Abstract1_26 (Hasumi)

Kakegawa, M., F. Kishi, Y. Saikawa, and M. Hasumi: Seasonal changes in body shape and mass in a lotic-breeding and externally fertilizing salamander Hynobius kimurae. Zoologischer Anzeiger (Germany, International) 268: 55-63, May 2017. doi: 10.1016/j.jcz.2017.04.003 ReadCube

Abstract: Physiological condition linked to reproduction-related morphological traits (e.g., body mass, head width, tail height) is a key determinant of ecotypes related to fitness in ecological selection. In migratory salamanders such as the families Ambystomatidae (internal fertilization), Salamandridae (internal), and Hynobiidae (external), such morphological traits change at the transition between terrestrial and aquatic habitats. Unlike many other migratory salamanders, Hynobius kimurae (Hynobiidae) immigrates from land to water for aquatic hibernation during fall, and the immigration is not related to fall breeding. In this context, does fall immigration to water for winter dormancy induce changes in reproduction-related morphological traits? We analyzed changes in body shape and mass concurrent with physiological condition of 244 males and 131 females of H. kimurae with only data on first capture during fall and spring from 1996 to 2016. Although reproduction-related morphological traits in other migratory salamanders change simultaneously when they enter the water and subsequently initiate breeding during either season of fall-spring, such changes occurred both in male and female H. kimurae firstly during fall (shortly after entering the water) and secondly during spring (shortly after awaking from hibernation), except for head width being static throughout seasons. The differences suggest that these two-step changes during a prolonged period from fall to spring would be concentrated in a short period of breeding activity during either season of fall-spring in other migratory salamanders without hibernating in the water. As sexually selected, sexual dimorphism was detected in size and shape, especially shape of the tail, both height and length of which were greater in males than in females regardless of the sexes being terrestrial or aquatic. The male's larger tail during the terrestrial phase may be a stock for a more developed tailfin (amount of reproductive output) in the aquatic-phase male potentially related to fitness.