Pinnotheridae

Pinnotheridae is a family of crabs known as pea crabs, or sometimes “pea crabs”, because some species live in the mantle cavities of bivalve molluscs and are small enough to fit in a pea. This family is found worldwide, mainly in coastal waters of the Indo-Pacific region.

Characteristics

Pinnotherid crabs are typically small, with a broad, flattened carapace and a reduced abdomen. Most species are less than 1 cm in length, though some species can reach 3 cm. Their coloration can vary greatly, depending on the species and their environment.

One of the most distinctive features of Pinnotheridae is their symbiotic relationship with bivalve molluscs. These crabs are commonly found in the gills or mantle cavity of clams, oysters, mussels, and other bivalves. This relationship is often mutualistic, meaning both species benefit. The crabs benefit by gaining access to food and shelter, while the bivalves benefit from the crabs' cleaning services, removing parasites and debris from their gills. Some species of pea crabs, however, are parasitic, feeding on the reproductive organs of their host.

Environment

Pinnotherid crabs are found in a variety of marine environments, including intertidal zones, estuaries, and the open ocean. They prefer habitats with soft sediments and abundant bivalves. Some species of Pinnotheridae can tolerate brackish water, making them adaptable to a wide range of environments.

Common Names

Members of this family are commonly known as:

  • Pea crabs
  • Pea-crabs
  • Gall crabs
  • Pinnotherid crabs

References