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 number of conceptacles on the receptacles was enumerated and related to the dry weight of the receptacles. It was found that conceptacle number per receptacle correlated well to the weight of the receptacle and that, 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 developed a greater number of conceptacles per unit weight than the terete receptacle type. Reproductive:somatic biomass ratios indicated that the three-cornered receptacle type had a lower reproductive expenditure than the terete receptacle type in terms of biomass. Ecological and possible taxonomic implications are discussed.