Assessing the Effects of the Pharmaceutical Environmental Contaminant Atorvastatin on the Molting Cycle of the Red Swamp Crayfish, Procambarus clarkii

Abstract

Atorvastatin, one of the most prescribed pharmaceuticals in the United States, lowers cholesterol in humans by competitively inhibiting hydroxymethylglutaryl-CoA reductase in the mevalonate pathway. The mevalonate pathway is integral to arthropod development, since it is the primary biochemical pathway to produce juvenile hormones that aid in growth and reproduction. Atorvastatin has been detected in the environment in the parts per billion range and may pose a threat to aquatic invertebrates. Crayfishes are a large group of benthic aquatic invertebrates that can occupy several niches and function as keystone species in many environments and might be sensitive to atorvastatin contamination. In this study, adult and juvenile red swamp crayfish (Procambarus clarkii) were used as model organisms in a controlled lab environment to assess the sublethal, chronic effects of atorvastatin on molting. Adult crayfish were reared and exposed to atorvastatin for six months, and juveniles were exposed for one full molt cycle. We measured the lengths, weights, intermolt duration, and ambient chitobiase activity in the water of all crayfish. For the adults, no significant differences were noted across treatments and controls. For the juveniles, only intermolt duration was significantly affected. Out of the four treatments (0.15 µg/L, 1.5 µg/L, 15 µg/L, and 100 µg/L), solvent control, and control groups, the highest dosed group (100 µg/L) showed a significant increase in intermolt duration from all other treatments (ANOVA: F = 8.036, df = 5, p = 3.02 × 10-5), averaging 91.875 days (maximum 120 days, minimum 76 days) compared to an average of 60.806 days for all other groups combined (maximum 84 days, minimum 25 days). All other treatments were not statistically different from the controls.