Ranges Of Offshore Decapod Crustaceans In The Eastern Pacific Ocean

Distributions of offshore decapods in the eastern Pacific fall into a pattern of at least five clusters: the Aleutian Islands to Washington, Washington or Oregon to southern California, Baja California and the Gulf of California to central America, Panama or Colombia to Peru, and Chile to Cape Horn. These clusters are supported by distributional data at all depths considered, although there is more blurring of provincial boundaries at depths greater than 1500 m than at lesser depths. There is a sharp break in faunal distributions between that of northern Baja California and all areas to the south, largely due to the replacement of species of Pandalus to the north by species of Heterocarpus to the south. The northeastern Pacific is particularly rich in species of hippolytid shrimps and lithodid crabs and contains endemic genera of the families Crangonidae and Majidae. Species in these and other groups probably underwent extensive radiation in the late Cenozoic and dispersed from the northern Pacific into the northern Atlantic and less readily into the southern hemisphere. Compared to the northeastern Pacific, the western coast of South America is poor in the total number of species and the degree of endemism in decapods. Except for a few cosmopolitan species of the lower continental slopes, North and South America have no species in common.