Initial development of Prochilodus hartii (Pisces: Prochilodontidae) submitted to induced reproduction.

Abstract

The Prochilodontidae prepare for reproduction in captivity, but neither ovulation nor spawning occurs, thus requiring induced reproduction for breeding and restocking. This study analyzed for the first time the embryogenesis and larval ontogeny of P. hartii submitted to induced reproduction by hypophysation with crude common carp pituitary extract. The extrusion of oocytes and sperm was performed manually and fertilization was done using the dry method. After fertilization, the eggs were kept in incubators at 23°C. A stereomicroscope was used to measure egg diameter and to monitor embryo development. Samples of larvae were collected daily for 7 days for histological and biometric analyses. The recently extruded oocytes, non-hydrated, are spherical, grey, and non-adhesive with a diameter of 1480 ± 39 μm and after hydration, have a diameter of 2860 ± 120 μm. The positive response to hypophysation was 100% for females and 80% for males. Spawning occurred 7 h after the third hormonal dosage. The fertilization rate was 77% at 23°C. Blastopore closure occurred at 6 h 45 min and embryonic development was completed 36 h 10 min after fertilization. After 204 h post fertilization (hpf) the larvae reached a standard length of 6.56 ± 0.14 mm with the yolk sac completely resorbed. In P. hartii, the oral cavity opening occurred 132 hpf. The results of this study provide knowledge to better understand induced reproduction, breeding, and management of P. hartii, a species with a high potential for pisciculture, and which is commercially important in the Jequitinhonha River basin.