Food rationing affects dietary selenium bioaccumulation and life cycle performance in the mayfly Centroptilum triangulifer

Abstract

Selenium effects in nature are mediated by the relatively large bioconcentration of aqueous Se by primary producers and smaller, yet critical, dietary transfers to primary consumers. These basal processes are then propagated through food webs to higher trophic levels. Here we quantified the movement of dissolved Se (as selenite) to periphyton, and used the resultant periphyton as a food source for conducting full life-cycle dietary Se exposures to the mayfly Centroptilum triangulifer. Periphyton bioconcentrated Se ~2,200-fold from solution in a log-linear fashion over dissolved Se concentrations ranging from 1.1 to 23.1 μg L(-1). We examined the influence of two feeding ration levels (1x and 2x) on trophic transfer, tissue Se concentrations, maternal transfer, and functional endpoints of mayfly performance. Mayflies fed a lesser ration (1x) displayed greater trophic transfer factors (mean TTF, 2.8 ± 0.4) than mayflies fed 2x rations (mean TTF, 1.1 ± 0.3). In 1x exposures, mayflies exhibited significant (p < 0.05) reductions in survivorship and total body mass at dietary [Se] ≥ 11.9 μg g(-1), reduced total fecundity at ≥ 4.2 μg g(-1), and delayed development at ≥ 27.2 μg g(-1). Mayflies fed a greater ration (2x) displayed reduced tissue Se concentrations (apparently via growth dilution) relative to 1x mayflies, with no significant effects on performance. These results suggest that the influence of Se on mayfly performance in nature may be tied to food resource availability and quality. Furthermore, nutritional status is an important consideration when applying laboratory derived estimates of toxicity to risk assessments for wild populations.

Periphyton uptake and trophic transfer of coal fly‐ash–derived trace elements

“…Tissue Se concentrations in N. triangulifer were 0.91‐ to 2.19‐fold (mean = 1.55 ± 0.29) higher than their dietary Se concentrations. These 7‐d values are slightly lower than the trophic transfer factors determined from whole‐life cycle studies (1.2–4.7 fold; Conley et al ), because both periphyton treatment durations and mayfly exposure durations were considerably shorter in our experiment. A likely reason for differences in Se mayfly accumulation (when fed oxic‐ or anoxic‐treated periphyton) may be the speciation of periphyton Se, which we did not measure.…”

Assessing Different Mechanisms of Toxicity in Mountaintop Removal/Valley Fill Coal Mining-Affected Watershed Samples Using Caenorhabditis elegans

“…Though the toxic effects of the metalloid selenium in aquatic invertebrates are well-documented [6,33-35], there is considerably less published work on the toxicity of selenium to nematodes. The mechanism of toxicity of selenium in nematodes is not well studied, though oxidative stress-induced cholinergic neurodegeneration has been demonstrated [36].…”

Physiological responses to short-term thermal stress in mayfly (Neocloeon triangulifer) larvae in relation to upper thermal limits

“…This parthenogenetic species (see Funk et al, 2006) has emerged as a useful laboratory model for ecological (Sweeney and Vannote, 1984) and physiological/toxicological studies (Sweeney et al, 1993;Conley et al, 2009Conley et al, , 2011Conley et al, , 2013Conley et al, , 2014Kim et al, 2012;Kunz et al, 2013;Soucek and Dickinson, 2015;Xie et al, 2010;Xie and Buchwalter, 2011;Johnson et al, 2015). We established chronic upper thermal limits by rearing newly hatched eggs to adulthood across several temperatures.…”