The patterns of the changes in nuptial pad and vocal sac developments during an annual reproductive cycle of the Chinese bullfrog (Rana rugulosa Wiegmann) are reported for the first time. The frogs, hatched in April 1986, were collected from November, 1986 through November, 1987, at monthly intervals or more frequently during the breeding season, from a frog culture farm located in Taiwan. Nuptial pad development was histologically determined and vocal sac development was recorded by observing subgular wrinkling and pigmentation. In November and December, the nuptial pad epidermis was smooth and thin; the mucous gland diameter was small with a low cellular height. Nuptial pad epidermis and mucous
glands developed rapidly in January and February. During the breeding season (March-July), the welldeveloped nuptial pad was rough, papillate and thick; mucous glands were hypertrophied and lumen secretions were abundant. Nuptial pads regressed during the postbreeding period (August-October). Vocal sac development coincided with both the breeding season (March-July) and the male calling season (March-September). Thus, both nuptial pad and vocal sac developments of Rana rugulosa exhibit a unimodal pattern during the annual reproductive cycle. The correlations between developments of these two secondary sexual characteristics and the plasma androgen levels are presented.
Seasonal changes of nuptial (thumb) pad and vocal sac, Anuran, Plasma androgen levels
