Early development in the annual fish Cynolebias viarius

The detailed characteristics and timing of early development in Cynolebias viarius , an annual fish endemic to Uruguay, were obtained from in vivo observations of embryos cultured under standardized laboratory conditions. The chorion ultrastructure is reported for this species for the first time. Comparison with previous data from other annual fishes showed that C. viarius exhibited the longest early development including cleavage, blastula formation and epiboly.