Taxonomic status of two morphotypes of Coryphaena hippurus (Perciformes: Coryphaenidae)

Two Coryphaena hippurus morphotypes (dourado and palombeta) are found along the Brazilian coast and are considered by Rio de Janeiro’s fisherman and fishmongers as two different species. Furthermore, these morphotypes are commercialized under different values and suffer different fishing pressure. Therefore, a definition of their taxonomic status is an important economic and biological matter. In order to investigate this problem, allozyme electrophoresis method was undertaken for seventeen loci on 117 individuals of C. hippurus sampled at Cabo Frio/RJ (Brazil). The data indicate homogeneity between the morphotypes gene pools. Nevertheless, differences were found for genetic variation among dourado and palombeta, especially due to alcohol dehydrogenase locus. Natural selection hypothesis is discussed in explaining these findings.(AU)

Dois morfotipos de Coryphaena hippurus (dourado e palombeta) encontrados ao longo da costa brasileira são considerados espécies diferentes por pescadores e mercadores das regiões de desembarque do estado do Rio de Janeiro. Além disso, esses morfotipos são comercializados por valores diferentes e sofrem diferentes pressões de pesca. Desta forma, a definição do status taxonômico desses morfotipos é importante, tanto em termos econômicos quanto biológicos. A fim de investigar esse problema foi utilizado o método de eletroforese de aloenzimas com a amostragem de dezessete loci para 117 indivíduos dos dois morfotipos de C. hippurus obtidos em desembarques pesqueiros na região de Cabo Frio/RJ (Brasil). Os dados indicaram uma homogeneidade entre os conjuntos gênicos dos morfotipos. A despeito disso, diferenças entre os conjuntos gênicos de dourado e palombeta foram encontradas, devido, especialmente, ao locus álcool desidrogenase. A hipótese de seleção natural é discutida como possível explicação para esses resultados.(AU)

Genetic and morphological variability in South American rodent Oecomys (Sigmodontinae, Rodentia): evidence for a complex of species.

The rodent genus Oecomys (Sigmodontinae) comprises ~16 species that inhabit tropical and subtropical forests in Central America and South America. In this study specimens of Oecomys paricola Thomas, 1904 from Belém and Marajó island, northern Brazil, were investigated using cytogenetic, molecular and morphological analyses. Three karyotypes were found, two from Belém (2n = 68, fundamental number (FN) = 72 and 2n = 70, FN = 76) and a third from Marajó island (2n = 70, FN = 72). No molecular or morphological differences were found between the individuals with differing cytotypes from Belém, but differences were evident between the individuals from Belém and Marajó island. Specimens from Belém city region may represent two cryptic species because two different karyotypes are present in the absence of significant differences in morphology and molecular characteristics. The Marajó island and Belém populations may represent distinct species that have been separated for some time, and are in the process of morphological and molecular differentiation as a consequence of reproductive isolation at the geographic and chromosomal levels. Thus, the results suggest that O. paricola may be a complex of species.

Determination of the non protein amino acid ß-N-methylamino-l-alanine in estuarine cyanobacteria by capillary electrophoresis.

A capillary electrophoretic method for the determination of the amino acid ß-N-methylamino-l-alanine (BMAA) was achieved using a fused-silica capillary column (50 cm × 75 µm I.D.) filled with 5 mM sodium tetraborate solution (pH 9), with an applied voltage of 25 kV, at 25 °C. The method was then applied in quantifying BMAA in eighteen strains of lyophilized estuarine cyanobacteria, following amino acid extraction using 0.1 M trichloroacetic acid and 6 M hydrochloric acid, sequentially.