ANTENNULAR FLAGELLA: A USEFUL CHARACTER FOR DISTINGUISHING SUBGENERA AMONG POSTLARVAL SHRIMP OF THE GENUS PENAEUS (DECAPODA) FROM THE GULF OF CALIFORNIA

Abstract

ABSTRACT A new character for the distinction of subgenera in postlarval shrimp of the genus Penaeus from the Gulf of California (Mexico) is described. The four main shrimp species, Penaeus stylirostris, P. vannamei, P. californiensis, and P. brevirostris, present clear differences in the internal/external length ratio of the two first segments of the antennular flagella. Penaeus stylirostrisand P. vannamei, both belonging to the subgenus Litopenaeus, have low ratio values, e.g., mean values ranging from 0.4-1.0, whereas P. californiensis and P. brevirostris of the subgenus Farfantepenaeus have high ratio values, e.g., mean values ranging from 1.1-3.1. When total ranges are considered, overlapping occurs in only one of the four categories in which the postlarvae were grouped according to the number of dorsal teeth of the rostrum. Even in this case, the subgeneric distinction is possible by comparing the level of the distal margin of the second segment of the internal antennular flagellum in relation to that of the first segment of the external antennular flagellum. Differences are more pronounced within each of the categories. An identification method to the specific level is given after the subgeneric discrimination. The greatest advantage of this character over the use of chromatophore distribution patterns is the feasability of identifying postlarvae of Penaeus after prolonged storage periods.