UPOGEBIAAFFINIS (SAY): ITS POSTLARVAL STAGE DESCRIBED FROM LOUISIANA PLANKTON, WITH A COMPARISON TO POSTLARVAE OF OTHER SPECIES WITHIN THE GENUS AND NOTES ON ITS DISTRIBUTION

Abstract

ABSTRACT The first postlarval stage of Upogebia affinis (Say) is, for the first time, completely described. It is easily distinguished in the plankton by its rounded, densely setose rostrum and the strongly asymmetric fingers of its chelipeds, resembling those of the adult. Morphological characters which are most useful in distinguishing postlarvae of U. affinis from those of other species include: rostrum shape, spination, and setation; number of antennule endopod segments; number of antennal segments and nature of antennal scale; relative lengths of cheliped fixed and movable fingers; telson distal margin shape and spination. Seventeen postlarval specimens of U. affinis were identified from 1,320 plankton samples collected between June 1983 and August 1984 from 10 stations located approximately 10 km southwest of Calcasieu Pass, Louisiana, in the northern Gulf of Mexico. Postlarvae were rarely observed, although zoeal stages were regularly encountered. Postlarvae were collected more commonly at night, especially near the surface. Daytime occurrences were exclusively near the bottom. Zoeal stages of Atlantic and Gulf coast specimens of U. affinis were essentially identical except for slight size differences, suggesting that Atlantic coast postlarvae would be similar morphologically but slightly larger than those from the Gulf of Mexico.