Female reproductive impacts of dietary methylmercury in yellow perch (Perca flavescens) and zebrafish (Danio rerio)

Abstract

The purpose of this study was to evaluate the effects of environmentally relevant dietary MeHg exposures on adult female yellow perch (Perca flavescens) and female zebrafish (Danio rerio) ovarian development and reproduction. Yellow perch were used in the study for their socioeconomic and ecological importance within the Great Lakes basin, and the use of zebrafish allowed for a detailed analysis of the molecular effects of MeHg following a whole life-cycle exposure. Chronic whole life dietary exposure of F zebrafish to MeHg mimics realistic wildlife exposure scenarios, and the twenty-week adult yellow perch exposure (where whole life-cycle exposures are difficult) captures early seasonal ovarian development. For both species, target dietary accumulation values were achieved prior to analyses. In zebrafish, several genes involved in reproductive processes were shown to be dysregulated by RNA-sequencing and quantitative real-time polymerase chain reaction (QPCR), but no significant phenotypic changes were observed regarding ovarian staging, fecundity, or embryo mortality. Yellow perch were exposed to dietary MeHg for 12, 16, or 20 weeks. In this species, a set of eight genes were assessed by QPCR in the pituitary, liver, and ovary, and no exposure-related changes were observed. The lack of genomic resources in yellow perch hinders the characterization of subtle molecular impacts. The ovarian somatic index, circulating estradiol and testosterone, and ovarian staging were not significantly altered by MeHg exposure in yellow perch. These results suggest that environmentally relevant MeHg exposures do not drastically reduce the reproductively important endpoints in these fish, but to capture realistic exposure scenarios, whole life-cycle yellow perch exposures are needed.

Alterations to the Intestinal Microbiome and Metabolome ofPimephales promelasandMus musculusFollowing Exposure to Dietary Methylmercury

“… , However, it is important to reiterate that these concentrations are representative of fish muscle concentrations found in freshwater ecosystems in North America. ,,, The amount of dietary Hg female FHM transfer to eggs is small and resulted in WW Hg concentrations in exposed larvae that were roughly 0.04 μg/g higher than those of controls ( n = 7 clutches/treatment, Table S1). ,, Nevertheless, the results reported herein add to the body of evidence indicating this rate of transfer is sufficient to induce developmental toxicity in several species of teleosts. ,,− …”

Transcriptomic Points of Departure Calculated from Rainbow Trout Gill, Liver, and Gut Cell Lines Exposed to Methylmercury and Fluoxetine

“…Overall, the enriched pathways were related to various functions including stress response (adenosine monophosphateactivated protein kinase signaling pathway, FoxO signaling pathway), synthesis and metabolism of biomolecules (glutathione, carbohydrates, steroids), promotion of cell growth, proliferation, and metabolism (PI3K-Akt signaling pathway), DNA repair, mineral absorption, immune response (cytokine-cytokine receptor interaction and antigen processing and presentation), muscle contraction (regulation of actin cytoskeleton), fatty acid and energy metabolism (fatty acid elongation, carbon metabolism), and cell death (apoptosis, ferroptosis, necroptosis). These pathways have similarly been identified in previous transcriptomic studies concerning methylmercury exposure in fish species including rainbow trout (Liu et al, 2013), zebrafish (DeBofsky et al, 2018;Hausen et al, 2018;Zhu et al, 2019), Atlantic cod (Yadetie et al, 2013), and European cusk (Olsvik et al, 2021). Furthermore, an overall examination of the Comparative Toxicogenomic Database (CTD; North Carolina State University, 2022) showed that many of these same pathways were dysregulated in response to exposure to methylmercury compounds (i.e., the top three were metabolism, immune system, and signal transduction).The significantly enriched pathways with the lowest BMD values (i.e., those with pathway BMD values below 10 ppb) included those involved in mineral absorption, metabolism, and biosynthesis (e.g., glutathione metabolism and steroid biosynthesis), and ferroptosis.…”

Nutritional quality of different starches in feed fed to juvenile yellow perch, Perca flavescens

“…Stained slides were digitally scanned for analyses using Nano Zoomer digital pathology system (Hamamatsu Photonics K.K.). To determine the number of clearly visible hepatocytes, hepatocyte diameter and number of Kupffer cells, a 10,000 mm 2 area of similar location on each serial section was identified (Debofsky et al, ; Kovi et al, ). Digital measurements of hepatocyte diameters were accomplished using NDPview2 desktop software package (v. 2.6.13, Hamamatsu Photonics).…”

“…The following parameters were determined on 100 μl serum for each sample: albumin, alkaline phosphatase, alanine aminotransferase, amylase, calcium, globulin, glucose, total bilirubin, inorganic phosphorus and total protein. identified (Debofsky et al, 2018;Kovi et al, 2011). Digital measurements of hepatocyte diameters were accomplished using NDPview2 desktop software package (v. 2.6.13, Hamamatsu Photonics).…”