GENETIC-VARIATION IN 2 POPULATIONS OF THE MARINE CALANOID COPEPOD ACARTIA-CALIFORNIENSIS TRINAST

Genetic variation of the marine calanoid copepod Acartia californiensi s Trinast was studied from two close populations, Estero de Punta Band a, Baja California (Mexico) and Mission Bay, California (USA). The stu dy was conducted with allozymes using a vertical polyacrylamide microe lectrophoresis of 11 enzymatic systems and one buffer system. Acartia californiensis presented reliable banding patterns in six systems and eight loci, from which only PGI-1 was polymorphic, with P-0.95 = 0.125 in both populations. The heterozygosity observed in Estero de Punta B anda was 0.060 +/- 0.060 and 0.035 +/- 0.035 in Mission Bay. There was a statistically significant deficiency in heterozygosity in Mission B ay (D = -0.477) when compared to the expected Hardy-Weinberg equilibri um, but not in Estero de Punta Banda (D = -0.096). Nei's genetic simil arity (1978) between the two populations studied was 0.994, with a gen etic distance of 0.006, which proves the lack of differentiation betwe en these populations. The results showed the existence of a genetic fl ow which was very likely established by a passive dispersal of diapaus e (resting) eggs that this species produces. They are very likely carr ied inward and outward by the tidal flux and reflux, and transported s outh by the California Current and north by Davidson's Coastal Counter current. The polymorphism and heterozygosity of the A. californiensis populations studied here are among the lowest when compared to other g enetically characterized copepods. This is the first study conducted o n the genetic variation of a calanoid copepod confined to estuarine wa ters or coastal lagoons using allozymes. A broader study is needed tha t covers a greater number of populations (locations) and loci.