RELATIONSHIP OF SOME COLEOID CEPHALOPODS ESTABLISHED BY 3'-END OF THE16S RDNA AND CYTOCHROME-OXIDASE-III GENE SEQUENCE COMPARISON

Phylogenetic relationships for extant cephalopods have been based, so far, mainly on morphology and paleontology. Nucleotide sequence data a re still rare. Sequence analyses from the 3' end of the 16S rDNA gene of cephalopods have shown that this portion of gene can provide valuab le information on taxonomic relationships at the infrafamilial level. Another mitochondrial gene, cytochrome oxidase III, is investigated to analyze higher (i. e. ordinal) taxonomic levels. The results obtained by the two gene portions are compared, but the low number of species does not allow a definitive answer on interfamilial relationships. The low divergence between nucleotide sequences of two populations of Lol igo vulgaris Lamarck, 1798, and of L. reynaudii Orbigny, 1845, suggest s that the latter is not a clearly distinct species. The grouping of t he three families of Sepioidea (Sepiidae, Spirulidae, and Sepiolidae) is not supported. Idiosepiidae groups with the oegopsid squid Enoplote uthis irregardless of the analysis (parsimony or distance).