Registro de ocorrência de raias de água doce e alguns aspectos da biologia reprodutiva de potamotrygon leopoldi (Castex & Castello, 1970) e Potamotrygon orbignyi (Castelnau, 1855) (Chondrichthyes: Potamotrygonidae) na região do médio Rio Xingu-Pará

Abstract

Freshwater rays are elasmobranchs of restricted occurrence in the Neotropics region and the Amazon presents the greatest diversity of species. The present study aims to provide a list of species occurring in the middle Xingu River and some aspects of the reproductive biology of Potamotrygon leopoldi and P. orbignyi. A previous species list was obtained through a bibliographic survey in library databases (MPEG, UFRA and UFPA) and 16 rays deposited in the Ichthyological Collection of MPEG were also analyzed. During a collection in March-April03, 27 specimens of P. leopoldi (17 males; 10 females) and 3 of P. orbignyi (males) were collected from which the reproductive apparatus were removed for laboratory analysis. The results of the literature survey and analysis of collected specimens indicate the existence of two genera and four species of rays in the studied region: P. leopoldi, P. orbignyi, P. motora and Paratrygon aiereba. The mean IHS values for P. leopoldi were 2.85 (males, n= 15) and 4.15 (females, n=10) and for P. orbignyi was 1.74 (males, n=3). P. Ieopoldi and P. orbignyi showed no external secondary sexual characteristics that differentiated males from females, other than the pterigopodia. The presence of embryos in different stages of development was observed in 8 females of P. leopoldi and the average uterine fecundity of this species was 6.87. Linear regression between disc width and clasper length for P. leopoldi and P. orbignyi provided an e of 0.72 and 0.70, respectively. The preliminary results of reproductive aspects of P. orbignyi and P. leopoldi indicate that these two species probably present part of their reproductive cycle associated with the flood period of the Xingu River.