Biologia reprodutiva do Peixe Voador Hemiodus unimaculatus na Vila Tauiry, área de influência da Usina Hidrelétrica de Tucuruí - PA

Abstract

This study compiles information on the ecological and reproductive aspects of the flying fish Hemiodus unimaculatus in the area influenced by the Tucuruí Hydroelectric Power Plant (PA, Brazil). The literature review showed that this species, a member of the family Hemiodontidae, has a wide distribution throughout the Amazon basin and exhibits remarkable trophic plasticity. Previous studies indicate that, prior to river impoundment, its diet was predominantly detritivorous and periphytic. After the formation of the reservoir, it began to display more diversified feeding habits, including omnivorous strategies. Additionally, changes in the average body size of individuals and a reduction in relative frequency in sampling surveys were observed, suggesting significant effects of damming on the local population. From a reproductive perspective, the species reaches first sexual maturation between 11 and 15 cm and exhibits an extended reproductive period from October to April, associated with the seasonality of the Amazonian flood pulse. A predominance of females has been recorded, a strategy that may maximize reproductive success but raises concerns regarding the potential reduction of genetic diversity. In Chapter 2, the histological analysis of spermatogenesis revealed testes with an anastomosed tubular pattern, typical of Characiformes, and cystic spermatogenesis characterized by synchronized development of germ cells. Four types of spermatogonia, different meiotic stages, three types of spermatids, and type III spermiogenesis were described, evidencing a continuous process of gamete production. The spermatozoa exhibited a rounded head and a long flagellum, a conformation adapted to external fertilization in aquatic environments. These findings reinforce the importance of understanding the reproductive biology and ecology of the species, providing essential support for management and conservation strategies in the face of pressures from impounded environments and hydrological modifications imposed by Amazonian dams.