Population structure of two freshwater amphipods (Crustacea: Peracarida: Hyalellidae) from southern Brazil

Abstract

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Population and reproductive traits of a freshwater amphipod (Crustacea, Peracarida, Hyalellidae) from northwest of the state of Rio Grande do Sul, Brazil

“…The sex ratio of H. palmeirensis favored females in intermediary classes and males in the upper classes, which characterizes an anomalous sex ratio pattern (Wenner 1972). Similar results were found in other species of Hyalella from Brazil (Castiglioni & Bond-Buckup 2008a;Castiglioni et al 2016;Ozga et al 2018). These results could be related to the same reasons used to explain sexual dimorphisms in relation to body size.…”

“…This feature may be related to the seasonal reproduction and, consequently, to the recruitment peaks in the population. This pattern of population frequency distribution is common in other species of Hyalella such as H. azteca (Pickard & Benke 1996), H. pleoacuta and H. castroi (Castiglioni & Bond-Buckup 2008a), H. bonariensis (Castiglioni et al 2016) and H. georginae and H. gauchensis (Ozga et al 2018). According to Appadoo & Myers (2004), bimodal distributions are apparently advantageous since recruitment occurs in warmer months, when food availability is higher, increasing the survival rate.…”

“…Females of H. palmeirensis are almost 5 times more frequent than males in total and in most months of the year. Sexual deviations in favor of females have already been observed in H. pleoacuta and H. castroi (Castiglioni & Bond-Buckup 2008a), H. bonariensis (Castiglioni et al 2016), H. longistila (Bastos-Pereira & Bueno 2016), H. georginae and H. gauchensis (Ozga et al 2018). Deviations in sex ratio appear to be related to reproductive behavior of species of Hyalella, because males spend more time exposed in the environment by choosing, holding and carrying the female and thus the males are more susceptible to predators (Moore 1981;Poweel & Moore 1991;Wellborn 1994;Wellborn & Cothran 2007;Kevrekids 2005;Castiglioni & Bond-Buckup, 2008b;Castiglioni et al, 2016).…”

Potential of A Trait-Based Approach in the Characterization of An N-Contaminated Alluvial Aquifer

“…Trait#4 highlighted that the sex ratio departed from 1 and was equal to 0.38 in favor of females. In diploid populations, sex ratio is usually equal to 1 [83,84], however, surface water populations' sex ratio tends to be skewed as result of seasonality, environmental conditions, and contamination level [54][55][56].…”

“…We analyzed these traits since previous studies have demonstrated that they are reliable indicators of impairment of groundwater communities, with particular references to organic contamination. In detail: i) groundwater assemblages dominated by non-crustacean taxa and a high nSB/SB ratio should be considered impaired [34]; ii) the sex ratio of some populations of copepods may be skewed in favor of female individuals in impaired water bodies [54][55][56]; iii) the development of juvenile copepods is slowed down in populations exposed to ammonium with respect to control populations [57]; and the survival of copepodids under N-compound exposure is significantly lower than that of adult individuals of the same species [58]. Finally, we analyzed the biomass because its relationship with abundances provides key information about community impairment [49,50].…”