Morphological and temporal variations in the gametogenic development of the killifish Melanorivulus rossoi (Cyprinodontiformes, Rivulidae) in an area under crop influence

Abstract

Abstract Melanorivulus rossoi has a restricted distribution and, due to land modifications for agricultural use, may be on the verge of extinction. So, understanding its gametic development and reproductive cycle can expand the knowledge of the species and possible reproductive and/or ecological interventions. Specimens were collected in swamps adjacent to crop areas in Campo Grande, Mato Grosso do Sul, Brazil. Individuals were fixed in Karnovsky's solution, gonadal samples were extracted and submitted to the histological preparation protocol. 221 individuals were analyzed, with the highest abundance of individuals collected from February to August. Larger fish were observed in the last months of the year, especially in November, while the smallest ones were collected in June. For females, all individuals presented ovarian follicles in different periods of maturation and gonadal differentiation. The same was observed for males, with constant proportions of spermatic cells. Thus, for M. rossoi, it has been found that the production of gametic cells in both male and female gonads is constant, characterizing a synchronous cell development in males and females. The data observed for Melanorivulus rossoi compared to M. punctatus, previously studied by our research group, showed that despite the species being related, the gametogenesis data have some differences.