Reproductive biology and induced breeding of two Characidae species (Osteichthyes, Characiformes) from the Sao Francisco River basin, Minas Gerais, Brazil

摘要

Astyanax bimaculatus (Linnaeus, 1758) and Tetragonopterus chalceus Spix & Agassiz, 1827 are two important foraging species occurring at the Sao Francisco River basin. Specimens from both species were submitted to spawning induction through hypophysation, to study some reproductive features and to obtain subsidiary information for the definition of the artificial reproduction protocol. Males and females were treated with a single dose of crude carp pituitary extract (6 mg/ kg). In water at 26 degrees C, the extrusion of the oocytes was made 12,8 and 11 hours after the hypophisis injection, for A. bimaculatus and T chalceus respectively. More than 70% of the females of both species showed a positive response to the treatment and mean egg fertilization rates were above 70%. The eggs of A. bimaculatus and T chalceus are yellow or medium brown,spherical, opaque, demersal, and slightly adhesive. The ova contained 4774 and 2563 eggs (mean values per gram) respectively. The embryonic development in both species was fast, lasting less than a day when water temperature was between 24 and 25 degrees C.