A new species of axiid shrimp from chemosynthetic communities of the Louisiana continental slope, Gulf of Mexico (Crustacea: Decapoda: Thalassinidea)

Calaxius carneyi, new species (Axiidae), is described from two male specimens collected by manned submersibles working near hydrocarbon seeps in deep waters (544 m) on the continental slope off Louisiana, in the northern Gulf of Mexico. Both specimens were taken adjacent to communities of clams that comprise a major constituent of chemosynthetic assemblages at the collection site. The new species is characterized in part by ventrally truncate abdominal pleura, as opposed to the acutely triangular or broadly rounded pleura found in other known members of Calaxius, only one of which is known to occur in the Atlantic Ocean. The new species is readily distinguished from its congeners by unique dentition of its heavy triangular rostrum and postrostral carapace, its short eyestalks and antennal acicle, the absence of well-defined teeth on the massive chelipeds, and the narrow, subtriangular telson. Chelipeds, pleopods and uropods of the two known specimens herewith described are covered extensively by long setae, many of which are plumose and densely fouled by flocculent debris.