Gonadal development and reproductive period of the characin Astyanax aff. bimaculatus (Characiformes: Characidae) in a tropical reservoir in southeastern Brazil

Abstract

The gonadal development of the characin Astyanax aff. bimaculatus from Funil Reservoir, an impoundment in the middle reaches of the Paraiba do Sul River in southeastern Brazil was analysed through histological, histochemical and histometric techniques, and the spawning season was determined. Unbalanced sex ratio was found, with females outnumbering and reaching larger sizes than males. The following stages of oogenic cell development were identified for females: primary growth, pre-vitellogenic (cortical alveolar) and vitellogenic. In males, the following stages were determined: spermatogonia primary and secondary, spermatocyte primary and secondary, spermatid and spermatozoa. The spawning occurs most of the year, peaking in January-February, as indicated by the gonadosomatic index. In the peak of the spawning period, the condition factor and hepatosomatic indices decreased suggesting use of stored body energy reserves during the reproduction. Spawning in batches, small-sized oocytes and a long reproductive season suggest that Astyanax aff. bimaculatus fits to an opportunist strategy. Such strategy may facilitate the use of a wide range of lentic and lotic body waters in the Neotropical region.

Evidence of reproductive disturbance in Astyanax lacustris (Teleostei: Characiformes) from the Doce River after the collapse of the Fundão Dam in Mariana, Brazil

“…Some populations use total reproduction as a strategy to maximize tness, such as the population of A. lacustris in the upper Paraná River basin. Other populations -such as A. bimaculatus, studied by Araújo et al (2019)-presented results, similar to the present study, in a reservoir in Paraíba do Sul in southeastern Brazil Araújo et al (2019). justify this behavior as a way of reducing juvenile predation and competition for food and shelter.…”

“…Species of the Astyanax genus usually have a seasonal breeding strategy, increasing in the rainy season, between spring and summer (Dala-Corte and Azevedo 2010). Gurgel et al (2004) and Araújo et al (2019) reported the same reproductive peak in the summer, coinciding with rainy peaks in the region. These results corroborate the results obtained in the present study.…”

Distribution modeling of Psellogrammus kennedyi (Eigenmann, 1903) and new records in the Lower Paranapanema River, Brazil

“…This allows males to always reproduce, making the release of sperm possible in the most favorable conditions. This reproductive strategy can assist in the colonization of new areas, where different niches in temporal and spatial scales are occupied with different size classes (de Carvalho et al 2009;Agostinho et al 2016;Araújo et al 2019). In addition, P. kennedyi has a laterally depressed body, and its body is taller than several small characiforms which have a fusiform body.…”

Reproduction and fecundity of invader of internal insemination Trachelyopterus galeatus in a Neotropical floodplain

“…This scale has been adopted for investigations of freshwater fish reproduction in Brazil since 2013 for Hoplias malabaricus and Sorubim lima (Quagio-Grassiotto et al, 2013), Pimelodus maculatus and Serrasalmus maculatus (Wildner, Grier, & Quagio-Grassiotto, 2013), and more recently for Hyphessobrycon igneus (Longoni, Giora, & Fialho, 2018), Devario aequipinnatus (Jesus-Silva, Oliveira, Ribeiro, Ninhaus-Silveira, & Veríssimo-Silveira, 2018) Astyanax aff. bimaculatus (Araújo, Nascimento, Gomes, Sales, & Oliveira, 2019) and Rhamdia quelen (Mazzoni, Bombardelli, & Quagio-Grassiotto, 2020).…”