Eunotia panda Veselá et Johansen, 2014

Veselá, Jana & Johansen, Jeffrey R., 2014, Three new Eunotia (Bacillariophyta) species from Acadia National Park, Maine, USA, Phytotaxa 175 (4), pp. 181-200 : 189-190

Eunotia panda Veselá et Johansen spec. nov. ( Figs 56–103 )

Type:— USA. Maine: Acadia National Park, Big Heath (wetland next to Rd 102A), 44.233962° N, 68.320719° W, 5 June 2008, Veselá 008 ( ANSP!). The holotype designated here, holotype slide ANSP GC 59085, Fig. 71 depicts the holotype (14.35 mm south by 5.05 mm east from the benchmark cross on the slide); isotype slide ACAD 54522b, stored at J. R. Johansen’s collection at John Carroll University, Ohio , USA (isotype specimen in Fig. 74 , 7.0 mm south by 9.0 mm east from the benchmark cross on the slide).

Valves are arcuate, isopolar, having a curvature of 0.74–1.00 radians, with a slight increase in curvature from the largest to the smallest valves ( Figs 56–86 ), with length to breadth ratio 12–27:1, 33–97 µm long, 3–4 µm wide (mostly 3.5 µm). Ventral and dorsal valve margins are parallel through most of the valve, only tapering very near the apices, slightly reflexed dorsally at the weakly protracted ends ( Figs 56–87 ). Valve apices bear many minute, sharp siliceous protrusions, which are situated irregularly between the striae or areolae ( Figs 88, 90, 93, 95 ). Valve margins are typically sharply beveled with a single row (rarely double rows) of areolae in the beveled portion ( Fig. 89 ). In LM the raphe is distinct, but short. It begins on the valve mantle ( Fig. 92 ), and curves subapically on the valve face back towards the main part of the valve ( Figs 87–93, 95 ) as visible from SEM. The raphe is centered in the apical region, with external fissures visible on the external portion of the valve (e.g., Figs 88, 95 ), but not penetrating the internal part of valve past the helictoglossa ( Figs 96–103 ). Helictoglossa is visible in the LM ( Figs 56–86 ). A single rimoportula, placed at the apex, is present per valve ( Figs 96–103 ). Striae are lowered in between hyaline ridges, parallel in the center of the valve, radiating towards the apices ( Figs 56–93 ), 14.5–17(20) in 10 µm in the center valve, up to 21 in 10 µm near the apices. Areolae are open, rounded with irregular edges or irregular in shape ( Figs 88–90, 92–95 , 98, 99, 101, 102 ), 33–40 in 10 µm.

Etymology:—From the Latin adjective pandus (i.e. curved, arched), referring to the curvature of the valves.

Ecology and distribution:—Our populations of E. panda were observed in ponds, streams and wetlands in all three major parts of Acadia National Park ( Table 1). The taxon is probably more widely distributed in suitable habitats around the Holarctic region (see below).

Observations:— Eunotia panda is similar in shape to Eunotia bilunaris ( Ehrenberg 1832: 87) Schaarschmidt (1881: 159) but differs in the apices which are slightly recurved dorsally. It is also similar in shape to Eunotia cantonatii Lange-Bertalot et Tagliaventi in Lange-Bertalot et al. (2011: 72), but differs by having valve ends much less tapered, by the absence of the single apical hollow protrusion visible in SEM views of E. cantonatii and by possessing small irregular sharp protrusions between striae at the tip of each valve apex ( Figs 88, 93, 95 ). Eunotia panda differs from both species and other members of the E. bilunaris complex by the coarser areolation, 33–40 in 10 µm as opposed to 40–45 in 10 µm ( Table 2).

Eunotia panda is probably related to E. bilunaris , because it possesses a similar valve outline and fits most of the measurements ( Table 2). However, our populations are very distinct and probably represent a semicryptic species within E. bilunaris sensu lato. The valves of E. panda are mostly 3.5 µm wide and slightly arched. Valve ends are slightly narrowed toward rounded and weakly dorsally reflexed ends. It is worth noticing that the valve outline of this taxon is very constant throughout the size-diminishing process of its life cycle.

The distribution of Eunotia panda is probably not restricted to North America. It has also been observed in Europe, although always identified as E. bilunaris ( Krammer & Lange-Bertalot 1991, Lange-Bertalot et al. 2011). Several such specimens, very similar to E. panda , were reported, for example, from various localities around Europe by Lange-Bertalot et al. (2011): a dystrophic habitat in Black Forest, SW Germany (pl. 27, fig. 7), a peat bog in the European part of Russia (pl. 27, fig. 17), the spring of Odra River, Czech Republic (pl. 30, fig. 13), and a peat bog in Tatra Mountains, Poland (pl. 31, fig. 14). Unfortunately, no published reports of SEM or LM examinations of the type material of E. bilunaris have yet appeared, so we do not know the exact nature of this taxon. Lange-Bertalot et al. (2011) provide ultrastructural characterization of what they consider to be E. bilunaris (pl. 33, figs 1–7), and their specimens significantly differ from the ultrastructure details of E. panda . Eunotia panda possesses small, unoccluded, rounded to irregularly shaped areolae as opposed to the well occluded larger areolae and smooth valve surface of the apices of E. bilunaris .

Besides the taxa mentioned in the diagnosis, E. panda also shares some features with E. juettnerae Lange-Bertalot in Lange-Bertalot et al. (2011: 127) or E. mucophila (Lange-Bertalot, Nörpel-Schempp et Alles) Lange-Bertalot in Metzeltin et al. (2005: 53). Despite the fact that E. juettnerae has slightly arched valves and similar valve breadth in the center of the valve, it differs in the valve outline as the valves are narrowed significantly from the valve center toward the tapered ends. In contrast, E. mucophila has similarly shaped valves to E. panda , i.e., slightly arched, with parallel margins throughout the valve, and even with apices slightly recurved dorsally. However, E. mucophila is usually less silicified (appearing more delicate), has narrower valves (1.9–2.7 µm) with denser striation (18–25 in 10 µm) and areolation (43–48 in 10 µm, Lange-Bertalot et al. 2011).

Figures

FIGURES 56–66. Size reduction series of Eunotia panda sp. nov., LM (part 1 – upper size range). Scale bar = 10 µm.

FIGURES 67–86. Size reduction series of Eunotia panda sp. nov., LM (part 2 – lower size range). Fig. 71 Photograph of the holotype specimen (H). Fig. 74 Photograph of the isotype specimen (Is). Scale bar = 10 µm.

FIGURES 87–95. Eunotia panda sp. nov., external views, SEM. Figs 87–90 and 91–92 each represent parts of the same specimen. Figs 87, 91 Whole valves. Figs 88, 90, 92, 93, 95 Apices with raphe fissures reflexed proximally and terminating ca. in the center of the valve face. Irregular small protrusions are evident between the striae at the tip of each apex, and the beveled, rather sharp edges of the valve face. Fig. 89 Detail of striae lowered in between hyaline ridges in the central part of the valve with the sharply beveled valve edges. Fig. 94 Detail of unoccluded rounded to irregularly shaped areolae. Scale bars = 10 µm (in Figs 87, 91), 1 µm (in Figs 88–90, 92–93, 95) or 100 nm (in Fig. 94).

FIGURES 96–103. Eunotia panda sp. nov., internal views, SEM. Figs 97–99 and 100–102 each represent the same specimen. Figs 96, 97, 100 Valve views. Figs 98, 102 Apices without rimoportulae. Figs 99, 101, 103 Apices with large rimoportulae. Scale bars = 10 µm (in Figs 96–97) or 1 µm (in Figs 98–103).