ldentifying a spinnerdolphin, Stenella longirostris (Gray, 1828), stranded in Bahia State, Brazil, using mtDNA sequences

Abstract

On June 7'h 1995, a young dolphin (genus Stenella) was found dead at 5tella Mares beach (13°00'30"5; 38°27'20"W), Salvador-Bahia. Externai characteristics of this individual suggested that it should be a spinner dolphin, Stenella longirostris. However, because morphometry and color patterns of young Clymene's dolphin, S. clymene, are very similar to S. longirostris the chances of this dolphin being a Clymene's could not be dismissed. In an attempt to confirm the identification of this animal, a 401-bp fragment of the cytochrome b mitochondrial DNA (mtDNA) gene was amplified and sequenced jrom muscle tissue. DNA sequences from 8 other Delphinidae species (Stenella attenuata, S. frontalis, S. longirostris, Steno bredanensis, Sotalia fluviatilis, Delphinus delphis, Tursiops truncatus and Lagenorhynchus acutus) were obtained from fresh tissue or from the NCBI GenBank and were used to perform a phylogenetic analysis with the blue whale (Balaenoptera musculus) sequence as an outgroup. Two base pairs substitutions were observed
between the mtDNA sequence of the unidentified individual and the sequence of a S. longirostris from Fernando de Noronha Island, and nine differences were found between it and a same species of dolphin from North Atlantic, while 17 substitutions were reported between this dolphin and S. clymene. These results confirm that the dolphin from Bahia
is a spinner dolphin. Phylogenetic analysis using maximum parsimony supported the results. This paper is an example of how molecular genetics can be useful to solve problems of identification of marine mammals.