CHARACTERIZATION OF DEVELOPMENTAL EMBRIONIC STAGES OF THE SILVERSIDES BASILICHTHYS AUSTRALIS (EIGENMANN, 1927)

Abstract

The embryonic stages of development of the silversides, Basilichthys australis Eigenmann, a freshwater fish of wide distribution in Chile are characterized. Oocytes from mature females were obtained by abdominal massage and fertilized with seminal fluid from male specimens. The evolution of embryonic development was observed from the uncleaved egg stage up to hatching. Eighteen stages were obtained by using temperatures of 14°C to 22°C. The fertilized egg is recognized for its turgescence, the increase of the perivitelline space, the conspicuous micropyle in the animal pole, and its great transpareney. Cleavage occurs between the second and twenty fourth hour of incubation, until the blástula stage is reached. The period of morphogenetic movements takes place between twenty four and seventy two hours of incubation and last until the formation of the embryonic shield, when organogénesis begins. Between fourteen and sixteen days later, hatching occurs; the larvae show a conspicuous yolk sac and a marked pigmentation.