Ontogenic events and swimming behavior of larvae of the characid fish Salminus brasiliensis (Cuvier) (Characiformes, Characidae) under laboratory conditions

Abstract

The larval ontogeny and swimming behavior of the characid fish Sa/minus brasiliensis (Cuvier, 1816) were studied under experimental laboratory conditions, from hatching to yolk absorption . At day I, the larvae were transparent, with sparse dendrite chromatophores and a well -developed adhesive organ on the head. The retinal epithelial cells were initiating pigmentation. The branchial arches were at the initial phase of differentiation. The larvae were able to perform only vertical displacements and, when resting on the tank bottom, remained in lateral decumbency, in groups of 3 to 15 larvae. On day 2, the mouth was open, with conical teeth, and the digestive tube presented lumen and folded mucosa. The gaseous bladder and pectoral fins also were in differentiation. The larvae performed vertical and horizontal move- ments, adhered to the water surface by means of the adhesi ve organ or formed groups of three to six on the tank bottom. On day 3, the adhesive organ turned dorsal, the retina was pigmented, the digestive tube mucosa showed goblet cells, and the yolk sac exhausted. The larvae were now scattering in the water column forming no groups on the bottom.