Gamete discharge by Bryopsis plumosa (Codiales, Chlorophyta) induced by blue and UV-A light

SUMMARY Gamete discharge by the coenocytic green alga Bryopsis plumosa (Hudson) C. Agardh is induced by light. The mature male gametangia consist of a mass of quiescent male gametes and a large central vacuole. Within a few minutes after the onset of irradiation, breakdown of the tonoplast of the central vacuole and initiation of gamete motility occur simultaneously. This is followed by a forced discharge of moving gametes through a hole ruptured at the subapical region of the gametangium. The action spectrum for the light‐induced gamete discharge was determined from a series of fluence‐response curves. This action spectrum, having two major maxima at 370 and 450 nm, indicates the involvement of a blue light/UV‐A‐absorbing photoreceptor previously described as ‘cryptochrome’.