The effects of water temperature and hybridization on embryonic development and gametogenesis of two species of Amazonian tetra

The study of embryonic development in fish and how water temperature affects the life stage in this group is of pivotal importance to support works that aim at the conservation, management, and recovery of endangered or high economic valuable species. It allows a better evaluation of the species and the identification of morphophysiological changes related to the environmental factor in question. In addition, hybridization emerges as a biotechnological tool that may be applied as a technique for the creation of sterile animals that can be used as recipients for the germ cell transplantation approach, thus contributing to the conservation of different fish species. Based on this, we artificially reproduced two Amazonian fish species, Astyanax bimaculatus, and Moenkhausia oligolepis, and the resulting offspring of each species had their embryonic development followed at room temperature (25 °C) and at high temperature (30 °C). In addition, we performed interspecific crossbreeding between the species, and the offspring were also incubated and observed under the above conditions. The results showed that the high temperature accelerates the embryonic development of both, the offspring from A. bimaculatus and from hybridization. However, no larvae survived. Regarding M. oligolepis, the embryos did not develop, dying at 4:40 post-fertilization. For the hybridization, only the crossbreeding between females of A. bimaculatus and males of M. oligolepis resulted in normal larvae. They presented their own morphological characteristics, showing no total or partial characteristics from the parents, besides presenting atrophied and sterile gonads. Heat waters were proven to compromise the embryonic development of both Amazonian species. On the other side, the hybridization between those two Amazonian species has shown to be a tool with great potential for sterilization and the development of individuals suitable for use as surrogate breeders aiming for the ecological maintenance of various fish species.