Stages of rock bream oplegnathus fasciatus (Temminck et Schlegel 1844): embryonic development

Abstract

The embryonic development of rock bream, Oplegnathus fasciatus, was studied from fertilization until hatching. The hatching occurred approximately at 25 h after fertilization at 23.5 ± 0.5 °C. The embryogenesis is divided into seven stages: Zygote period, Cleavage period, Morula period, Blastula period, Gastrula period, Segmentation period and Hatching period. The first cleavage furrow of rock bream fertilized eggs is vertically oriented, as is usual until horizontal cleavage occurs at the fifth cleavage. The blastocoel is observed between the blastoderm and I-YSL at blastula period. At 90%-epiboly stage, the earliest somitic furrow appears in the middle of embryo. The myotomes develop from somites at 15 h 30 min post fertilization. The Kupffer's vesicle consisting of ventrally I-YSL and dorsally columnar cells appears with the completion of epiboly. It degenerates gradually with the penetration of some eosinophilic granules and disappears completely at 20 h 30 min after fertilization. The digestive tract, a straight tubule, is differentiated into foregut, midgut and hindgut. The epithelium of midgut and hindgut are the monolayer cubic and columnar cells respectively. The staging series provides a preliminary baseline reference for future studies on embryos of the rock bream.