Diurnal periodicity of spore-shedding in some red algae of Visakhapatnam coast

Experiments were conducted for 2yr from September 1976 to August 1978 on the diurnal periodicity of spore-discharge in Gelidium pusillum (Stackhouse) Le Jolis, Pterocladia heteroplatos (Boergesen) Umamaheswara Rao & Kaliaperumal, and Gelidiopsis variabilis (Greville) Schmitz, growing in the intertidal region of Visakhapatnam. Regular diurnal periodicity of spore-shedding was found with peak output of spores during night-time in Gelidium and during daytime in Gelidiopsis. The pattern of diurnal curves for these two species varied seasonally with a 4-h delay in the peak shedding of spores during December to February–March. Results obtained with Pterocladia were irregular without any seasonal fluctuations in the daily liberation of spores. The variation in the diurnal rhythm of spore-shedding in Gelidium and Gelidiopsis may be due to seasonal changes in sea-water temperature.