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PM05 Aquatic Vertebrate/Invertebrate Toxicology
(PM088) Growth Inhibition of Early Life Stages of Mya arenaria by 2,4-D.
Tonneson, J 1, Butler, R1, Lindsay, S1, Gardner, G2, Van Beneden, R1, 1 University of Maine, Orono, Maine, USA2 US EPA, Narragansett, Rhode Island, USA
ABSTRACT- The purpose of this study was to look at the effect of 2,4-dichlorophenoxyacetic acid (2,4-D), a common active ingredient in many agricultural herbicides, on soft-shell clams (Mya arenaria) at various early life stages. The stages focused on were: trochophore, early veliger, late veliger and juvenile. Twenty-four hour exposures were done for each life stage with a formulation of 2,4-D at 0, 0.5, 5, 10*, 50, and 500 ppm (* juveniles only). Percent survival was determined for each life stage immediately following exposure. A significant decrease in survival was seen at 500 ppm in the trochophore, early and late veliger stages. Juvenile clams were grown out in a flow-through seawater system in order to monitor growth (as determined by shell length). Initial observations 3 months post-exposure indicated a significant difference in shell length of exposed juveniles compared to controls, although no dose response to treatment was evident. Half of the exposed juveniles (0, 5 and 10 ppm) were subjected to additional forty-eight hour exposures once a week for 1 month. Nine months after the initial exposure, all exposure groups exhibited significantly lower growth compared to control clams. Growth was significantly inhibited by additional 2,4-D exposure. Further measurement of juvenile growth/development (e.g. histology) will be done 12 months post exposure. Additional exposures to 2,4-D and other herbicides/pesticides will be conducted to generate data for population level modeling.
Key words: mya arenaria, 2,4-d, herbicide, growth
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