hermit crab walking over red sand
It’s a fact, house-proud hermit crabs have bigger organs. Photo: ©Tony Neilson

Well endowed, and house-proud of it


Beware: This item contains potentially offensive language and sexual references.

‘Hot’ news from the research world suggests that the size of the penis has a lot to do with how much house remodelling you do.

That might be stretching a point, to coin a phrase, but in the world of the hermit crab, big ‘privates’ are apparently an indication of the extent to which they are house-proud.

National Geographic reports that many of the charismatic crustaceans that leave those trademark tracks from the beach to higher ground at night are very well endowed indeed.

Outsized organs

Their penises can sometimes be half the length of their shell-anchored bodies, and new research suggests the crabs evolved such outsized organs to help them mate without straying far from home.

Some hermits expend a lot of energy smoothing and ‘remodelling’ the inside of their shells, which unlike most crabs they cannot grow themselves, says Mark Laidre, a biologist at Dartmouth College, US.

These animals can whittle their shells and secrete erosive chemicals, allowing them to create a smooth and expansive interior. Their refurbished homes give them space to grow and may even provide room for egg storage—making the shells extremely valuable. But they are also much harder to grip.

Hermit crabs in a tight group on sand
Could this gathering of hermit crabs be a ‘hermitage’, or are they house-swapping? Photo: ©Tony Neilson

Varied in size

While studying land-dwelling hermit crabs at Smithsonian’s National Museum of Natural History, Laidre noticed that the animals’ penises, also known as sexual tubes, varied widely in size.

And the species that did the most remodelling—and thus had the most valuable shells—had the largest penises.

The cunning creatures are ruthless when it comes to spotting and stealing superior shell property from their neighbours. “They get into quite a lot of shell shenanigans, where individuals are constantly at risk of being evicted,” says Laidre.

Sensible solution

Enlarged genitalia are “really a very sensible evolutionary solution to what is one of the most dangerous things [the crabs] can get involved in,” he says.

Losing a pimped-up shell makes fatal desiccation all but inevitable, and the crabs have become so specialised, they can’t even fit into unimproved shells as a temporary fix. “If these guys lose that shell, within 24 hours, they’re doomed.”

Natural Images 2019


©2018 TONY NEILSON All Rights Reserved. All images are protected by Australian copyright law and cannot be downloaded or reproduced without my permission. Please contact me.


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