Usefulness of the hermaphroditic marine fish, Rivulus marmoratus, in carcinogenicity testing.

Hepatocellular carcinoma and other pathological changes were induced in the self-fertilizing hermaphroditic fish Rivulus marmoratus by aqueous exposure to 15, 30, and 45 ppm diethylnitrosamine (DENA). Fish exposed as larvae for 12 weeks and adults exposed for 5 weeks showed rates of hepatocellular carcinoma as high as 76.5 and 31.3%, respectively, when examined 1 year later. Fish exposed as embryos in various stages of development for 1 week to 10, 32, 100, 320, and 1,000 ppm DENA were without neoplasms when examined 1 year later. Other pathological changes of rivulus livers were cholangioma, adenofibrosis, and granuloma with incidences as high as 38.9, 88.9, and 61.1%, respectively. Simple rearing methods were developed and relevant biological data pertaining to reproduction, embryonic development, and subsequent growth of R. marmoratus are discussed. Advantages and disadvantages of the use of R. marmoratus as a carcinogenicity test animal are assessed.