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(74-02) Development of a post-exposure egestion rate bioassay with the freshwater snail Lymnaea peregra: linking short-term responses to life-cycle consequences of toxic exposure. Crichton, Corinne*,1, Conrad, Anne1, Nogueira, Antonio2, Baird, Donald1, 1 Institute of Aquaculture, Stirling, Scotland2 Dept. Biologia da Universidade de Aveiro, Aveiro, Portugal ABSTRACT- The EC-funded TARGET project seeks to develop rapid bioassessment tools for determining the ecological quality of rivers under the EC Water Framework Directive. As part of this project, a short-term bioassay to assess the effects of changes in water quality on macroinvertebrate grazer response has been developed using the freshwater snail Lymnaea peregra. This field-deployed bioassay assesses grazing performance indirectly through egestion rate (in terms of faecal pellet production), quantified in the laboratory immediately after in situ exposure. This type of short-term measure offers some unique advantages over other in situ methods in terms of the use of a more sensitive nonlethal endpoint, and the ability to quantify response under environmentally controlled conditions. However, the question remains: how can we interpret these short-term responses, measured over a few days, in terms of their effects on the animal's life history? One approach is to extrapolate the short-term response over a longer time period using a physiologically based simulation model. We employ this approach here in order to predict the consequences of varying levels of egestive depression in terms of growth performance. Model predictions are tested by laboratory experiments using a reference compound: the heavy metal cadmium. Findings are discussed in relation to the general applicability of short-term in situ measures of grazing rate to predict functional impairment within natural food webs, and the relevance of Lymnaea peregra as a surrogate for macroinvertebrate grazing guilds within European rivers. Key words: Bioassay, Lymnaea peregra, model, cadmium |
