PAGUROIDEA Latreille, 1802

Wicksten, Mary K., 2012, Decapod Crustacea of the Californian and Oregonian Zoogeographic Provinces 3371, Zootaxa 3371, pp. 1-307 : 171-172

SUPERFAMILY PAGUROIDEA Latreille, 1802

The most familiar of all anomurans are the hermit crabs. These crabs usually inhabit shells or tubes but may live inside hollows in sponges, bits of crab exoskeleton, twigs or even bones. Species occur from the upper tide pools to the abyssal plains.

In hermit crabs, the abdomen is soft and ends in a small telson and uropods. The pleopods usually are reduced at least along one side of the abdomen. The carapace, although present, usually is lightly calcified. The eye are stalked and well developed, with pigmented corneae. The antennules are well equipped with sensory setae, the aesthetascs. In life, the antennae flick, aiding the crab in tracking chemosensory cues. The second antennae are long and whip-like in most species, but setose and used in gathering particles in some species of the Diogenidae . The rostrum varies from long and pointed to almost absent. The third maxillipeds are leg-like and setose. The first pereopods bear chelae, one often larger than the other. In some species, the major cheliped ends in an enlarged chela that can block the aperture of the shell. The size and shape of the chelae can be sexually dimorphic. Pereopods 2, 3 are ambulatory. The last pairs of pereopods are short and grip the shell.

Older books classified all hermit crabs in a single family, the Paguridae . Today, three families are recognized as occurring in California and Oregon. The Paguridae , most often observed and studied, range from the continental slopes to the intertidal zone. Species of the Diogenidae usually are subtidal, and may be able to bury themselves in sand. The Parapaguridae are found on the continental shelf and deeper areas. The work by McLaughlin (1974) provides keys, illustrations and further information on hermit crabs occurring north of Point Conception, California. Lemaitre & Castaño (2004) presented a list of all the species of Pagurus of the eastern Pacific with species group assignments, but noted that, as of their writing, many species had yet to be assigned.

The key to the Paguroidea presented here is modified from a manuscript key by Janet Haig, and includes one as yet undescribed subtidal species from southern California. I have included another artificial key based on color patterns to aid in the identification of living or photographed hermit crabs. Both of these keys originally were presented to a meeting of the Southern California Coastal Water Research Project in February 1977, but never were formally published .