EMBRYONIC AND LARVAL DEVELOPMENT OF THE "PIABANHA" Brycon insignis, STEINDACHNER, 1876 (PISCES, CHARACIDAE)

Abstract

This study presents preliminary observations on the embryonic and larval development until alevine stage of the "piabanha" Brycon insignis. This is an indigenous and endemic species from Paraí­­ba do Sul River Basin, Brazil. The eggs were obtained after reproductive induction utilizing breeders kept in captivity at "Estação Experimental de Paraibuna, São Paulo" which belongs to CESP (Companhia Energética de São Paulo), during the period of January-February/1996. Soon after artificial fertilization, the eggs were kept in incubators under constant temperature (26 ± 1°C). Samples were taken every 10 minutes during the first 3 hours, and after that, every 20 minutes, until hatching have occurred. After hatching, daily observations took place until the attainment of the fingerling stage. The eggs presented coloration varying from dark to brownish green, rigid chorion and large perivitelline space. They were spherical, demersal, non-adhesive, and showed high hydration degree and their diameter varied from 3.750 to 4.100 mm. The stages of embryonic development observed and described began with cleavage, followed by morula, blastula, gastrula, neurula until hatching of non-pigmented larvae, which displayed total average length of 6.0 mm ± 0.22, 14 hours after fertilization. On the second day of life, the larvae displayed total average length of 8.0 mm ± 0.21, pectoral fins already formed, open mouth and intense cannibalism. On the fifth day of life, all fins were formed and the individuals were very similar to adult. On the 15^th day of life, the alevine presented total length of 3.4 cm ± 0.39.