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Porcelain crab

Petrolisthes eriomerus


Petrolisthes eriomerus is a species of marine porcelain crab found in the eastern Pacific Ocean. It is commonly known as the flattop crab. It is a flattened, rounded animal, with a carapace up to 20 mm (0.8 in) across. It is a filter feeder, and also sweeps food from rocks. (Wikipedia)


Spotted in a tide pool at the Tongue Point Marine Life Sanctuary.


Like other porcelain crabs, P. eriomerus sometimes casts off limbs as a diversion when trying to escape from a predator, a process known as autotomy. In this species however, the claws of the cast limb continue to grip vigorously after separation. The limb is regrown by the porcelain crab over the period of several moults. (Wikipedia)

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Tukup 3 years ago

Thanks Sukanya. Now you know why I have trouble seeing tiny fungus & slime molds :-) These eyes are to the point where things sort of blur together. Thanks for pointing out the difference between a "t" and an "n." :-) I sincerely appreciate it.

SukanyaDatta 3 years ago

Autotomy ...discarding limbs or tail to save life is seen in salamanders, lizards and spiders too. Auto To mous...not auto it has this trick up its evolutionary sleeve too.

Tukup 3 years ago

Interesting that "autonomous" means "having the freedom to govern itself or control its own affairs." One wonders what the etymological relation is between the two words.

Neil Ross
Neil Ross 3 years ago

A very interesting species. I'm was counting the legs and wondering why they were coming up short. Not being a 'true crab' explains it to a certain degree for a dummy like me. It pays to read previous comments. Autotomy is a very interesting process. I must read up on it.

Brian38 3 years ago

Thank you so much Tukup! I'm right there with you Tukup. These tidal-pools have been a whirlwind of learning for me as well.

Tukup 3 years ago

Another present from the tide pool. Cool. Thanks for the pics and notes Brian. I appreciate learning about them as well as seeing them.

Brian38 3 years ago

Thank you for your kind words Sukanya. Porcelain crabs are really interesting. they are not true crabs but they have evolved to resemble crabs. They have one less set of walking legs than true crabs.

SukanyaDatta 3 years ago

You have some of the most anazing spottings...a blue crab! Wow.

Spotted by

Washington, USA

Spotted on Apr 7, 2019
Submitted on Apr 13, 2019

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