NEW COCCONEIS TAXA FROM CORAL SANDS OFF REUNION ISLAND (WESTERN INDIAN OCEAN)

Abstract

Coral sands and affiliated environments off the Réunion Island (Mascarene archipelago, Western Indian Ocean) are inhabited by diversified diatom communities. The Monoraphidineae taxa are particularly numerous. A preliminary survey (June 2005) of coral sands from the fringing reefs “Ferme Corail”, “St Leu” and “l'Hermitage”, has made it possible to observe and describe four new species pertaining to the genus Cocconeis Ehrenberg. The larger one, Cocconeis alucitae, is closely related to C. scutellum Ehrenberg but shows a striking sternum valve (SV) valvocopula with long and thin fimbriae proximately joined in a median-valve ring, and short chambers on the internal face of the SV. C. coralliensis, C. borbonica and C. mascarenica are smaller taxa, close to C. molesta Kützing, C. finmarchica Grunow and C. neothumensis Krammer respectively, but with differences in their valves ornamentation, particularly in striation, denser than in the mentioned taxa. This paper presents light (LM) and scanning electron microscopic (SEM) observations for each taxon and comparison with similar or relevant taxa.

Keywords:

• diatom flora
• Cocconeis
• coral sands
• fringing reefs
• Réunion Island
• Indian Ocean