Allozyme electrophoretic technique and phylogenetic relationships in three species of Sepia (Cephalopoda: Sepiidae)

Abstract

Samples of Sepia officinalis, S. orbignyana, and S. elegans from Galician waters (NW Iberian Peninsula) were obtained from commercial catches in three fishing ports. A preliminary screening for 47 and 33 enzymes in mantle muscle and digestive gland, respectively, was carried out using seven buffer systems. Thirty-seven enzyme loci were resolved from these tissues using only two buffer systems. Most enzymes showed equal or higher activity for the digestive gland than for the mantle muscle in freshly-caught samples of S. officinalis and S. orbignyana. The activity of a large number of enzymes decreased faster in the digestive gland than in the mantle muscle after 6–12 h at room temperature. Consequently, we suggest that mantle muscle rather than digestive gland be used for routine electrophoretic studies in Sepia species obtained from commercial catches. A phylogenetic reconstruction analysis, applying the Wagner parsimony method and using the ommastrephid species Illex coindetii as outgroup, showed only one most parsimonious tree. S. orbignyana and S. elegans were found to be a sister group. The topology agreed with that recently obtained from mitochondrial rDNA sequences, and both molecular data are in line with previous morphological results. They confirm the view that S. orbignyana and S. elegans belong to a different subgenus (Rhombosepion) from that of S. officinalis (Sepia “sensu stricto”).