Encyonopsis krammeri Reichardt

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 : 113-117

Encyonopsis krammeri Reichardt ( Figs 417–480 )

Description: Two different forms with differing apices are documented here. Valves are moderately dorsiventral and narrow-lanceolate in outline in the most widespread form. Dorsal margin is more clearly curved relative to the weakly convex ventral side, without shoulders. Poles are rostrate and may be weakly deflected ventrally, but variable in populations. Axial area very narrow and central area absent to weakly developed. Length 9.6–23.5 μm; width 2.6–3.8 μm; maximum L:W ratio 7.0.A more clearly capitate form with a near lanceolate outline ( Figs 461–472 ) was found with type material of E. alpina and also occurs in calcareous lakes in Ireland. It shares the same ultrastructural combination of features as E. krammeri , including identical raphe design, a characteristic thin plate-like silica thickening visible internally between the helictoglossa and apices ( Fig. 442 ; 479–480 ) and transapically elongate linear shaped puncta. Striae density is higher (32–36 in 10 μm) in these populations than originally published for E. krammeri .

Ecology: A cosmopolitan and widespread diatom found in 31 lakes and reaching a maximum relative abundance of 43%. It occurs at higher densities in calcareous lakes in oligotrophic to mesotrophic conditions ( Fig. 532 ).

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 417–448. Encyonopsis krammeri Reichardt. Figs 417–448. LM. Figs 417–440. Valves showing morphological range and size reduction series in Irish lakes. Figs 441–448. SEM. Figs 441 & 443–446. External view. Figs 442 & 447. Internal view. Fig. 448 Girdle view. Scale bar in Fig. 440 = 10 μm for all LM figures. Scale bar in all SEM micrographs = 1 μm.

FIGURES 449–480. Encyonopsis krammeri Reichardt. Figs 449–472. LM. Figs 449–454. Valves illustrating the dorsiventral form and narrow rostrate poles for the most commonly encountered form. Figs 455–460.A population with more protracted subcapitate poles. Figs 461–472. A more lanceolate form corresponding to E. angusta Krammer & Lange-Bertalot with more clearly capitate rounded ends. Figs 473–480. SEM. Figs 473–478. External view of frustules with differing outline and apices but with equivalent ultrastructural morphology. Figs 479–480. Internal view with thickened silica between helictoglossa and end of apices. Scale bar in Fig. 472 = 10 μm for all LM figures. Scale bar in all SEM micrographs = 1 μm.