SYMPOSIUM: Amphibian Metamorphosis: An Integrative Approach:American Society of Zoologists Meeting in Washington, D.C., January 1996

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9529567 Hayes This symposium brings together experts in ecology, endocrinology, developmental biology, and molecular biology to address integrative studies on amphibian metamorphosis. Metamorphosis is one of the most remarkable biological processes described. During amphibian metamorphosis, one animal (the tadpole) virtually transforms into another (an adult frog). In addition to the obvious external changes, such as the resorption of the tail, the growth of limbs, and the beginning of terrestrial life, there are many other less obvious changes. Tadpoles are typically vegetarian whereas adults feed on insects or small animals, thus the structure of the gut and all of its enzymes change at metamorphosis; the immune system is destroyed and rebuilt to suit the frog; the gills resorb and are replaced by lungs; the structure of hemoglobin (the oxygen carrying molecule) changes; the structure and function of the eye transform from one that sees underwater to one better suited for seeing in air; the skin glands (which produce mucous, important antibiotics, and toxins) develop; the reproductive organs develop; etc. All of the changes in structures and functions are regulated by hormones. Although, thyroid hormone is the principal hormone stimulating these changes, other hormones such as prolactin and the stress hormone, corticosterone, modulate development. All of these hormones function by regulating genes, turning off the "tadpole genes" and turning on the "frog genes". In addition, these hormones are controlled by external factors such as temperature, food level, water quality, the presence of predators, and population density. Because of these complex interactions across levels of organization, environment-organism gene, metamorphosis is an excellent process for integrative studies. Amphibians can be used as a model to examine how environmental changes affect physiological processes as well as to examine gene regulation. Amphibian metamorphosis is a vital model for understanding development an d the role of genes in all vertebrates (including humans), because the developmental processes at metamorphosis can be observed directly (unlike embryonic development in other animals that typically occurs inside an egg or inside the mother). In addition, understanding changes in physiology and gene expression in response to environmental changes is vital in understanding how animals adapt to changes in environment. This understanding will result in better utilization of amphibians as indicators of environmental degradation, which is urgent given evidence for the recent global decline in amphibian populations.