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.