Response of the Unicellular Giant Alga Acetabularia Acetabulum to Cadmium Toxicity and Accumulation*

Accumulation of cadmium by the unicellular marine alga Acetabularia acetabulum (=A. mediterranea) was studied by using the radioactive isotope ¹⁰⁹Cd. Column chromatography (Sephacryl S-200) of labelled extracts showed that after a short incubation (1–2 h)¹⁰⁹Cd was eluted at the position characteristic for ionic cadmium and for low molecular weight compounds. However, after a longer incubation (one week or more), ¹⁰⁹Cd was present also in high molecular weight molecules. Cadmium is very toxic to Acetabularia: cell growth and cap formation were reduced at concentration as low as 1 μg L^-1. For concentrations higher than 0.1 mg L^-1, various morphological anomalies appeared, such as formation of short and thick stalks and condensation of cytoplasm in apical or basal parts, eventually followed by cytolysis.