Reproduction and development of the annual fish Austrolebias nigrofasciatus Costa & Chefe, 2001 in laboratory

Author: Alinca Peres da Fonseca (Currículo Lattes)
Supervisor: Dr Ricardo Berteaux Robaldo

Abstract

Annual fish are considered extreme organisms because they live exclusively in humid seasonal areas and have unique adaptations for survival in these environments. Despite being considered good models for laboratory tests, few studies have been carried out in order to improve the management techniques of Neotropical Rivulidae. Thus, three studies were carried out to elucidate issues of the development and reproduction of Austrolebias nigrofasciatus in the laboratory. In the first chapter, the number of females was manipulated, maintaining one (T1), two (T2), three (T3) and four (T4) females for each male per experimental unit, with five replications, to check oviposition (OV), the fertilization rate (TF), and the neutrophil (N): lymphocyte (L) ratio. The average OV per female did not differ,but the TF was lower at T4, coinciding with the increase in the N: L ratio in males. Up to T3, the addition of females increases the total number of fertilized eggs available. In view of the results, we observed that increasing the ratio of females to up to three per male favors the reproductive performance of the species. The second experiment analyzed the survival, trajectory and time of embryonic development in different incubation media. It was verified that until diapause II (DII) there is no influence of the media on the development pattern, but from this stage onwards the water medium with powdered coconut shell showed a delay in the development time. The wet medium with Yamamoto's solution showed the first fully developed embryos, 27 days after laying.Eggs that were kept in the same water as the breeders since laying remained in the DI. Survival in all incubation media was high (70 to 98%). It is concluded that all the means are viable for the maintenance of the embryos, being able to alter the development trajectories through the manipulation of the diapauses. In the third and final study, to identify how the initial filling of the gas vesicle is compromised, preventing normal swimming (belly sliders), and to determine the implications of this for the growth of juveniles, we histologically analyzed the gas vesicle of fish with normal swimming and of ramps during initial growth. We verified that the ramps present metaplasia with desquamation of the gas vesicle epithelium and hemorrhage, in addition to presenting inferior growth.We conclude that in the laboratory the incidence of this pathology is a relevant problem and responsible for a large number of unviable juveniles.

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