Vegetative and reproductive morphology of Sargassum orotavicum sp. nov. (Fucales, Phaeophyceae) from the Canary Islands (eastern Atlantic Ocean)

Abstract

A population of seaweeds from the Canary Islands successively reported as Sargassum diversifolium, S. vulgare f. diversifolium, or S. vulgare was examined monthly at the climax of vegetative and reproductive stage development to evaluate morphological taxonomic features. The primary and secondary blades are morphologically different (primary blades are spirally twisted and sinuous with serrate to nearly entire margins, whereas secondary blades are thinner with entire to slightly dentate-serrate margins); the vesicles are subspherical to slightly oblong, muticous or ending in a mucro or in a coronal blade; and the receptacles are furnished with spines. These characters are not applicable to Sargassum diversifolium, or to an infraspecific taxon of Sargassum vulgare or S. furcatum as previously suggested, and consequently, Sargassum orotavicum sp. nov. is described. Nomenclatural problems related to the name diversifolium and the affinities of the species involved are presented. According to their morphological characters, S. orotavicum, S. vulgare and S. furcatum belong to the subgenus Sargassum. However, S. vulgare and S. furcatum constitute genuine species of the subsection Cymosae of the section Malacocarpicae, whereas S. orotavicum appears related to species of the subsection Biserrulae of the section Acanthocarpicae.