Experimental transmission of walleye dermal sarcoma to yellow perch

Walleye dermal sarcoma was transmitted under experimental conditions to yel low perch Perca flavescens. Fish (20 weeks posthatch) were challenged with cell-free tumor filtrates by topical application on the right flank and the n held for observation for 25 weeks in 15 degreesC dechlorinated municipal water. Additional treatment groups included yellow perch challenged with ce ll-free filtrates of walleye discrete epidermal hyperplasia, yellow perch d iscrete epidermal hyperplasia, normal yellow perch skin (control), and norm al walleye skin (control). Walleye dermal sarcoma was first observed on yel low perch at 20 weeks postexposure, at which time the tumors were small (1- 2-mm), slightly raised masses on the right flank of the fish. At the end of the 25-week study, walleye dermal sarcoma was grossly observed in 42% (22 of 53) of the remaining fish and was confirmed by microscopic examination i n an additional 29% (9 of 31). Gross and microscopic evaluation of fish at, 25 weeks postexposure did not reveal development of lesions in any of the o ther treatment groups. This study extends the host range of experimentally transmitted walleye dermal sarcoma virus to include the yellow perch.