ANNUAL PATTERNS OF NUPTIAL PAD AND VOCAL SAC DEVELOPMENT IN THE MALE CHINESE BULLFROG (RANA-RUGULOSA WIEGMANN)

The patterns of the changes in nuptial pad and vocal sac developments during an annual reproductive cycle of the Chinese bullfrog (Rana rugu losa 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, f rom a frog culture farm located in Taiwan. Nuptial pad development was histologically determined and vocal sac development was recorded by o bserving subgular wrinkling and pigmentation. In November and December , the nuptial pad epidermis was smooth and thin; the mucous gland diam eter was small with a low cellular height. Nuptial pad epidermis and m ucous glands developed rapidly in January and February. During the bre eding season (March-July), the well-developed nuptial pad was rough, p apillate and thick; mucous glands were hypertrophied and lumen secreti ons were abundant. Nuptial pads regressed during the postbreeding peri od (August-October). Vocal sac development coincided with both the bre eding 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 c orrelations between developments of these two secondary sexual charact eristics and the plasma androgen levels are presented.