. Somehow the brain felt it had had enough liquid, and that it was time to stop drinking.

Drinking disorders

This may sound pointlessly academic, but that’s only because it works so well for most of us. Whatever mechanism the thirst center may be using to measure our water intake, it’s generally helping us obtain a safe amount of water. If we ignore the thirst center, as some marathon runners have done, or the mechanism is damaged, as with people with psychogenic polydipsia, the results can be dangerous or even fatal. Cells swell and burst like balloons as they try to absorb the incoming water, a fate particularly damaging when it occurs in the brain. On the flip side, as people age they often have a weaker thirst response, and may forget to hydrate on a regular basis.

At this point, the investigation into how we feel thirst is actually moving out of the brain. Researchers are interested in muscle cells in the throat that help with swallowing, as there’s a chance that our sip-stopping thirst center may be gauging our water intake based on how quickly we swallow.

Source: Still Thirsty? It's Up To Your Brain, Not Your Body by Jon Hamilton, The Salt

On February 26th, 2018 we learned about

Bat immune systems can safely endure viruses in order to enable flight

Bats adding a new twist to the concept of “compromised immune systems” The term usually refers to organisms that have weakened immune systems, and are at higher risk for infection as a result. Bats, on the other hand, seem to have taken the idea of “compromise” in a new direction, as their immune system has an unusual tolerance for viruses in order to benefit the bats. Not only do the bats seem to survive well enough with extra viruses in their bodies, but a dampened immune response may be a crucial component of their ability to fly.

Permissive of pathogens

The key to bats’ strange immune system are stimulators of interferon genes (STING). Humans, cats and dogs all have our own versions of STING, which allows our bodies to create interferon proteins, which help us fight off invasive viruses. Interferons are powerful, and if STING pathways are active when a virus isn’t present, an animal can face severe consequences in the form of an auto-immune disease. So while our STING pathways are triggered selectively, bats seem to take a very different approach, as their STING pathways are always on, but at a reduced degree of intensity.

This basically means that bats’ immune systems are always activated, but not at full power. As a result, many viruses from rabies to Ebola, can take up residence in a bat’s body, turning it into a viral reservoir. However, the bat seems to suffer no debilitating symptoms from those diseases, letting them be controlled without any dramatic immune reaction one way or another. Researchers describe this dynamic as a “balance” with the bats’ viral load, and as nice as being able to ignore a SARS virus sounds, dealing with pathogens was probably only a happy byproduct of another evolutionary pressure.

First required for flight

It’s suspected that the reason bats needed a constant but dampened STING pathway was to deal with self-inflicted metabolic damage to cells. The energetic demands of flight can cause some DNA to be released into cells, outside the cell nucleus where it belongs. In most mammals, those DNA fragments would be activate STING pathways to produce interferons, leading to a big immune reaction. Since bats need to fly on a daily basis, this arrangement would be problematic. By altering the sensitivity of their interferon reactions, bats were able to cope with these metabolic demands without freaking out their immune systems. Safely harboring viruses then made sense, since their immune systems were already functioning on different level of activity than other mammals.

My five-year-old asked: So do the bats that help farmers have lots of viruses?

Since the STING dampening probably first evolved to enable flight, it’s safe to assume this compromising immune response is present in all bats. Many of the viruses these bats may be carrying require direct contact of some kind, such as with an infected bat’s saliva, so as long as people aren’t handling the animals, there’s not too much risk there. However, bats are more likely to transmit a virus to a domesticated animal, so it’s good to try to inoculate livestock against viruses like rabies whenever possible.

Source: Switched-on bats: hosting viruses is a cost of flying by Tanya Loos, Cosmos Magazine

On February 19th, 2018 we learned about

A runny nose’s excessive boogers are made in our body’s best interest

It’s only been three days since my son’s nose started getting snotty, but that’s long enough to make you wonder why, and how, all this mucus keeps coming out of his nose. At just shy of five-years-old, he’s technically able to handle a tissue himself, but not to the point where he can be expected to be effective in his booger management. Coupled with the sore throat and cough of a nasty cold virus, all this mucus-production feels like a bit of a curse. Of course, it’snot— it’s simply our body’s way of purging pathogens that are trying to take up residence in our respiratory tract.

On any given day, your sinuses are doing double-duty at a minimum. They warm and moisten air before it gets to the sensitive tissue in our lungs, plus captures junk that we don’t really want to be inhaling in the first place. That can be dust, dirt, pollen and of course, viruses and bacteria. Ideally, the layer of mucus that coats the inside of your nose and sinuses is enough to capture these potential irritants, moving the sticky stuff back down your throat with hair-like structures called cilia.

Purging pathogens

As my son’s clogged nose can attest, sometimes things get through. There’s likely to be some resistance in your mucus from benign bacteria, but your immune system revs up when a pathogen start penetrating cell walls in your nose. Proteins called cytokines are released, which then activate T and B cells that will attack the pathogen directly. To help in that battle, the lining of your nose swells and increases its booger production, hopefully creating enough mucus to grab and flush the offending pathogens out of your body. Unless of course you’re five, in which case you’ll probably get the contaminated snot on your hands and spread it far and wide, infecting everyone around you. (Not that we hold that against you, son!)

From the outside, this all looks like a runny nose. The excess fluid in the swollen mucus lining can lead to gross, drippy discharge in a condition known as rhinorrhea. Sometimes the extra mucus just clogs things up, making us feel horribly congested in the process. You can blow your nose to help with that, but violently trying to force the boogers out of your face can actually damage the cilia that help move mucus around. It can also end up sending pathogens deeper into your sinuses, kicking of new infections. So even though a drippy nose is annoying, it’s actually working as intended.

External influences

Of course, sometimes your nose is drippy when it doesn’t need to be. For instance, cold weather can trigger a runny nose in healthy people, albeit for very different reasons than described above. In those cases, the air is probably cold and dry enough to make your mucus linings activate in an effort to keep air properly warmed and moistened on its trip to the lungs. That can lead to extra fluid in your nose that then starts dripping out. Alternatively, there’s a chance that moisture in the air is condensing just inside your nose, forming noticeably large droplets that feel like snot.

Finally, crying can lead to a runny nose because eyes are just filling the place with fluid. As tears drain into your nose, they soften the layer of mucus that’s always present enough to start flowing. That way, your emotional moment can feel a bit sticky too.

My third grader asked: Is the runny nose you get from cold air the reason we call it a ‘cold?’

Basically. A “cold” was first used to describe illness in the 1530s, long before anyone knew to look for the rhinovirus or coronavirus that was actually causing a person’s symptoms. The resulting infection felt enough like the unpleasant effects of being chilled that it easily described what was wrong with someone, even if it did lead to confusion about what actually causes the illness (mostly.)

Source: Why Does Your Nose Run When You’re Sick? by Alexandra Ossola, Popular Science

On February 12th, 2018 we learned about

Unintended weight-loss is a consequence of astronauts’ weightlessness

Weight loss in microgravity is unavoidable, in more ways than one. Most directly, anyone on the International Space Station (ISS) will feel weightless thanks to their orbit around the Earth. They’re never in a position where the Earth’s gravity can noticeably pull them “down,” meaning they’d weigh zero pounds if they tried to stand on a scale. However, once astronauts get back to Earth’s surface, NASA’s medical staff has found that they have lost weight in another sense, having lost as much as 10 percent of their overall body mass. This has raised concerns about how people might spend extended amounts of time in space without putting their muscle, bone and cardiovascular health at risk.

Astronauts aren’t eating enough

As it turns out, weightlessness may be contributing to astronauts’ weight loss. On earlier visits to space, astronauts were asked to fill out weekly surveys about what food they were eating, although it’s suspected that those answers weren’t terribly accurate. Astronauts on the ISS are now prompted to record every snack and meal they eat on touch-screen app, giving medical staff on Earth a much better sense of how much food is consumed in space. The resulting pattern is that astronauts unconsciously eat less in space, probably thanks to being weightless all the time.

Living in space dulls appetites in a few different ways. Your muscles need to work less in microgravity, and are thus consuming fewer calories every day. Over time, this can contribute to muscle atrophy, giving you even less muscle tissue to feed at each meal. It’s also suspected that microgravity affects how well your stomach’s stretch receptors can do their job. As organs tend to be reshaped without the constant tug of Earth’s gravity, astronauts’ stomachs may start signaling that they’re full earlier in meal, even if they haven’t hit their nutritional needs for the day. Finally, most of the food on the ISS is carefully packaged in sealed containers, food doesn’t have a chance to stimulate appetites like it does cooking on the stove at home. This isn’t to say that there are no food smells on the ISS— seafood gumbo was actually banned by mission commanders because of its lingering odor. Then again, anyone in an open office probably knows how uninvited fish smells don’t do much for one’s appetite.

Fish and fitness

It’s unfortunate that seafood smells have been a problem, because seafood may be one of the easier ways for astronauts to help keep their bodies healthy in microgravity. Crew members that eat more fish have been found to retain more bone tissue, which is likely thanks to the omega-3 fatty acids found in seafood. The benefit seems most pronounced in astronauts who also skip other kinds of meat, clearly indicating that astronauts should eat a lot of sushi. The second element towards keeping one’s body fit has turned out to be exercise. Some residents of the ISS have managed to avoid unintended weight-loss, and their six-day-a-week exercise program has probably helped keep their muscles and bones in shape, countering the atrophying effects of microgravity.

Source: Astronauts lose weight in space, and it might be because their food is literally floating around inside them by Mary Beth Griggs, Popular Science

On January 30th, 2018 we learned about

Thinking with our body and getting hungry with our brain

Cognition occurs in the brain. Millions of specialized neurons send signals to each other, processing stimuli and sending out new commands to our bodies that help us understand and interact with the world. Of course, this system seems to be overridden when we’re feeling particularly hungry, in which case a lot of rational thinking seems to go out the window until we satisfy our tummy again. While there’s obviously no neurons working directly in our digestive tract, researchers studying the relationship between thought and physiology are finding some interesting dynamics that may help explain how we might sometimes find ourselves ‘thinking with our stomach.’

Figuring things out with physiology

As one of the larger-brained animals on the planet, humans generally deride the idea of being guided by hunger or other biological needs. However, researchers from the University of Exeter argue that a complex, calorie-hungry brain isn’t necessarily every species’ best option. Many animals do quite well using things like hunger as a sort of analog for memory in the brain. If an animal feels especially hungry, it doesn’t need to do a lot of complex analysis to know that its needs aren’t being met in its current environment, and so either its location or behavior needs to change. In this model, physiology can step in to motivate animals to seemingly smart choices, reducing the amount of calorie-hungry gray matter an animal needs to survive.

Stressed cells seek sugar

This isn’t to say that our brain plays no role in making choices in our lives. Indeed, tests with mice have shown that brain activity may effectively override physiological needs under the right conditions. The mice had brain cells in their paraventricular hypothalamus, which are associated with social stress, artificially stimulated. When offered different foods rich in either fat or sugar, the mice overwhelmingly binged on carbohydrates, beyond any dietary need for that much starch. With the similarities between human and mouse brains, this is likely tied to the concept of ‘stress eating,’ where we load up on foods even though we don’t necessarily need them. It’s a good reminder that neither our stomach nor our brain operates in isolation, and that what may feel like a choice or craving is probably the result of interactions between multiple systems in our body.

Source: Gut instinct makes animals appear clever by University of Exeter, Phys.org

On January 28th, 2018 we learned about

Human digestive tracts can handle eating insect exoskeletons

A mouth full of canines, bicuspids and molars is enough to prove that humans are omnivores. We’re not as specialized at slashing flesh as a tiger may be, but our teeth and jaws can handle a lot of different kinds of foods. However, chewing is only the beginning of the story, as we don’t necessarily have the means to digest everything we can swallow. Some fiber, for instance, can get broken down by bacteria, but without multiple stomachs like a cow, won’t provide a lot nutrition for us. One supposed gap has recently been closed though, as it turns out there’s nothing stopping us from eating, and benefiting, from eating insects.

Insects are covered in tough exoskeletons made from a substance called chitin. This gives their bodies a tough outer shell that was thought to be impervious to our digestive system. Nobody argued that our teeth couldn’t crack a beetle’s shell, but that once it was swallowed it would be a relatively inefficient source of nutrition that would basically need to be passed through us. Even insectivorous species of bats are known to pass a fair amount of chitin in their poop, suggesting that only a small portion of a bug can actually be used as food.

However, bats, mice and various primates obviously included insects in their diets for a reason. Researchers then identified a specific stomach enzyme, known as CHIA, that helped each of these mammal groups break down exoskeletons. They then looked at various primates’ genomes to see how many copies of the enzyme-producing genes each species carried. More copies of the gene would then lead to more enzyme production, presumably to help digest more bugs.

Genetic gut-check

It became clear that some of our ancient primate ancestors ate a lot more bugs than we do. Many older primates had three copies of the CHIA-producing gene, with the record going to modern tarsiers, which carries five copies to enable its insect-rich diet. It seems that insects’ role in primate diets has diminished over time though, probably after being replaced by other plants and fruit. Still, as proper omnivores, bugs aren’t off our menu entirely— humans still have one copy of the gene needed to let us safely digest an insect’s outer shell.

This confirmation probably isn’t news to the two billion people around the world who already eat insects on a regular basis. However, it may help make people who don’t eat bugs a bit more comfortable with the idea enough to give roasted grasshoppers, or at least pulverized cricket flour. In many cases, the recipes that people use to prep their bugs add one more tool to our digestive toolbox, which is heat. Even if our stomachs are ready to handle a bit of chitin, cooking our creepy crawlies will make things that much easier.

My four-year-old said: I don’t want to eat bugs. That’s yucky, and bugs are cute!

Source: Study says humans can digest bugs, assuming they want to by Robin Lally, Phys.org