Genetic Diversity of Sodefrin-Variant Pheromones and Pheromone Responsiveness in Subspecies of the Japanese Sword-Tail Newt Cynops ensicauda

Experiments were conducted to examine whether the abdominal glands of <i>Cynops ensicauda</i> subspecies (<i>C. e. ensicauda</i> and <i>C. e. popei)</i> express different mRNAs for sodefrin-like female-attracting pheromone precursors. A precursor mRNA encoding a novel sex pheromone candidate, [Gln⁸]sodefrin, was widely detected in the abdominal glands of both of <i>C. ensicauda</i> subspecies. Female partners exhibited a considerable preference for synthetic [Gln⁸]sodefrin. Thus, [Gln⁸]sodefrin was designated caudarin. In <i>C. e. ensicauda</i>, the abdominal glands of males expressed sodefrin precursor mRNA as well, and sodefrin was also effective in attracting female partners. In addition to caudarin precursor mRNA, the abdominal glands of <i>C. e. popei</i> males expressed silefrin ([Leu³, Gln⁸]sodefrin) precursor mRNA, as reported previously. Moreover, imorin, a male-attracting pheromone previously identified in <i>C. pyrrhogaster</i> females, was effective in attracting <i>C. e. ensicauda</i> males but not males of <i>C. e. popei</i>. Molecular phylogenetic analysis indicated that trans-specific possession of sodefrin genes was likely because of gene occurrence preceding speciation of <i>C. ensicauda</i> and <i>C. pyrrhogaster</i>, and that the additional occurrence of silefrin in <i>C. e. popei</i> possibly resulted from duplication of the caudarin gene. Differences in pheromone components among <i>Cynops</i> species and subspecies reflect the speciation route estimated by previous molecular genetic analyses.