| Abstract: | Conventional (whole animal) toxicity tests were made with Scrobicularia plana (Da Costa), an infaunal estuarine bivalve, and compared with the responses recorded from siphonal preparations. Exposure of Scrobicularia to low concentrations of triethyllead chloride and trimethyllead chloride, for 35 and 60 days respectively, produced typical response curves. However, mortality had not become asymptotic with time at lower concentrations, suggesting further mortality with increased exposure time. An approximate incipient lethal concentration was predicted. A siphonal preparation technique with isolated and in-situ inhalent siphons of Scrobicularia was used to estimate the lowest effect concentrations of alkyllead compounds. Response to alkyllead was indicated by contraction of the siphon, recorded via an isotonic transducer. Trialkyllead compounds were more toxic than the respective dialkylleads and inorganic lead. Toxicity of trialklleads and inorganic lead. Toxicity of trialkylleads increased with alkyl chain length. Pure tetraethyllead did not cause any siphonal contraction even when applied directly to the preparation. It was concluded that tetraethyllead has a low toxicity or is non-toxic in pure form. |
