You are here:
Development of a juvenile fathead minnow fin regeneration assay for use in evaluating chemical involvement in fin regeneration impairment
Citation:
Tilton, C., C. Blanksma, J. Cavallin, G. Ankley, J. Swintek, K. Jensen, M. Kahl, AND Dan Villeneuve. Development of a juvenile fathead minnow fin regeneration assay for use in evaluating chemical involvement in fin regeneration impairment. SETAC North America, Sacramento, CA, November 04 - 08, 2018.
Impact/Purpose:
The St. Louis River estuary near Duluth, MN and Superior, WI has been identified as a Great Lakes Area of Concern (AOC). During recent routine fish monitoring, several species of fish with severely eroded fins were detected in a refinery-effluent impacted stream that discharges to the St. Louis River estuary. If the source cannot be identified, this represents a potential barrier to delisting of the St. Louis River AOC. The present study reports on a laboratory-based assay under development at the US EPA Mid-Continent Ecology division that can be used to explore the link between contaminant exposure and the fin erosion observed in wild-caught fish. Results of this assay will help the state of Wisconsin and Minnesota define the source of the fin degeneration and develop appropriate management and/or mitigation strategies. Additionally, the assay will have broader use for screening of other chemicals and/or complex mixtures extracted from environmental samples for their ability to impair fish fin regeneration
Description:
Over their lifetime, fish experience damage to their fins from a variety of natural sources (e.g., predators, abrasion). Generally, that damage is repaired through the process of fin regeneration. However, some chemicals have been shown to impair the fin regeneration process. Aquatic exposures to such chemicals can reduce the fitness of exposed individuals leading to potential adverse effects on the aquatic ecosystem. The present work describes the development of a laboratory-based bioassay to screen chemicals or mixtures for their ability to impair the fish fin regeneration process. The assay can be applied to help ensure the safety of chemicals to aquatic ecosystems. Teleost fish are among the few vertebrates with the ability to nearly perfectly regenerate an amputated or damaged limb (i.e., fins). Fin damage can result from a wide range of natural sources including abrasive habitat surfaces, predation, conspecific aggression, and nutritional deficiencies. However, increased incidence of fin erosion has also been observed at sites impacted by a wide range of pollutants including pulp mill effluents, coal-ash runoff, oil sands process waters, etc. This suggests that exposure to certain chemical contaminants may impair the processes that support fin regeneration and repair. Development of a laboratory-based fin regeneration assay would have utility for both testing this hypothesis, as well as screening of both individual chemicals and complex mixtures for their ability to impair fin regeneration processes. The present study reports on the time-course of fin regeneration in 30 d posthatch fathead minnows (Pimephales promelas) following partial caudal fin amputation. Fish were sampled daily from 0-7 days post amputation (dpa). Fish length, caudal fin area, and specific fin ray lengths were measured at each time point using image analysis. Additionally, RNA was extracted from caudal fin samples and expression of several genes known to play a role in fin regeneration, including fibroblast growth factor receptor 1a (fgfr1a), lysyl hydroxylase (lhl1) and patched-1 (ptch1), was evaluated using quantitative polymerase chain reaction (qPCR). Based on averaged fin ray length and/or fin area as determinants, statistically significant regrowth was detectable by 4-5 dpa (25o C). Both ptch1 and lhl1 expression was significantly increased at 3 dpa compared to unclipped controls, suggesting these as potential molecular markers of the initiation of fin regrowth. A statistical power analysis focused on the phenotypic measurements of fin regrowth suggest that a sample size of n=10 measured at 7 dpa would likely be statistically robust for detecting treatment effects on regeneration. Results inform development of a standardized test that can be used for routine screening.