A chronic bioassay with the estuarine amphipod Corophium volutator: Test method description and confounding factors

Chronic sediment studies were conducted using the marine amphipod Corophium volutator as part of an environmental risk assessment of the novel antifouling compound medetomidine. Two studies were performed, starting with neonates of less than 7 d old. A 28-d study considered endpoints of survival and growth (length and wet wt) and a 76-d study looked at survival, growth (length and wet wt), and reproduction (number of gravid females and neonates). Medetomidine was dosed via the sediment at nominal test concentrations of 1.0 µg/kg, 3.2 µg/kg, 10 µg/kg, 32 µg/kg, and 100 µg/kg (dry wt). In the 28-d growth study, a significant increase in mortality was observed at 32 µg/kg and 100 µg/kg. In the 76-d reproduction study, there were significant adverse effects on survival (32 µg/kg and 100 µg/kg), growth (100 µg/kg), and reproduction (100 µg/kg). The overall lowest-observed-effect concentration was 32 µg/kg medetomidine. For this test substance the increased study duration did not increase the overall sensitivity of the test. The present study suggests that the predicted sediment environmental concentration (PECsediment ) of 0.003 µg/kg for medetomidine would not be expected to cause adverse effects on the life history of C. volutator.

Section: Test Designsupporting

confidence: 79%

The use of a Corophium volutator chronic sediment study to support the risk assessment of medetomidine for marine environments

Fox

Ohlauson

Sharpe

et al. 2014

“…Longer exposure durations are expected to provide results that are of greater ecological relevance and amenable to modeling contaminant effects on population dynamics [12][13][14]. However, chronic tests have not always been determined to be more sensitive than acute methods [9,15], and long test durations sometimes result in greater variability in the performance of these tests [9,15,16].…”

Section: Introductionmentioning

confidence: 97%

Performance and sensitivity of rapid sublethal sediment toxicity tests with the amphipod Melita plumulosa and copepod Nitocra spinipes

Simpson

Spadaro

2011

Sublethal whole-sediment toxicity tests are an important tool for assessing the potential effects of contaminated sediments. However, the longer duration required for evaluating potential chronic effects may increase endpoint variability and test costs compared to survival endpoints. In the present study we compare the performance and sensitivity to contaminants of 10-d sublethal sediment toxicity tests with the amphipod Melita plumulosa and harpacticoid copepod Nitocra spinipes. For both tests, sublethal effects were consistently observed when sediment contaminant concentrations exceeded sediment quality guideline (SQG) concentrations. The response of these bioassays in metal-contaminated sediments was shown to conform ideally with respect to the mean SQG quotient calculated on the basis of the Australian and New Zealand lower SQG trigger value, with toxicity being observed only in those sediments where the mean quotient exceeded one. Better predictions of nontoxicity were obtained when dilute acid-extractable rather than total metal concentrations were used. Using the upper SQG, toxicity frequently occurred at mean quotients below one. The effects were generally consistent with predictions from the acid-volatile sulfide and simultaneously extracted metal model. Effects on reproduction of M. plumulosa were detected for sediments that did not cause effects on survival and highlighted the environmental relevance and importance of using these sublethal endpoints. When using four replicates for M. plumulosa and five replicates for N. spinipes, the endpoint variability (standard error) was less than 10%. Variations in sediment particle size and organic carbon content did not affect endpoint variability. Both species are relatively easily cultured in the laboratory, and the estimated effort and cost of achieving the sublethal endpoints is 1.5 times that of the acute survival test endpoints.

“…Species survival depends ultimately on the reproductive success and quality of offspring; thus, reproductive variables are sometimes considered more predictive indicators of toxicological effects at population and community levels that may be occurring at more slightly impacted sites in the field [14]. Sublethal endpoints in laboratory-based sediment toxicity tests using amphipods have been found to be more sensitive to low concentrations of contaminants approaching the sediment quality guideline trigger values [15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Review of the reproductive biology of amphipods and their endocrine regulation: Identification of mechanistic pathways for reproductive toxicants

Hyne¹

2011

Abstract-The reproductive biology of amphipods is reviewed to update the knowledge of the male and female reproductive processes of oogenesis and spermatogenesis as well as the endocrine systems of amphipods with the aim of advancing studies of reproductive toxicology. The ovarian and reproduction cycles of female gammaridean amphipods are closely correlated with the molt cycle, which is under direct control by the steroid hormone 20-hydroxyecdysone. The ability of males to copulate and subsequently for females to ovulate is restricted to the early postmolt period of the females. New developments in our understanding of the molt cycle and the endocrine regulatory pathways for reproduction using genomics techniques on other crustacean species are also discussed. The arthropod sterol ponasterone A or xenobiotics such as the fungicide fenarimol have been shown to elicit endocrine disruption in some crustaceans by acting as an agonist for 20-hydroxyecdysone at the ecdysone receptor or by inhibiting the synthesis of 20-hydroxyecdysone, respectively, resulting in disruption of molting and reproduction. Recent studies suggest that cadmium can inhibit secondary vitellogenesis in amphipods. Experimental approaches for examining the metabolic pathways associated with ecdysteroid hormonal signaling or metabolism, exoskeleton maintenance and molting, and the regulation of vitellogenin in amphipods are discussed. This information should aid in the identification of useful biomarkers for reproductive toxicity. Environ. Toxicol. Chem.