Male Sunfish Research Articles

Linking Trace Organic Contaminants in On-Site Wastewater-Treatment Discharge with Biological Effects.

Around the globe, on-site wastewater-treatment systems (OWTSs) are critical for rural communities without access to a municipal sewer system. However, their treatment efficiency does not match that of modern wastewater-treatment plants. The impact of OWTS discharge on nearby aquatic ecosystems and their resident fish species is poorly understood. In the present study, larval and adult fathead minnows (Pimephales promelas) and adult sunfish (Lepomis macrochirus) were exposed for 21 days to two trace organic contaminant (TOrC) mixtures replicating water chemistry derived from a previous environmental study. Larval fathead minnows were assessed for survival, growth, predator avoidance, and feeding efficiency. Adult fathead minnows and sunfish were assessed for a suite of physiological endpoints (condition indices, vitellogenin, glucose), histological changes, and fecundity. The only observed effect of TOrC mixture exposure on larval fathead minnows was a decrease in feeding efficiency. Effects were mixed in exposed adult fishes, except for male sunfish which realized a significant induction of vitellogenin (p < 0.05). The consequences of TOrC mixture exposure in the present controlled laboratory study match effects observed in wild-caught sunfish in a corresponding field study. The present study begins to bridge the gap by connecting nonpoint OWTS pollution with biological effects observed in resident lake fish species. Given the effects observed despite the brevity of the laboratory mixture exposure, longer-term studies are warranted to understand the full impacts of OWTS discharge to nearby aquatic ecosystems. Environ Toxicol Chem 2021;40:3193-3204. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Prioritizing potential endocrine active high resolution mass spectrometry (HRMS) features in Minnesota lakewater

Liquid chromatography high-resolution mass spectrometry (LC-HRMS) shows great potential for expanding our understanding of relevant unknown chemical components present within complex environmental mixtures. This study identified potentially endocrine active components within Minnesota lakewater by prioritizing LC-HRMS features uniquely present at sunfish spawning habitats where male fish showed signs of estrogen agonism. Porewater samples from four locations within the same lake were analyzed using liquid chromatography quadrupole time of flight mass spectrometry (LC-QToF/MS) with positive (ESI+) and negative (ESI−) electrospray ionization. Plasma vitellogenin concentrations of captured male sunfish was used to designate sites as either endocrine active (ACT; 2 sites) or reference (REF; 2 sites). Assuming unique chemical presence at active sites contributed to endocrine activity, features at significantly higher intensities (p-value < 0.05, t-value > t-critical, log-fold change > 0.1; equal variance t-test of log2 transformed data) in ACT sites were then compiled into a suspect search list for feature identification. Adducts and isotopes of prioritized features were deprioritized using pattern recognizing algorithms using mass, retention time, and intensity. Feature identities were reported according to established confidence metrics using spectral libraries and elemental composition algorithms. This LC-HRMS approach identified a number of features omitted by targeted analysis with higher relative abundances in ACT sites, including plant essential oils, fatty acids, and mycotoxins. Multivariate analysis determined whether features were either present at both sites (AB) or unique to individual ACT sites (A or B). Detection frequency across datasets indicated bias in feature prioritization influenced by the chosen sampling method and sample acquisition mode. The majority of features prioritized by this workflow remain tentatively identified or unidentified masses of interest, reflective of current limitations in shared spectral libraries for soft ionization analyses. Strategies similar to this workflow have the potential to reduce bias in database-driven toxicological prioritization frameworks.

Trace organic contaminant (TOrC) mixtures in Minnesota littoral zones: Effects of on-site wastewater treatment system (OWTS) proximity and biological impact

On-site wastewater treatment systems (OWTSs) are an international wastewater management strategy for rural and semi-rural communities without access to centralized sewage treatment. These systems are a suspected source of trace organic contaminants (TOrCs) that may be responsible for endocrine disrupting effects to resident fish species in Minnesota Lakes. This study assessed localized porewater concentrations of TOrCs in near-shore environments across five Minnesota Lakes. Sampling sites were designated as either likely (HOME) or unlikely (REF) to receive OWTS discharges based on their proximity to shoreline households. Sampling sites also served as sunfish spawning habitats concurrently studied for biological impacts to resident adult males. Two-group hypothesis tests demonstrated significantly (p = .02) higher total TOrC concentrations in HOME (Mean = 841 ng/L) versus REF (Mean = 222 ng/L) sites. HOME sites also contained a wider suite of TOrC detections relative to REF sites. The distance to the nearest household (most proximal distance; MPD) negatively correlated (r = −0.62) with total TOrC concentrations. However, 2,4-D and DEET were major contributors to these total concentrations, suggesting that anthropogenic influence from households may not be exclusively attributed to OWTS discharges. Further, TOrC presence and elevated nitrogen concentrations in REF site porewater suggest additional, non-household TOrC discharges to these lakes. Significantly higher blood concentrations of vitellogenin (p = .03) and 11-ketotestosterone (p = .01) were observed in adult male sunfish captured from HOME versus REF sites. Comparisons between chemical and biological data indicate enhanced bioactive effects of co-contaminants. The findings from this study demonstrate multiple diffuse transport pathways contribute to the presence of biologically active TOrC mixtures in Minnesota Lakes, and mitigation efforts should consider minimizing residential inputs of chemicals associated with both outdoor and OWTS activity.

Treated municipal sewage discharge affects multiple levels of biological organization in fish

The objectives of this study were to examine cellular-, organ-, and organism-level responses in longear sunfish ( Lepomis megalotis) and fish community structure in a stream in which treated municipal sewage effluent is discharged and in a nearby reference stream with little surrounding land use. A modified version of the U.S.E.P.A. Rapid Bioassessment Protocol V, which combines a habitat assessment with Karr's index of biotic integrity, was used on 400-m reaches of each stream. The study site had a higher proportion of tolerant species and omnivores and a lower proportion of top predators, suggesting alterations in the fish community and a slight level of water quality impairment. Significant increases in condition factor, hepatosomatic index, serum testosterone, and plasma vitellogenin concentrations were observed in male sunfish collected from the study stream in comparison to fish collected from the reference stream. There were no differences between sites in hepatic expression of the 70-kDa stress protein (HSP70). In conclusion, effects were observed at cellular, organ, organism, and community levels of biological organization in fishes exposed to treated municipal sewage effluent.

Alternative Mating Tactics in Sunfishes (Centrarchidae): A Mechanism for Hybridization?

Lepomis hybridization occurs frequently in natural systems. Previous investigations of sunfish hybridization have focused on courtship behavior of interspecific pairs. We observed spawning in Lepomis nesting colonies where interspecific nest intrusions occurred. Nesting male Lepomis microlophus (redear sunfish) attempted to fertilize eggs in the adjacent nests of spawning Lepomis megalotis (longear sunfish). Male sunfish commonly employ this reproductive tactic in the nests of conspecifics. When colonies contain more than one species, hybridization may occur through interspecific nest intrusion by males on adjacent nests.

Reproductive investment and somatic growth rates in longear sunfish

Allocation of energy to current reproduction at the expense of other functions, such as growth, can limit future reproductive potential. This cost of reproduction is a central concept of life history theory but has been difficult to verify in comparative field studies. Three levels of comparison of growth rates and reproductive investments were evaluated within and among populations of longear sunfish,Lepomis megalotis. All three demonstrated high levels of reproductive investment associated with reduced somatic growth. Within populations of central longear sunfish there are precociously mature sneaker makes and later maturing parental makes; sneakers have greater gonadosomatic index (GSI) values and slower somatic growth rates than parental makes. Between subspecies of longear sunfish grown under common conditions, there are differences in age at maturity and in the level of physiological reproductive investment that are associated with distinct differences in growth rates. Between populations of central longear sunfish inhabiting different sites, there are differences in the level of reproductive investment that are also associated with differences in somatic growth. Each comparison produced evidence that trade-offs occur between these life history traits, supporting the hypothesis that there is a cost of reproduction among male sunfish and suggesting that differences in strategies of reproductive investment contribute to variation in somatic growth.

Neuroanatomical substrates of reproductive behavior in male sunfish (Genus Lepomis)

Neuroanatomical substrates of reproductive behavior in male sunfish (Genus Lepomis)