Early ontogeny of yellowtail tetra fish Astyanax lacustris (Characiformes: Characidae)

The ontogeny of the tetra fishAstyanax lacustris, from embryogenesis through the larval and juvenile periods, is presented. The eggs and larvae were obtained through induced reproduction. The larvae were collected at hatching and daily, until all stages of development were obtained and, later, once a week, until the juvenile period. The eggs are small, slightly adhesive and demersal, and have a transparent chorion, yellowish calf and meroblastic cleavage. The larvae hatch 19 hr after fertilization (26oC). The standard length during initial development ranges from 2.17 to 18.10 mm. The larvae have a subterminal mouth, simple nostrils, a pair of adhesive organs on the back of the head (newborn larvae), spherical eyes and medium-length intestines. The initial pigmentation is scarce, concentrated in the anteroposterior ends of the yolk sac, but intensifies from the flexion stage, with chromatophores in the mouth and in the cephalic region; the humeral region and the caudal peduncle have a macula at the end of the larval development. The total number of myomeres: 32-38, 15-20 preanal and 14-20 postanal. Juveniles showed similar morphology and pigmentation to adults. The number of fin rays: pectoral 11-12; pelvic 6-7; dorsal 10-11; and anal 27-29.