Citotaxonomia de arraias de água doce (Myliobatiformes, Potamotrygonidae) da Bacia Amazônica Central

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

26/10/2011

RESUMO

The family Potamotrygonidae in the order Myliobatiformes comprises all the Neotropical freshwater ray species. The knowledge about this fish group is limited, for example, the species number is uncertain, some species names are questionable, there is no information about how their diversification in freshwater happened, and there are no studies about their real marine sister group. Cytogenetic studies in this family are incipients. With the objective of widen the knowledge about this fish group, that arouses interests in aquarium, and are indicated as an overfishing group, were analyzed, cytogenetically, seven nominal species and two cytotypes: Plesiotrygon iwamae (2n=74, FN=120), Potamotrygon sp. C (cururu) (2n=67♂/68♀, FN=104/106), with a sex determination system XX/X0, Potamotrygon sp. C1 female (2n=68, FN=108), Potamotrygon scobina (2n=66, FN=102), Potamotrygon cf. scobina (2n=66, FN=101), both with a probable sex determination system XX/XY, Potamotrygon constellata (2n=66, FN=110), Potamotrygon leopoldi (2n=64, FN=102), Potamotrygon orbignyi (2n=66, FN=106), with a confirmed XX/XY system and Potamotrygon motoro from differents localities of the central Amazon basin. Among the specimens of Potamotrygon sp. identified a distinct female specimen, which showed the same diploid number (2n=68) of Potamotrygon sp. C, but with different morphology and karyotype formula. Therefore, it may represent another species to be recognized and described this taxon, provisionally named Potamotrygon sp. C1. However, the occurrence of the system XX/XO may for now be characterized only in Potamotrygon sp. C. All the species presented multiple nucleolar organizer regions (NORs), although those regions were not always active, and the silver nitrate stains number ranged from four to eight, in most of the metaphases they were localized in the terminal position of the long arms, except in one pair in P. constellata that was localized in the short arm. The constitutive heterochromatin is located, in the centromeric regions of all the complement chromosomes, in all the species. Chromosomal rearrangements, specially fusions or fissions, inversions and translocations, were indispensable mechanisms of karyotype evolution in the freshwater stingrays, and may be involved in the speciation processes of this group.

ASSUNTO(S)

genetica animal cromossomos sexuais arraias chondrichthyes citogenética potamotrygonidae

ACESSO AO ARTIGO

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