Meeting Abstract
Pesticides have the potential to impact development and growth in non-target organisms like zooplankton. Most toxicological studies involving zooplankton test the effects of potential toxicants on active adults or larvae, but fail to consider dormant life-stages. Artemia franciscana, commonly known as the brine shrimp, is a species of zooplankton that lives in diverse hyper-saline environments. We used A. franciscana as a model organism for this study because it is commercially available as a dormant (post-diapause) embryo, and has high hatching rates under simple culture conditions. We hypothesized that the pesticides, fenoxycarb and carbaryl, would delay post-diapause development in A. franciscana by disrupting endocrine signaling and neurotransmission, respectively. Fenoxycarb is an insect growth regulator that blocks metamorphosis and interferes with molting. Carbaryl, on the other hand, disrupts neurotransmission in insects, and thereby alters behavior and muscle control. Dechorionated embryos were exposed to carbaryl or fenoxycarb for 24 h on ice prior to a 72 h hatching test in the continued presence of the chemical. Preliminary results suggest that 1ug/ml fenoxycarb delays emergence and hatching without decreasing hatching success. Preliminary results for carbaryl suggest that disruption of neurotransmission decreases hatching success in an all-or-none fashion; animals treated with 5 ug/ml carbaryl either hatch normally or stop developing as E2 prenauplii. A comparison with published data on Daphnia magna indicates that generalizations about the effects of these compounds on branchiopod zooplankton is not possible.
