Influência do LHRH comum na ovulação induzida do tambaqui Colossoma macropomum (Cuvier) (Characiforme,Characidae), em diferentes fotoperíodos

Abstract

Tambaqui Colossoma macropomum is one of the most important fishes in the brazilian fish culture. Since it is an amazonic migrating fish, its ovulation and spawning do not occur in captivity; therefore the induced reproduction is this fish is always needed. The present work investigated the effects of the common LHRH on the ovulation in tambaqui kept in different photoperiods. Seventeen mature females and sixteen males were used in the investigation. Females were induced to ovulate with the common LHRH, under two different photoperiods: In photoperiod A, the first hormonal injection started in later afternoon, while in the photoperiod B it started at early morning time. In each group, the second hormonal injection was done 12-13 after first injection. The total concentration of the LHRH applied in the female fish varied from 500-1200 μg/fish. All male received a single dose of 50-100 μgLHRH/fish. No ovulation occurred in the females of the photoperiod A, while all females in the photoperiod B, ovulated. There was statistic difference in the levels of the 17α OH-P hormone between the two groups, during the considered period of latency of the inducer hormone. The results appoint to an existence of a photoperiodic cue, which can favor the occurrence of the ovulation in tambaqui, when is induced with the common LHRH of veterinary use.