両生類保全のための環境毒性学

抄録

Over the past two decades, amphibian conservation has been a growing concern with the realization of worldwide amphibian declines and high prevalences of frog deformities. Chemical contaminants have attracted significant attention as a causative agent of these amphibian abnormalities. Japanese amphibians also seem to decrease in number, and deformed frogs have been frequently observed in the Kitakyushu area. Toxicity or teratogenicity tests conducted with Japanese amphibian larvae or Xenopus laevis embryos indicate that the most common herbicide in Japan and some organic compounds detected from the Kitakyushu area have the potential to induce amphibian mortality or malformation. However, these toxicological data have limited relevance to the amphibian abnormalities occurring in the field. In general, laboratory tests conducted by use of wellcontrolled and standardized methods provide only the basic data to evaluate the toxicity of chemicals. Various biological and physical-chemical factors such as geographic, ecological, and physiological diversity in amphibians, susceptibilities that may be variable during larval stages, and environmental fate of chemical contaminants should be in consideration for the risk assessment. Mathematical models may facilitate to assess the effects of chemicals using these complex factors. Amphibian toxicology should therefore make connections with developmental biology, ecology, physiology, mathematical biology, and physical chemistry. Extensive and interdisciplinary investigation would be required to progress toward amphibian conservation focusing on the protection of wild amphibians from chemical contaminants.