How to Distinguish from Similar Species: Glebocarcinus branneri is also small but has spiny ridges and no tubercles on the chelae; plus is not as common. Lophopanopeus bellus is similar size and shape, is found in similar areas, and has black claw tips and an oval carapace but does not have the 5 teeth between the eyes characteristic of Cancer crabs, plus its carapace is often an off-white.
Note: Species formerly in genus Cancer have been recently subdivided into several genera (Ng et al., 2008; Schweitzer and Feldmann, 2010). Of our local genera, Cancer, Romaleon, and Metacarcinus have a carapace wider than long plus only scattered setae on the carapace margins and legs while Glebocarcinus has a carapace of approximately equal length and width, often with granular regions and with setae along the edges; and setae on the outer surface of the chela as well as on the legs. Metacarcinus can be distinguished from Cancer because Metacarcinus has anterolateral carapace teeth which are distinct and sharp plus the male has a rounded tip to the telson, while Cancer has anterolateral carapace teeth which are low and lobed, separated by deep fissures plus the male has a sharply pointed telson (Schram and Ng, 2012). Romaleon can be distinguished from Cancer and Metacarcinus because it has a distinct tooth on the anterior third of the posterolateral margin of the carapace while the other two genera do not.
Geographical Range: Pribilof Islands to Palos Verdes, CA; uncommon S of Pt. Arena, CA. Common in the north but not common in the southern part of its range.
Depth Range: Intertidal to 436 m
Habitat: Often nestles in small holes such as dead barnacles and under rocks (photo). Often uses its rounded carapace to block the entrance to the hole.
This crab is very
common in the intertidal zone in small spaces under and between rocks,
and also subtidally in dead barnacles. It emerges at night to feed
mainly on small barnacles, but also on snails, bivalves, worms, and some
green algae. Is an important predator on small Japanese oysters Crassostrea
gigas. Males have larger chelipeds than do females.
Predators include pacific cod, and occasionally river otter and red rock
crab Cancer productus. May be found in "harems" of one male
and several females in their crevices, especially during the summer breeding
season (photo). Mating takes place after
the females molt, and the males often carry females who are preparing to
molt, and afterward until she has hardened. Ovigerous females are
found in Puget Sound from November to April/May. May be infected
by parasitic sacculinid barnacles. When disturbed outside its hole,
this crab may fold its legs and roll like a stone.
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Flora and Fairbanks, 1966
Kozloff 1987, 1996
Smith and Carlton, 1975
Schram, Frederick R. and Peter K.L. Ng, 2012. What is Cancer? Journal of Crustacean Biology 32:4 pp. 665-672
C.F. and R.M. Feldmann, 2000. Re-evaluation of the Cancridae
Latereille, 1802 (Decapoda: Brachyura) including three new genera and three
new species. Contributions to Zoology 69:4 pp. 223-250
General Notes and Observations: Locations, abundances, unusual behaviors:
Two individuals are nestling in adjacent holes (top right and bottom
left) in this intertidal rock at Beach #4, Kalaloch. The bottom left
hole is also occupied by an anemone. Photo by Dave Cowles, July 2012.
Authors and Editors of Page:
Dave Cowles (2005): Created original page