Romaleon

Common in the low rocky intertidal. Often found under rocks, sometimes partly buried in sand under the rocks. Subtidally may be on gravel bottoms or in kelp beds. Especially common on the exposed coast.

Depth Range: Intertidal to 91 m, usually less than 45 m.

This large Cancer crab has a dark tip to its claws. The dorsal surface of the carapace is nearly smooth or only slightly rough, but does not have rough tubercles or setae. The carapace is at least 1.5 times as wide as long and frequently exceeds 6 cm. The ventral surface of living individuals has red spots on a pale yellow background, and the dorsal surface is purplish red. The undersurface of the carapace also has setae, as does the dorsal surface of young ones. Carapace usually up to about 13 cm wide but may be up to 15 cm. The carapace has 11 anterolateral teeth and is widest at the 8th tooth. Some of the teeth curve forward.

How to Distinguish from Similar Species: This is one of the two large local Cancer crabs with black tips on their chelae. The other, Cancer productus, has a rough dorsal surface on its carapace and a few tubercles and has no ventral red spots. Its carapace is also produced forward between the eyes. Other Cancer crabs with black chelae, such as Glebocarcinus oregonensis, have a tuberculate carapace which is usually less than 6 cm wide and is not 1.5x or more as wide as long.Note: Species formerly in genus Cancer have been recently subdivided into several genera. 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. 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.

Biology/Natural History: Food irncludes scavenged bits and animals such as Tegula funebralis and hermit crabs. It captures the hermit crabs by gradually chipping away the edges of the hermit's shell until the hermit crab has nowhere else to hide. Sometimes harvested by humans for crab legs. In California, become mature in about 2 years. Berried females are most often seen November to January. The young have vivid color patterns on the carapace similar to those of C. productus young. Most active at night.

Geographical Range: British Columbia to Cabo San Lucas, Baja California but rarely seen north of Coos Bay, Oregon.

Romaleon is a genus of marine crabs formerly considered in the genus Cancer.