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Smithsonian Tropical Research Institute
Smithsonian Tropical Research Institute

This Snail's Sex Change Is Triggered by Touch

Smithsonian Tropical Research Institute
Smithsonian Tropical Research Institute

Tropical slipper limpets are pretty unremarkable. They spend most of their lives sitting in one spot under a rock filtering their food out of the water. When it comes time for the limpets to mate, though, things get interesting. 

Compared to their body size, male limpets have some of the most impressive penises in the animal kingdom—almost as long as the snail’s entire body. They don’t hang on to these massive members forever, though. Slipper limpets begin their lives as males and turn into females as they age and grow—a process called sequential hermaphroditism. Their penises slowly shrink and then disappear while their female organs develop. 

A recent study in The Biological Bulletin shows that this dramatic change is set off by a simple touch.

Plenty of animals—including some starfish, crustaceans, and fish—change sex at some point in their lives. The timing of a sex change has to do both with an animal’s size and the company it keeps. Bigger animals can produce and carry more eggs than smaller ones, while sperm production is less size-dependent, so the switch usually happens when an animal reaches a certain size. For many sex-changing animals, there’s also a social factor, and the animals in a mating group or population can “tell” each other when it’s the best time to switch. 

Chemical cues are used by sea snails and other mollusks to warn one another about predators, recognize each other, and choose sites to live, among other things. Rachel Collin, a biologist at the Smithsonian Tropical Research Institute, figured that limpets used similar chemical signals to prompt each other's sex changes, too.

To test that idea, she and intern Allan Carrillo-Baltodano collected small male slipper limpets at Playa Chumical on Panama’s Pacific coast. They paired the snails off and placed them in different cups of seawater that allowed them different degrees of access to any chemical cues their cup mates might release. In some cups, the snails were free to roam around and come in contact with each other. In others, a mesh barrier kept them on separate sides of the cup. Some of the barriers had a finer mesh that only allowed water through, while others were a little wider and let the snails touch each other through the screen. Still other pairs were separated by fine mesh, but the snails were switched from one side of the cup to the other every week, letting them come in contact with their cup mate’s pedal mucus, the gluey substance snails and slugs use to help them move around.

When the limpets were allowed total access to each other, the larger one in each pair grew faster and changed sex sooner than their counterparts that were separated from their partners, while smaller, free-roaming partners delayed their own sex changes longer than the smaller snails in the separated pairs. The snails that were separated by the fine mesh and those that switched sides in their cups changed sex on the same, slower schedules, while the ones that were separated by the wider mesh fell in the middle.

Collin and Carrillo-Baltodano said they expected the sex change to be triggered by chemical cues since limpets are sedentary, but their results suggest that the change “requires some kind of physical interaction that is lost when the snails are separated.” For now, they aren’t sure what it is about physical contact that sets the change in motion. It might have to do with the way one snail positions itself relative to another, or a certain type of physical stimulation. Chemical signals could also still be at work, but ones that are contact-based instead of waterborne.

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Slow Motion Is the Only Way to Appreciate a Chameleon’s Lightning-Fast Tongue
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From the unusual way they walk, to their ability to change color, the evolutionary adaptations of chameleons are pretty bizarre, and some of them remain mysterious even to scientists. Their super-powered tongues, for instance, can dart out so quickly that the movement can barely be seen with the naked eye. But modern high-speed cameras have enabled researchers at the University of South Dakota to observe this appendage at work like never before. The video below, shared over at The Kid Should See This, includes some of that groundbreaking footage, and it's pretty amazing to watch.

Shooting at 3000 frames per second, the camera was able to capture every split-second aspect of the chameleon's tongue strike. Slowed down, the video allows you to see how every component of the process works in harmony: First, muscles in the lizard’s tongue contract like the string of a bow. Then, when that tension is released, the bony base of the tongue shoots forward, pushing the sticky, elastic part toward the chameleon’s prey.

According to Christopher Anderson, one of the scientists who conducted the high-speed camera research, larger chameleons can catapult their tongues forward at distances of one to two times their body length. For smaller chameleons, this distance can reach up to two and a half times their body length. “Small chameleons need to be able to eat more food for their body size than large chameleons,” he tells bioGraphic in the video, “and so by being able to project their tongues proportionately further than these large species, they basically are opening up additional feeding opportunities to themselves that they wouldn’t have if they had a shorter tongue.”

To see one of nature’s greatest hunting tools in action, check out the full video below.

[h/t The Kid Should See This]

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There May Be an Ancient Reason Why Your Dog Eats Poop
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Dogs aren't known for their picky taste in food, but some pups go beyond the normal trash hunting and start rooting around in poop, whether it be their own or a friend's. Just why dogs exhibit this behavior is a scientific mystery. Only some dogs do it, and researchers aren't quite sure where the impulse comes from. But if your dog is a poop eater, it's nearly impossible to steer them away from their favorite feces.

A new study in the journal Veterinary Medicine and Science, spotted by The Washington Post, presents a new theory for what scientists call "canine conspecific coprophagy," or dogs eating dog poop.

In online surveys about domestic dogs' poop-eating habits completed by thousands of pet owners, the researchers found no link between eating poop and a dog's sex, house training, compulsive behavior, or the style of mothering they received as puppies. However, they did find one common link between the poop eaters. Most tended to eat only poop that was less than two days old. According to their data, 85 percent of poop-eaters only go for the fresh stuff.

That timeline is important because it tracks with the lifespan of parasites. And this led the researchers to the following hypothesis: that eating poop is a holdover behavior from domestic dogs' ancestors, who may have had a decent reason to tuck into their friends' poop.

Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.

Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home. However, the theory isn't foolproof. The surveys also found that so-called "greedy eaters" were more likely to eat feces than dogs who aren't quite so intense about food. So yes, it could still be about a poop-loving palate.

But really, it's much more pleasant to think about the behavior as a parasite-protection measure than our best pals foraging for a delicious fecal snack. 

[h/t The Washington Post]

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