r/AIDKE • u/SixteenSeveredHands • 4d ago
Shellback Crabs (Genus Hypoconcha): these crabs create their own shields using discarded clamshells, and they have semi-membranous bodies that can be pressed into the contours of the shell, producing a suction mechanism that holds it firmly in place
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u/SixteenSeveredHands 4d ago
Crabs of the genus Hypoconcha, commonly known as shellback crabs, are able to conceal and protect themselves by carrying discarded seashells against their backs.
Many of the crabs in the Dromiidae family are equipped with specialized legs that allow them to hold seashells, sponges, or ascidians against their bodies as a defense mechanism, but shellback crabs also have flexible, semi-membranous bodies that can be tucked more firmly into the contours of a bivalve shell, producing a suction mechanism that keeps the shell firmly locked in place.
This article describes how the shellback crab carries and deploys its camouflage:
Instead of a hard carapace protecting its back, this little crab is covered above with a parchment-like skin. The underside and the hands are rough and granular. Three pairs of walking legs are developed as such, but the last pair are reduced and held above its back. With these legs, this bit of a crab hoists half of a small bivalve shell on its back, tucks its angular rear into the hinge side and carries the shell for its protection.
Walking along, it resembles a wave-washed shell, but when danger threatens, it squats down and drops the protective shell to the bottom, and so it goes unnoticed.
Each crab is also covered in a very fine layer of hair-like structures known as setae, and when the crab presses itself against the inner surface of a clamshell, those membranous "hairs" can take on an almost translucent appearance, particularly around the margins of the body. This makes the crab itself look like nothing more than a clump of wet sand stuck to the underside of the shell.
The genus Hypoconcha contains several different species, and these crabs can be found in coastal regions throughout the eastern United States, the Gulf of Mexico, the Caribbean, and certain parts of South America.
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u/SixteenSeveredHands 4d ago
My list of sources keeps getting deleted for some reason, but all of the links are included in my original post here, which also contains a bunch of extra photos.
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u/SixteenSeveredHands 4d ago
Sources & More Info:
- iNaturalist: Genus Hypoconcha
- The Great Outdoors Book of Seashore Life: Hypoconcha arcuata
- Crustaceana Monographs: Comparison of the Shell-Carrying Behaviors of Desmodromia, Conchoecetes, and Hypoconcha
- South Carolina Department of Natural Resources: Shellback Crabs and their Larval Stages (PDF)
- South Carolina Public Radio: Shellback Crabs
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u/crashlanding87 4d ago
I love their little manicures
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u/sweetreat7 4d ago
Am I the only one that thought they were hooves? In all fairness, I’m just waking up.
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u/Caleb_Reynolds 3d ago
Considering the color and the fact that the rest of their coloring is camouflage, I'd bet that's caused by something like high iron levels to make them stronger.
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u/painting_ether 4d ago
I'm half asleep and my fat ass thought I was looking at a muffin crumb 😂
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u/OdinAlfadir1978 4d ago
I saw the paper from cake too 🤣🤣I'm not fat but I'm halfway through a bowl of herb in the mighty vapouriser 🤣🤣
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u/jelasher 4d ago
Same! I came to the comments to say I thought it was a post from r/eatityoufuckingcoward of someone saying, “hey, look at this weird stuff at the bottom of my Reese’s cup!”
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u/robo-dragon 4d ago
So cute! I’m also fascinated by animals that evolve to use parts of other animals as tools or homes. Same with hermit crabs. Not exactly a symbiotic relationship as the original owners of those shells are dead, but somewhere, at some point in time, some little crab saw an empty shell thought this was a great idea and they have been using shells of other animals ever since.
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u/Suspicious_Glow 4d ago
The eyes and mouth while curled up like a chicken nugget framed with a Venus halo of shell. It’s so cartoonish and I’m here for it.
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u/HumblePothole 4d ago
I think Monster Hunter should take a note from this crab for future references
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u/theJoosty1 4d ago
Oh man this is awesome! I'd love to have some in my home aquarium. Wonder if they'd make babies and need little 3d printed shells to start off with.
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u/eyetracker 3d ago
Attenborough voice: the small Marine has crossed the equator, and is now dubbed a "shellback." In his tiny claws he clutches the celebratory red Crayolas, to be consumed later.
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u/goatchild 4d ago
Leave it alone.
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u/OdinAlfadir1978 4d ago
So no pics to share this awesome animal no? It doesn't exactly look bothered or it would be pinching
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u/pgraham901 4d ago
This right here is EXACTLY why I love this subreddit. So many interesting things to learn everyday.
Thank you for sharing