Embryonic and larval development of yellow perch (Perca flavescens) and its sensitivity to incubation temperature.

The ontogenetic development in teleost fish is sensitive to temperature, and the developmental rate has a direct relationship with the environmental temperature within a species' thermal tolerance limit. Temperature determines time to and survival at hatching. Yellow perch is a North American species of ecological and commercial importance, and its phenology is vulnerable to climate change. The embryonic development of yellow perch was comparable to closely related members of the family Percidae. Developmental progression was fastest at 18°C and slowest at 12°C, with medial progression at 15°C. Time to hatch and swim-up, feeding onset, and exogenous feeding phases were different across all incubation temperatures regardless of a gradual post-hatch warming of the 12 and 15°C groups to a common garden temperature of 18°C. Incubation temperature may lower the rate of survival to hatch at 15°C and had complex impacts on developmental abnormalities. Temperature had significant effects on the development rate, time of hatch, survival, and incidence of developmental abnormalities. Early ontogenetic thermal history in ectotherms is an important factor determining phenotypic variation. It will be important to link the thermally induced changes in development described here to the physiological and morphological differences and to link the developmental abnormalities to functional performance.

Prostaglandins prevent acetaminophen induced embryo toxicity in zebrafish (Danio rerio).

Previous research in our laboratory showed that acetaminophen (ACE) induced embryonic mortality and abnormalities in zebrafish. Here, we examined the dose response of ACE (0.05-50 µg L-1) in zebrafish embryos. Concentrations as low as 0.1 µg L-1 significantly increased abnormalities, and all test concentrations significantly increased mortality rates. In mammals, ACE inhibits cyclooxygenase (COX) enzymes to decrease prostaglandin production. Here we report COX activity and expression of the cox-1, cox-2a, and cox-2b genes in zebrafish embryos. COX activity was significantly inhibited by specific mammalian cox-1 (SC-560) and cox-2 (DuP-697) inhibitors in unexposed and ACE-exposed embryos. COX activity declined with development time. Maternal transcripts of all cox genes were found at 1 -h post fertilization and embryonic expression began in gastrulation or early segmentation. Co-exposure of ACE and prostaglandin E2 abolished the ACE-induced effects. This strongly supports that ACE elicits embryo toxicity in zebrafish though the same molecular mechanism of action of their therapeutic effects in mammals.

Chronic exposure of Brown (Hydra oligactis) and green Hydra (Hydra viridissima) to environmentally relevant concentrations of pharmaceuticals.

Low concentrations of pharmaceuticals in the environment (ng/L to µg/L) are an environmental concern. We used the invertebrates, Hydra oligactis and Hydra viridissima, as freshwater models for primary toxicity testing to study effects of chronic low concentrations of pharmaceuticals in the environment. H. oligactis were exposed to three concentrations (0.1, 1.0 and 10 µg/L) of either fluoxetine, carbamazepine, or triclosan; H. viridissima were exposed to three concentrations (0.1, 1.0 and 10 µg/L) of triclosan. Ecologically relevant endpoints including morphology, budding rate, feeding behaviour, and regenerative capacity were examined during the 14 days exposure period. The interstitial:epithelial stem cell ratios was also examined in H. oligactis. There were no significant effects on the morphology, budding rate and feeding behaviour of the H. oligactis across all concentrations of fluoxetine, carbamazepine, and triclosan. However, regenerative capacity significantly decreased in comparison to the controls when H. oligactis was exposed to 10 µg/L of triclosan and fluoxetine, although there was no significant difference when exposed to carbamazepine. Neither fluoxetine nor carbamazepine treatment altered stem cell ratios. Exposure to triclosan at any concentration did not impact H. viridissima morphology, budding rate, regeneration or feeding behaviour. These results show there are limited effects in Hydra after exposure to chronic, low concentrations of fluoxetine, carbamazepine, and triclosan, except for regeneration in H. oligactis. These endpoints can be used effectively (and cost effectively) to study the effects of environmentally relevant concentrations of pharmaceuticals in Hydra species.

Paternal Exposure to Carbamazepine Impacts Zebrafish Offspring Reproduction Over Multiple Generations.

Chronic low-concentration chemical exposures may have both direct health outcomes on adults and indirect effects on their offspring. Using zebrafish, we examined the impacts of chronic, low-concentration carbamazepine (CBZ) exposure on a suite of male reproductive endpoints in the parents and four generations of offspring reared in clean water. CBZ is one of the most frequently detected pharmaceutical residues in water, is a histone deacetylase inhibitor in mammals, and is reported to lower androgens in mammals and fish. Exposure of adult zebrafish to 10 µg/L CBZ for 6 weeks decreased reproductive output, courtship and aggressive behaviors, 11-ketotestosterone (11KT), and sperm morphology but did not impact milt volume or sperm swimming speed. Pairwise breeding generated lineages of offspring with both parents exposed and two lineages where only one parent was exposed; the control lineage had unexposed parents. Reproductive output and male reproductive indices were assessed in F1-F4 offspring to determine whether parental CBZ exposure had transgenerational impacts. The offspring of CBZ-exposed males had lower 11KT, reproductive output, altered courtship, aggression, and sperm morphology compared to the lineage from unexposed parents. Our results indicate that parental carbamazepine exposure history impacts the unexposed progeny up to the F4 generations and that paternal, but not maternal, exposure is most important for the reproductive health of male offspring.

Parental gemfibrozil exposure impacts zebrafish F1 offspring, but not subsequent generations.

Gemfibrozil (GEM) is a fibrate lipid regulator and one of the most commonly occurring fresh water pharmaceuticals. The negative effects of fibrates including GEM on fish reproduction have been frequently reported including effects of F0 GEM exposure on reproduction of the unexposed F1 offspring. We predicted that chronic, direct exposure of zebrafish with low concentrations of GEM would adversely affect parental male reproduction and unexposed offspring for multiple generations. Adult zebrafish were exposed to 10 µg/L GEM for 6 weeks and a range of reproductive indices were analyzed. The F1-F4 offspring were reared in clean water from 3 distinct lineages where only a single or both parents were exposed and compared to a control lineage where parents were unexposed. Reproductive indices were examined in unexposed F1-F4 offspring to test the hypothesis of multi- or trans- generational impacts. Exposure to GEM caused a decline in breeding success and mean embryo production in F0 parents and a reduction in whole body 11-ketotestosterone (11-KT), altered male courtship, aggression and sperm morphology. Our results indicate that paternal exposure alone is sufficient to result in reproductive effects in unexposed male offspring but that effects are mostly limited to F1. We suggest that GEM may act as a reproductive endocrine disruptor in fish and that chronic exposure reduced male reproductive fitness but not over multiple generations.

Gemfibrozil and carbamazepine decrease steroid production in zebrafish testes (Danio rerio).

Gemfibrozil (GEM) and carbamazepine (CBZ) are two environmentally relevant pharmaceuticals and chronic exposure of fish to these compounds has decreased androgen levels and fish reproduction in laboratory studies. The main focus of this study was to examine the effects of GEM and CBZ on testicular steroid production, using zebrafish as a model species. Chronic water borne exposures of adult zebrafish to 10 µg/L of GEM and CBZ were conducted and the dosing was confirmed by chemical analysis of water as 17.5 ±â€¯1.78 and 11.2 ±â€¯1.08 µg/L respectively. A 67 day exposure led to reduced reproductive output and lowered whole body, plasma, and testicular 11-ketotestosterone (11-KT). Testicular production of 11-KT was examined post exposure (42 days) using ex vivo cultures to determine basal and stimulated steroid production. The goal was to ascertain the step impaired in the steroidogenic pathway by each compound. Ex vivo 11-KT production in testes from males chronically exposed to GEM and CBZ was lower than that from unexposed males. Although hCG, 25-OH cholesterol, and pregnenolone stimulation increased 11-KT production in all treatment groups over basal levels, hCG stimulated 11-KT production remained significantly less in testes from exposed males compared to controls. 25-OH cholesterol and pregnenolone stimulated 11-KT production was similar between GEM and control groups but the CBZ group had lower 11-KT production than controls with both stimulants. We therefore propose that chronic GEM and CBZ exposure can reduce production of 11-KT in testes through direct effects independent of mediation through HPG axis. The biochemical processes for steroid production appear un-impacted by GEM exposure; while CBZ exposure may influence steroidogenic enzyme expression or function.

The effects of parental carbamazepine and gemfibrozil exposure on sexual differentiation in zebrafish (Danio rerio).

The effects of parental exposure to pharmaceuticals on sexual differentiation in F1 offspring were examined in zebrafish (Danio rerio). Adult zebrafish were exposed to 0 or 10 µg/L of carbamazepine or gemfibrozil for 6 wk and bred in pairwise crosses to generate 7 distinct lineages. Lineages were formed with both parents from the same treatment group or with only one parent exposed, to delineate between maternal and paternal effects. The F1 offspring from each lineage were reared in clean water and sampled at 45 and 60 d post fertilization (dpf). Gonadal differentiation was assessed by histology. The morphological stages of the gonads were converted to a quantitative day-equivalent based on data from offspring of untreated parents sampled from 15 to 75 dpf, which enabled a quantitative statistical analysis on the timing of sexual differentiation. Paternal, but not maternal, exposure to carbamazepine resulted in significantly faster sexual differentiation and a male-biased sex ratio; these effects were not observed when both parents were exposed. Combined paternal and maternal exposure to gemfibrozil resulted in significantly faster sexual differentiation, and paternal, but not maternal, exposure to gemfibrozil led to male-biased sex ratios. The present study demonstrates the ability of parental exposure to pharmaceuticals to disrupt sexual differentiation in the F1 offspring and also shows that effects may be uniquely influenced by which parent was exposed. Environ Toxicol Chem 2018;37:1696-1706. © 2018 SETAC.