The relationship between the pea crab and its host is one of parasitism, rather than commensalism, since the host may be harmed by the crab's feeding activities.
The pea crab relies solely on its host for food, safety, and oxygen.

Pea crabs have a variety of hosts, the most important of which are mollusks.
The pea crab lives in the mantle cavity of these hosts.
Other hosts, in addition to oysters, include sea urchins and sand dollars.
Pinnotheres can be found inside sand dollars, in the rectum of sea cucumbers, in the tubes of parchment worms, in the burrows of mud shrimp, or in the gills of sea squirts.

Little is known about the pea crab's feeding habits, but in the related oyster crab (Zaops ostreus), larval stages feed on plankton brought in by the oyster, while adults feed by taking the food that is a part of the oyster's diet, as well as what is not.
The feeding process can be harmful to the crab's host when it feeds on the mucous strings that help carry the food to the host's mouth.
The relationship between the pea crab and its host is one of parasitism, rather than commensalism, since the host may be harmed by the crab's feeding activities. The pea crab relies solely on its host for food, safety, and oxygen.
Pea crabs have a variety of hosts, the most important of which are mollusks. The pea crab lives in the mantle cavity of these hosts. Other hosts, in addition to oysters, include sea urchins and sand dollars. Pinnotheres can be found inside sand dollars, in the rectum of sea cucumbers, in the tubes of parchment worms, in the burrows of mud shrimp, or in the gills of sea squirts.
Little is known about the pea crab's feeding habits, but in the related oyster crab (Zaops ostreus), larval stages feed on plankton brought in by the oyster, while adults feed by taking the food that is a part of the oyster's diet, as well as what is not. The feeding process can be harmful to the crab's host when it feeds on the mucous strings that help carry the food to the host's mouth.
Pea crab