Revision of the genus Hantzschia (Bacillariophyceae) on Livingston Island (South Shetland Islands, Southern Atlantic Ocean)

Abstract

Diatoms (Bacillariophyta) are one of the most abundant groups of micro-algae present in the Antarctic Region, both in terms of number of species and of number of individuals (Jones 1996, Van de Vijver & Beyens 1999). The past ten years, the taxonomy of the Antarctic non-marine diatom flora has been thoroughly revised resulting in the description of a large number of new species (a.o. Van de Vijver et al. 2002, Van de Vijver & Mataloni 2008, Van de Vijver et al. 2010). An important part of these revisions focused on the typical terrestrial genera Luticola, Muelleria and Diadesmis. This is not surprising since one of the principal biomes in the Antarctic Region is formed by large, terrestrial ice-free areas, fellfields, wet soils, seepage areas and rocks. The soils of these areas form a suitable habitat for a large variety of terrestrial diatoms. Diatoms living in these habitats are welladapted to survive the sometimes severe conditions such as a continuously changing soil humidity and freeze-thaw cycles. Apart from the above-mentioned (already revised) genera, two other terrestrial genera form large populations within the Antarctic Region: Eunotia and Hantzschia. The present paper revises the taxonomy of the genus Hantzschia, based on observations made during a survey of the non-marine diatom flora of Livingston Island. Several unknown Hantzschia species were observed, that could not be assigned to any of the already described taxa. Five taxa will be described as new to science whereas three others are illustrated. The genus Hantzschia is a relatively small genus with less than fifty species known worldwide, occurring in a wide variety of habitats ranging from freshwater to terrestrial and even intertidal and marine environments (Round et al. 1990). Described in 1877 by Grunow, the genus, belonging to the family Bacillariaceae, is characterized by a typical asymmetrical valve outline with usually a more convex dorsal side and a concave ventral side, the presence of uniseriate striae composed of small rounded areolae containing hymenes, a raphe that is subtended by fibulae and a complex girdle structure (Round et al. 1990). Species within the genus are separated based on number of striae and areolae per stria, the position and shape of the fibulae, the shape of the external and internal proximal raphe endings and the shape of the valve apices. Hantzschia amphioxys (Ehrenb.) Grunow is considered to be the most common and well known species in this genus, living almost exclusively in (semi-wet) soils. The spe-