Ecotoxicological Effects of Potassium Dichromate on the Tadpole Shrimp Triops longicaudatus.

Simple Summary: Over the years, research from other areas has suggested that tadpole shrimps could be a useful model to detect and evaluate the effects of aquatic contamination and environmental health. Its size, active swimming, short generation time, and easy lab maintenance make it an attractive alternative to the use of higher sentient animals. This investigation has thus aimed at evaluating the sensitivity of Triops longicaudatus to potassium dichromate, a common contaminant in aquatic systems, also used as reference compound in ecotoxicology. Lethal and sublethal exposure assays were carried out and biochemical to apical endpoints with an impact at the population level were measured. We found negative impacts in the growth rate, delayed reproductive maturity, and alteration in the locomotor behavior upon exposure to potassium dichromate. The sensitivity of the species was higher than that of various freshwater animals commonly used in toxicity testing. Behavior appeared as the most sensitive response to chromium exposure, discriminating well the test concentrations from the control group and from each other. The tadpole shrimp Triops longicaudatus is a freshwater crustacean with fast embryonic and larval development, short life cycle, and high fecundity. They are very active swimmers of a reasonable size, easy to spot and record. Such characteristics make it a promising candidate as an experimental model in ecotoxicology to evaluate the effects of aquatic pollutants, particularly using its locomotor behavior as an endpoint. To evaluate the sensitivity of T. longicaudatus and develop endpoints of interest, we conducted exposure experiments with lethal and sub-lethal concentrations of potassium dichromate, a compound known for its ecotoxicological importance and as a hexavalent chromium source. The endpoints evaluated were mortality, growth, sexual maturation, reproductive output, cholinesterase activity and locomotor/swimming behavior. The 96 h median lethal concentration was found to be 65 µg/L. Furthermore, exposure to potassium dichromate at higher concentrations had a significant negative impact on the growth rate of T. longicaudatus in terms of both body mass and length. The time for maturation was also delayed at higher concentrations. In addition, locomotor behavior allowed for the discrimination of all tested chromium concentrations and the control group and from each other, proving to be the most sensitive endpoint. Overall, the data support the potential of T. longicaudatus as a model for ecotoxicity testing, using apical endpoints with impact at the population level; in particular, results suggest that behavior assessments in this species might be useful for detecting hazardous compounds in environmental monitoring of freshwater ecosystems. [ABSTRACT FROM AUTHOR]