Eunophora gen. nov. (Bacillariophyta) from Tasmania and New Zealand: description and comparison with Eunotia and amphoroid diatoms

Abstract

A new raphid pennate diatom genus, Eunophora, and three new species are described from highland lakes and streams in Tasmania and New Zealand. Eunophora tasmanica and E. indistincta are only found in Tasmania; E. oberonica and a fourth species (Eunophora sp. 1) also occur in New Zealand. The presence of polar rimoportulae in E. tasmanica and E. oberonica, the relatively simple structure and arrangement of the raphe system and the stria pattern indicate that Eunophora belongs to the subclass Eunotiophycidae. However, it differs from the other genera in this subclass in the amphoroid symmetry of the cells, the length of the raphe slits and the non-coaxial internal central raphe endings; also unusual are the position of the raphe on the valve face instead of on the ventral mantle and the presence of many small discoid or band-like chloroplasts. Eunophora may represent a link between the Eunotiophycidae and the amphoroid genera of the Bacillariophycidae. Eunophora is characteristic of dystrophic to (ultra-)oligotrophic lakes and appears to be restricted to the Southern Hemisphere. The four species display a characteristic distribution in Tasmania: Eunophora tasmanica is common and widespread in all highland lakes, E. oberonica occurs mainly in the dystrophic western lakes, while E. indistincta and Eunophora sp. 1 were found mainly in intermediate lakes along the limnological corridor between the western dystrophic lakes and the eastern oligotrophic lakes.