Abstract
Abstract The study of population and reproductive traits provides information about the ecological structure of natural populations. This study aimed to characterize dynamics and reproductive traits of Hyalella palmeirensis from a natural pond from southern Brazil. The amphipods were sampled monthly (August 2012 to July 2013) by a person with the aid of a hand net for 20 minutes. Ovigerous females and pre-copulatory pairs were individualized in the field. A total of 12,325 individuals were sampled, being 1,421 males, 6,983 females (including 215 ovigerous females) and 3,921 juveniles. Paired and unpaired males were significantly greater in size than females. There was a positive correlation between body size (CL) of paired males and females. Males and females showed bimodal distribution. Total sex ratio favored females, and these were more frequent in almost all months. Ovigerous females and precopulatory pairs were found throughout the year, but with high frequency in winter and autumn, respectively, characterizing a seasonal reproduction. Juveniles were sampled throughout the year, with greater intensity in the spring. The mean fecundity was 19.6 ± 4.34 eggs. No reduction in the number of eggs was observed during embryonic development. The results observed in H. palmeirensis demonstrate that this species has a population and reproductive dynamics very similar to other species of Hyalella already analyzed in southern Brazil. Moreover, it can be seen that although the H. palmeirensis occurs in an environment with anthropic influence (soy cultivation,) the population is managing to remain in the area, with reproduction and recruitment in most months of year.
Highlights
Características populacionais e reprodutivas de um anfípodo de água doce (Crustacea, Peracarida, Hyalellidae) do noroeste do estado do Rio Grande do Sul, Brasil
There was a positive correlation between body size (CL) of paired males and females (r= 0.73; p
There was a positive correlation between body size (CL) of ovigerous females and egg production (r= 0.79; p
Summary
Características populacionais e reprodutivas de um anfípodo de água doce (Crustacea, Peracarida, Hyalellidae) do noroeste do estado do Rio Grande do Sul, Brasil. Fêmeas ovígeras e casais em pré-cópula foram amostrados ao longo do ano, mas com elevada frequência no inverno e outono, respectivamente, caracterizando uma reprodução sazonal. Ecological studies of the Hyalella genus in South America are mainly focused on the abundance, body size, sex ratio, reproduction, fecundity, recruitment and, pairing success (Lopretto 1983; Casset et al 2001; Poretti et al 2003; Galassi et al 2006; Castiglioni & BondBuckup 2007, 2008a, 2008b, 2009; Castiglioni et al 2007; Torres et al 2015; Bastos-Pereira & Bueno 2016a, 2016b; Castiglioni et al 2016; Ozga & Castiglioni 2017; Ozga et al 2018; Colla & César 2019). This study aimed to characterize the population and reproductive traits of the freshwater amphipod H. palmeirensis from southern Brazil, and for this the abundance, body size, frequency distribution, body size, sexual maturity, sex ratio, reproductive period, fecundity and recruitment were analyzed
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