GENETIC DIFFERENTIATION IN 3 SEPIA SPECIES (MOLLUSCA, CEPHALOPODA) FROM GALICIAN WATERS (NORTH-WEST IBERIAN PENINSULA)

The systematics of the genus Sepia is not yet clear. Morphological evi dence has led to S. officinalis Linnaeus, 1758 being considered as bel onging to the subgenus Sepia sensu stricto, and S. orbignyana Ferus-sa c, 1826 and S. elegans Blainville, 1827 as belonging to the subgenus R hombosepion. Samples of 30 individuals of S, officinalis and S. orbign yana from both sides of an oceanographic boundary off the north-west I berian Peninsula, and a sample of S. elegans from the northern side, w ere collected in 1993-1994. Allozyme electrophoresis for 32 presumptiv e loci revealed low levels of genetic variability for the three Sepia species (mean expected heterozygosity estimates were < 0.052). No sign ificant differences in allozyme frequencies were detected among popula tions of either S. officinalis or S. orbignyana. The genetic identitie s (I) of S. officinalis and S. orbignyana (I = 0.12) and of S. elegans (I = 0.13) were significantly different from that of S. orbignyana an d S. elegans (I = 0.49). The former are typical of values for confamil ial genera, and a new generic status is proposed for the latter two sp ecies, which become Rhombosepion orbignyana (Ferussac, 1826) and R. el egans (Blainville, 1827).