Vegetative, reproductive and molecular characterization of Gloiocladia microspora (Faucheaceae, Rhodophyta)

Abstract

Morphological and molecular studies of Gloiocladia microspora were carried out to confirm its position in the genus Gloiocladia. The thallus is compressed and complanately irregularly branched, and develops narrow, cylindrical segments from the apices, which give rise to new compressed branches in adult specimens. The cortex is composed of an outer section of loose anticlinal filaments, slightly arched at the base, and a single-layered subcortex of cells that form a network parallel to the thallus surface. The medulla is composed of large, longitudinally elongated, hyaline cells. Female gametophytes are procarpic with a three-celled carpogonial branch and a two-celled auxiliary cell branch, both borne on the same subcortical cell. After fertilization, a fusion cell is formed from the auxiliary mother cell, the auxiliary cell, and probably adjacent vegetative cells. Simultaneously the auxiliary cell divides to cut off the primary gonimoblast cell. Components of the mature fusion cell are indiscernible. Nutritive cells and a tela arachnoidea are conspicuous and present at the early procarp stage. Cystocarps are sessile or substipitate, ostiolate, and usually situated around the narrow segments of fronds or, sometimes, on the margins of the compressed branches that arise from narrow segments. Spermatangia are unknown. Tetrasporangia develop in raised nemathecia located on small compressed proliferations or on the narrow segments, and usually surround them. Phylogenetic analyses of partial rbcL sequences resolved G. microspora as a distinct species within the clade of other Gloiocladia species. Vegetative and reproductive morphology, together with molecular analyses support the position of G. microspora within Gloiocladia.