Hermit crabs line up by order of size to exchange shells [video]

It should be 5 plates / 4 consumers, were it not for the late-arriving crab throwing a wrench in at the last minute.

I have a reef tank on my desk at work I get to watch this process happen on a daily basis. I have to keep adding larger shells to the tank because if I don't they will kill the snails and steal their shells. If there are enough shells available they leave the snails alone. Recently one of the medium size crabs decided to take the a shell that used to belong to a turbo snail, much too big for him as he can barely drag it around. I've come to the conclusion this crab is American and is going to fake it until he makes it.

Hermit crabs don't grow their first shell. They find all the shells they live in, often from sea snails apparently.

The hermit crabs don't grow the shells. They use snail shells.

http://en.wikipedia.org/wiki/Gastropod_shell

Well, this is not so simple as wikipedia says. Crustaceans are a really big and wide group of life forms, and Carcinisation can be applied only to some groups of decapods (about 15.000 extant species). There are also about 11.500 species of Copepoda, 10.000 Isopoda, 13.000 Ostracoda, 9.500 Amphipoda and 1.300 Thecostraca, for instance, and none of these are crabs.