TWO MARINE COCCONEID DIATOMS FROM KERGUELEN'S LAND (AUSTRAL OCEAN, INDIAN SECTOR): CAVINULA KERGUELENSIS NOM. NOV. AND COCCONEIOPSIS WRIGHTII

Abstract

Two small diatoms with a cocconeid shape were sampled infrequently on subtidal muddy sediments under the Macrocystis pyrifera canopy and on a mussel bed mud in the subantarctic Kerguelen Archipelago (Indian part of the Austral Ocean). They are described and illustrated by means of light and SEM micrographs. The first one looks very much like a species first described from Kerguelen as Navicula kerguelensis Heiden [nom. Meg., non (Ehrenb.) Ralfs, nee Castracane]. This taxon was later treated as a synonym of N. pseudoscutiformis Hustedt, and then transferred to Cavinula pseudoscutiformis (Hustedt) Mann & Stickle. However, the Kerguelen diatom, isolated from marine sediments, shows slight morphological and possible important ecological differences from the type of N. pseudoscutiformis, originally described from freshwater lakes in northern Germany. We propose that it should be considered as a different taxon from Cavinula pseudoscutiformis, under the new name Cavinula kerguelensis Riaux-Gobin & Compère, reinstating for it Heiden's illegitimate epithet. The second small diatom clearly belongs to the species first described as Cocconeis wrightii O'Meara from Ireland and renamed Navicula schonkenii by Hustedt. It has also been found in subantarctic and other southern areas by several diatomists and recently transferred to the genus Cocconeiopsis as Cocconeiopsis wrightii (O'Meara) Witkowski et al. Some details complement the previous descriptions of these two relatively rare taxa.

Keywords:

• marine diatoms
• biraphideae
• Cavinula
• Cocconeiopsis
• Kerguelen's Land