Morphological, taxonomic and nomenclatural analysis of species of Odontella, Trieres and Zygoceros (Triceratiaceae, Bacillariophyta) from Anegada Bay (Province of Buenos Aires, Argentina)

Abstract

While conducting surveys of marine phytoplankton from coastal waters of the Anegada Bay (Province of Buenos Aires, Argentina) we found several eupodiscoid diatoms belonging to the genus Odontella sensu lato. Raw and cleaned samples collected at Los Pocitos, Riá del Jabalí and San Blas between 2008 and 2010, were analyzed with light and scanning electron microscopy. Based on a morphological analysis, species with loculate areolae and ocellus-bearing elevations are included in the genera Trieres (T. mobiliensis and T. sinensis) and Zygoceros (Zygoceros atlanticus comb. nov.), while species with poroid or pseudoloculate areolae and ocellus-bearing elevations are provisionally included in Odontella (O. longicruris, O. obtusa and O. rostrata). Zygoceros is revisited based on analysis of type material of species previously included in Odontella (O. atlantica, O. rhomboides and O. rhombus), their description is emended, and correct names of the transferred species are established (Zygoceros atlanticus comb. nov. and Z. ehrenbergii nom. nov.). Trieres differs from Zygoceros by having a ridge between its valve surface and mantle, longer slender polar elevations, longer external rimoportula tubes, and a planktonic style life. Following transfer of taxa with loculate areolae to Trieres and Zygoceros, Odontella only includes species with poroid and pseudoloculate areolae. Further research is necessary to establish the circumscription of Odontella, thus our conclusions are provisional.