Kobayasiella saxicola (Manguin) Lange-Bertalot (Figs 32 −37)

SEM (Figs 32 −37): Valves linear with rostrate to capitate apices (Figs 32, 36). Axial area narrow, hardly widening near central area (Figs 32, 36). Striae radiate, 34−40 in 10 μm, becoming abruptly convergent near apices. Shift in stria orientation marked by a branched stria (simulating a candelabra) on either side of raphe (Figs 32, 33, 36). Central area bordered by long and short striae (Figs 34, 36). Alveolate striae with hymenate occlusions perforated externally by at least four rows of tiny pores (Fig. 37), interrupted near margin with narrow hyaline area all around valve (Fig. 32, arrowhead, Figs 34, 36, arrows). Mantle bearing single alveolate striae (Fig. 34, arrowhead, Fig. 35, arrow). External raphe fissure straight with an umbilicus on primary side of valve (Figs 32, 33, arrows). Proximal raphe endings elongated, weakly expanded (Fig. 34). Terminal raphe fissures terminating on valve face, strongly hooked backwards towards same direction (Figs 32, 35), curvature corresponding to terminal fissure extended in three alveolate striae (Fig. 35). Internally, raphe branches straight with simple proximal endings, distal endings terminating onto poorly developed helictoglossae (Fig. 36). New valve dimensions (n=55): length: 14−27.5 μm, width: 3.0−5.0 μm, stria density 34−40 in 10 μm.

Distribution and ecology: — Kobayasiella saxicola is known from New Caledonia and was identified as “probably aerophilic” by Manguin (1962). Moser (1999) observed this species quite commonly but exclusively in ultramafic bedrock areas. Running waters on ultramafic soils are very poor in nutrients, with an extremely low calcium/ magnesium ratio due to a high magnesium concentration (Weninger 1968, Trescases 1969). Based on the results of the new sampling campaign, it is clear that the taxon is only found in the southern part of New Caledonia (Figure 1). In these localities, the diatom community showed a low diversity in genera with several species considered to be endemic to the island, including E. guillauminii, G. ricardii, B. angusta, A. indicatrix and F. neocaledonica. Kobayasiella saxicola may reach up to 20% of the total diatom community in some samples.