Small Mud Crab

Dyspanopeus sayi is a small crab, similar in appearance to Eurypanopeus depressus. It reaches a maximum carapace width of 30 millimetres (1.2 in), with sexually mature females having a carapace 6.1 millimetres (0.24 in) or more across. The carapace is roughly hexagonal, about 1.3–1.4 times as wide as long and strongly convex. It has a finely granular surface, and has a light covering of hair, especially towards the front and sides. The chelae (claws) are unequal: either the right or the left may be the larger. The carapace is olive-green to brown, but the fingers of the claws are black, with lighter tips.

The natural range of Dyspanopeus sayi extends from the Baie des Chaleurs in eastern Canada to the Florida Keys in the southeastern United States. It lives from the intertidal zone to depths of 46 metres (151 ft) and tolerates a wide range of temperatures and salinities.

Dyspanopeus sayi lives predominantly on muddy bottoms, where it is a predator of bivalve molluscs. In its native environment, it hides among colonies of polychaetes to avoid being preyed on by the Atlantic blue crab, Callinectes sapidus. It is an important predator of the quahog, Mercenaria mercenaria, in Narragansett Bay, and of the barnacle Balanus improvisus in Delaware Bay. In the Adriatic Sea, it has been observed to feed on the striped venus clam, Chamelea gallina, and the introduced Asian date mussel, Arcuatula senhousia.

The life cycle of D. sayi begins with copulation, which normally takes place shortly after the female has moulted, while her exoskeleton is still soft. Spawning occurs within hours or days of copulation, and the eggs are brooded on the female's pleopods (swimmerets) until they are ready to hatch. Females have been found carrying eggs from April to October; in a study of crabs caught at Gloucester Point, Virginia in 1978, females were observed to carry between 686 and 14,735 eggs. The number of eggs increases with carapace width according to a power law; extrapolation of the power law suggests that the largest D. sayi females are capable of carrying over 32,000 eggs each.