Molecular identification of stranded rorquals in the Northern coast of Argentina confirms the presence of Balaenoptera brydei Olsen 1913 in the South Western Atlantic Ocean

RODRÍGUEZ, D; MUÑOZ, G; GIARDINO, G; DENUNCIO, P; MANDIOLA, M A; DASSIS, M; BASTIDA, J; BASTIDA, R; WADA, S

Florianopolis

Congreso; XIV Reunión de Especialistas en Mamíferos Acuáticos de América del Sur; 2010

SOLAMAC

Several factors make the identification of stranded rorquals (Cetacea: Balaenopteridae) particularly challenging. The degree of decomposition and body position on the beach sometimes prevents ventral groove count, colour identification or baleen inspection. Some body sizes overlap between maximum lengths of intermediate species with medium sizes of big species. These factors result in most of the cases in a poor assignation of species. Molecular identification of rorqual species not only have increased the possibility of species assignments, but also have proved successful in enlightening the Family taxonomy. Although seven balaenopterid species have been reported for the northern coast of Argentina, the strandings of these whales are very infrequent. In the last 6 years, three strandings have been reported in the area. The first rorqual was a male (12.7m) stranded in Mar del Sur (August 2004), and provisionally identified as a sei whale according to ventral grooves count. The second was another male (14.7m) stranded in Mar del Plata (April 2006), tentatively identified as a Bryde’s whale based on the presence of three rostral ridges. The third one was a 16.0m specimen stranded in Ensenada (April 2009) of unknown sex and unidentifiable species. A partial cytochrome b gene (640 nucleotide sites from the beginning) was sequenced from skin samples of the three specimens, and compared with 8 Balaenoptera species retrieved from the GenBank. The analysis resulted in a positive identification of the three specimens as Balaenoptera borealis (Mar del Sur), Balaenoptera brydei (Mar del Plata) and Balaenoptera physalus (Ensenada). The number of different nucleotides compared with published sequences was 3, 2 and 2, respectively. To reconfirm B.brydei identification, comparisons were made with an unpublished 416 bp Bryde´s whale control region sequence from the North Atlantic Ocean (DQ340979), resulting in a positive identification and a difference of 6 nucleotides and 2 indels. The record of sei and fin whales in northern Argentina adds new records on existing information, but this is the first confirmation of B.brydei inhabiting the southern SW Atlantic Ocean. Unavailable morphological diagnoses between edeni and brydei led to conservative assignation of B.edeni to all rorquals with three rostral ridges, leaving the correct species assignation unresolved. Our results confirm the presence of Bryde’s whale in South America, but remains unclear if other morphologically identified “B.edeni” specimens in the region are in fact Bryde’s or Eden’s whales.