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.
