The diatom genus Gomphonema Ehrenberg in India: Checklist and ...

Figs 41–46. LM of Gomphonema diminutum, from the type population; valve view showing the size
diminution series. Scale bar represents 10 µm.
ellipsoidal stigmal opening (Fig. 51). Marginal laminae are present on each side of
the valve (Fig. 51). Helictoglossae at the headpole and footpole are offset from the
raphe branches. Pseudosepta are present at the poles (Fig. 51).
In girdle view the mantle of the valve has striae with areolae that terminate as slits or
in double rows of punctate striae. Striae have round areolae at the headpole (Fig. 49).
At the footpole the round apical pore field porelli extend onto to the end of the
mantle (Fig. 50). Girdle bands are of the open type, following the contour of the
valve. Closed ends of the bands possess septa.
Gomphonema diminutum resembles G. incognitum Reichardt, Jüttner & Cox in Jüttner
et al. (2004, p. 245) in size range and having a wide axial area. The species from
India is linear in shape, is narrower and has finer striae than the species described
from Nepal. Superficial resemblance in terms of having a broad axial area exists
between G. diminutum and G. schweickerdtii Cholnoky (which was, in part, recently
suggested to be conspecific with G. clevei Fricke, Reichardt 2005), but the Indian
species is longer but narrower than the South African taxon (Cholnoky 1953).
ECOLOGY: Gomphonema diminutum was found in many central Western Ghats Rivers.
This species was present throughout the year with relative abundance ranging from
20–40%. This species occurred in a stream with circumneutral pH (7.08 ± 0.17),
poor nutrients (Phosphate: 0.04 ± 0.02 mgl-1 ; Nitrates: 0.29 ± 0.37 mgl-1 ) and
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