CHANGES IN ATP CONCENTRATION, MITOCHONDRIAL STRUCTURES, AND RHODAMINE-123 BINDING IN 2 MARINE DINOFLAGELLATES CULTURED IN THE PRESENCE OF PARATHION

Parathion, an organophosphorus insecticide, is highly toxic to the. tw o free-living marine dinoflagellates Prorocentrum micans Ehrenberg (au totrophic) and Crypthecodinium cohnii Biechler (heterotrophic). To stu dy its non-antiacetylcholinesterase action we assessed its effect on t he mitochondrial system, as shown by changes in intracellular ATP conc entration and in rhodamine 123 fluorescence evaluated by image analysi s. The technique of image analysis permits direct assessment of change s in the overall activity of mitochondria in living cells. Mitochondri al structures were also examined in the electron microscope. The three methods of investigation yielded complementary results. In P. micans, parathion noticeably altered mitochondria but did not significantly a lter ATP concentrations. In C. cohnii, however, mitochondrial disturba nce was slight, whereas ATP increased greatly. We think, therefore, th at parathion has different effects on mitochondria in the two organism s, and in particular that it increases mitochondrial activity in C. co hnii.