Copper tolerance in fathead minnows: II. Maternal transfer

Science of The Total Environment

Snow

Kohno

et al. 2007

Self Cite

Recent studies of surface waters in North America, Japan, and Europe have reported the presence of steroidogenic agents as contaminants. The current study has three objectives: 1) to determine if steroidogenic compounds are present in the Elkhorn River, 2) to determine if sediments collected from the Elkhorn River can act as a source of steroidogenic compounds to aquatic organisms, and 3) to determine if site-specific biological effects are apparent in the hepatic gene expression of fathead minnows. Evidence was obtained using three approaches: 1) deployment of polar organic chemical integrative samplers (POCIS), 2) deployment of caged fathead minnows, and 3) a laboratory experiment in which POCIS and fish were exposed to sediments from the deployment sites. Deployment sites included: the Elkhorn River immediately downstream from a Nebraska wastewater treatment plant, two waterways (Fisher Creek and Sand Creek) likely to be impacted by runoff from cattle feeding operations, and a reference site unlikely to be impacted by waste water inputs. The PO-CIS extracts were analyzed for a number of natural steroids and metabolites, as well as four different synthetic steroids: ethinylestradiol, zearalonol, 17β-trenbolone and melengestrol acetate. Estrogenic and androgenic metabolites, as well as progesterone and trace levels of melengestrol acetate were detected in POCIS deployed at each site. POCIS deployed in tanks containing field sediments from the four sites did not accumulate the synthetic steroids except for ethinylestradiol, which was detected in the aquarium containing sediments collected near the wastewater treatment plant. Fish deployed in Sand Creek and at the wastewater treatment plant experienced significantly elevated levels of gene expression for two genes (StAR and P450scc) relative to those deployed in Fisher Creek. Fish exposed to the sediments collected from Sand Creek had significantly higher levels of hepatic StAR and P450scc gene expression than did fish exposed to sediments from the two other field sites, as well as the no-sediment control tank. In conclusion: 1) detectable levels of steroidogenic compounds were detected in passive samplers deployed in the Elkhorn River, 2) sediments do not appear to be a significant source for steroidogenic compounds, and 3) site-specific differences were found in mRNA expression among the different treatment groups of fish; however, a functional explanation for these differences is not readily forthcoming.

Section: Field Fishmentioning

confidence: 99%

Occurrence and biological effect of exogenous steroids in the Elkhorn River, Nebraska, USA

Science of The Total Environment

Snow

Kohno

et al. 2007

Self Cite

“…Thee fish used in this study were produced by the University of Nebraska at Omaha fathead minnow colony (Peake et al, 2004). For the two experiments discussed below, the fish were produced by a minimum of nine parental pairs.…”

Section: Fish Maintenancementioning

confidence: 99%

Copper acclimation in juvenile fathead minnows: Is a cycle of branchial damage and repair necessary?

Tate-Boldt

2008

Aquatic Toxicology

Self Cite

Fathead minnows exposed to sublethal Cu concentrations may undergo branchial damage followed by repair, and may also develop enhanced Cu tolerance. The primary objective of this study was to determine whether the cycle of damage and repair was necessary for the development of enhanced Cu tolerance. Inferences regarding damage and repair were made from changes in the whole body Na + of juvenile (0.5 g) fathead minnows (Pimephales promelas). Two experiments were conducted in which juvenile minnows were exposed to various sublethal Cu concentrations for 16 d. In the first experiment, fish were exposed to one of four different Cu concentrations (0, 73, 118, 189 μg/L Cu) then challenged with an 8-d exposure at 302 μg Cu/L. Only the fish exposed to the highest Cu dose experienced enhanced Cu tolerance relative to the other three doses. In the second experiment, whole body Na + was monitored in fish exposed to one of five different Cu exposures (0, 70, 127, 202, 289 μg/L Cu). Fish exposed to 70 μg/L Cu did not experience a significant decline in whole body Na + at any point during the 16-d exposure period. The reduction in whole body Na + was short lived and moderate (17%) in the fish exposed to 127 μg/L Cu, but more severe (>30%) and longer lasting in the fish exposed to 202 μg/L Cu. At 289 μg/L Cu, the fish experienced irreversible reductions in whole body Na + and ultimately died. When taken together, results from these two experiments suggest that enhanced tolerance will only develop in fathead minnows that have experienced a pronounced, relatively long-term cycle of branchial damage and repair.

“…All fish used in these experiments were produced by the University of Nebraska at Omaha fathead minnow colony according to the protocols outlined in Peake et al (2004).…”

Section: Fish Maintenancementioning

confidence: 99%

Cd Exposures in Fathead Minnows: Effects on Adult Spawning Success and Reproductive Physiology

Sellin

Arch Environ Contam Toxicol

2006

Self Cite

The primary objective of this study was to determine whether cadmium (Cd) exposures alter reproduction in fathead minnows (Pimephales promelas). Pairs of sexually mature minnows were exposed to waterborne Cd at 0, 12.5, 25, or 50 μg/L for 21 days. During this exposure period, the reproductive success of pairs was assessed. Following the exposure, gonadosomatic index (GSI), male secondary sexual characteristics, male plasma 11-ketotestosterone (11-KT) concentrations, and female plasma estradiol (E 2 ) concentrations were determined. Results of this study show that Cd exposures impair reproduction in fathead minnows. Pairs exposed to 50 μg/L experienced a significant decline in spawning frequency and fecundity relative to unexposed minnows. Cd exposures also caused alterations in male secondary sexual characteristics, as males exposed to 25 μg/L had significantly fewer nuptial tubercles than controls. Furthermore, males exposed to 12.5 μg/L Cd experienced a significant increase in plasma 11-KT concentrations relative to controls. No alterations in GSI or female plasma E 2 concentrations were observed.Cadmium (Cd) is a common environmental pollutant that poses a significant threat to the health of aquatic ecosystems due to its persistent release through anthropogenic activities such as mining and smelting operations (Henson and Chedrese 2004). Cd concentrations in the water range from background levels of 1 μg/L to 400 μg/L in contaminated sites (Tilton et al. 2003). Like many heavy metals, Cd has a long half-life and can bioaccumulate over time in various organs including the liver, kidneys, testes, and ovaries (Henson and Chedrese 2004). The effects of Cd on the health of freshwater fish have been well studied especially with regard to survival (Benoit et al. 1976;Middaugh and Dean 1977;Hwang et al. 1995), calcium ionoregulation (Roch and Maly 1979;Wendelaar Bonga and Lock 1992), and skeletal development (Muramoto 1981;Cheng et al. 2000). However, fewer studies have investigated the effects of Cd exposure on the reproductive success of fishes despite evidence that Cd can act as a reproductive toxin (Signhal et al. 1985) and endocrine disruptor (Henson and Chedrese 2004).Studies have shown that exposure to Cd damages gonads and impairs gametogenesis. The testes appear to be particularly sensitive to Cd exposures. Several studies have shown that Cd causes testicular apoptosis and necrosis (Singhal et al. 1985;Das 1988). Exposure to 10 mg/ L Cd increases capsase 3 gene expression, an indicator of apoptosis, in the testes of black gobies (Gobius niger) (Migliarini et al. 2005). Male and female Asian cyprinids (Labeo bata) exposed to a range of Cd concentrations (1-15 mg/L) for four months experienced reductions in gonadosomatic index (GSI) relative to unexposed fish (Das 1988). In addition, the testes of exposed males lacked spermatids and spermatozoa, while the ovaries of exposed females In addition to alterations in gametogenesis, exposure to Cd has been shown to alter steroidogenesis. For example, female ...