Endocrine regulation of reproductive behavior in the newt Cynops pyrrhogaster

Abstract

Hormonal control of the expression of courtship behavior and of secretion of the female-attracting pheromone sodefrin by the male red-bellied newt, Cynops pyrrhogaster, together with the hormonal influence on the responsiveness to the pheromone in the female, is reviewed.Expression of the initial stage of the courtship behavior, i.e., tail vibration by the male in front of the female, is dependent on prolactin (PRL) and androgen. During the courtship, sodefrin seems to be released from the cloaca through the ducts of the abdominal gland. Both content of immunoreactive sodefrin and preprosodefrin mRNA levels in the abdominal gland are elevated by a combination of PRL and androgen, indicating that the pheromone synthesis is stimulated by these two hormones. On the other hand, the discharge of sodefrin is accelerated by AVT, its action being mediated by V1 receptor. In female newts, responsiveness of the vomeronasal epithelium to the pheromone is elevated by a combination of PRL and estrogen. Thus, it can be concluded that PRL, AVT, and sex steroids are key hormones for the reproductive performance in the red-bellied newt. In this article, the significance of the structure of the pheromone molecule as a peptide is also discussed in terms of its species-specificity and its effectiveness in an aquatic environment.

Cell proliferation and neurogenesis in the adult telencephalon of the newt Cynops pyrrhogaster

“…As in the majority of urodeles, fertilization in the red‐bellied newt ( C. pyrrhogaster ) takes place internally by transferring spermatophores from male to female. Prior to the spermatophore transfer, male newts exhibit a unique courtship behavior (Salthe, 1967; Toyoda & Kikuyama, 2000). Following the recognition of a sexually responsive female by the tripeptide pheromone imorin, which was recently identified as a female sexual attractiveness peptide pheromone (Nakada et al, 2017), the male blocks her path with his neck contacting with her snout and then vibrates the tail vigorously to send the female‐attracting peptide pheromone (sodefrin) released from the male cloacal gland (Kikuyama et al, 1995) toward the female partner.…”

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

“…It is known that administration of PRL and gonadotropin elicits a sexually developed state in both sexes of red‐bellied newts (Toyoda et al, 1993), and the sexually developed male newts exhibit a unique courtship behavior toward the female partners (Houck, 1986; Kikuyama et al, 2003; Salthe & Mecham, 1974). Hormonal involvement in the courtship behavior of the male newts was analyzed (Toyoda et al, 1994, 2015; Toyoda & Kikuyama, 2000). Meanwhile, it was presumed that pheromones contribute to sex recognition and courtship behavior in the sexually developed red‐bellied newts (Toyoda et al, 1994).…”

Possible hormonal interaction for eliciting courtship behavior in the male newt, Cynops pyrrhogaster

“…Extensive studies have been carried out using intact, castrated, and hypophysectomized male red-bellied newts, both in the breeding and non-breeding season, with the aim of elucidating the hormonal factors involved in the expression of this courtship behavior (Toyoda and Kikuyama, 2000;Kikuyama et al, 2003). Earlier work on the male red-bellied newt suggested that both prolactin (PRL) and androgen are required to maintain male courtship behavior for extended periods of time (Kikuyama et al, 1980;Toyoda et al, 1993).…”