We observed male courtship behavior of Tylototriton (Echinotriton) andersoni in the laboratory. In some males, the cloaca swelled and became wet with mucous secretions from December to May. A male in this condition crept around a female, sniffing around her body and drawing a thread of mucus from his cloaca, so that the female was surrounded by spiderweb-like string of mucous attached to the substrate. The male then deposited a spermatophore by rubbing his cloaca against the substratum while swaying his body to and fro. The male behaved similarly towards females from different localities, though we could not observe any female reaction to the male. Under a phase-contrast microscope, the gross morphology of sperms from a male from Amamioshima Island was similar to that reported for males from Okinawajima.

View full abstract

Clutch parameters, such as clutch size, egg size, and clutch volume were studied in relation to female body size for two closely related species of stream-breeding frogs, Rana sakuraii and R. tagoi tagoi, in the Kanto district of Honshu, Japan. Two populations were studied for each species. Mean clutch size (approximately 130) did not show significant interspecific or intraspecific variation. In contrast, mean egg size differed between species or conspecific populations. Rana sakuraii laid larger eggs than any other anuran species in Japan (3.20 and 3.36mm in mean diameters of two populations), but the eggs of R. t. tagoi were slightly smaller (2.79 and 2.94mm). We could not detect any significant effect of age on clutch parameters in R. t. tagoi, after adjusting for female body size. We reviewed data on the relationship between female size and egg size in amphibian species, and found that most (71%) of the species or populations so far studied show a significantly positive correlation between these parameters. In the present study, no significant correlation was recognized between female size and egg size in R. sakuraii, but they were significantly positively correlated in R. t. tagoi. The evolutionary significance of variation in the relationship between these parameters is discussed.

View full abstract

A breeding site of the salamander Hynobius tokyoensis in a flowing stream was surveyed in the Yamanaka District of Miura Peninsula, central Japan, from March to April 2000, and from February to March 2002. The numbers of males, females, and egg sac pairs found in the stream were 32, three, and 31 in 2000, and 27, three, and 32 in 2002, respectively. The results of field observations suggest that the salamander prefers hollows under broader stones in the stream for breeding and/or spawning, presumably in order to avoid accidental washing away of egg sacs.

View full abstract

Nesting of the leatherback turtle Dermochelys coriacea in Japan was confirmed for the first time on the basis of two nests, each containing a clutch of eggs, found on Katoku Beach of Amami-oshima Island, central Ryukyus. There were no indications of development in eggs obtained from them. These nests were likely to have been made by the same individual.

View full abstract