The presence of the seahorse Hippocampus patagonicus in the Argentine Sea based on the cytochrome b sequence of mitochondrial DNA

This study aimed at sequencing the mitochondrial cytochrome b gene (cyt b) of seahorses morphologically identified as Hippocampus patagonicus Piacentino & Luzzatto, 2004 from the two known localities where the species occur in the Argentine Sea (San Antonio Oeste and Mar del Plata). Based on the lack of substitutions within cyt b found between the individuals of both localities, the geographical range of H. patagonicus was extended up to the Northern limit of the Argentine Sea. A phylogenetic analysis comparing the cyt b sequences of Hippocampus species revealed that H. patagonicus together with H. hippocampus and H. erectus belong to a monophyletic group of species. The comparison of the cyt b sequence of Hippocampus cf. erectus from Southern Brazil with that one of H. patagonicus resulted in scarce differences. This could suggest the presence of H. patagonicus in southern Brazil, although further investigation is needed to resolve the taxonomic status of H. erectus in the South Western Atlantic.Original Abstract: Presence de l'hippocampe Hippocampus patagonicus en mer d'Argentine demontree par sequencage du cytochrome b. La presente etude a pour but de determiner la sequence du cytochrome b (cyt b) d'hippocampes echantillonnes dans la mer d'Argentine (a San Antonio Oeste et Mar del Plata) et prealablement identifies sur des bases morphologiques comme appartenant a l'espece Hippocampus patagonicus Piacentino & Luzzatto, 2004. L'absence de substitutions observee entre les sequences de cyt b provenant d'individus des deux localites echantillonnees permet d'elargir l'aire de repartition de l'espece H. patagonicus depuis le sud de la Patagonie jusqu'a la limite nord de la mer d'Argentine. Une analyse phylogenetique comparant les sequences de cyt b issues de differentes especes du genre Hippocampus demontre que H. patagonicus, H. hippocampus et H. erectus (preleve au large du Bresil) appartiennent a un groupe monophyletique. En outre, le peu de differences relevees entre les sequences de cyt b de H. erectus (individu bresilien) et de H. patagonicus indiquent que la resolution du statut taxinomique de H. erectus present dans l'Atlantique sud-ouest necessite de nouvelles investigations.