PHOTOTAXIS IN FUNGIIDAE CORALS (SCLERACTINIA)

Corals within the scleractinian family Fungiidae were observed to move toward light (positive phototaxis). Negative phototactic movement was not observed in any of the specimens tested. On sandy substratum, Dia seris distorta moved faster (max. speed of 3 cm h(-1)) than other spec ies, Although D. distorta has symbiotic algae, phototactic movement al so was observed both in bleached corals and in those treated with a sp ecific inhibitor (dichlorophenyl dimethyl urea) of photosynthesis. D. distorta was phototactic even on a glass plate, and climbed up a steep slope (up to 30 degrees), Based on experiments with Fungia fungites a nd D. distorta, soft tissues at the peripheral region of the disc seem to be responsible for movement via peristalsis. It is suggested that positive phototaxis in symbiont-bearing fungiid corals is an important trait for selection of favorable habitats.