| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1998: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
Effects of the insecticide fenobucarb on 2 mayfly species, Epeorus latifolium and Baetis thermicus, and a caddisfly species, Hydropsyche orientalis, were examined in indoor model streams. Aqueous concentrations of fenobucarb residues in the model streams were 69-71% of its nominal level until 24 h, except at low concentrations (less than 2μg 1ィイD1-1ィエD1 in the water) in the water. Chronic effects of fenobucarb on the growth and emergence of Ephemeropteran larvae were examined over 2 months. For concentrations of 1 and 2μg 1ィイD1-1ィエD1, the numbers of individuals of the third larval growth stage (average head width 【greater than or equal】3.0 mm) gradually decreased up to 20 days after the applications ; the number of emergent individuals also remained 20 to 25 by the end of the experiment. The number of individuals to emerge at 1 to 2μg 1ィイD1-1ィエD1 fenobucarb was restricted in the long-term experiment. These results suggest that fenobucarb affects the emergence of this species through disruption of the endocrine system. On the other hand, the number of emergent individuals of B. thermicus at low concentrations of fenobucarb was not significantly less than that in the control. Next, chronic effects of fenobucarb on the nesting behavior, growth and emergence of Hydropsychidae larvae were examined over 80 days. For over 4μg 1ィイD1-1ィエD1, some or all (16μg 1ィイD1-1ィエD1) of H. orientalis larvae did not build the nests. For 4 and 8 μg 1ィイD1-1ィエD1, the number of 30-50% individuals of the larvae died. For 16μg 1ィイD1-1ィエD1, all of the larvae died until 2 weeks from the beginning of the experiment.
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