NEW MARINE LITTORAL DIATOM SPECIES (BACILLARIOPHYTA) FROM KERGUELEN ISLANDS. II. HETEROPOLAR SPECIES OF FRAGILARIACEAE

Kerguelen is a Subantarctic archipelago, far from other islands or continents. Its isolation provides an interesting field of investigation concerning species diversity and the emergence of morphological differentiation, particularly in diatoms (Bacillariophyta). Several surveys using light (LM) and scanning electron (SEM) microscopy yielded more than 20 new species and (possibly) two new genera. Most of the new species are from Navicula s.s. and were the subject of a separate paper. Here we describe six new species of araphid diatoms. A common feature of these taxa is their various degrees of heteropolarity and the ultrastructure of the transapical striae, typical for species of Opephora defined in the broader sense. A detailed analysis of valve ultrastructure reveals data relevant to the classification of these new taxa into the genera Nanofrustulum (N. squammatum), Pseudostaurosira (P. gersondei, P. quasielliptica, P. latesternum and P. versiformae) and Staurosirella (S. poulinii). Their relationships to Opephora s.s., as defined by Round et al. (1990), are also discussed.