Morphological and toxicological variability of Prorocentrum lima clones isolated from four locations in the south-west Indian Ocean.

Eight clones of the toxic dinoflagellate Prorocentrum lima (Ehrenberg) Dodge from four sites (two clones per site) on the coral reef of La Réunion, Mayotte, Europa, and Mauritius Islands in the SW Indian Ocean were isolated and cultivated under the same conditions. Morphological features of each clone, including cell size and valve and marginal pore numbers, were examined by scanning electron microscopy. The toxic potential of each clone was determined by protein phosphatase type 2A (PP2A) inhibition test and fibroblast cell line FR3T3 bioassay. Scanning electron microscopy showed that variation in morphological features of clones within and between sites was minimal and not significant. However, equivalent okadaic acid content, determined by PP2A assay, was different within and between clones isolated from the four islands. Cytotoxicity bioassay with the FR3T3 cell line confirmed the variation on global toxic potential within and between the eight P. lima clones. This test also suggested the presence of other toxic compounds without PP2A inhibiting activity in crude extracts of some clones.