Influence of Life Cycle Stage on Toxicity: The Matacil 1.8D - Chlamydomonas Example

Abstract

The toxicological effects of the pesticide Aminocarb and its adjuvants in the Matacil 1.8D formulation were separately determined using synchronized cultures of Chlamydomonas segnis as the test organism. The parameters followed included number of cells, biomass changes in terms of total dry weight, protein, carbohydrate and nucleic acids (DNA and RNA). The pesticide or its adjuncts were added at four different phases of the algal life cycle, namely at the end of G₂ and S-phase, the beginning of G₁ and at cytokinesis.

The formulated pesticide (Matacil 1.8D containing 1 mg⋅L⁻¹ Aminocarb, 2.5 mg⋅L⁻¹ nonylphenol and 1.5 mg⋅L⁻¹ diluent oil) was both algicidal and algistatic when applied at the S-phase. The concentrations of Aminocarb and oil in the formulation were at the no effect (NOE) level. The toxicological responses were generally similar to those evoked by nonylphenol alone, (algistatis), apart from the RNA response, where augmentation was obtained above that evoked simply by the treatment with nonylphenol.

The use of developmentally and physiologically comparable test organisms for QSAR determinations is emphasized.