Encyonema appalachianum Potapova, 2014

Potapova, Marina, 2014, Encyonema appalachianum (Bacillariophyta, Cymbellaceae), a new species from Western Pennsylvania, USA, Phytotaxa 184 (2), pp. 115-120 : 116-118

Encyonema appalachianum Potapova , sp. nov. ( Figs 1–12 )

Valves linear-lanceolate, very slightly dorsiventral, 6–7 μm wide, 26–34 μm long. Ends rounded, very slightly protracted. Raphe lateral with shraply bent terminal fissures. Axial area narrow linear. Central area formed by considerably shortened stria on ventral side and very slightly shortened stria on dorsal side. Striae parallel, 9–10 in 10 μm, mostly uniseriate, occasionally biseriate. Areolae apically elongated, approximately 26 in 10 μm. Striae continue uninterrupted around valve apices.

Type:— USA. Pennsylvania: Youghiogheny River , 39.87505° N, 79.4958° W, M. Potapova, May 4, 2013. (Holotype: circled specimen on slide ANSP GC 59137 , illustrated in Fig. 5 ; Isotypes: circled specimens on slides ANSP GC 59138 and CANA 105723 ) .

1–6), 1 µm (in Figs 7, 8 ), 5 µm (in Figs 9, 10 ).

Etymology: — Encyonema appalachianum is named after Appalachian Region where it has been discovered.

Additional morphological data:

There is little variation in valve shape and striation pattern in the type population of Encyonema appalachianum ( Figs 1–6 ). A Voigt discontinuity is occasionally observed on the ventral side of the valve ( Fig. 4 ). The external raphe slits are slightly curved ventrally ( Figs 11 and 12 ), while the internal slits are straight ( Fig. 10 ). The external proximal raphe ends are dorsally deflected and moderately dilated ( Figs 11 and 12 ). Terminal raphe fissures are very long and reach the mantle ( Fig. 11 ). They form an angle of approximately 105 o –115 o with the external raphe slit ( Figs 11 and 12 ). The intermissio, which is the space between internal proximal raphe ends, is quite small ( Figs 7 and 8 ), and in some valves it appears to be missing ( Fig. 9 ). Typically uniseriate striae occasionally become biseriate ( Fig. 12 ). No stigma is present.

Ecology and distribution:— Encyonema appalachianum was found in 12 rivers and reservoirs located in State Parks of southwestern Pennsylvania ( Table 1). Water conductivity in these water bodies varied from 32 to 650 µS cm- 1 and pH from 6.9 to 9.0. The highest pH numbers observed in eutrophic reservoirs Yellow Creek Lake (8.4–8.8) and Lake Arthur (9.0) in the daytime in areas of dense aquatic vegetation should be most likely attributed to high levels of photosynthesis. This diatom was also found in 2013 and 2014 in Susquehanna River (Sonja Hausmann and Jack Holt, pers. comm.).

Figures

FIGURES 1–10. Encyonema appalachianum, type material. Figs 1–6 LM micrographs. Fig. 5 Holotype specimen. Figs 7–10 SEM, internal views. Figs 7–9 Central portions of valves showing variability of intermissio. Fig. 10 Whole valve. Scale bars = 10 µm (in Figs

FIGURES 11, 12. Encyonema appalachianum, type material, SEM, external views. Fig. 11. A typical valve with uniseriate striae. Fig. 12. A valve with partially biseriate striae. Scale bars = 5 µm.