MA4 Pesticides
204 Oregon Ballroom
8:00 AM - 12:00 PM, Monday
() Endocrine active insecticides stimulate a putative stress-signaling pathway in daphnids.
Rider, C1, Buslinger, L1, Olmstead, A1, Wasilak, B1, LeBlanc, G1, 1 North Carolina State University, Raleigh, NC, USA
ABSTRACT- Microcrustaceans such as daphnids serve an important function in aquatic ecosystems by passing nutrients through food chains from phytoplankton to higher organisms. Measurements of the health and fitness of microcrustaceans can provide valuable information on the general condition of the ecosystems in which they live. This presentation describes progress in elucidating a stress-induced signaling pathway that may facilitate population survival during environmental adversity. Elevated temperature, an environmental stressor likely to be encountered by daphnids, stimulated both hemoglobin accumulation and male offspring production. Hemoglobin accumulation and male offspring production are two disparate physiological responses to stress which can protect the organism from extinction in the face of unfavorable environmental conditions. Methyl farnesoate, a crustacean analog to the insect juvenile hormone, also stimulated both responses suggesting that methyl farnesoate may function as a hormone mediator that transduces environmental stress signals. Several insecticidal juvenile hormone analogs were shown to induce both hemoglobin accumulation and male offspring production presumably by mimicking methyl farnesoate. Potency in elevating hemoglobin and inducing male offspring production were significantly correlated among insecticides tested, suggesting that these two responses share a common signaling pathway. Several clonal populations of D. pulex/pulcaria were evaluated for responsiveness to methyl farnesoate. Individual clonal populations typically responded to hormone treatment with both increased hemoglobin and increased male offspring production or did not respond at all. This provided further evidence that these two responses share a common signaling pathway and identified several non-responsive clones that may be deficient in a functioning methyl farnesoate receptor. These results provide evidence for a stress-responsive signaling pathway in daphnids involving methyl farnesoate.
Key words: methyl farnesoate, environmental stress, hemoglobin, crustacean