Acute and sublethal toxicity of tributyltin oxide (tbto) and its putative environmental product, tributyltin sulfide (tbts) to zoeal mud crabs, rhithropanopeus harrisii

Abstract

Mud crab larvae, Rhithropanopeus harrisii were exposed to tributyltin oxide, (TBTO) (0.5, 1, 5, 10, 15, or 25 μg l⁻¹) or tributyltin sulfide (TBTS) (0.5, 1, 5, 20, 30, or 50 μg l⁻¹). Differential survival was observed in TBTO concentrations equal to or greater than 10 gg l⁻¹ and in TBTS concentrations equal to or greater than 20 μg l⁻¹ Growth and development rate were assessed as sublethal indices of stress. Of the two, development rate was more sensitive. All groups exposed to either compound had slower development rates than controls. Growth of the larvae, as shown by weight gain, was slightly increased in low exposures (a hormetic response) and decreased significantly in higher concentrations. The mean weight of the 50 μg l⁻¹ TBTS group showed the largest decrease, to 57% of the control. The hormesis response was further examined by measuring daily growth of the zoeae. All groups exposed to tributyltin compounds showed an initial growth lag. The hormesis response occurred in the fourth zoeal stage or megalops. While R. harrisii is relatively tolerant to the acute toxicity of tributyltin compounds compared to other marine crustaceans tested, sublethal responses occur in very low concentrations. This points to the need for analyses to characterize tributyltin environmental concentrations.