Abstract

Insecticides are used to eliminate pests through direct contact or systemic methods to produce a high crop yield; however, there is a cost to the use of such substances. Previous studies have established that pesticides, when introduced into aquatic ecosystems, can alter an organism's habitat selection. We hypothesized that imidacloprid, a common neonicotinoid insecticide, will interfere with habitat selection in the freshwater crustacean, Hyalella azteca, that utilizes its preferred habitat (algae) both as shelter and a food source. Our prediction was that higher concentrations of imidacloprid would disrupt habitat selection, causing amphipods to move out of their preferred habitat. Laboratory experiments were conducted using amphipods and natural vegetation collected from the San Marcos River. For 24 hours, groups of five amphipods were placed in small Tupperware containers holding stream water with different imidacloprid concentrations (0.0, 0.5, 1.0, and 1.5 µg/L) and were presented with two potential habitats: algae (preferred) and coontail (less preferred). After 24 hours, amphipods were removed from the habitat in which they were found and counted. Two statistical analyses were run: a two-way ANOVA to test the difference between the sex of the amphipod and treatments (p< 0.5), and a Chi-square to test the difference between the number of amphipods that decided their preferred habitat to the expected (p < critical value). Statistical values did not support our hypothesis, which may be due to the small group of amphipods in each Tupperware or how the pesticide affected them physiologically even after they chose their preferred habitat.

Authors

• Jonatan Valentin Salinas, St. Edward's University

• Raelynn Deaton Haynes, St. Edward's University