MOLECULAR EVIDENCE FOR CRYPTIC SPECIES AMONG THE ANTARCTIC FISH TREMATOMUS-BERNACCHII AND TREMATOMUS-HANSONI

The notothenid species Trematomus bernacchii has previously been shown , by allozyme analysis, to be a complex of two cryptic species, one of which being more closely related to T. hansoni than to the other T. b ernacchii cryptic species. Two T. bernacchii colour morphs, ''white bl otch'' and ''brown'', at McMurdo Sound, may correspond to these crypti c species. In this study, we present mitochondrial DNA sequences of th e 12S and 16S ribosomal regions for six ''white blotch'' morphs, eight ''brown'' morphs collected in McMurdo Sound, one individual collected off the Antarctic Peninsula, and two T. hansoni individuals from McMu rdo Sound. These sequences were compared with those of T. bernacchii a nd T. hansoni in the literature. Based on 14 phylogenetically informat ive sequences, no differences were found between ''white blotch'' and ''brown'' morphs. Furthermore, only one substitution separated these s equences from the previously published T. hansoni sequence, while 10 s ubstitutions separated them from the previously published T. bernacchi i sequence. Misidentified specimens, and sequence misreadings may be a t the origin of these discrepancies. However, the presence of cryptic species within T. bernacchii and T. hansoni is not ruled out.