TAXONOMY, ULTRASTRUCTURE AND BIOGEOGRAPHY OF THE ACTINELLA-PUNCTATA SPECIES COMPLEX (BACILLARIOPHYTA, EUNOTIACEAE)

Members of the Actinella punctata species complex are investigated wit h light and scanning electron microscopy. A. punctata var. punctata is shown to range in length from 36 to 169 mu m. Spines outline the exte rnal valve margin, and the ventral margin has a protrusion or point th at is elongate. A labiate process is present at both poles. A. punctat a var. punctata is known from North America and Scandinavia only. A. a ustralis comb. nov. and A. manguinii spec. nov. are species originally identified as subspecific taxa with A. punctata and known only from M adagascar. These two species are much smaller than the nominate variet y of A. punctata and have a variable number and placement of labiate p rocesses. Both A. australis and A. manguinii either lack labiate proce sses or have a single process per valve, which may be positioned at th e headpole or footpole. Actinella punctata var. curta could not be con firmed from North America, and the original illustrations of this taxo n, and specimens observed from Sierra Leone display an elongated protr usion or point on the dorsal margin of the valve. This feature suggest s A. punctata var. curta may be more closely allied to African and Sou th American Actinella species since they also have an elongate protrus ion or point on the dorsal margin. Previous discussions about a broad biogeographic distribution of Actinella punctata do not seem to be sup ported, since the taxa previously assigned to this species complex do not appear to be closely related.