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Tiny zebras at your service
February 03, 2004Before new pesticides can be approved, their environmental impact must be assessed. Due to the complexity of ecological systems, researchers require simple yet representative laboratory models. Among vertebrates, schools of zebra fish are especially suitable.
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Studying the ways substances affect living organisms in their environment is the job of the ecotoxicologist. Particularly with deliberately produced toxic substances such as pesticides, the practical aim of these scientists is developing standardized test procedures that are easy to run, yet capable of providing clear results. Such tests form the basis for developing manufacturer regulations and user information. For pesticides used in or near bodies of water, fish toxicity must be assessed. One aspect that has increasingly gained importance over the past few years relates more to subtle endocrine effects than acute toxicity. Some pesticides are suspected of interfering with vertebrate hormone systems. This can negatively affect the reproductive capacity of fish, disrupting egg development and upsetting the ratio of adult males to females.
One species of fish frequently used as a model organism is the zebra fish (Danio rerio). A favorite of aquarium owners, this small, hardy fish is easy to maintain and breeds rapidly. This makes it possible to observe the impact of substances over several generations. Researchers at the Fraunhofer Institute for Molecular Biology and Applied Ecology IME are investigating the effect of new pesticides on the vital parameters of these animals, under realistic exposure conditions. "Our aquariums have artificial sediment beds," emphasizes Dr. Christoph Sch'¤fers, IME department manager. "This is because, in the case of pesticides, we need to know the long-term consequences of short periods of peak exposure. In other words, how quickly are these substances released from the sediment and ingested by the fish? We can observe this by using pesticides that are radioactively marked."
These tests provide essential information for protecting natural fish resources, for the fishing industry and finally for human health as well. The IME studies reveal a clearer picture of the potential impact of pesticides than other commonly used methods. The results are much more meaningful because three life stages are examined - egg, larva and mature adult. A reliable indication can be given of the concentration below which a pesticide has no discernable effect. To date, the IME has conducted studies on behalf of several of the world's leading pesticide manufacturers, representing a total contract volume of EUR 700,000. The IME's studies of endocrine effects and on the capacity of sediment to store and release pesticides enjoy high international esteem.
Fraunhofer-Gesellschaft
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