Optimization of effects‐assessment of greenside darter (Etheostoma blennioides) exposed to tertiary treated municipal wastewater based on seasonal changes of reproductive endpoints

Abstract

The present study describes the seasonal changes in reproductive endpoints of the greenside darter (Etheostoma blennioides) and its implications for environmental monitoring. Fish collections conducted at the appropriate time for the site-specific sentinel fish species can provide a wide variety of population-level information including recruitment, reproduction, and energy storage. The objectives of the present study were to: 1) characterize seasonal changes in reproductive endpoints of the greenside darter (both sexes) to determine the appropriate period for monitoring of this sentinel species; and 2) evaluate the effect of exposure of this sentinel species to tertiary treated municipal effluent at the selected monitoring period. Based on the selected parameters (gonadosomatic index [GSI], liver somatic index [LSI], condition factor, and in vitro gonadal steroid production [testosterone (T) in both sexes; estradiol (E2) in females; and 11-ketotestosterone (11KT) in males]), the present study provides evidence for the value of collecting darters during recrudescence (late fall/early winter) to ensure temporal stability, minimum variability, and stable steroid production capacity. Darters exposed to tertiary treated municipal effluent tended to be larger and heavier relative to reference fish but did not demonstrate any consistent responses in terms of condition or relative liver size. No effect on gonadal development was observed, even though these tertiary-effluent-exposed fish demonstrated a significant reduction in the ability to produce hormones. The present study suggests that although fish exposed to tertiary treated effluent demonstrate no population-level effects, they are still responding at a physiological level. Documentation of the reproductive cycle of sentinel species allows for selection of the most appropriate sampling period to reduce variability and greatly enhances the reliability and interpretation of biological responses.

Characterizing Transcriptional Networks in Male Rainbow Darter (Etheostoma caeruleum) that Regulate Testis Development over a Complete Reproductive Cycle

“…In this study, we examined 5 defined stages of the male reproductive cycle at the molecular level in order to better understand the mechanisms underlying testis development. The somatic indexes evaluated (k, GSI and LSI) showed expected patterns as previously reported by Tetreault in 2013 [23], confirming that the wild fish collected for the molecular analysis had the expected somatic changes over the year of monitoring. Noteworthy was that we observed the same pattern of change between the LSI and the gene cluster 4, suggesting that genes in that cluster are related to LSI.…”

Whole organism responses and intersex severity in rainbow darter (Etheostoma caeruleum) following exposures to municipal wastewater in the Grand River basin, ON, Canada. Part A

“…These males also had significantly lower male steroid production (in vitro) compared to reference males, but steroid production did not differ between males with intersex and normal males exposed to MWWEs at the same site, suggesting a dominant site effect. In previous studies, there have been positive correlations between circulating levels of steroids and in vitro basal production measurements, and in vitro have often been used as surrogates when using small bodied species (McMaster et al, 1995a;Villeneuve et al, 2009;Tetreault et al, 2014). Stimulated levels of in vitro production provide a measure of the capacity of the gonads to produce steroids and are often used as a measure of the functioning of the gonad tissue (Van Der Kraak et al, 1992;McMaster et al, 1995b).…”

Assessing recovery of in vitro steroid production in male rainbow darter (Etheostoma caeruleum) in response to municipal wastewater treatment plant infrastructure changes

“…The recrudescence period starts in mid‐September and continues to January. A study conducted in the Grand River on a related species, the greenside darter ( Etheostoma blennioides ), showed that production of sex steroids was consistent and stable during the recrudescence period (October–January) and suggested that the fall season is appropriate for sampling and measuring in vitro sex steroid production (Tetreault et al ) in that species. In the present study, it was confirmed that the fall season is an appropriate time for conducting the in vitro androgen production bioassay with the rainbow darter because this species goes through recrudescence in this period of the year, which allows for detection of relatively stable levels of androgen production.…”

“…We focused on the production of sex steroids because this reflects the culmination of effects at multiple sites in the hypothalamic pituitary gonadal axis. The quantification of sex steroids at different stages of the reproductive cycle can be a powerful biomarker indicative of stress‐induced perturbations in the reproductive process (Tetreault et al ; Donaldson ). Small alterations in steroid production have the potential to be translated into important changes at higher levels of biological organization in both males and females.…”