Tributyltin-induced effects on early life stages of minnows Phoxinus phoxinus

Toxicity and histopathological effects of tributyltin chloride (TBT) were studied in early life stages of minnows Phoxinus phoxinus. Eggs and yolk sac fry (newly hatched larvae) were exposed in a static-renewal procedure to aqueous TBT concentrations ranging from 0.82 to 19.51 micrograms/L for 3 to 10 days at 16 degrees C and 21 degrees C, respectively. Aqueous TBT concentrations were determined by capillary GC-FPD and revealed a concentration decrease during the static phase. TBT exposure led to mortality, behavioral, gross morphological and histopathological effects. In larvae, increased mortality, deformation of body axis, paralysis and opaque eyes occurred at 4.26 micrograms/L TBT and higher both in the embryonic-larval and larval exposure. Histological changes were evident at initial TBT concentrations of 0.82 up to 19.51 micrograms/L, and were more pronounced after embryonic-larval exposure than after larval exposure. Degenerative alterations occurred in skin, skeletal muscle, kidney, corneal epithelium, lens, pigment layer of the retina and choroid, retina, and CNS including spinal cord. Hydropic vacuolation of the cytoplasm and, in more pronounced cases, irreversible nuclear alterations such as pycnosis, karyorrhexis and karyolysis were also evident. Exposure to 0.82 micrograms/L TBT resulted in alterations in skin, muscle and kidney, with greater effects occurring at 21 degrees C than at 16 degrees C. Toxicity was significantly reduced in the presence of sediment. The observed histopathological effects suggest that early life stages of fish may be negatively affected in environments that are considerably polluted by TBT.