Encyonopsis subminuta Krammer & Reichardt, 1997

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 : 119-120

Encyonopsis subminuta Krammer & Reichardt ( Figs 511–529 )

Description: Valves are symmetric or appear only very slightly dorsiventral, lanceolate with weakly convex dorsal and ventral sides. Valve apices are clearly protracted capitate to subcapitate, rarely rostrate and without clear shoulders. Axial area is narrow linear and central area absent. Length 10–25 μm; width 3.0–4.5 μm; maximum L:W ratio 5.8. Striae parallel to weakly radiate at centre, weakly radiate towards apices and uniform in appearance. The upper range of stria density in Irish populations is slightly higher than reported elsewhere ( Table 1) and a form with distinct peanut-shaped puncta ( Figs 528–529 ) was also well represented and co-occurs with nominate valves ( Figs 523–527 ). Raphe is filiform, proximal ends curve dorsally with slightly dilated endings. Distal fissure deflected ventrally, terminating in a small pore on the valve face.

Ecology: A cosmopolitan species in well buffered alkaline lakes with low nutrient concentration ( Fig. 532 ). It occurs in 30 lakes with a maximum relative abundance of 25%.

Figures

FIGURE 532. Scatter plots of the distribution of Encyonopsis taxa in relation to A. Total phosphorus (TP) and B.Alkalinity. Vertical lines indicate the location of optima derived from weighted averages of species occurrences for TP (red) and alkalinity (blue). Taxon codes correspond to Fig. 530, with All (ENCY All) and Unidentified (ENCY unid.) Encyonopsis categories illustrated for comparison.

FIGURES 511–529. Encyonopsis subminuta agg. Figs 511–522. Valves showing morphological range and size variation in populations from Irish lakes. Figs 523–529. SEM. Figs 523–527. External and internal view of Encyonopsis subminuta Krammer & Reichardt. Fig. 528–529. Internal and external of E. aff. subminuta. Scale bar in Fig. 522 = 10 μm for LM figures. Scale bar in all SEM micrographs = 1 μm.