Aspects of the Zoogeographic Distribution of Callinectes (Brachyura:Portunidae)

Three aspects of the geographic distribulions of swimming crabs in the genus Callinectes are examined. C. maracaiboensis, previously thought to be endemic to the Lake Maracaibo area, occurs in Jamaica, Colombia, and Curaçao. Although typically found in fresh and brackish waters, available evidence indicates that C. maracaiboensis cannot complete its life cycle in waters of low or highly variable salinity, and could not have evolved in Lake Maracaibo when it was cut off from the Caribbean.

The larvae of C. sapidus, the species most successful in temperate waters, can neither hatch nor molt much below 20°C, and females in the northerly part of the range spawn only during the warm season. The occurrence of Callinectes in a geographic area implies settlement from the plankton, rather than adult immigration. Callinectes make their farthest poleward penetration in West Atlantic areas having warmer summers and cooler winters than those at comparable latitudes in the East Pacific and East Atlantic. Thus, latitudinal distribution seems to be limited by the effects of summer temperatures on larvae, rather than winter temperatures.

Caribbean high islands, typically possessing brackish and fresh as well as marine environments, have most or all potentially occurring Callinectes. Low islands, typically without significant amounts of water of reduced salinity, lack C. bocourti, C. maracaiboensis, C. sapidus, and C. danae. Analysis of geographic records shows that low salinity water may be an ecological requirement for some Callinectes, which are distributed similarly to freshwater shrimps, genus Macrobrachium. The most eurytopic Callinectes are absent from areas of the Caribbean populated by their less eurytopic congeners due to their lack of suitable reduced salinity refuges.