Abstract1_11 (Hasumi)

Hasumi, M.: Seasonal fluctuations of female reproductive organs in the salamander Hynobius nigrescens. Herpetologica (USA, International) 52(4): 598-605, December 1996. Stable URL

Abstract: I examined annual changes in the ovaries and accessory sex organs in Hynobius nigrescens. During the March breeding season, all gravid females collected just before entering a breeding pond were still in a preovulatory condition, and ovulation occurred in the pond. After ovulation, remaining ovarian eggs were translucent until August, and they assumed a mint green color in August when vitellogenesis (i.e., the accumulation of yolk granules) was initiated. Melanin deposition in the ovarian eggs began in September, and the eggs were entirely dark brown in October and the following winter months. Ovary mass began to increase in August and in January reached the maximum level, maintained into March when females possessed ripe ova before entering the pond for breeding. Sizes of both ovarian eggs and ventral glands increased sharply from July-November and further increased gradually during hibernation. The mass of the oviduct plus ovisac increased from August toward the breeding season. The maximum mass of the fat bodies was recorded in August. This is the first documentation of the annual reproductive cycle in any female hynobiid species.