A new Cocconeis (Bacillariophyceae) from Moorea island, Society Archipelago, South Pacific Ocean with distinctive valvocopula morphology and linking system

C. Riaux Gobin (1) , O.E. Romero (2) , Michel Coste (3) , R. Galzin (1)

1 CRIOBE - Centre de recherches insulaires et observatoire de l'environnement
2 IACT - Instituto Andaluz de Ciencias de la Tierra
3 UR REBX - Réseaux épuration et qualité des eaux

The study of coral reef diatoms on Moorea Island in the Society Archipelago, South Pacific Ocean revealed a strong representation of the Achnanthales, with many taxa of Cocconeis. One of these Cocconeis, examined by light and scanning electron microscopy, shows a sternum valve (SV) with a close resemblance to the Cocconeis scutellum lineage, whereas the raphe valve (RV) and the valvocopula system are different from that of C. scutellum, therefore a new name has been given to it, Cocconeis spina-christi sp. nov. This new taxon has several remarkable features: 1) the RV stria density is, on average, twice as high as that of the SV; 2) the RV valvocopula extended and structurally complex, has large marginal fenestrae, irregular digitiform fimbriae and one longer spine-like fimbria at each apex; and 3) an anchor system between the valvocopula of each valve is observed, consisting of a rounded papilla with transverse furrows lying on each basal RV valvocopula fimbria and fitting into a rounded concavity - or cupule - in the corresponding marginal edge of the SV valvocopula. Such an anchor system between valvocopulae seems a characteristic common to several Cocconeis species bearing fimbriae on each valvocopula. The definition and limit of the concept of varieties in the C. scutellum lineage is also addressed.

Mots clés: BACILLARIOPHYCEAE; MORPHOLOGIE; ZONE TROPICALE

Domaines: Sciences de l'environnement

C. Riaux Gobin, O.E. Romero, Michel Coste, R. Galzin. A new Cocconeis (Bacillariophyceae) from Moorea island, Society Archipelago, South Pacific Ocean with distinctive valvocopula morphology and linking system. Botanica Marina, 2013, 56 (4), pp.339-356. ⟨10.1515/bot-2012-0162⟩. ⟨hal-01123877⟩