Embryogenesis and larval development of migratory matrinchãBrycon orthotaeniaGünther 1864 (Characiformes: Bryconidae)

Abstract

The present study aimed to characterize the embryogenesis and larval development of matrinchã (Brycon orthotaenia), through the analysis of egg and larval morphology. Fertilized eggs had a mean diameter of 1.17 mm, with yolk occupying most of the egg (1.06 mm). Embryogenesis lasted for 15 hr at an average temperature of 27°C. At hatching, yolk-sac larvae measured 3.67 mm in mean standard length (SL). Pre-flexion, flexion and post-flexion larva had 5.01, 8.24 and 11.88 mm mean SL, respectively, with significant increases observed particularly in head length, head height, and eye diameter. The yolk persisted in the yolk-sac and pre-flexion stages (5.96 mm SL). The mouth opening could first be observed 13 hr after hatching, and cannibalism was observed 29 hr after hatching in pre-flexion larvae after absorption of the yolk sac; in such cases, the larvae had already developed teeth and a complete digestive tract. For an endangered species such as matrinchã, early life history studies are important because they provide researchers with a better understanding of critical stages of development and thus enhance captive management by rearing and restocking of the species.