Tuesday, 28 October 2003

This presentation is part of : Display Presentations, Section Cd. Behavior and Ecology

Hexavalent chromium effects at the bottom of the food web

John T. Trumble and Peter Jensen. University of California, Riverside, Department of Entomology, Riverside, CA

The effects of hexavalent chromium (Cr VI) on ovipositional response, development, and survival of a terrestrial detritivore, Megaselia scalaris (Diptera: Phoridae) were assessed. Ovipositing females did not discriminate between substrates containing 0, 50, 500 or 1000 mg/g, indicating a lack of avoidance behavior. Eggs placed on diets containing up to 1000 mg/g either did not absorb Cr VI, or were unaffected as measured by eclosion rates. However, development and survival of larvae were significantly reduced at the higher concentrations tested. Concentrations of 500 mg/g in their food increased larval development times by nearly 65%. At 1000 mg/g, larval developmental times doubled. Although males eclosed before females, there was no significant difference between the sexes in the time required for adult eclosion or differences in the percentage of males and females emerging from any treatments. At concentrations of 500 or 1000 mg/g, Cr VI decreased larval survival. Survival was reduced by 44.3% at 500 mg/g as compared to the controls. At 1000mg/g Cr VI, larval survival decreased by 86.6%. An additional 7.4% mortality was recorded in the puparial stage, for a decrease in total survival (larval plus puparial stages) of 94%. Thus, nearly all of the observed mortality occurred during the larval stage rather than the puparial stage. The population level implications of lack of avoidance of contaminated food, and the effects of increased developmental times and reduced survivorship are discussed.

Species 1: Diptera Phoridae Megesilia scalaris
Keywords: pollution, detritovore

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