Dungeness Crab

Most common in sand or muddy-sand bottoms in subtidal regions, often in or near eelgrass beds. Often partly buries itself in the sand.

Geographical Range: Occurs from Alaska to Santa Barbara, California.

Depth Range: Lives from intertidal to a depth of 230 m.

A Red-brown to purple carapace with a spine-tipped edge on the front half; contains ten teeth on the anterolateral margins. The tenth tooth is the largest and is at the widest portion of the carapace. There are no teeth on the posterolateral margins. The chelipeds are purple to brownish at the base and the chelae are white at the tips. The carpus, propodus, and dactyl of the chelipeds have spiny ridges. The rear legs are more flattened than are those of most local cancer crabs, and are fringed with setae. Some hairlike setae can also be found on the underside of the carapace. This species alone accounts for the large majority of all crabs taken commercially in the Pacific Northwest. It is the largest cancer crab in North America. Width of carapace up to 25 cm in males and 18 cm in females.

How to Distinguish from Similar Species: The most similar-appearing local species is Metacarcinus gracilis, which has similar coloration and white claw tips as does this species. However, it has a distinct tooth behind the widest point of the carapace and has no spiny ridges on the carpus, propodus, and dactyl of the chelae. It also does not grow as large. Cancer productus, also often found intertidally and subtidally in the Pacific Northwest, has black tips to the dactyls of the chelae.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: This crab is the largest edible crab from Alaska to California, making this species important for fisheries commercially and economically. There appear to be five subspecies in California alone. The female Dungeness crab can lay up to 2.5 million eggs and can live up to at least 6 years. Females can store sperm received during one mating season and use it during the next season. This species is a carnivore that feeds on more than 40 different species including small clams, oysters, fish, shrimp, worms and according to recent studies even feeds on Velella velella nematocysts. The larvae of this species is often attached to the bells of jelly fishes and to their tentacles; these larvae feed on the gonozooids, and by doing so gain protection from pelagic fish predators and are transported to juvenile crab habitats nearshore as long as associated with the cnidarian. Dungeness crab larvae feed primarily on zooplankton, however phytoplankton are also eaten. The larvae are crepuscular migrators, being found near the surface at dawn and dusk but deeper in midday and midnight. The stage 1 zoeae are nearest the surface with later zoeal stages in deeper water. In spring, larvae of this species may be advected north along the coast as far as Alaska. In springtime, adults of this crab can be found buried in sand or in tidepools, where it can hide and wait for its new shell to harden. On average, males will cover more ground in an hour than females, and ovigerous females move less than nonovigerous females or males. Near Vancouver Island, adults have more epibionts than do juveniles. Common epibionts include barnacles on the dorsal surface, green, red, and brown algae, tube-dwelling polychaetes, hydrozoans, bryozoans on any region of the carapace. A few had sponge, tunicate, or mollusk epibionts. Feeding in ovigerous females is greatly reduced below that of non-ovigerous females. Females are able to survive an entire winter without feeding, at least in the laboratory. Both juvenile and adult crabs may sometimes be cannibalistic. Dudas et al. found that the common local cancer crabs Metacarcinus magister and Cancer productus preferred the thin-shelled introduced varnish clam Nuttallia obscurata to the thicker-shelled clams Leukoma staminea and Venerupis philippinarum if access to all was equally easy. However, Nuttallia obscurata typically lives deeper in the sediment than do Leukoma staminea or Venerupis philippinarum. If they had to dig for them, Metacarcinus magister still ate more Nuttallia obscurata than it did of the other clam species, but C. productus' preference switched to Leukoma staminea and Venerupis philippinarum. Jensen and Bentzen found that the egg clutches of females frequently have multiple paternity. Adult females molt once a year and mate with one male per molt. They can store sperm for up to 2.5 years.The hoplonemertean worm Carcinonemertes errans, an ectosymbiont and egg parasite in Metacarcinus magister, is in turn eaten by a Riserius sp nemertean whose larvae have previously been classified as pilidium recurvatum