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.

Everything You Ever Wanted to Know About Dogs

Dogs: They’re cute, they’re cuddly … and they can smell fear!

Today on Scatterbrained, John Green and friends go beyond the floof to reveal some fascinating facts about our canine pals—including the story of one Bloodhound who helped track down 600 criminals during his lifetime. (Move over, McGruff.) They’re also looking at the name origins of some of your favorite dog breeds, going behind the scenes of the Puppy Bowl, and dishing the details on how a breed gets to compete at the Westminster Kennel Club Dog Show.

You can watch the full episode below.

For more episodes like this one, be sure to subscribe here!

Sploot 101: 12 Animal Slang Words Every Pet Parent Should Know

For centuries, dogs were dogs and cats were cats. They did things like bark and drink water and lay down—actions that pet parents didn’t need a translator to understand.

Then the internet arrived. Scroll through the countless Facebook groups and Twitter accounts dedicated to sharing cute animal pictures and you’ll quickly see that dogs don’t have snouts, they have snoots, and cats come in a colorful assortment of shapes and sizes ranging from smol to floof.

Pet meme language has been around long enough to start leaking into everyday conversation. If you're a pet owner (or lover) who doesn’t want to be out of the loop, here are the terms you need to know.


You know your pet is fully relaxed when they’re doing a sploot. Like a split but for the whole body, a sploot occurs when a dog or cat stretches so their bellies are flat on the ground and their back legs are pointing behind them. The amusing pose may be a way for them to take advantage of the cool ground on a hot day, or just to feel a satisfying stretch in their hip flexors. Corgis are famous for the sploot, but any quadruped can do it if they’re flexible enough.


Person holding Marnie the dog.
Emma McIntyre, Getty Images for ASPCA

Unlike most items on this list, the word derp isn’t limited to cats and dogs. It can also be a stand-in for such expressions of stupidity as “duh” or “dur.” In recent years the term has become associated with clumsy, clueless, or silly-looking cats and dogs. A pet with a tongue perpetually hanging out of its mouth, like Marnie or Lil Bub, is textbook derpy.


Cat laying on desk chair.
PoppetCloset, Flickr // CC BY-NC-ND 2.0

If you’ve ever caught a cat or dog poking the tip of its tongue past its front teeth, you’ve seen a blep in action. Unlike a derpy tongue, a blep is subtle and often gone as quickly as it appears. Animal experts aren’t entirely sure why pets blep, but in cats it may have something to do with the Flehmen response, in which they use their tongues to “smell” the air.


Mlems and bleps, though very closely related, aren’t exactly the same. While blep is a passive state of being, mlem is active. It’s what happens when a pet flicks its tongue in and out of its mouth, whether to slurp up water, taste food, or just lick the air in a derpy fashion. Dogs and cats do it, of course, but reptiles have also been known to mlem.


Very fluffy cat.
J. Sibiga Photography, Flickr // CC BY-NC-ND 2.0

Some pets barely have any fur, and others have coats so voluminous that hair appears to make up most of their bodyweight. Dogs and cats in the latter group are known as floofs. Floofy animals will famously leave a wake of fur wherever they sit and can squeeze through tight spaces despite their enormous mass. Samoyeds, Pomeranians, and Persian cats are all prime examples of floofs.


Dog outside barking.

According to some corners of the internet, dogs don’t bark, they bork. Listen carefully next time you’re around a vocal doggo and you won’t be able to unhear it.


Shiba inu smiling up at the camera.

Speaking of doggos: This word isn’t hard to decode. Every dog—regardless of size, floofiness, or derpiness—can be a doggo. If you’re willing to get creative, the word can even be applied to non-dog animals like fennec foxes (special doggos) or seals (water doggos). The usage of doggo saw a spike in 2016 thanks to the internet and by the end of 2017 it was listed as one of Merriam-Webster’s “Words We’re Watching.”


Tiny kitten in grass.

Some pets are so adorably, unbearably tiny that using proper English to describe them just doesn’t cut it. Not every small pet is smol: To earn the label, a cat or dog (or kitten or puppy) must excel in both the tiny and cute departments. A pet that’s truly smol is likely to induce excited squees from everyone around it.


Hands holding a puppy.

Like doggo, pupper is self-explanatory: It can be used in place of the word puppy, but if you want to use it to describe a fully-grown doggo who’s particularly smol and cute, you can probably get away with it.

10. BOOF

We’ve already established that doggos go bork, but that’s not the only sound they make. A low, deep bark—perhaps from a dog that can’t decide if it wants to expend its energy on a full bark—is best described as a boof. Consider a boof a warning bark before the real thing.


Dog noses poking out beneath blanket.

Snoot was already a dictionary-official synonym for nose by the time dog meme culture took the internet by storm. But while snoot is rarely used to describe human faces today, it’s quickly becoming the preferred term for pet snouts. There’s even a wholesome viral challenge dedicated to dogs poking their snoots through their owners' hands.

12. BOOP

Have you ever seen a dog snoot so cute you just had to reach out and tap it? And when you did, was your action accompanied by an involuntary “boop” sound? This urge is so universal that boop is now its own verb. Humans aren’t the only ones who can boop: Search the word on YouTube and treat yourself to hours of dogs, cats, and other animals exchanging the love tap.


More from mental floss studios