The toxicity of bis(tri- n-butyltin)oxide (TBTO) and di- n-butyltindichloride (DBTC) in the small fish species Oryzias latipes (medaka) and Poecilia reticulata (guppy)

Abstract

Toxicity studies were carried out on the Japanese medaka ( Oryzias latipes) with bis(tri- n-butyltin)oxide (TBTO) and di- n-butyltindichloride (DBTC), with emphasis on histopathological effects. Freshly fertilized eggs were exposed for 1 and 3 months to a concentration range of 0.1–32 μg TBTO/l in tank water. The range for DBTC was 320–3200 μg/l (1 month only). The histopathological effects included vacuolation of hepatocytes, tubulonephrosis and glomerulopathy, vacuolation of the retinal pigment epithelium, keratitis, hyperplasia and inflammation of oral and skin epithelium, hyperplasia and swelling of the gas gland epithelium and thyroid activation. No atrophy of the thymus was found. Except for the retinal and liver lesions, these changes occurred predominantly in the highest concentration with no essential differences in the lesions between 1 and 3 months, or between TBTO and DBTC exposure. Liver cell vacuolation was apparently caused by glycogen accumulation, as was confirmed in an additional experiment with guppies, a more expedient species. It is concluded that TBTO and DBTC have effects on the liver and gas gland, probably as a result of impaired glycogen breakdown. Effects on superficial epithelia are attributed to the irritative properties of these compounds. In addition, these compounds were toxic to kidney and retina. No-observed-effect concentrations using histopathology were 0.32 μg/l for TBTO, and lower than 320 μg/l for DBTC. Total tin and butyltins were determined by molecular absorption spectrometry, and gas chromatography with flame photometry, respectively, in guppies exposed to TBTO and DBTC. Considerable amounts of TBT were measured in DBTC-exposed fish, and chemical analysis indicated that DBTC contained TBT at a level that may account for the observed toxicity of DBTC.