On the toxic effects of tetraethyl lead and its derivatives on the chrysophyte Poterioochromonas malhamensis: II. Triethyl lead, diethyl lead, and inorganic lead

Abstract

The toxic effects of the tetraethyl lead (TEL) derivatives triethyl lead (TriEL), diethyl lead (DiEL), and of inorganic lead (Pb 2+) on the Chrysophyte Poterioochromonas malhamensis were studied. The algae's parameters of interest were cell growth, and the formation of giant cells and of polyploid nuclei. (1) Based on their zero-growth-inducing concentrations, the tested lead compounds reveal the following relative toxicities to the algae: Pb 2+, light/darkness = 1 1 ; DiEL, light/darkness = 11 10 ; TriEL, light/darkness = 55 33 ; TEL, light/darkness = 7 0 . (2) The lead compounds differ greatly in the concentration ranges which cause slight inhibitory to lethal effects. The ranges are: Pb 2+ = 5 to >1000 μ m (>200×); DiEL = 5 to 100 μ m (20×); TriEL = 5 to 25 μ m (5×). (3) Pb 2+ is the least toxic TEL derivative. Its growth-inhibiting effect is remarkably high at very low concentrations (10μ m) but it increases only slightly with rising concentrations. Even 3-day treatment with 1000 μ m Pb 2+ is not lethal to the whole culture. Between 10 to 500 μ m Pb 2+, the nuclear indices of the cultures stay nearly unaffected, whereas there is a moderate but distinct increase in the percentage of polyploids, with maxima of 10% in the light and 6% in darkness. (4) DiEL is about ten times more toxic to Poterioochromonas than Pb 2+. It inhibits cellular growth and leads to the formation of giant cells and of polyploid nuclei under light and dark conditions. DiEL is much less stable to light than TriEL. In the course of the experiments it obviously tends to decompose upon illumination to a less active and less water-soluble compound. (5) Among the tested TEL derivatives, TriEL is the most toxic. In light as well as in darkness it inhibits algal growth and leads to the formation of giant multinucleated cells and of polyploid nuclei. The effects of TriEL are identical to those which were observed in TEL-treated illuminated cultures of Poterioochromonas. (6) Although DiEL has TriEL-like activity, there is evidence suggesting that in these experiments DiEL is not formed from TEL in critical amounts. The present studies further support the idea that TriEL is the primary derivative of TEL in illuminated algal cultures and that TriEL is the agent which causes the severe inhibitory effects in TEL toxicity to Poterioochromonas malhamensis.