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The Deepwater Horizon oil spill resulted in the release of over 640 million L of crude oil into the Gulf of Mexico, affecting over 2000 km of shoreline, including estuaries that serve as important habitats and nurseries for aquatic species. Cyprinodon variegatus (sheepshead minnow) are small-bodied fish that inhabit northern Gulf of Mexico estuaries, are easily adaptable to laboratory conditions, and are commonly used in toxicological assessment studies. The purpose of the present study was to determine the somatic, reproductive, and developmental effects of an environmentally relevant polycyclic aromatic hydrocarbon (PAH) mixture, the oil high-energy water accommodated fraction (HEWAF), on experimentally exposed sheepshead minnow (F 0 ) as well as 2 generations of offspring (F 1 and F 2 ) without additional exposure. The F 0 generation exposed to HEWAF had increased liver somatic indices, altered egg production, and decreased fertilization. Several developmental endpoints in the F 1 were altered by F 0 HEWAF exposure. As adults, low HEWAF-exposed F 1 females demonstrated decreased weight and length. Both the F 1 and F 2 generations derived from high HEWAF-exposed F 0 had deficits in prey capture compared to control F 1 and F 2 , respectively. Correlations between endpoints and tissue PAHs provide evidence that the physiological effects observed were associated with hydrocarbon exposure. These data demonstrate that PAHs were capable of causing physiological changes in exposed adult sheepshead minnow and transgenerational effects in unexposed offspring, both of which could have population-level consequences. Environ Toxicol Chem 2019;38:638-649. © 2018 SETAC., (© 2018 SETAC.)

The sheepshead minnow (Cyprinodon variegatus) is able to withstand a wide range of salinities. Salinity acclimation involves physiological and biochemical changes, which may influence how organisms respond to a stressor. The present study investigated effects of salinity acclimation on subsequent Cu toxicity. In experiment 1, fish were acclimated to a hyposmotic, isosmotic, or hyperosmotic salinity for 14 d and then exposed at these salinities to 16.6 µM Cu(2+) for 12 h. Survival differed during this Cu challenge; fish acclimated to 2.5 ppt salinity were much more sensitive to Cu than those acclimated to 10.5 or 18.5 ppt seawater. In experiment 2, fish were exposed to 14.6 µM Cu(2+) for 6 h after the 14-d salinity acclimation. Whole-body Cu, whole-body Na, liver lipid peroxidation (LPO), liver catalase activity, and liver glucose levels were determined before and after Cu exposure. Prior to Cu exposure, the acclimation groups differed only for liver glucose levels, which were higher in the 2.5 ppt acclimated fish than in the others. These same 2.5 ppt acclimated fish were markedly affected by Cu, having increased whole-body Cu and liver LPO and decreased whole-body Na levels. Copper exposure had generally insignificant effects for the 10.5 ppt and the 18.5 ppt acclimated fish. This study showed that even in euryhaline fish, salinity acclimation can have a drastic effect on Cu toxicity., (Copyright © 2012 SETAC.)

Estimating long-term effects of endocrine-disrupting chemicals on a species is important to assessing the overall risk to the populations. The present study reports the results of a 42-week exposure of estuarine sheepshead minnows (Cyprinodon variegatus) to the androgen, 17beta-trenbolone (Tb) conducted to determine if partial-(F0) or single-generation (F1) fish exposures identify multigenerational (F0-F3) effects of androgens on fish. Adult F0 fish were exposed to 0.007, 0.027, 0.13, 0.87,and 4.1 microg Tb/L, the F1 generation to < or =0.87 microg Tb/L, the F2 fish to < or =0.13 microg Tb/L, and the F3 fish to < or =0.027 microg Tb/L. The highest concentrations with reproducing populations at the end of the F0, F1, and F2 generations were 4.1, 0.87, and 0.027 microg Tb/L, respectively. Reproduction in the F0, F1, and F2 generations was significantly reduced at 0.87, 0.027, and 0.027 microg Tb/L, respectively. Fish were significantly masculinized in the F1 generation exposed to 0.13 microg Tb/L or greater. Female plasma vitellogenin was significantly reduced in F0 fish exposed to > or =0.87 microg Tb/L. Gonadosomatic indices of the F0 and F1 generations were significantly increased at 0.87 and 0.13 microg Tb/L in the F0 and F1 generation, respectively, and were accompanied by ovarian histological changes. Reproduction was the most consistently sensitive measure of androgen effects and, after a life-cycle exposure, the daily reproductive rate predicted concentrations affecting successive generations. The present study provides evidence that a multiple generation exposure of fish to some endocrine-disrupting chemicals can result in developmental and reproductive changes that have a much greater impact on the success of a species than was indicated from shorter term exposures.

Environmental estrogens can activate genes of the reproductive system, such as vitellogenin (VTG), a precursor to egg yolk protein, by activating the estrogen receptor (ER), whereas antiestrogens can inhibit ER activation. Adult lab-reared male sheepshead minnows (Cyprinodon variegatus) were exposed to estrogenic 4-tert-octylphenol (OP) and females to antiestrogenic cadmium (Cd), and the effects on four potential indicators of impaired reproductive function were examined: VTG in F0 male blood as sign of feminization, F0 generation fecundity/fertility, embryonic development/egg hatching/survival rate of F1 generation fry, and F0 gonadal histology. Mean VTG in the control, 11.5, 33.6, and 61.1 microg/L OP male fish were 0, 10.7, 38.7, and 65.6 mg/ml postexposure and 0, 2.5, 19.4, and 30.0 mg/ml postreproduction. A significant inverse relationship between increasing VTG in male blood and reproductive success of mating groups involving these males was shown, with higher OP decreasing percent viable eggs (fertility) by approximately 60%. Histology showed increased testis anomalies and decreased spermatozoa with increasing OP exposure. No effects on F1 embryonic development, egg hatching, or fry survival rate were observed. A significant decline in percent viable egg production involving Cd-exposed females occurred only when mated with OP-exposed males, with no eggs produced by fish exposed to the highest OP and Cd concentration. A three-week field exposure near a wastewater treatment plant outfall showed no elevated VTG in male plasma, but significantly higher total egg production per female per collection day (approximately 45%) was observed at the site furthest from the outfall.

Resistance heritability (the additive genetic variance out of the total phenotypic variance, signifying a population's potential to genetically adapt to detrimental levels of contamination) was quantified in the sheepshead minnow (Cyprinodon variegatus). Heritability was estimated for tolerance to individual contaminants (phenanthrene, zinc) and to contaminant mixtures (phenanthrene plus zinc, and a complex mixture with three metals and three polycyclic aromatic hydrocarbons). Estimates were obtained from resemblances between relatives, both parent-offspring pairs, and families of sibs and half-sibs. Heritabilities determined from parent-offspring regressions averaged only 0.08 (scale, 0-1), whereas resemblance among full sibs yielded heritabilities averaging 0.85. The half-sib analysis yielded heritabilities of -0.01 (sire component) and 0.77 (dam component). This pattern in the magnitude of heritabilities indicates that heritabilities for the resistance of C. variegatus to these chemicals are low (with the high resemblances among sibs being due to common environmental and dominance genetic variation rather than additive genetic variation). The parent-offspring regressions provide evidence that heritabilities may be lower if more contaminants are involved. Our results mean, then, that C. variegatus in contaminated environments is not likely to become resistant to these contaminants very rapidly, and that resistance may develop even more slowly as more contaminants become involved.

Methylmercury (CH3Hg(II)) was measured in various tissues and whole body of sheepshead minnows; Cyprinodon variegatus, following exposure to 100 ng/L methylmercury chloride (CH3HgCl) alone or in combination with one of the organic compounds cysteine (CH3Hg-Cys), thiourea (CH3Hg-Thu), or thioglycolate (CH3Hg-Thg). Overall, the CH3Hg(II) concentration in sheepshead minnows in all the treatments increased with time and was significantly different from the unspiked controls after 24 h. Addition of the organic compounds increased the bioavailability of CH3Hg(II) in the whole body of the fish after 72 h. In particular, the CH3Hg(II) concentration after CH3Hg-Thg and CH3Hg-Thu exposure was, respectively, approximately 1.3- and 1.6-fold higher than with CH3HgCl exposure. A composite of the CH3Hg(II) concentrations in the visceral organs (gill, liver, and intestine) highlighted the effect of the organic compounds, where concentrations in all mercury-thiolate treatments were significantly higher than CH3HgCl alone after 72 h. The most dramatic changes in the different tissues measured were observed in the liver, where the CH3Hg(II) concentrations in the sulfur treatments were significantly higher than the CH3HgCl treatment after 72 h. The results of this study suggest that the CH3Hg-thiolate complexes were bioavailable to sheepshead minnows and effectively induced CH3Hg(II) uptake in tissues at environmentally realistic CH3HgCl concentrations.

Changes to indicators of reproductive performance have been documented in fish exposed to some bleached kraft pulp mill effluents (BKPMEs). However, responses are not consistent across mill types or processes. It is not clear where the sources of the effects are within mills, what the causative compounds are, or what process changes are effective to remove these sources. Our previous studies suggested that condensates were a source of compounds that reduced plasma testosterone in the mummichog (Fundulus heteroclitus). Results also suggested that reverse osmosis (RO) treatment of condensates removed this source. The objective of this study was to use a toxicity identification evaluation approach and expose mummichog to various waste streams in the laboratory to identify the effluent source that depressed plasma testosterone in the mummichog and the effects of RO treatment. In 7- and 21-d exposures, mummichog were exposed to dilutions of RO feed condensate, RO permeate, combined mill effluent (CME), and final effluent. Results confirmed that condensates depressed plasma testosterone in mummichog. Chemical characterization of the condensate indicated that plant phytosterols were likely not the responsible compounds. Results also confirmed that RO treatment removed the potential of the condensates to depress plasma testosterone in mummichog at environmentally relevant concentrations of final mill effluent (1%).

This research determined the potential for methylmercury or Aroclor 1268 to disrupt reproduction and sexual differentiation in Fundulus heteroclitus. The research determined whether fish that are exposed to mercury or Aroclor 1268 survive and successfully reproduce; whether offspring of exposed fish hatch, survive, produce eggs, and fertilize them; and whether the second-generation offspring of exposed fish hatch and survive. Fundulus heteroclitus were exposed to mercury or Aroclor 1268 via contaminated food. Endpoints evaluated included survival, growth, fecundity, fertilization success, hatch success, larval survival, sex ratios, and the prevalence of gonadal abnormalities. In general, polychlorinated biphenyls were highly bioavailable and accumulated well through feeding. The only statistically significant effect observed as a result of treatment with Aroclor 1268 was an increase in growth in the offspring of exposed fish. Mercury was accumulated in a dose-dependent fashion via food exposures. Exposure to mercury in food increased mortality in male F. heteroclitus, which possibly occurred as a result of behavioral alterations. Increased mortality was observed at body burdens of 0.2 to 0.47 microgram/g. Offspring of F. heteroclitus fed mercury-contaminated food were less able to successfully reproduce, with reduced fertilization success observed at egg concentrations of 0.01 to 0.63 microgram/g, which corresponds with parent whole-body concentrations of 1.1 to 1.2 micrograms/g. Offspring of exposed fish also had altered sex ratios, with treatment at moderate concentrations producing fewer females and treatment at the highest concentration producing more females than expected. Alterations in sex ratios were observed at concentrations of less than 0.01 microgram/g in eggs or between 0.44 and 1.1 micrograms/g in parents. Offspring of mercury-exposed fish also had increased growth in moderate treatments, when egg concentrations were less than 0.02 microgram/g, or when parent whole bodies contained 0.2 to 0.47 microgram/g. In summary, exposure to mercury reduced male survival, reduced the ability of offspring to successfully reproduce, and altered sex ratios in offspring. Both direct effects on exposed fish and transgenerational effects were observed.