Encyonopsis sp. 2

Kennedy, Bryan, Buckley, Yvonne & Allott, Norman, 2019, Taxonomy, ecology and analysis of type material of some small Encyonopsis with description of new species in Ireland, Phytotaxa 395 (2), pp. 89-128 : 113

Encyonopsis sp. 2 ( Figs 353–396 )

Description: Outline symmetric to weakly dorsiventral, lanceolate with weakly convex dorsal and ventral sides. Poles are narrow rostrate. Vales with gently sloping outline lacking shoulders. Axial area is very narrow and central area absent. Length 9.5–17.2 μm; width 2.7–3.6 μm; maximum L:W ratio 5.2. Striae parallel at valve centre becoming weakly radiate and visible over the length of the valve. Stria density 27–30 dorsally and 24–29 ventrally in 10 μm. Raphe filiform, dorsally deflected at centre, with a distinctive short section recurved back towards centre on ventral side and lacking obvious expanded terminal raphe endings. Areolae always small and round.

This form closely resembles E. minuta with smaller valves converging in morphology and occasionally were not possible to differentiate in LM and SEM. Larger valves are more linear lanceolate in outline and have narrow rostrate ends compared to the broadly rounded apices of E. minuta . Valves lack a very clear separation of proximal raphe endings that are always more clearly visible internally in the latter. All remaining characters are equivalent and its relationship with E. minuta requires further investigation. Ultrastructually, it has an affinity with E. eifelana Krammer (1997: 102) but lacks the more obviously truncate ends and lower striae density of this taxon.

Ecology: Found in 25 lakes but usually at low densities (<1–3%) with a maximum relative abundance of 6.3% in L. Lene, a calcareous lake in the midlands. Its ecology is equivalent to E. minuta and both diatoms co-occur.

Figures

FIGURES 353–396. Encyonopsis sp. 2 aff. minuta Figs 353–385. LM. Figs 353–385. Valves showing morphological range and size reduction in populations. Figs 386–396. SEM. Figs 386–395. External valve view with narrow rostrate apices. Fig 396. Internal view lacking a clear intermission at central area. Scale bar in Fig. 385 = 10 μm for all LM figures. Scale bar in all SEM micrographs = 1 μm.