Hormonal and pheromonal studies on amphibians with special reference to metamorphosis and reproductive behavior.

Abstract

In this article, we have reviewed studies which have been conducted to investigate the hormonal influence on metamorphosis in the bullfrog (Rana catesbeiana) and Japanese toad (Bufo japonicus) larvae, in addition to studies conducted on the hormonal and pheromonal control of reproductive behavior in red-bellied newts (Cynops pyrrhogaster). Metamorphosis was studied with an emphasis on the roles of prolactin (PRL) and thyrotropin (TSH). The release of PRL was shown to be regulated by thyrotropin-releasing hormone (TRH) and that of TSH was evidenced to be regulated by corticotropin-releasing factor. The significance of the fact that the neuropeptide that control the secretion of TSH is different from those encountered in mammals was discussed in consideration of the observation that the release of TRH, which stimulates the release of PRL, is enhanced when the animals are subjected to a cold temperature. Findings that were made by using melanin-rich cells of Bufo embryos and larvae, such as the determination of the origin of the adenohypophyseal primordium, identification of the pancreatic chitinase, and involvement of the rostral preoptic recess organ as the hypothalamic inhibitory center of α-melanocyte-stimulating hormone (α-MSH) secretion have been mentioned in this article. In addition, the involvement of hormones in eliciting the courtship behavior in the male red-bellied newts and discovery of the peptide sex pheromones and hormonal control of their secretion have also been included in the present article. This article is protected by copyright. All rights reserved.