Reproductive strategies in two inseminating species of Glandulocaudini, Mimagoniates microlepis and Mimagoniates rheocharis (Characiformes: Characidae: Stevardiinae)

Abstract

The reproductive biology of two inseminating Glandulocaudini species, Mimagoniates microlepis and Mimagoniates rheocharis, was investigated and compared with reproductive patterns described for other inseminating and non-inseminating characids, hypothesizing the evolutionary history of these reproductive traits. The long reproductive period, with higher activity in colder months, distinguishes the reproductive strategy of these species when compared with most characiforms. The M. rheocharis population was structured in two groups of males throughout the year, mature males with high gonado-somatic index (IG = 2·0 and 4·4) and immature and maturing males with low IG values (0·0 and 1·2). Mimagoniates rheocharis and M. microlepis showed the lowest absolute mean fecundities known for characids, indicating that inseminating species allocate less energy to oocyte production and reinforcing the hypothesis that insemination has an adaptive advantage, which provides a higher chance of fertilization.

Fishes from Parque Estadual de Itapeva, Rio Grande do Sul state, Atlantic Forest biome, Brazil

“…Mimagoniates microlepis (Steindachner, 1877) Table 2 Mimagoniates rheocharis Menezes & Weitzman, 1990: Figure 3G Mimagoniates rheocharis Menezes & Weitzman (1990) Table 2 It may be distinguished from the sympatric species Mimagoniates microlepis by the smaller number of branched anal-fin rays (usually 24-26 versus 28-31), larger number of scale rows between dorsal-and anal-fin origins (17-22 versus 14-17), and smaller number of scale rows around caudal peduncle (19-23 versus 15-18). Additionally, according to Azevedo et al (2016), M. rheocharis and M. microlepis have the lowest absolute mean fecundity known for characids, indicating that inseminating species allocate less energy to oocyte production and reinforcing the hypothesis that insemination has an adaptive advantage, which provides a higher chance of fertilization. Category "Near Threatened" (NT) according to State Decree 51.797/ 2014.…”

Ficha de Mimagoniates rheocharis

“…Dados levantados por Becker (2002), especificamente na bacia do rio Maquiné, permitem afirmar que as regiões de fundo de vale e base da encosta foram aquelas onde houve maior perda e alteração das formações florestais originais, com a modificação das características gerais dos riachos como hábitats para peixes, tendo sido afetados desde o sombreamento e aporte de material alóctone (de fora do rio) até o regime hidrológico. Ao longo do estudo de Azevedo (2000), foi possível constatar que o lambari-azul desaparece mais rapidamente do que outros peixes em ambientes sujeitos a pequenas alterações de qualidade da água, principalmente devido à deposição de matéria orgânica. Adicionalmente, dois locais onde a espécie ocorria foram impactados por efluentes oriundos da suinocultura e da criação doméstica de patos e galinhas (M.…”