Tumor induction by carcinogenic agents in aquarium fish.

The effects of nine carcinogens on 1,220 guppies [Poecilea reticulata (Lebistes reticulatus)] and 40 zebra fish (Danio rerio) were studied. Multiple exposure techniques included skin application, im and ip injections, feeding, implantation in pellets, and dissolving of the compound in the aquarium water. 7-12-Dimethylbenz[a]anthracene, 3-methylcholanthrene, and benzidine produced no tumors in the fish. N-2-Fluorenylacetamide, omicron-aminoazotoluene, 4-dimethylaminoazobenzene, diethylnitrosamine, and dimethylnitrosamine induced tumors in the livers of some of the fish. These neoplasms included cholangiomas, hepatoadenomas, cholangiocarcinomas, and hepatocellular cancers. Nitrosomorpholine caused not only hepatic tumors in guppies and zebra fish but also intestinal adenocarcinomas and poorly differentiated connective-tissue lesions in the abdominal cavities of zebra fish. Experimental induction of tumors in aquarium fish offers wide possibilities for comparative cancer research. Fish are a suitable model for the testing of compounds for carcinogenic activity and for the screening of environmental carcinogens.