Two new Eunotia species with subapical costae, an uncommon structure for the genus

Abstract

Two new Eunotia species, E. ibitipocaensis Canani & Torgan and E. saltoensis Canani & Torgan are described. The specimens were found in acidic oligotrophic rivers from pristine watersheds located at 940 m above sea level in Ibitipoca State Park, southeastern Brazil. Both species have costae adjacent to the helictoglossae, which is an uncommon structure for the genus Eunotia Ehrenberg. Eunotia ibitipocaensis has mostly heteropolar valves with apices of variable shape and relatively low stria density. The valves of E. saltoensis are isopolar with ventrally bent apices and possess higher stria density than E. ibitipocaensis. The heteropolarity observed is a less common condition in Eunotia, but it is usually found in the genus Actinella Lewis. The diagnostic features that distinguish Eunotia and Actinella are discussed.

Keywords:

• acidic water
• Eunotia ibitipocaensis
• Eunotia saltoensis
• rivers
• taxonomy

Acknowledgements

We thank Koen Sabbe and Shigeki Mayama for valuable information, the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for providing the Doctoral and Research Fellowships for the first and second authors, respectively, the Museu de CiênciasNaturais, Fundação Zoobotânica do Rio Grande do Sul for the infrastructure and the Instituto Estadual de Florestas de Minas Gerais (IEF-MG) for licensing and supporting the field campaigns. We are grateful to Daniel de Aguirres for the English revision.