Egg Development of Paralichthys orbignyanus (Valenciennes, 1839)

Abstract

Eggs of the Southern Brazilian flounder Paralichthys orbignyanus were obtained through spawning induction and reared in laboratory. The eggs released were free-floating or pelagic. Other important characteristics were: spherical shape, smooth chorion, narrow perivitelline space, and a single oil globule. Egg and oil globule diameter were about 0.792 ± 0.008 mm and 0.114 ± 0.003 mm, respectively. The blastodisc was observed approximately 1 h after fertilization and followed by blastodisc cleavage. Blastula stage started after about 5 h and gastrula stage after 9 h. Approximately 20 h after fertilization, blastopore closure was observed. Neurula or early embryo occurred after 24 h. Cardiac beats and movements of the free embryonic tail were recorded after 40 h of incubation. Hatching occurred after an incubation period of 40-50 h at temperatures ranging from 18 to 20 ºC. Newly hatched larvae were about 2.04 ± 0.024 mm long and quite undeveloped, with a large yolk sac with a posterior oil globule and sparse pigmentation. These results were greatly similar to those obtained by previous studies regarding congener species. This is one of the first steps towards the artificial propagation of this species under controlled conditions.