Vegetative and reproductive anatomy of some Laurencia (Ceramiales, Rhodophyta) species with a description of L. maris-rubri sp. nov. from the Red Sea

Abstract

The vegetative and reproductive anatomy of some species of Laurencia Lamouroux (Ceramiales, Rhodophyta) belonging to the subgenus Chondrophycus Tokida et Saito [L. tumida Saito et Womersley, L. intermedia Yamada, L. capituliformis Yamada and L. maris-rubri sp. nov.] have been investigated using type and additional material from Australia, Korea, Japan and the Red Sea. The species share several features: (1) vegetative axial segments with two pericentral cells, (2) procarp-bearing segments with four pericentral cells, the fourth of which becomes the supporting cell of the carpogonial branch, (3) tetrasporangia produced from the second pericentral cell of fertile axial segments and (4) the production of additional tetrasporangium-bearing pericentral cells. An assessment of these anatomical features suggests that the occurrence of two pericentral cells in vegetative axes provides a stable basis for delimiting the subgenus Chondrophycus from the subgenus Laurencia, in which four pericentral cells are found. The coincidence of procarp-bearing segments with four pericentral cells and tetrasporangia produced from the second pericentral cell of fertile segments suggests that the species examined are a monophyletic assemblage within the subgenus. Laurencia maris-rubri sp. nov. is described from specimens collected from the Red Sea. The new species produces vegetative axial segments with two pericentral cells and is therefore referable to the subgenus Chondrophycus. It differs from the known species within the subgenus in not producing additional tetrasporangium-bearing pericentral cells. Laurencia tumida is also unique within the genus Laurencia in that the two presporangial cover cells divide into several small cells.