Characteristics of a fish colony of Poeciliopsis and its use in carcinogenicity studies with 7,12-dimethylbenz[a]anthracene and diethylnitrosamine.

The viviparous fish Poeciliopsis from northwestern Mexico is characterized according to its potential in cancer research. A colony of these fishes started in 1961 includes inbred strains of P. lucida (M61-9, M61-31, M61-35, and S68-4), P. monacha (S68-4 and S68-5), and P. viriosa (M65-23), which have been demonstrated by electrophoresis and tissue graft analysis to be homozygous. All-female species of hybrid origin are represented by 12 clones which, although highly heterozygous, are genetically identical or isogenic and readily accept within-clone tissue transplants. Two studies are cited in which hepatic tumors were chemically induced. In one, liver neoplasms were induced in P. lucida and P. monacha by repeated short-term exposures to an aqueous suspension of 5 ppm 7,12-dimethylbenz[a]anthracene. In the other, dose responses to the carcinogen diethylnitrosamine (DENA) were compared among 4 inbred strains, 3 hybrids from crosses between inbred strains, and 2 wild stocks of P. lucida. The incidence of hepatic tumors gradually increased from 0 to 93% depending on the concentration of the compound and the number of exposures, but no significant difference was found among the inbred strains, their hybrids, or the wild stocks. Hepatic tumors, initially induced with DENA have been successfully transplanted into the muscle tissue and abdominal cavity of members of the same strain.