BEULIG, A.*; PILONIETA, M.C.; New College of Florida; New College of Florida: The effects of estrogenic pesticide on reproductive behavior of Cyprinodon variegatus, the sheepshead minnow .

Endosulfan is an estrogenic insecticide commonly used in agriculture. Because it may become part of agricultural runoff it is important to assess its possible impact on the physiology and behavior of aquatic organisms. The sheepshead minnow Cyprinodon variegatus has been used extensively as a toxicological assay and its reproductive behavior makes it a particularly favorable species for assessing possible subacute effects of pesticides on organisms. We determined that the 24-hour LC₅₀ value of endosulfan for male and female fish, 120-140 days old, weighing 0.28g and 2.24cm standard length was 0.3l &microg/L. We conducted a behavioral study in which we observed reproductively significant acts in four groups of sixteen subjects. Each group was given a single exposure to one of three concentrations of endosulfan and the fourth, a control group was exposed only to the triethylene glycol medium. Observations were carried out in circular plastic wading pools 2m in diameter, the bottoms of which were covered with sand. Treatments were introduced once into the the pool water and subjects were exposed to the concentration as it declined over 40 days thus mimicking a one-time, point source contamination. Treatment levels were: 0.0022; 0.0087; 0.034 &microg/L endosulfan. Overall, fish exposed to endosulfan showed significant decreases in Chase, Avoidance, Pacing, Fight, and Nesting behaviors compared with controls. Loss of coloration also occurred at the concentration of 0.034 &microg/L indicating the possibility of feminization. These results suggest that even at the lowest concentrations tested, and with no observable physical effects, endosulfan can have significant impact on fish populations by disrupting their reproductive behavior.