The influence of Gomphosphaeria aponina on the growth of Gymnodinium breve and the effect of aponin on the ichthyotoxicity of Gymnodinium breve.

Cells of the marine blue-green alga Gomphosphaeria aponina survive in mixed culture with the marine dinoflagellate, Gymnodinium breve (the Florida red tide organism), but G. breve cells lysed within 4-7 days. It has been established that the cytolytic effect of G. aponina, not nutrient competition, is responsible for the decrease in number of cells. The material elaborated by G. aponina has been termed aponin and has been extracted from the cells. The effect of aponin on the ichthyotoxicity of G. breve cultures was measured using Poecilia sphenops, adapted to sea water, as the assay organism. Aponin is not ichthyotoxic toward P. sphenops, though this material, when incubated with G. breve cultures does destroy the cells and increases the ichthyotoxicity of the cultures. At certain concentrations of aponin, the ichthyotoxicity of G. breve cultures appeared to be mitigate d.