Passage to the Terrestrial Life in Amphibians II. Endocrine Determinism

概要

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In many amphibians, the departure from water associated with the metamorphic events is controlled by a number of hormones. The most important are the thyroid hormones. After they bind to the nuclear receptors, the thyroid hormones trigger a number of mechanisms by acting at the genome level. These hormones control the synthesis of many specialized proteins during cell differentiation and degeneration. Thyroid hormone activity is a necessary condition for metamorphosis and departure from water in many amphibians. However, it is not in itself sufficient and other hormones intervene also. Cortical steroids such as corticosterone or aldosterone play a part in up-regulating metamorphosis. On the contrary, prolactin and growth hormone can inhibit certain metamorphic events in larvae, thus maintaining them in an aquatic environment. Moreover, neurohypophyseal hormones, aldosterone or prolactin regulate the hydromineral equilibrium which optimizes water conservation in the metamorphosed animals, while they migrate towards the terrestrial habitat. Finally, a complex endocrine determinism presides over the environmental transitions observed in modern amphibian development.
社団法人日本動物学会の論文
1993-12-15