This species is widely distributed amongst the North American Pacific coast from Oregon to Santa Margarita Island, Baja California and along the coast of Japan and Korea (1). Although dense populations of this species inhabit rocky intertidal zones, they may also be found in estuarine mud banks (2). Morphological characteristics include transverse striations with a red, purple, and green dark coloration of the body (3). Once a female reaches a carapace (shell) width of 22 millimeters, it becomes shorter and narrower compared to males of the same molting stage (1). They utilize the crevices of large rocks for protection and resume normal activity in tidal pools (1). Molting (ecdysis) of the shell consists of a volumetric growth passive phase and active muscular phase that is complete once the old exoskeleton is shed (1).
(1) Hiatt, R. (1948). The biology of the lined shore crab Pachygrapsus crassipes. Pacific Science, 2, 135-213.
(2) Bovbjerg, R. V. (1960). Behavioral ecology of the crab, Pachygrapsus crassipes. Ecology, 41(4), 668-672.
(3) Garth, J. S., & Abbott, D. P. (1980). Brachyura: the true crabs. Intertidal invertebrates of California. Stanford University Press, Stanford, 594-630.
(Photograph) Stonebird. Striped Shore Crab.