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Using killifish (Fundulus heteroclitus) early life stage assessment to connect mechanisms of toxicity to adverse outcomes
Citation:
Burke, T., M. Francoeur, H. Schrader, B. Clark, B. Khan, L. Mills, N. McNabb, AND D. Nacci. Using killifish (Fundulus heteroclitus) early life stage assessment to connect mechanisms of toxicity to adverse outcomes. North Atlantic Chapter, Society of Environmental Toxicology and Chemistry, 27th Annual Meeting, NA, Virtual, April 05 - 07, 2021.
Impact/Purpose:
This presentation evaluates developmental biological endpoints in Atlantic killifish (Fundulus heteroclitus) that contribute to our understanding of the survivability of individuals and the persistence of their populations when exposed to chemical pollutants in the marine environment. To assess the risks associated with chemical exposures, a variety of biological endpoints were measured and a subset of embryos were sacrificed for ‘omics analyses. By connecting molecular mechanisms to developmental endpoints, adverse outcomes measured in killifish for specific chemical exposures can be extrapolated to untested species and chemical pollutants. The information presented in this research provides more insight to managers and scientists about how human activities can affect natural dynamics, ecological stressors and ecosystem conditions.
Description:
Environmental contaminants adversely impact fish on the organismal level through a variety of pathways that may affect their development, survival, and ability to reproduce. The early life stages of fish are useful to assess the effects of pollutants because they are often more sensitive than adult stages and have the potential for later life impacts that together can affect population persistence. Moreover, linking developmental endpoints to underlying genetic alterations can provide insights into the molecular mechanisms by which pollutants produce adverse biological outcomes, which can serve as a basis for extrapolation of risk to diverse species and pollutants. To assess the risks associated with chemical exposures, early developmental stages of Atlantic killifish (Fundulus heteroclitus), an ecologically important species with a well-annotated genome, were exposed via maternal transfer or directly by aquatic exposures in standardized embryo larval assays (ELAs). In ELAs, non-destructive measurements of growth and development are monitored in individuals after exposure until 16 days post-hatching (dph). A subset of embryos were sacrificed for ‘omics analyses to reveal molecular mechanisms affected by pollutant exposures. In the presented ELAs, a variety of biological endpoints were measured including embryonic survival, development, phenotypic abnormalities, heart rate and swim bladder size, as well as larval survival and growth. In addition to daily observations, detailed microscopic phenotyping is conducted 10 days-post-fertilization (10 dpf) and was used to examine embryos for developmental abnormalities including, but not limited to abnormal head or body size, hemorrhages of the tail, head, and pericardial area, and heart features such as offset heart chambers and an elongated sinus venosus. Images were taken using a mounted Nikon camera and analyzed with ImageJ processing software. To assess heart function, video analysis of 10 dph killifish embryos was performed with DanioScope software to determine average heart rate in beats per minute by individual embryo. Swim bladder measurements were taken to discern possible treatment effects on inflation. Larval length measurements were taken at 0 (dph), 7 dph, and 16 dph to determine larval growth rates. Our results provide examples showing that the concentration and type of chemical exposures had varying effects on the frequency and severity of each developmental endpoint. The evaluation of developmental endpoints at the organismal level is an important component in the risk assessment of chemical exposures. These data can be used directly to inform ecological models, including Individual Based Models, under development for killifish that predict adverse chemical outcomes at the population level, which often cannot be measured directly. Furthermore, by connecting molecular mechanisms to developmental endpoints, adverse outcomes measured in killifish for specific chemical exposures can be extrapolated to untested species and chemical pollutants.
