Rotifer Ecotoxicology: Behavioral Avoidance of Toxicants

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Weigel, Emily Grace
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Previous rotifer ecotoxicology studies have shown varied effects of sublethal concentrations of hormones and metals on species but have largely ignored toxicant effects on behavior. Given the importance of chemical cues for mating, grazing, and predator avoidance, the phenomenon of behavioral response to pollutants is a critical topic impacting rotifer survival and reproduction. Dual- and tri-chamber test slides similar to Y-tubes were developed to test rotifer behavioral responses to sublethal concentrations of several toxicants. Rotifers were placed in a start chamber between a control chamber and test chamber containing a toxicant, and after fifteen minutes, rotifer distribution in all chambers was recorded. No significant distributional effects were observed for cadmium (2μg/L), pentochlorophenol (2μg/L), flutamide (8μg/L) nor progesterone (8μg/L). Significant deviation from a random distribution was recorded for selenium (2μg/L), lead (8μg/L), and rotifer conditioned medium. In addition, significant avoidance was found for copper (2μg/L) and mercury (0.2μg/L), even in tests with the start chamber containing the toxicant. These data suggest that rotifers can detect and avoid certain toxicants at sublethal levels. Avoidance often occurs at levels below published lethal concentrations (LC50s) on which many water quality criteria are based. Avoidance can alter rotifer survival and reproduction, leading to reductions in rotifer abundance and energy transfer to higher trophic levels.
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