Eunotia novaeangliae 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 : 185-189

Eunotia novaeangliae Veselá et Johansen spec. nov. ( Figs 1–55 )

Type:— USA. Maine: Acadia National Park, Breakneck Ponds (the north one), 44.390116° N, 68.255590° W, 280 m a.s.l., 10 June 2008, Veselá 080b ( ANSP!). The holotype designated here, holotype slide ANSP GC59084 , Fig. 10 depicts the holotype (7.35 mm south by 10.55 mm east from the benchmark cross on the slide); isotype slide: CBFS A-016 (isotype specimen in Fig. 6, 8.45 mm south by 12.25 mm east from the benchmark cross on the slide) .

In girdle view frustules are rounded-rectangular, slender, and 3.2–5.2 µm wide ( Figs 35–39 ). Valves are linear with straight ventral margin and slightly arcuate dorsal margin, widest in the center and gradually tapering toward the ends throughout the whole length of the valve, with ends often slightly ventrally reflexed; with length to breadth ratio of 7–24:1, 15–54 µm long, 2–2.6 µm wide in the widest part ( Figs 1–34 ). No siliceous protrusions on the valve exterior are present ( Figs 40–48 ). Transition of the valve face towards the ventral valve mantle is sharp ( Figs 41–48 ), whereas the transition is gradual on the dorsal side ( Figs 41–48 ). Raphe is long, extending along the mantle for 5–7 µm, barely coming onto the valve face in subapical position ( Figs 40–44, 46–48 ), and not extending past the helictoglossa. Helictoglossa at each apex is massive, expanded into an internal costa which extends obliquely across the valve apex and is penetrated by a single stria ( Figs 49–55 ), with costae clearly visible in the LM ( Figs 1–34 ). One rimoportula per valve is present ( Figs 49, 51, 53–55 ), centered apically on the valve face, with a large external pore easily distinguishable from the external areolae apertures in SEM ( Figs 40–41, 43, 46, 47 ), occasionally visible in LM (e.g., Figs 1, 9, 10, 32 ). Striae are parallel throughout the valve ( Figs 1–34 , 40, 43 ), slightly radiating at the apices (e.g., Figs 41, 42, 48 ), 21–22 in 10 µm. Areolae are circular, and externally occluded ( Figs 40–46 ), 45–55 in 10 µm.

Etymology: —From the Latin adjective novaeangliae (from New England), referring to the area of the species occurrence.

Ecology and distribution:—Our populations of E. novaeangliae from Acadia National Park, Maine, USA, were found in Kebo Brook and in several ponds on Mount Desert Island (sites 037, 043, 068, 069, 080, 107; Table 1). In the study of Cape Cod Peninsula, Massachusetts, Siver et al. (2005) show a single “narrow form” of Eunotia incisa Gregory (1854: 96) , which is a close fit to our taxon (with a similar striae density of 23 striae in 10 µm; pl. 26, fig. 12). Eunotia novaeangliae was also collected in Big Moose Lake in the Adirondack Mountains of New England ( Camburn & Charles 2000, pl. 13, fig. 9) and from Canada ( Lange-Bertalot et al. 2011, pl. 36, fig. 39). Lange-Bertalot et al. (2011) indicated that this form likely did not belong in E. incisa , but did not name it in their study of European Eunotia . This species is likely more widely distributed throughout New England and Eastern Canada.

Observations:— Eunotia novaeangliae is most similar to Eunotia tenelloides Kobayasi, Ando et Nagumo (1981: 97) , but differs in several distinct characteristics: in the presence of ventral flexure of the apices (as opposed to the dorsally reflexed valves of E. tenelloides ); by the clearly abrupt transition of the valve face towards the ventral valve mantle (as opposed to the gradual transition in E. tenelloides ); by the internal paired costae divided by a single stria (as opposed to a single costa with no stria in E. tenelloides ); in the different position of the rimoportula (central in E. novaeangliae in contrast with closely associated with the outer margin of the apex in E. tenelloides and most other Eunotia species ); and by the slight but consistent differences in valve dimensions and striae density.

Eunotia novaeangliae has distinctive, very thin linear valves with slightly pointed ends. Terminal nodules are distinct and relatively large given the narrow valve width, and are removed from the valve ends to the ventral side (similar to the configuration in E. incisa Gregory 1854: 96 ). This species has likely been confused with E. incisa in the past, and this is likely the cause for it not being described before this time. Eunotia incisa is a common, abundant taxon distributed throughout the Holarctic Zone, and is likely a closely related taxon. It differs from E. novaeangliae by having much broader valves, smaller length-to-width ratio, and generally coarser striae ( Table 2). The raphe of E. incisa is placed entirely on the valve mantle unlike the raphe of E. novaeangliae ( Figs 40–44, 46–48 ). Shorter valves of E. novaeangliae could be potentially confused with E. incisatula Metzeltin & Lange-Bertalot (1998: 62) , E. acutinasuta Metzeltin & Lange-Bertalot (1998: 50) , and maybe also E. acicularis Metzeltin & Lange-Bertalot (1998: 47) , other three taxa from the E. incisa group. However, these three Eunotia species have all been described from South America (Guayana and Venezuela, Table 2), and together with E. incisa share terminal raphe fissures that never extend onto the valve face (as far as can be assessed from LM pictures, since no SEM pictures were available). In addition, all four taxa possess much less prominent helictoglossae compared to E. novaeangliae , lack the internal apical costae, and each can be distinguished from E. novaeangliae by at least two morphometric characters ( Table 2).

areolae and parallel striae in the middle section of the valve. Scale bars = 10 µm (in Fig. 40 ) or 1 µm (in Figs 41–48 ).

indicates length of the reflexed portion of the raphe on the valve face – the distance from the farthest raphe point closest to the apex to the point where the raphe ends; L-B = Lange-Bertalot, NE = Northeastern, SE = Southeastern.

The fully developed and prominent internal apical costae seem like a feature that only a small number of Eunotia taxa share. In addition to E. novaeangliae , this feature has been observed in E. tenelloides , E. lewisii Siver & Hamilton in Siver et al. (2009: 410), E. pienitzii Lange-Bertalot in Lange-Bertalot et al. (2011: 196), E. ibitipocaensis Canani & Torgan (2013: 396) and in E. saltoensis Canani & Torgan (2013: 403) . These taxa together with E. novaeangliae also share the prominent helictoglossae and terminal raphe fissures that at least slightly extend onto the valve face (unlike the above mentioned taxa around E. incisa ). Although Eunotia lewisii and E. pienitzii have been described from the Northeastern USA and represent the only similar species (together with cosmopolitan E. incisa ) which co-occur with E. novaeangliae , both cannot be confused with E. novaeangliae generally due to their much larger and more robust valves ( Table 2). Eunotia ibitipocaensis and E. saltoensis also could be hardly mistaken for E. novaeangliae , because both these Brazilian species have, apart from other dissimilarities, significantly wider valves and lower striae densities ( Table 2).

In general, Eunotia novaeangliae belongs to the group of taxa containing E. incisa , E. acicularis , E. acutinasuta , E. ibitipocaensis , E. incisatula , E. lewisii , E. pienitzii , E. saltoensis and E. tenelloides , which all share nose-like apices and terminal raphe fissures which are distinctly distant from the ends.

Figures

FIGURES 1–39. Size reduction series of Eunotia novaeangliae sp. nov., LM. Figs 1–34 Valve views. Fig. 6 Photograph of the isotype specimen (Is). Fig. 10 Photograph of the holotype specimen (H). Figs 35–39 Frustules in girdle views, with noticeably long raphe slits. Pairs of photographs representing the same specimen in different focal planes are marked with “=”. Scale bar = 10 µm.

FIGURES 40–48. Eunotia novaeangliae sp. nov., external views, SEM. Figs 40–42, 43–46 and 47–48 each represent the same specimen. Figs 40, 43, 47 Whole valves in valve or oblique views. Figs 40–44, 46–48 Distinctive character of the raphe, which is situated mostly on the valve mantle and terminates on the valve face only with a very short slit (expanding to less than 1/5 of the valve width). Figs 41, 46 Details of the apices with openings to rimoportulae. Figs 42, 44, 48 Apices without rimoportula apertures. Fig. 45 Detail of the externally occluded

FIGURES 49–55. Eunotia novaeangliae sp. nov., internal views, SEM. Figs 49–51 and 52–53 each represent the same specimen. Figs 49, 52, 54, 55 Whole valves. Figs 50, 51, 53 Details of internally unoccluded areolae and thickened helictoglossa structures with two expanding ribs to the opposite side of the valve. Fig. 50Apex without a rimoportula. Figs 51, 53 Details of apices with rimoportulae. Scale bars = 1 µm.