Thickclaw Porcelain Crab

Biology/Natural History: Are often found in male-female pairs in holes, which they may grow too large to escape from. The larger claw may be either the right or the left. Males and females are of similar size. The branchial chamber of this crab is sometimes parasitized by the bopyrid isopod Aporobopyrus muguensis. This reduces fecundity by about 50%. Porcellanid crabs are filter feeders.

In rocky areas, especially on semiprotected coasts. May be in abandoned holes of boring clams, kelp holdfasts, empty barnacle shells, eelgrass roots, mussel clumps, pilings.

Geographical Range: Kodiak, Alaska to Bajia Magdalena, Baja California

Depth Range: Low intertidal to 29 m; mostly intertidal in Puget Sound

This porcelain crab has thick chelae of unequal size and with tubercles and few to many setae on the cheliped surface. Its telson has 5 plates and the anterior margin of the carpus of the cheliped is a broad, nearly triangular lobe. Carapace width to 19 mm. Color dull brown, often mottled with gray.

How to Distinguish from Similar Species: Petrolisthes species have flat, smooth chelae. Pachycheles pubescens has 7 plates on the telson, a thick covering of setae on the chelae, and the carpus of the cheliped has 3-4 uneven, serrated teeth on the anterior margin.

Pachycheles rudis, the thickclaw porcelain crab, is a species of porcelain crab in the family Porcellanidae. It is found in the East Pacific.