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(M/EH023) Improvements to baseline data for amphibian larval developmental tests. Pounds, Nadine1, Pickford, Daniel1, Hutchinson, Thomas1, 1 ABSTRACT- With increasing interest in the endocrine disruption area, the African clawed frog Xenopus laevis is of significant importance as a candidate amphibian test species. In spite of its obvious advantages as an amphibian model for laboratory testing, relatively little attention has been given to defining Xenopus larval development under flow-through conditions. Control data from several amphibian larval developmental studies have been collated to demonstrate the experimental improvements we have made to our flow-through exposure system. Changes in food types and feeding regimes have played a significant role in improving baseline survival and developmental data. The flow-through system delivered dechlorinated water at 40-80 mls per min to replicate tanks containing 20 to 45 larvae per tank. The diet used has been altered from algal tablets, a proprietary tadpole food to a commercial algal fry food and increased to three feeds per day. The diet changes have decreased the high larval mortality observed at the study starts, reducing the cumulative mortality from 46.8% to <5%. These modifications have also led to a reduction in the time taken to achieve 90% metamorphosis within a study from 117 to 90 days, although development was still asynchronous. The time reduction to complete an amphibian larval development study will no doubt reduce the high costs associated with early life stage studies. These data have significant implications for future development of robust standard protocols (eg OECD) to assess endocrine-mediated and other effects of products and effluents on the growth and development of Xenopus larvae. Key words: Xenopus, development, diet, Amphibia |
