A new flat Gracilaria: Gracilaria lantaensis sp. nov. (Gracilariales, Rhodophyta) from the Andaman coast of Thailand

Collection of a flat red alga of the genus Gracilaria from the Andaman coast of Thailand was described as a new species, G. lantaensis sp. nov. based on detailed morphological characteristics and rbcL sequence analysis. This species typically grew intertidally on exposed mud-sand shores. It was characterized by its slender thalli with narrow-bladed branches, its smooth margin with a few brachlets and its reddish-pink color. Spermatangial conceptacles were of the textorii-type. Cystocarps were spherical and possessed numerous nutritive filaments at lateral and basal positions in the cystocarp cavity. Gracilaria lantaensis was morphologically similar to G. yamamotoi but differed in branching pattern and cystocarp structure. RbcL sequence data also indicated the genetic distinction between G. lantaensis and other species of Gracilaria. Gracilaria lantaensis was grouped with a major assemblage of Gracilaria species, and sister to some Indian Ocean species with denticulate margins, e.g. G. beckeri, G. capensis and G. denticulata.