Tumorigenic, Growth, Reproductive, And Developmental Effects In Medaka Exposed To BIS(Tri-N-Butyltin) Oxide

Japanese medaka (Oryzias latipes) were exposed to varying concentrations of bis(tri-n-butyltin) oxide in two different but related studies in an attempt to elicit tumorigenic, growth, reproductive, and developmental responses. 7-day post-hatch medaka were exposed under flowthrough conditions for 90 days to 0.5 and 3.3 pg/L TBTO continuously, to 4.5 pg/L TBTO intermittently, and to two TBTO-free diluent water controls. Neither a tumorigenic nor a delayed pathological response was detected. Standard lengths and fecundity of exposed medaka relative to unexposed fish were significantly reduced in the 0.5 and 4.5 pg/L TBTO treatments. Embryo viability was significantly reduced in the 4.5 pg/L concentration, and percent hatch was significantly reduced in both continuous TBTO treatments. Fry survival was not affected, and no abnormal embryos or fry were detected. In the initial study, In a follow-up study, 7to 9-month-old medaka were continuously exposed under nearly identical conditions to those of the initial study to 0.09, 0.40, 0.70, and 3.6 pg/L TBTO. Tumorigenicity was not an end point in this study. Fecundity in the follow-up study was significantly increased over that in unexposed fish, possibly as a stress response, whereas viable embryos were significantly reduced in the highest TBTO concentration and the number of abnormal embryos was significantly increased in the 0.40, 0.70, and 3.6 pg/L TBTO treatments relative to unexposed fish. abnormalities encountered are discussed. Time to hatch and fry survival were not significantly affected. Types of embryonic and fry