Seasonal fluctuation of frog renal adenocarcinoma. Prevalence in natural populations.

A study was made of spontaneous renal adenocarcinoma in Rana pipiens collected from natural populations. Previous studies of prevalence have been made on purchased frogs and it is now well documented that renal tumor rate increases with storage. The present study provides tumor data on unstored R. pipiens taken directly from their native habitat. Collections of over 2,000 frogs were made in springs and summers of two years in Minnesota and South Dakota. Renal adenocarcinoma prevalence was disproportionately higher in spring collections (18 tumors from 491 frogs) than in summer collections (1 tumor from 1,554 frogs). Prevalence of spring frog renal tumors varied from 0% in several collections to a high of 9% in Otter Tail County, Minnesota. The only summer renal tumor detected was discovered in a frog of the same county. Renal tumors were more common among female frogs (4:8%) than among male frogs (2.8%).