CLOTRIMAZOLE, A MODEL-COMPOUND FOR THE HOST RELEASE FACTOR OF THE CORAL PLESIASTREA-VERSIPORA

Crude homogenates of animal host tissues stimulate the release of phot osynthetic products from symbiotic dinoflagellates isolated from coral s and several other invertebrates. It is believed that specific 'host release factors' stimulate the symbiotic algae to release water-solubl e compounds, chiefly glycerol and amino acids, to the host. Crude host homogenates also contain compounds which sometimes inhibit photosynth esis in isolated algal cells, although this inhibition is not apparent in the intact association. Therefore, use of crude homogenates in tra nslocation experiments may sometimes lead to inconsistent results. We have found that the commercially available synthetic fungicide, clotri mazole (mycosporin), a chemical analogue of naturally occurring mycosp orine-like amino acids, can be used as a model for the host release fa ctor of the coral Plesiastrea versipora (Lamarck). Clotrimazole stimul ated isolated algal cells from Ii versipora to release carbon fixation products to the external medium. Chromatography experiments showed th at the released compounds were similar to those found when algae were incubated with crude homogenates of P. versipora. We propose that, in Plesiastrea versipora, clotrimazole may be used as an internal control in experiments using crude host homogenate and in screening partially purified fractions for 'host factor' activity. Clotrimazole is the fi rst commercially available compound found to have effects similar to t he 'host factor' of a coral.