Eunotia enigmatica sp. nov., a new planktonic diatom from Brazil and the transfer of Fragilaria braunii Hustedt to the genus Peronia (Bacillariophyceae)

Abstract

Eunotia is a diatom genus characterized by a short raphe system restricted to both valve poles and by the presence of rimoportulae. As part of a survey examining the genus, Eunotia enigmatica sp. nov. is described from ultra oligo– to oligotrophic and slightly acidic reservoirs in São Paulo State, southeast Brazil. The species is unusual in having a short distinct raphe, and a ‘fragilarioid’ appearance with long cells and marginal spines. It was commonly found in the planktonic community as well as on sediments of the studied reservoirs. It seems to be adapted to an open water existence, and is similar to E. croatana and E. pseudofragilaria both described from North America. Additionally, type material of another similar looking species, Fragilaria braunii, was analysed using light and scanning electron microscopy and a new combination is proposed for it in the genus Peronia.