A Party in a Seashell: Meet the Tusk Shell Hermit Crabs

I just wrapped up a class in invertebrate zoology last semester, and oh my goodness y’all, there are so many more wacky little animals out there than I ever could have imagined.

Exhibit A: tusk shell hermit crabs. Exhibit B would be the tusk shells themselves, but this is an arthropod blog, and those wacky little Scaphopods sadly belong to the wrong phylum (Mollusca).

Tusk shell hermit crabs belong to the family Paguridae, also known as the “right-handed hermit crabs,” so I guess we all know which cheliped (claw) these guys are using to write their Christmas thank-you cards. On the other hand (ha), Diogenidae is a family of entirely left-handed hermit crabs, which means a Pagurid and a Diogenid could never have a fair arm-wrestling match.

Tusk shell hermit crab profiles from the Biodiversity Heritage Lab on Flickr

Take a look at the cheliped the tusk shell hermit crab in the bottom right is using like a front door. That circular door-claw and the relative symmetry of the crab’s body (most hermit crabs are asymmetrical to fit into spiraled shells) make it a perfect fit for any empty tusk shell its size. In fact, a 1999 study on tusk shell hermit crab behavior found that the crabs prefer tusk shells even when given the option of a traditional gastropod shell. Yep, these funky little dudes were specifically designed to live in deep-sea party hats, and they know it.

Can we call them party crabs? I’m gonna call them party crabs.

In addition to closing the front of their shell, party crabs have to plug up the end of their party hat as well. Because the Scaphopod mollusk likes to burrow in the sand, it uses the hole in the tip of its shell like a snorkel for obtaining and expelling water for gas exchange. However, the party crab isn’t a burrower, so it doesn’t need to circulate water to its gills this way.

Unfortunately, party crabs are somewhat rare and tend to live pretty deep in the ocean, so not much is known about them. That means this is turning into one of my shorter posts, but hey – we’re all on break from school right now, so I’m letting you read less. You’re welcome.

I really just wanted to talk about these crabs because of how cute they are (my motivation behind the majority of ArthroBlogger posts, honestly), but because of the whole super-rare, not-much-known-about-them thing, there aren’t a lot of party crab photos in the public domain. Instead, I’m just going to leave this hyperlink here for you to click on to see how adorable these little guys are for yourself. Aren’t they great? And they’re colored like orange candy canes! Plus, those party hats kind of look like elf hats; I should’ve posted these guys on Christmas.

Happy (almost) New Year everyone! I hope 2022 will be a great year for you to learn, grow, have tons of fun, and leave 2020 just a little further behind.

In the meantime, if you’re looking to spice up your New Year’s Eve celebration, I know a few hermit crabs who were born to party.

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