MA4 Pesticides
204 Oregon Ballroom
8:00 AM - 12:00 PM, Monday
() Toxicity of pesticides used to control mosquitoes in the American lobster, Homarus americanus.
De Guise, S1, Maratea, J1, Perkins, C2, 1 Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT, USA2 Environmental Research Institute, University of Connecticut, Storrs, CT, USA
ABSTRACT- A lobster die-off reduced the 1999 fall landings in western Long Island Sound by up to more then 99%. The die-off corresponded in time with the application of pesticides for the control of mosquitoes that carried West Nile virus, a new emerging disease in North America at the time. In order to determine the possible implication of pesticide application as a direct cause or contributing factor in the die-off, we studied the effects of experimental exposure to malathion, methoprene and resmethrin on the health of lobsters. Lobsters were exposed in 20 gallon tanks, and the direct toxicity as well as sub-lethal effects on the immune system were determined. The 96 hour LC50 for malathion upon single exposure was 33.5 ppb, while the highest concentrations used for methoprene (221 ppb) and resmethrin (1 ppb) did not result in acute mortality. Malathion and methoprene degraded rapidly in our system, half life of less than a day. Phagocytosis was significantly decreased by water concentration as low as 5 ppb malathion, 33 ppb methoprene and 0.01 ppb resmethrin in acute (5 days) or subacute (weekly exposures for 4 weeks). Cell counts did not change consistently or significantly upon exposure to pesticides. Only methoprene bioaccumulated in muscle and hepatopancreas of exposed lobsters. Evaluation of phagocytosis is a sensitive indicator of subtle sub-lethal effects of pesticides, and relatively small concentrations can affect lobsters defense mechanisms. While exposure of lobsters to pesticide was not precisely quantified during the 1999 lobster die-off, if they reached the concentrations demonstrated to be toxic to lobsters, it is possible that those pesticides could have affected the health of those animals and contributed to the die-off.
Key words: toxicity, American lobster, pesticides, immunotoxicity