MORPHOMETRIC STUDIES OF SARGASSUM SPP. (SARGASSACEAE, PHAEOPHYTA) FROM REUNION ROCKS, KWAZULU-NATAL, SOUTH-AFRICA - I - RECEPTACLES

Specimens of a mixed population of Sargassum spp. were collected from Reunion Rocks, KwaZulu-Natal, South Africa over a period of one year. Three general shapes of receptacle were recorded for Sargassum elegans , S. incisifolium and an undescribed species of Sargassum: i) terete, ii) three-cornered and iii) twisted receptacles respectively. The numb er of conceptacles on the receptacles was enumerated and related to th e dry weight of the receptacles. It was found that conceptacle number per receptacle correlated well to the weight of the receptacle and tha t each receptacle type had a different number of conceptacles per unit weight. Relationships were found to vary from one season to the next, however, it was found that the three-cornered receptacle type develop ed a greater number of conceptacles per unit weight than the terete re ceptacle type. Reproductive:somatic biomass ratios indicated that the three-cornered receptacle type had a lower reproductive expenditure th an the terete receptacle type in terms of biomass. Ecological and poss ible taxonomic implications are discussed.