The Pinnotheridae are a family of tiny soft-bodied crabs that live commensally or sometimes parasitic in the mantles bivalve molluscs and the occasional large gastropod mollusc species.
The mottled pea crab (Opisthopus transversus) lives in the folds of the Gumboot Chiton (Cryptochiton stelleri).Hosts. Symbiont in the giant Pacific chiton and other species.
Hosts for example:
Symbiont in the giant Pacific chiton Cryptochiton stelleri; the gastropods Aplysia vaccaria, Bulla gouldiana, Conus californicus, Lithopoma undosum, Megathura crenulata, Navanax inermis, and Neverita lewisii; the bivalves Atrina tuberculosa, the oyster Crassadoma gigantea, Crassostrea gigas, the chocolat clam Megapitaria squalida and others.