A Comparative Study on the Larval Life History in Two Populations of Hynobius boulengeri from Kyushu, Japan (Amphibia: Urodela)

Abstract

We compared larval life history between two populations of Hynobius boulengeri from Kyushu, Japan, one from Takachiho on the Sobo-Katamuki Mountains and the other from Kinko on the Osumi Peninsula. They showed variation in life history which seems to be induced partially by differences in water temperature and food availability, but may also reflect differences at the genetic level. Larvae from Takachiho, where the water temperature was lower in winter, developed more slowly but grew more quickly under higher summer temperatures and by eating larger prey than larvae from Kinko. In Takachiho, most larvae overwintered once or twice, and in one case, three times. In contrast, larger numbers of larvae metamorphosed without overwintering in Kinko. Takachiho larvae were larger at metamorphosis (SVL=ca 39 mm in average) than Kinko larvae (ca. 31 mm), and this difference is thought to affect the body size difference in adults. The relatively large mouth in Takachiho larvae is thought to be an adaptation not to cannibalism, but to larger prey. The relatively small mouth in Kinko larvae, unique among larvae of H. boulengeri populations and its ally, H. hirosei, seems to be also constrained by genetic factors.