Stellate chloroplast organization in Asteronema breviarticulatum comb. nov (Ectocarpales, Phaeophyta)

Light and electron microscope studies of vegetative cells of Asteronema breviarticulatum (J. Agardh) Ouriques & Bouzon comb. nov. demonstrated that groups of plastids are organized in a stellate arrangement. Each plastid has a terminal pyrenoid, and the centre of a group of chloroplasts is formed by a cluster of all the pyrenoids. The individual pyrenoids are separated by a thin interpyrenoid space. These cytological traits distinguish A. breviarticulatum from the genera Ectocarpus and Hincksia, in which this species has previously been classified. Morphological and reproductive characters within the genera of small brown algae with a stellate plastid arrangement (i.e. Bachelotia. Asterocladon. and Asteronema.) also suggest that the new combination A. breviarticulatum is justified.