PRESENCIA DE UROTRYGON MICROPHTHALMUM (ELASMOBRANCHII: UROLOPHIDAE) EN AGUAS BAJAS DE MARANHÃO (BRASIL) Y NOTAS SOBRE SU BIOLOGIA

Abstract

From October 1997 to April, 1998 seventy-nine specimens of the ray Urotrygon microphthalmumwere captured, all of them showing sexual dimorphism. They were processed in order to study their morphometrics, feeding habits, and reproduction. The largest was 300 mm in total length and the smallest one 64.4 mm, weighing 103.4 g and 12.5 g respectively. They fed mainly on crustaceans and ploychaeta; of the stomach contents 94.5 % were shrimp and 5.49% polychaeta. 7.6% of the total had empty stomachs. As far as reproduction, three sexual stages were found:  51% juvenile, 30% adult and 19% pregnant, with an average of three embryos per uterus. Among the male fishes analysed 84.4% were juvenile and 16.6% adults