The genus Eunotia Ehrenb. (Bacillariophyta) in the Cheremsky Nature Reserve, Ukrainian Polissya, and refined terminology relevant to the raphe system morphology

Lyudmila N. Bukhtiyarova

doi:10.3897/phytokeys.128.35566

Research Article

The genus Eunotia Ehrenb. (Bacillariophyta) in the Cheremsky Nature Reserve, Ukrainian Polissya, and refined terminology relevant to the raphe system morphology

Lyudmila N. Bukhtiyarova^‡

‡ Institute for Evolutionary Ecology, National Academy of Sciences of Ukraine, Kyiv, Ukraine

Corresponding author: Lyudmila N. Bukhtiyarova ( l.bukhtiyarova@gmail.com )

Academic editor: Kalina Manoylov

This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Citation: Bukhtiyarova LN (2019) The genus Eunotia Ehrenb. (Bacillariophyta) in the Cheremsky Nature Reserve, Ukrainian Polissya, and refined terminology relevant to the raphe system morphology. PhytoKeys 128: 1-31. https://doi.org/10.3897/phytokeys.128.35566

Abstract

Numerous species of Eunotia Ehrenb., widely distributed in the world flora, prefer acidic, dystrophic or oligotrophic freshwater habitats with low conductivity and usually occur in epiphytic or epilithic hydrotopes. In Ukraine, only 32 species and eight varieties of Eunotia were known until this study. For the first time, 9 more species have been recorded mainly from the Cheremsky Nature Reserve, located in Ukrainian Polissya. New findings include 2 species widely distributed in the world flora on most continents and 7 rare species known from several locations, among them E. genuflexa, E. jarensis and E. ruzickae, which are probably European endemics as they have not been reported from other continents. For the present time in the Cheremsky Nature Reserve, the 20 species recorded here, the highest species richness of Eunotia in Ukraine, bring the total number of Eunotia in Ukraine to 41 species, which comprises only 7% of Eunotia species in the world flora. This is indirect evidence of insufficient investigation of the wetlands in Ukraine where Eunotia usually is represented with high species richness. Several definitions are suggested to describe morphological features that are peculiar to the diatom frustule particular to the Eunotia species. The genus Eunotia possesses a mirror-symmetric, mantle-offset, brevisslit raphe system, which may or may not have terminal raphe fissures. Morphological analysis provided in this study revealed the absence of terminal raphe fissures for many species of Eunotia. Instead, the distal ends of the raphe slits finish on the outer valve surface by funnel holes, sometimes pore-like ones, connected with the helictoglossae. However, in the literature those distal ends of the raphe slits were described erroneously as terminal raphe fissures. For the first time different types of raphe system are grounded. Two species Eunotia implicata Nörpel-Schempp et al. in Alles et al. and Eunotia incisa W. Smith ex Gregory were lectotypified.

Keywords

Eunotia, functional morphology, mirror-symmetric, mantle-offset, brevisslit raphe system, taxonomy, rare species, distribution

Introduction

The Cheremsky Nature Reserve, located in Ukrainian Polissya, Volyn region, in the interfluve of Stokhid and Veselukha rivers, occupies about 3 thousand ha. The reserve includes large areas of untouched forests and unique wetlands which take up about 34% of the territory (Figs 1, 2). An eumesotrophic Cheremske bog (total area of about one thousand ha, peat deposition up to 10 m), relates to peripheral-oligotrophic type of development characteristic of bogs formed in lake-like basins. Two lakes within the Cheremsky Nature Reserve Cheremske (7,7 ha, max. depth 7 m) and Redychi (14,0 ha, max. depth 4,5 m) originate from glacial-karst (Konischuk and Didukh 2004, Konishchuk 2005).

Figures 1, 2.

Location of the studied area 1 The Cheremsky Nature Reserve on the map of Ukraine, indicated by red dot 2 map-scheme of the Cheremsky Nature Reserve.

Previous studies of the Bacillariophyta from the Cheremsky Nature Reserve revealed high species richness with 84 species reported by Bukhtiyarova (2008) and 57 taxa by Malakhov et al. (2017). The mesotrophic bogs contain a moderate quantity of nutrients that facilitate the development of a specific and rich diatom flora. The most species-rich genera in such habitats typically include Eunotia Ehrenb. and Pinnularia Ehrenb. Indeed, many of the diatom taxa recorded for the first time in Ukraine were from the Cheremsky Nature Reserve and included: Eunotia silvahercynia Nörpel et al. in Alles et al. (1991), Pinnularia complexa Krammer (2000), P. lokana Krammer (2000), P. nobilis var. regularis Krammer (2000), P. parvulissima Krammer (2000), P. polyonka (Bréb.) W. Smith (1856), P. rhombarea Krammer in Metzeltin and Lange-Bertalot (1998), P. stomatophora var. irregularis Krammer (2000), P. stidolphii Krammer (2000), P. subanglica Krammer (2000), P. subrupestris Krammer (1992) and its variety P. subrupestris var. cruciata Krammer (2000) (Bukhtiyarova 2008, 2009b); Eunotia myrmica Lange-Bert. in Lange-Bertalot et al. (2011) (Malakhov et al. 2017). In the Cheremsky Nature Reserve only 9 species of Eunotia were known from the Cheremske and Redychi lakes prior to this study.

As a part of documenting the Eunotia taxa it was necessary to describe the raphe system’s particular properties which have taxonomical value on species rank of taxonomy. In recently published terminological glossary the following definition for the raphe was proposed: “Raphe (Lat.) – an elongated slit or pair of slits through the valve wall. When a pair of slits is present each individual slit is a branch of the raphe” (Gogorev et al. 2018: p. 299), which does not include the position of the raphe system in the diatom frustule hierarchic structure and any of its functions. In another glossary about the same definition appears: “The raphe system is composed of one or two slits, or fissures, that penetrate the valve of some diatoms. If two slits are present, each is called a branch of the raphe. Branches may be separated by a silica thickening called the central nodule” and it was indicated that raphe allows diatom cells to move (Diatoms of North America 2019). In the latest one the possible raphe position on the valve is defined as axial (along the apical axis), eccentric (along one margin) or circumferential (around the whole margin of the valve) none of which does not specify raphe position on the valves of the Eunotia species. In both definitions several structural elements of the raphe system are omitted. Moreover, in the second, no distinction is made between the raphe slits and fissures, as both terms look like synonyms but they define different elements of the raphe system. The Eunotia taxa possess unique raphe system the morphology of which has not been studied yet in detail.

This study provides detailed information on the species of Eunotia Ehrenb. found in the Cheremsky Nature Reserve, including rare species recorded in Ukraine for the first time. Revised terminology to highlight morphological features of the raphe system relevant to the Eunotia species is also suggested.

Materials and methods

In 2003–2004 O. Petlyovany collected epiphytic samples of algae from mosses in the Volyn region, Manevichsky district, the Cheremsky Nature Reserve mainly from the lakes Cheremske and Redychi, both from open waters and marshy locations. Sample numbers correspond to those from the Algoteca of M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine – the largest phycological collection in Ukraine.

30586 The Cheremsky Nature Reserve, wetland area, Lake Cheremske, epiphyton on Sphagnum sp. 06/18/2003.

30588 The Cheremsky Nature Reserve, tract Obkopane, ditch, epiphyton on Sphagnum sp. 06/18/2003.

30599 The Cheremsky Nature Reserve, tract Obkopane, Lake Redychi, epiphyton on Sphagnum sp. 06/19/2003.

30635 The Cheremsky Nature Reserve, tract Obkopane, Lake Redychi, epiphyton on Fontinalis sp. 08/14/2004.

30637 The Cheremsky Nature Reserve, tract Obkopane, Lake Redychi, epiphyton on Sphagnum sp. 08/14/2004.

30640 The Cheremsky Nature Reserve, tract Obkopane, Lake Redychi, wetland area, epiphyton on Sphagnum sp. 08/14/2004.

In accordance with Malakhov et al. (2017) hydrochemical parameters of these lakes are very similar. Lake Cheremske: conductivity – 70 µS/cm, pH – 6.16–6.6, dissolved O₂ – 9.7 mg/L, NH₄⁺ – 0.22 mg/L, NO₂- < 0.01 mg/L, NO₃- < 0.01 mg/L, PO₄^3–< DL mg/L, Fe ³⁺ – 1.2 mg/L.

Lake Redychi: conductivity – 63 µS/cm, pH – 6.46, dissolved O₂ – 9.5 mg/L, NH₄⁺ – 0.20 mg/L, NO₂- < 0.01 mg/L, NO₃- < 0.01 mg/L, PO₄^3–< DL^* mg/L, Fe ³⁺ – 1.1 mg/L.

Two samples from other locations in Ukrainian Polissya collected by O.V. Kovalenko have been also studied.

27835 Zhytomyr region, Chervonoarmeisky district, swamp, dark films among mosses. 07/15/1983.

27895 Volyn region, Vladimir-Volyn district, near village Fedorovka, Western Bug River, floodplain basin, benthos. 07/21/1983.

Organic matter was removed by cold burning with concentrated sulfuric acid and cleaned materials were rinsed several times with distilled water (Wasser et al. 1989). Permanent slides with cleaned materials were mounted in Naphrax (R.1 = 1.7). Diatom species were examined with an Olympus BX 51 light microscope (LM) using a 100× oil immersion PlanAchromat objective. The fine structure of the diatom frustules was examined with a scanning electron microscope JEOL 6060LA. The micrographs were obtained with Canon EOS 600 D digital camera using program Helicon Remote (version 3.6.2 w).

Size ranges were based on measurements typically several, sometimes single valves as all species were found in very limited numbers. Therefore the size ranges from the relevant literature were included in the species description.

In many diatom species with bipolar symmetry including Eunotia different morphometric data present at different valve parts, e.g. width, striae density in 10 µm etc., their dimension can be helpful in the species correct identification.

Central valve part – valve part on both sides from the transapical axis where the measuring parameter has different value comparing with other valve parts (Fig. 3a, between the arrows).

Figure 3.

Scheme of the mirror-symmetric, mantle-offset, brevisslit raphe system in frustule of the genus Eunotia Ehrenb. A valve view, different parts of valve. TA – transapical axis. Central part – between the arrows, middle part – between upper and double arrows, the beginning of valve pole – double arrow B girdle view, arrow – central raphe pore C, D raphe system without terminal fissures C arrow – a pore outer at distal end of slit, that finishes at the middle of valve pole D arrow – a funnel-like outer at distal end of slit, that finishes at the venral corner of valve pole E, F raphe system with terminal fissures – dotted lines between arrows, arrow – distal end of a slit E double arrow – the end of terminal fissure F double arrow – lacuna at the end of terminal fissure. (Original by L. Bukhtiyarova)

Middle valve part – valve part between central part and the beginning of valve pole (Fig. 3a, between the upper and double arrows).

Valve pole – distal valve part from its narrowest part or from the beginning of a valve narrowing to the distal end (Fig. 3a, from the double arrow to distal end of a valve).

For the algae flora of Ukraine a 'very rare species' is defined as one recorded in 1–5 localities and 'rare species' – in < 10 localities within the country territory (Palamar’-Mordvintseva et al. 1998). A 'rare species in the world flora' is defined here as one recorded in fewer than 10 localities and restricted to 1–2 continents.

Abbreviations. Morphometric data example: length 45–97 µm, width c6–7, m9–12, p3–5 µm; striae density c12–16, p18–20 in 10 µm.

c5–7 the data for the central valve part.

m9–12 the data for the middle valve part.

p18–20 the data for the valve pole.

* species recorded for the first time in Ukraine.

^ rare species in the world flora.

Results

Morphology and refined terminology

The revised definitions suggested here for some widely used terms and new ones are grounded on the concept of functional morphology of the diatom frustule (Bukhtiyarova 2009a, 2019) which includes a number of theses, in particular the division of all diatom frustule structures on the basic elements and functional units. Thus, this concept allows us to describe any morphological structure on a common universal basis.

Because physical-chemical properties of any material depend on the size of the particles it is compounded from, it was suggested to introduce a size scale in all the definitions of the diatom frustule structures (Bukhtiyarova 2009a).

The basic element of the diatom frustule (db-element) is a morphologically detached, homogeneous part of the frustule that possesses special physical-chemical features and provides primary basis for the frustule hierarchical construction. They belong to db-elemets of the diatom frustule as different apertures and cavities in its thickness, regularly repeated and unique silica microelemets (Bukhtiyarova 2009a: figs 1–5).

Morph of the diatom frustule (df-morph) is compound structural unit of the diatom frustule that is constructed of db-elements and/or structural units of lower orders, realizes particular functions in the diatom organism and has its own evolution (Bukhtiyarova 2009a).

The refined definitions capture raphe system as a functional unit of the diatom frustule, its different db-elements and peculiar properties relevant to Eunotia species. For the first time different raphe system types are grounded.

Raphe system – a unique compound micro df-morph of second (first) order in the diatom frustule with bipolar symmetry that consists of one or two slits, which penetrate the valve thickness, and may include additional df-morphs (central nodule, helictoglossae, tube) and/or db-elements (terminal fissures, central pores and others). One of the functions of the raphe system is active moving of the diatom unicellular organism. For the species that have an attached mode of life other functions can be performed, e.g. an attachment to substrate or between neighboring cells in a colony.

Raphe slit – a unique micro db-element in the shape of uniformly narrowed through opening of different profile into the valve thickness and noticeable length relative to the valve length.

Central raphe pore – a unique micro db-element, through hole with usually a different shape on the inner and outer valve surfaces at the proximal end of the raphe slit (Fig. 3b, arrow).

Terminal raphe fissure (tr-fissure) – a unique micro db-element in the shape of uniformly narrowed non-through notch continuing distal end of the raphe slit on external valve surface only (Figs 3e, f).

Terminal raphe fissure with lacuna – kind of fissure that finishes on distal end by lacuna (Figs 3f, 4a, 5a, 6a, 8a).

Figures 4–6b.

New in Ukraine species Eunotia genuflexa Nörpel-Schempp in Lange-Bertalot and Metzeltin, outside valve surface, SEM. Arrows indicate distal ends of raphe slits, double arrows – funnel-like lacunae, terminal fissures are between the arrows. Scale bars: 10 µm (4–6); 2 µm (4a, 5a, 6a); 1 µm (6b).

Figures 7–12a.

New and rare in Ukraine species of Eunotia Ehrenb. from the Cheremsky Nature Reserve. 7–8a Eunotia julma Lange-Bert. in Lange-Bertalot et al., arrow indicates distal end of raphe slit, double arrow – funnel-like lacuna, terminal fissure is between the arrows 9 Eunotia sp. 1 (cf E. formica Ehrenb.) 10, 11 Eunotia formicina Lange-Bert. in Lange-Bertalot et al. 12, 12a Eunotia jarensis Lange-Bert. et al., arrow indicates rimoportula. Figs 7, 9–11 LM 8, 8a outside valve surface 12, 12a inside valve surface, SEM. Scale bars: 10 µm (7–17); 3 µm (8a); 2 µm (12a).

Lacuna – a unique micro or nano- db-element, non-through hollow of different shape and location on outer or inner valve surface.

In the genus Eunotia the lacunae of the raphe terminal fissures (rtf-lacuna) usually have a dish or funnel-like shape of about 100 nm in diameter (Figs 3f, 4a, 5a, 6a, 8a, double arrows).

Helictoglossa – a unique siliceous hyaline micro df-morph of first order on the internal valve surface usually in the shape of truncated cylinder or compressed (relative to the raphe slit) asymmetric frustum with smoothly roused up side bearing fissure at the distal end of the raphe slit and abruptly roused opposite side (Figs 13a, 29, 30a, arrows). Any functions of helictoglossae are unstudied, yet their morphology and position allow to suggest that they work like a stopper and may regulate a mucilage mass length of uniform shape that enters into the raphe slit from inside and goes out from the diatom frustule outside.

Figures 13–27.

New and rare in Ukraine species of Eunotia Ehrenb. from Ukrainian Polissya and the Lectotypes of two Eunotia species. 13, 13a Eunotia pseudoflexuosa Hust., arrow indicates rimoportula at the middle of pole where raphe slit distal end finishes on the outer valve surface, double arrow – position of terminal fissure distal end on the outer valve surface, between the arrows – hyaline field from inside valve surface where the terminal fissure is located on the outer valve surface 14 Eunotia ruzickae Bílý & Marvan 15, 16 Eunotia implicata Nörpel-Schempp et al. Lectotype: 15 = Eunotia impressa var. angusta Grunow in Van Heurck 1881: pl. 33/fig. 22, designated here 17, 17a Eunotia sp. 2 (cf. mongolica Kulikovskiy et al.) 18–20 Eunotia sp. 3 (cf. Eunotia paludosa Grunow) 21–23 Eunotia incisa W. Smith ex Gregory. Lectotype: 23 = Eunotia incisa W. Smith ex Gregory 1854: pl. 4/fig. 4, designated here 24 Eunotia sp. 4 (cf. Eunotia intermedia (Krasske ex Hustedt) Nörpel & Lange-Bert.) 25–27 Eunotia sp. 5 (cf. Eunotia meridiana Metzeltin & Lange-Bert.). Figs 13, 17, 18 SEM: 13, 13a inside valve surface 17, 17a, 18 outside valve surface; 19–28 LM. Scale bars: 10 µm (13–17, 19–27); 5 µm (18); 1 µm (13a, 17a).

Helictoglossa fissure (h-fissure) – a unique micro db-element in the shape of a uniformly narrowed short non-through notch on helictoglossa continuing distal end of the raphe slit on internal valve surface only.

Symmetric raphe system – type of raphe system with straight equal length of the slits and similar accompanied db-elements that are located symmetrically relatively both to the longitudinal and transapical axes of bipolar frustule. Examples of this type of raphe system can be found among species of Cavinula D.G. Mann & Stickle in Round et al. (1990), Hippodonta Lange-Bertalot et al. (1996), Navicula Bory (1822), Psammothidium Bukht. & Round (1996) and other diatom genera.

Mirror-symmetric raphe system – type of raphe system with equal length and same shaped raphe slits, similar accompanied db-elements that all together are located mirror symmetrically relative to the transapical axis or/and in girdle view of the diatom frustule. Examples of this type of raphe system can be found in species of Amphora Ehrenb. ex Kütz. (1844), Cymbella Agardh (1830), Eunotia and other genera.

Mantle-offset raphe system (Lat.) – type of raphe system which partially or completely disposes on the valve mantle. This type of raphe system characterizes the genus Eunotia.

Brevisslit raphe system (Lat.) – type of raphe system with the slits which disposes only along part of valve length and absent on the rest of it. The examples of this raphe system type can be found in the genera Actinella F.W. Lewis (1864), Eunotia, Rhoicospenia Grunow (1860) and in others.

Thus, species of the genus Eunotia possess of mirror-symmetric, mantle-offset, brevisslit raphe system.

Basal striae – type of striae in which the areolae and all additional db-elements accompanying them occupy interstria height in whole (Bukhtiyarova 2015: figs 2, 10–15), or by other words, the valve thickness completely.

Distant striae – kind of striae which occupy two or more times less area than interstria area (Bukhtiyarova 2015: figs 4, 6, 8, 9–13, 17).

The terms proportional, packed, distant kinds of striae have been defined on the ratio between stria and interstria areas (Bukhtiyarova 2015).

Taxonomy

In the hydrotopes of the Cheremsky Nature Reserve the following species of the genus Eunotia were recorded.

Eunotia dorofeyukiae Lange-Bert. & Kulikovskiy in Kulikovskiy et al. 2010b: p. 29, 65, pl. 20/figs 1–6. *^

Figs 28, 28a, 29 (SEM)

Illustrations

Krammer and Lange-Bertalot 1991: pl. 143/figs 22–23 (as Eunotia circumborealis Nörpel & Lange-Bert.); Rivera-Rondón and Catalan 2017: pl. 25/figs 7–9.

Diagnosis

Morphometric data: length 33–35 µm, width cm 7, p5–8 µm; striae density c12–14, p18–22 in 10 µm. Lange-Bertalot et al. 2010: length 37–58 µm, width 7.3–8.7 µm, striae density 10–13 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves dorsiventral, with undulate dorsal margin and weak depression in its central part, slightly concave ventral side and subcapitate broad rounded poles. Striae basal, uniserial, distant, denser at the poles. Areolae small with round outer foramina (Fig. 28a). Raphe system consists of two short filiform slits on ventral valve mantle, distal ends of slits finish on external valve surface on ventral pole corners by small round pore outers (Fig. 28a) connected with small helictoglossae (Fig. 29); tr-fissures absent.

Figures 28–35.

Species of Eunotia Ehrenb. from the Cheremsky Nature Reserve. 28, 28a, 29 Eunotia dorofeyukiae Lange-Bert. & Kulikovskiy 28a arrow indicates pore outer on the raphe slit distal end 29 arrow indicates rimoportula at the venral corner of pole where raphe slit distal end finishes on the outer valve surface 30, 30a Eunotia neocompacta S. Mayama 30a arrow indicates rimoportula at the venral corner of pole, absence of a hyaline field indicates absence of terminal fissure 31 Eunotia praerupta Ehrenb. 32 Eunotia sp. 6. 33 Eunotia sp. 7. 34, 35 Eunotia tetraodon Ehrenb. Figs 28–31 SEM: 28, 28a outside valve surface; 29–31 inside valve surface; 32–35 LM. Scale bars: 5 µm (28, 29, 30); 2 µm (28a); 1 µm (30a); 10 µm (31–34).

Ecology

Freshwater epiphytic species, often collected on different Sphagnum species, occurs in acidic (pH 5.5–5.6), oligotrophic waters with low electric conductivity and buffered by humic acids. The specimens from Type population were collected at 11–13 °C (Kulikovskiy et al. 2010b).

Distribution

ASIA: Type location: northern Mongolia, Nur bog (Kulikovskiy et al. 2010b); Russia (Kulikovskiy et al. 2016). EUROPE: Scandinavia (Krammer and Lange-Bertalot 1991 (as E. circumborealis); Germany (Kulikovskiy et al. 2010b); Ukraine (present paper); France, Pyrenees, Lake Mariola (Rivera-Rondón and Catalan 2017). AUSTRALIA: Tasmania (M. Guiry in Guiry and Guiry 2019). In Ukraine. The Cheremsky Nature Reserve, tract Obkopane, ditch, epiphyton on Sphagnum sp.

Comments

Illustrations of this species in Kulikovskiy et al. (2010b: pl. 20/figs 1–6) are not uniform in valve outline.

This species was described from a mountainous region with a harsh climate and was recorded later in a mountain lake in the Pyrenees. In Ukraine it inhabits in a flatland bog.

Eunotia formicina Lange-Bert. in Lange-Bertalot et al. 2011: p. 105–107, pl. 222/figs 1–7, pl. 223/figs 1–7. *^

Figs 10, 11 (SEM)

Eunotia formica var. elongta Hustedt, 1909

Eunotia formica f. elongata (Hustedt) Ant. Mayer, 1918

Eunotia formica sensu Germain, 1981

Holotype

Lange-Bertalot et al. 2011: pl. 222/fig. 1.

Illustrations

Bąk et al. 2012: p. 131, pl. 11/7 exemplars; Ector et al. 2012: p. 249–250, 3 exemplars; Costa 2015: p. 50, pl. 100/figs 1–5; Marra et al. 2016: fig. 53.

Diagnosis

Morphometric data: length 83–125 µm; width m8, cp9 µm; striae density m9–11, p12–15 in 10 µm. Lange-Bertalot et al. 2011: length 20–170 µm; width c7–10, m6–8 µm; striae density 8–12, p15–16 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves weakly dorsiventral, with gentle gibbosity in central valve part on ventral side and subcapitate broad rounded poles. Valve mantle high, of about 0.5 of valve width, perpendicular to the valve surface; valve/mantle junction narrow hyaline (see Lange-Bertalot et al. 2011: pl. 223/fig. 4). Striae basal, uniserial, distant, irregularly spaced along the valve; on the mantle additional short intercalar striae (see Lange-Bertalot et al. 2011: pl. 223/fig. 4). Areolae small with round outer foramina. Raphe system consists of two short filiform slits on ventral valve mantle; central raphe pores round; tr-fissures long, widely round, follow the pole outline and finish on dorsal valve margin (see Lange-Bertalot et al. 2011: pl. 223/figs 2, 3, 5–7).

Ecology

Freshwater benthic species, occurs in moderately acidic, dystrophic or oligosaprobic waters (Lange-Bertalot et al. 2011).

Distribution

EUROPE: France, Germany, Netherlands, Poland (M. Gury in Guiry and Guiry 2019); Ukraine (present paper). S. AMERICA: Brasil (Costa 2015, Costa et al. 2017; Marra et al. 2016). In Ukraine. The Cheremsky Nature Reserve, tract Obkopane, ditch, epiphyton on Sphagnum sp.; Lake Redychi, wetland area, epiphyton on Sphagnum sp.

Eunotia genuflexa Nörpel-Schempp in Lange-Bertalot and Metzeltin 1996: p. 50, pl. 9/figs 14–17. *^

Figs 4–6b (SEM)

Eunotia flexuosa f. beta A. Berg, 1939

Eunotioforma genuflexa (Nörpel-Schemp) Kociolek & Burliga in Burliga et al. 2013

Illustrations

Bąk et al. 2012: p. 132, pl. 17/1, 2, 5 exemplars from left to right; Kulikovskiy et al. 2016: p. 121, pl. 20/figs 10–14.

Diagnosis

Morphometric data: length 70–120 µm; width cm2–3, p1.5–2 µm; striae density c20, p23 in 10 µm. Lange-Bertalot and Metzeltin 1996: length 70–160 µm, width 1.5–2.6 µm, striae density 19–23 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves slightly dorsiventral, with narrowed rounded poles. Striae basal, uniserial, distant, uniformly spaced along the valve (Figs 4a, 5a, 6a, b). Areolae small with round outer foramina. Raphe system consists of two short filiform slits on ventral valve mantle; tr-fissures long, broadly curved, sited on 0.5 of valve width along 4–5 striae, end up by round lacunae (Figs 4a, 5a, 6a).

Ecology

Freshwater benthic species occurs in moderately acidic, dystrophic or oligosaprobic waters. Type location had extremely low concentration of inorganic nutrient and pH = 6.5 (Lange-Bertalot and Metzeltin 1996).

Distribution

EUROPE: Type location: Finland, Lake Julma Olkky (Lange-Bertalot and Metzeltin 1996); Poland (Bąk et al. 2012); Russia (Kulikovskiy et al. 2016); Ukraine (present paper). In Ukraine. The Cheremsky Nature Reserve, tract Obkopane, Lake Redychi, epiphyton on Fontinalis sp.

Comments

Specimens with straight valve outline and subcapitate poles presented in Costa (2015: p. 55, pl. 14/figs 1–11) differ from type population significantly, therefore the author has presented other species under this name. In Bąk et al. (2012) morphology of only three exemplars corresponds to type population.

Type species of the genus Eunotioforma Kociolek & Burliga is Eunotioforma mattogrossiana Kociolek, Burliga & Salomoni (Burliga et al. 2013) has several characters that differ from the genus Eunotia: axial area on valve surface (= sternum), large helictoglossae, different number of rimoportulae (2–8 per valve), small granules along all striae which are not present in E. genuflexa. Strongly curved long tr-fissures are the only common character with a new genus and it can be found in some other species of Eunotia, for instance, E. flexuosa (Bréb.) Kütz. (Pavlov and Levkov 2013: pl. 7/fig. 2), E. macedonica Pavlov & Levkov (Pavlov and Levkov 2013: pl. 10/fig. 2). The only one character is not enough for transferring of E. genuflexa to the genus Eunotioforma.

Eunotia implicata Nörpel-Schempp et al. in Alles et al. 1991: p. 206, pl. 7/figs 19–32. *

Figs 15, 16

Eunotia impressa var. angusta Grunow in Van Heurck, 1881: pl. 33/fig. 22 [Basionym]

Lectotype

Eunotia impressa var. angusta Grunow in Van Heurck 1881: pl. 33/fig. 22 (= Fig. 14 here), designated here.

Illustrations

Krammer and Lange-Bertalot 1991: p. 197, pl. 143/figs 1–7; Ortiz-Lerín and Cambra 2007: p. 424, pl. 3/fig. C, pl. 4/figs B, I (SEM); Furey et al. 2011: p. 50, pl. 28/figs 1–8; Lange-Bertalot et al. 2011: p. 119, pl. 97/figs 1–39, pl. 225/figs 16–19; Bąk et al. 2012: p. 133, pl. 16/1, 5 exemplars from left to right; Levkov and Pavlov 2013: p. 25, pl. 56/figs 1–26, pl. 57/figs 4–7 (SEM), pl. 65/figs 1–4 (SEM); Costa 2015: p. 54, pl. 27/figs 1–7, pl. 28/figs 1–5 (SEM); Ector et al. 2015: p. 251, 30 exemplars; Bahls et al. 2018: pl. 111/fig. 15.

Diagnosis

Morphometric data: length 26 µm, width 3.5 µm, striae density c18, p20 in 10 µm. Alles et al. 1991: length 18–30 µm, width 3–5 µm, striae density 14–20 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves slightly dorsiventral, linear with weakly convex dorsal margin, concave ventral margin and protracted rounded poles. The mantle’s height is equal to about 0.5 of valve width, abruptly perpendicular to the valve surface (see Costa 2015: pl. 28/figs 2, 4). Striae basal, uniserial, distant, uniformly spaced along the valve and compacted at the poles, uninterrupted on dorsal mantle/valve junction and interrupted by sternum on ventral mantle; on dorsal mantle short intercalar striae present (see Costa 2015: pl. 28/figs 2, 4). Areolae small with round outer foramina. Raphe system consists of two short filiform slits on ventral hyaline part of mantle, distal ends of the slits turned to the valve centre under right angle and finish on external valve surface in ventral corner of the poles by small round pores (see Costa 2015: pl. 28/figs 1, 2) connected with helictoglossae; tr-fissures absent.

Ecology

Freshwater, acidophilus, epiphytic species, inhabits moss vegetation, green filamentous algae. In Spain the species was collected in habitats with pH 4.3–7.9, conductivity 4.17–720 μS/cm, the altitude 76–1356 m asl, SPI 12.3–20. Optimum conditions with pH 5.3–6.8, conductivity 28.7–51 μS/cm, the altitude 472–624 m asl, SPI 19.3–19.7 (Ortiz-Lerín and Cambra 2007).

Distribution

EUROPE: Britain, France, Germany, Netherlands (M. Gury in Guiry and Guiry 2019); Macedonia (Pavlov and Levkov 2013), Poland, Romania, Slovakia, Spain (M. Gury in Guiry and Guiry 2019); Ukraine (present paper). AFRICA: Ghana. ASIA: Russia. AUSTRALIA: Australia, New Zealand. N. AMERICA: Canada, USA. S. AMERICA: Argentina, Brazil, Colombia (M. Gury in Guiry and Guiry 2019). In Ukraine. The Cheremsky Nature Reserve, tract Obkopane, Lake Redychi, epiphyton on Fontinalis sp.

Very rare species occurs only in Europe in three localities in low abundance.

Eunotia julma Lange-Bert. in Lange-Bertalot et al. 2011: pl. 7/figs 1–7, 8–10. *^

Figs 7, 8, 8a (SEM)

Holotype

Lange-Bertalot et al. 2011: pl. 7/fig. 1, designated by Lange-Bertalot in Lange-Bertalot et al. 2011.

Illustrations

Potapova et al. 2014: fig. 1; Kulikovskiy et al. 2016: p. 122, pl. 27/figs 14–17; Bouchard et al. 2018: pl. 1/fig. 1.

Diagnosis

Morphometric data: length 115–175 µm, width 6 µm, striae density c12, p16 in 10 µm. Lange-Bertalot et al. 2011: length 70–150 µm, 4,5–5 µm, striae density c14, p16 in10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves dorsiventral, uniform in width, arcuate, with rounded poles. Striae basal, uniserial, distant, evenly spaced (Figs 7, 8, 8a). Areolae small with round outer foramina. Raphe system consists of two short filiform slits on ventral valve mantle; tr-fissures curved on the valve surface, pass along four striae on the middle of valve and end up by round lacunae (Fig. 8a).

Ecology

Freshwater epiphytic species.

Distribution

EUROPE: Type locality: Finland, Lake Julma Olkky near Kuusamo (Lange-Bertalot et al. 2011); Netherlands (M. Gury in Guiry and Guiry 2019); Ukraine (present paper). ?ASIA: Russia, Eastern Siberia (Potapova et al. 2014); Russia (Kulikovskiy et al. 2016). N. AMERICA: Canada (Bouchard et al. 2018). In Ukraine. The Cheremsky Nature Reserve, tract Obkopane, ditch, epiphyton on Sphagnum sp.

Comments

In primary description it is indicated that “ … all specimens are consistently curved” (Lange-Bertalot et al. 2011). Our exemplars correspond to the species Holotype in valve outline and morphometry except our specimens are longer and wider. The illustrations of E. julma in Potapova et al. (2014: fig. 1), Kulikovskiy et al. (2016: pl. 27/figs 14–17), Bouchard et al. (2018: pl. 1/fig. 1) differ from the Holotype by almost straight valves.

Eunotia neocompacta S. Mayama in Mayama and Kawashima 1998: p. 69.

Figs 30, 30a (SEM)

Eunotia exigua var. compacta Hustedt, 1930: p. 176, fig. 225 [Basionym]

Eunotia compacta (Hustedt) S. Mayama, 1997

Eunotia neocompacta var. vixcompacta Lange-Bert. in Lange-Bertalot et al. 2011

Illustrations

Grunow in Van Heurck 1881: pl. 34/fig. 8 – second exemplar; Krammer, Lange-Bertalot 1991: pl. 134/figs 32, 35–38 (both citations as Eunotia nymanniana Grunow). Mayama 1997: p. 35, figs 22–25, 26–31 (SEM) (as E. compacta). Lange-Bertalot et al. 2011: p. 173–174, pl. 123/figs 1, 2–16, 25–28, 32–34 (SEM); Bąk et al. 2012: pl. 19/1, 2 exemplars from left to right; Genkal and Komulaynen 2015: fig. 2л; Rivera-Rondón and Catalan 2017: pl. 33/figs 15–19 (all citations as E. neocompacta var. vixcompacta). Kulikovskiy et al. 2016: p. 126, pl. 25/figs 7–11; Mimura and Ohtsuka 2016: fig. 34; Bahls et al. 2018: pl. 83/figs 8, 9.

Diagnosis

Morphometric data: length 27 µm, width 3.5 µm, striae density 20 in 10 µm.

Mayama 1997: length 18–57 µm, width 3.5–5 µm, striae density 20–22 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves dorsiventral, weakly arcuate, uniform in width, with truncated poles strongly deflected to dorsal side. Striae basal, uniserial, distant, evenly spaced (Fig. 30a). Areolae small with round outer foramina. Raphe system consists of two short filiform slits which are straight on ventral valve mantle and widely rounded at valve poles, distal ends of the slits finish on external valve surface on the middle of the poles by small round pores connected with helictoglossae of average size (Fig. 30a; see Mayama 1997: figs 28, 29); central raphe pores on outer valve surface are funnel-like (see Mayama 1997: fig. 31); tr-fissures absent (see Mayama 1997: fig. 31).

Ecology

Freshwater epiphytic species.

Distribution

EUROPE: Georgia, Ireland, Netherlands, Poland, Romania, Ukraine (M. Gury in Guiry and Guiry 2019); France, Pyrenees, Lake Monges (Rivera-Rondón and Catalan 2017); Russia (Genkal and Komulaynen 2015: as E. neocompacta var. vixcompacta). N. AMERICA: USA, Alaska, Atlantic Islands (M. Gury in Guiry and Guiry 2019); Canada (Bahls et al. 2018). ASIA: Japan (Mimura and Ohtsuka 2016); Russia (Kulikovskiy et al. 2016); Russia, Bering Island (M. Gury in Guiry and Guiry 2019). In Ukraine. First record in the Cheremsky Nature Reserve, tract Obkopane, Lake Redychi, epiphyton on Sphagnum sp.

Comments

In some publications the illustrations of this species are not uniform in valve outline, therefore only those microphotos which correspond to the species concept in Mayama (1997) are cited in the present paper. For instance, the specimen in Bouchard et al. (2018: pl. 1/fig. 6) has arcuate valve and longer poles therefore does not match to E. neocompacta sensu stricto.

Based on its morphology, Eunotia neocompacta var. vixcompacta (Lange-Bertalot et al. 2011) is conspecific with E. neocompacta, which has also been confirmed by other authors (Kulikovskiy et al. 2016, Mimura and Ohtsuka 2016, Bahls et al. 2018).

Eunotia praerupta Ehrenb., 1843: p. 414.

Fig. 31 (SEM)

Eunotia praerupta f. curta (Grunow) Mayer, 1917

Eunotia bidens var. praerupta (Ehrenb.) Aysel, 2005

Illustrations

Krammer and Lange-Bertalot 1991: pl. 148/figs 1–3; Pavlov and Levkov 2013: p. 35, pl. 18/fig. 7 (SEM), pl. 19/figs 1–10.

Diagnosis

Morphometric data: length 73 µm, width 20 µm; striae density c5, p8 in 10 µm. Pavlov and Levkov 2013: length 37–73 µm, width 13–17 µm; striae density c5–9, p8–12 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves dorsiventral, with strongly convex dorsal and weakly concave ventral margins, gradually narrowed to rostrate poles that are about perpendicular to the valve margins. Striae basal, uniserial, distant, irregularly spaced. Areolae small with round outer foramina. Raphe system consists of two short filiform slits on ventral valve mantle, distal ends of the slits finish on external valve surface on about 0.3 of pole width by small round pore-like outer connected with helictoglossae (see Pavlov and Levkov 2013: pl. 18/fig. 7); tr-fissures absent.

Ecology

Freshwater epiphytic species.

Distribution

Species was recorded in most European countries and on all continents except Antarctica (M. Gury in Guiry and Guiry 2019). In Ukraine. First record in the Cheremsky Nature Reserve, tract Obkopane, ditch, epiphyton on Sphagnum sp.

Comments

No illustrations were published by the author of this species, which has led to a very wide species concept and uncertain taxonomy. In this paper the concept of Eunotia praerupta sensu stricto proposed in Krammer and Lange-Bertalot (1991: pl. 148/figs 1–3) has been followed.

Eunotia pseudoflexuosa Hustedt, 1949: p. 71, pl. 2/figs 16–18. *^

Figs 13, 13a

Illustrations

Simonsen 1987: p. 340, pl. 522/figs 1–6; Kulikovskiy et al. 2010b: pl. 26/figs 1, 2, 4, 5 (LM), 3, 6, 7 (SEM); Kulikovskiy et al. 2016: pl. 26/figs 5–8; Bahls et al. 2018: pl. 83/fig. 1, pl. 112/fig. 6.

Diagnosis

Morphometric data: length 112 µm, width 4 µm, striae density 11 in 10 µm.

Kulikovskiy et al. 2016: length 80–180 µm, width 4–6 µm, striae density c11–14, p15–20 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves dorsiventral, uniform in width, with subcapitate poles deflected to dorsal side. Striae basal, uniserial, distant, evenly spaced (Fig. 13a). Areolae small with round outer foramina. Raphe system consists of two short filiform slits on ventral valve mantle; tr-fissures long, occupy 7–8 striae in the middle of valve width; helictoglossa average in size (Fig. 13a).

Ecology

Freshwater epiphytic species.

Distribution

AFRICA: Type location: [Democratic Republic of the Congo, Virunga National Park], vulkan region, Lake Karisimbi. EUROPE: Russia (Kulikovskiy et al. 2016); Ukraine (present paper). ASIA: Mongolia (Kulikovskiy et al. 2010b); Russia (Kulikovskiy et al. 2016). N. AMERICA: Canada (Bahls et al. 2018); USA, Alaska (M. Gury in Guiry and Guiry 2019). In Ukraine. The Cheremsky Nature Reserve, tract Obkopane, ditch, epiphyton on Sphagnum sp.

Type information

„Albert-National park in Belgisch-Kongo.”

Eunotia ruzickae Bílý & Marvan, 1962: p. 293, figs 1–5. *^

Fig. 14

Illustrations

Pavlov and Levkov 2013: pl. 58/fig. 7.

Diagnosis

Morphometric data: length 44 µm, width cp6, m7 µm; striae density c16, p22 in 10 µm. Bílý and Marvan 1962: length 40–90 µm, width 4.5–6 µm, striae density 13–14 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves dorsiventral, uniform in width, with slightly undulate dorsal margin and weak depression in its central part, usually straight ventral side, sometimes with weak central convexity (see Bílý and Marvan 1962: fig. 1), and broad rounded poles deflected to dorsal side. Striae basal, uniserial, distant, denser at the poles, irregularly spaced. Raphe system consists of two short filiform slits on ventral valve mantle, distal ends of the slits terminate at the poles about 0.3 of valve width from ventral margin.

Ecology

Freshwater epiphytic species.

Distribution

EUROPE: Type location: Czech Republic (Bílý and Marvan 1962); North Macedonia, (Pavlov and Levkov 2013); Germany, Scandinavia (M. Guiry in Guiry and Guiry 2019); Ukraine (present paper). In Ukraine. Zhytomyr region, Chervonoarmeisky district, swamp, dark films among mosses.

Type information

“In bentho piscinae Řežabinec prope vicum Ražice in Bohemia meridionali atque in nonnullis locis Moraviae merdionalis”, (Typus in herbario Inst. bot. Univ. Brunensis, Brno).

Comments

The found exemplar has denser striae than in type population. This species has typical raphe system without terminal raphe fissures, however SEM illustrations of the raphe to confirm this were not found.

Eunotia tetraodon Ehrenberg, 1838: p. 192, pl. 21/fig. 25.

Figs 34, 35

Himantidium tetraodon (Ehrenb.) Bréb. ex Kützing, 1849

Eunotia robusta var. tetraodon (Ehrenb.) Ralfs, 1861

Eunotia diadema var. tetraodon (Ehrenb.) A. Cleve, 1953

Eunotia serra var. tetraodon (Ehrenb.) Nörpel in Krammer and Lange-Bertalot 1991

Illustrations

Topachevsky and Oksiyuk 1960: p. 323, pl. 119/fig. 1 (as Eunotia robusta Ralfs); Bahls 2012: 6 exemplars; Bąk et al. 2012: pl. 15/4 exemplars; Ector et al. 2012: p. 270–271, 1 exemplar; Pavlov and Levkov 2013: pl. 16/figs 1–9, 10, 11 (SEM); Kulikovskiy et al. 2016: p. 133, pl. 29/figs 6–10; Malakhov et al. 2017: p. 67, fig. 10 (SEM); Bahls et al. 2018: pl. 21/fig. 2.

Diagnosis

Morphometric data: length 40 µm, width c8–10, m10–13, p4–8 µm; striae density c11–15, p16 in 10 µm. Pavlov and Levkov 2013: length 25–62 µm, width 9.5–16 µm, striae density 6–10, m12–16 in 10 µm.

Frustule bi-symmetric, bipolar, biraphid with mirror-symmetric, mantle-offset, brevisslit type of raphe. Valves dorsiventral, with strongly convex, four-times strongly undulate dorsal and weakly concave ventral margins, gradually narrowed to the protracted poles that continue the dorsal arc of valve margin. Striae basal, uniserial, distant, irregularly spaced, on dorsal side shortened intermediate striae present. Areolae small with round outer foramina. Raphe system consists of two short filiform slits on ventral valve mantle that follow pole margin and finish on about 0.5 of pole width by small round pore (see Pavlov and Levkov 2013: pl. 26/fig. 11) connected with helictoglossae; tr-fissures absent.

Ecology

Freshwater epiphytic species.

Distribution

Species was recorded in most European countries and on all continents except Antarctica (M. Gury in Guiry and Guiry 2019). In Ukraine. Volyn region, Manevychi district, Lake Bile; Rivnenska region, Bog Gala (Topachevsky and Oksiyuk 1960 – as Eunotia robusta Ralfs); Volyn region, the Cheremsky Nature Reserve, Lake Redychi (Malakhov et al. 2017); Lake Redychi, epiphyton on Fontinalis sp.

The genus Eunotia is one of the largest within the Order Bacillariophyta and totals 589 valid taxa. This can be considered as an evolutionary success of the genus, relevant to the frustule morphology that is well suited to the ecological conditions where the Eunotia species inhabit.

The presence of raphe system is certainly a progressive feature which has appeared in the diatom frustule evolution since the number of species bearing it exceeds significantly the ones without raphe.

The complicated morphology of Eunotia species has led to the numerous synonyms – more than 60% of taxonomic names (Guiry M in Guiry and Guiry 2019). Therefore it is a necessary task to find reliable morphological characters which can be useful in species identification and description.

The genus Eunotia possesses of mirror-symmetric, mantle-offset, brevisslit raphe system the combination of the characters in which is unique among diatom genera. At the same time different Eunotia species have peculiar details in the raphe system which belong to species rank of taxonomy: presence / absence of tr-fissures and their shape, shape of raphe slits and their position on the valve etc. (Table 1).

Table 1.

Download as

CSV

XLSX

Key morphological features in the genus Eunotia to recognize studied species. Abbreviations: dd-pore difficultly distinguishing pores, DS dorsal side, VM ventral mantle, VM+V ventral mantle + valve surface, VP valve pole, – absent, US unstudied

Species

Valve outline

Kind of striae

Striae arrangement

Raphe system on outer valve surface

Dorsal margin

Ventral margin

Shape of the poles

Shape of slits

Dispo- sition of slits

Shape of distal ends of the slits

Disposition of distal ends of the slits

Terminal fissures shape

Disposition of terminal fissures

Shape of central pores

E. dorofeyukiae

undulate

slightly concave

subcapitate, broad rounded

dis-tant

denser at the poles

VM+V

small round funnels

ventral VP corners

–

E. implicata

weakly convex

concave

protracted, rounded

dis- tant

irregularly spaced, denser at the poles

VM+V

turned to the valve centre under right corner, finish by small round pores

ventral VP corners

–

E. incisa

weakly convex

Straight

gradually contracted acutely rounded

dis- tant

gradually compacted to the poles

arcuate

round funnels

ventral margin

–

funnel-like

E. jarensis

uniform width, weakly convex

weakly concave

protracted, broadly rounded

dis- tant

evenly spaced

VM+V

ventral VP corners

E. neocompacta

uniform width, weakly convex

weakly concave

truncated, strongly deflected to DS

dis- tant

evenly spaced

straight on VM, rounded at VP

VM+V

small round pores

middle of VP

–

funnel-like

E. praerupta

strongly convex

weakly concave

rostrate

dis- tant

irregularly spaced

VM+V

small round pores

ventral VP corners

–

E. ruzickae

slightly undulate

straight

broad round, deflected to DS

dis- tant

irregularly spaced, compacted to the poles

VM+V

ventral VP corners

E. tetraodon

strongly convex, four-times strongly undulate

weakly concave

protracted,

dis- tant

irregularly spaced,

VM+V

small round pores

middle of VP

–

E. formicina

weakly convex

weakly concave, gentle gibbosity

subcapitate, broad rounded

dis- tant

irregularly spaced

VM+V

dd-pores

ventral VP corners

long, round

follow poles outline, finish on DM

round

E. genuflexa

weakly convex

weakly concave

narrowed rounded

dis- tant

evenly spaced

VM+V

dd-pores

ventral VP corners

long, round, with lacunae

mid-valve

E. julma

uniform width, convex

concave

round

dis- tant

evenly spaced

VM+V

dd-pores

–

long, round, with lacunae

mid-valve

E. pseudoflexuosa

uniform width, weakly convex

weakly concave

subcapitate, deflected to DS

dis- tant

evenly spaced

VM+V

long

mid-valve

The morphological analysis carried out in this study revealed that 8 of 12 studied species of Eunotia do not have terminal raphe fissures (Table 1). Instead, the distal ends of the raphe slits terminate on the outer valve surface by pore-like (Figs 3c, 28a, 30) or funnel holes (Fig. 3d, see Mayama 1997: fig. 31) which are connected with helictoglossae. However, in the literature those distal ends of the raphe slits were erroneously described as tr-fissures (e.g. Pavlov and Levkov 2013: p. 20, pl. 18/fig. 7; p. 43, pl. 26/fig. 11). Eunotia krammeri Kulikovskiy et al. also has a raphe system without tr-fissures that is clearly visible on SEM illustrations both from external and internal valve surfaces (Kulikovskiy et al. 2010a: p. 102, pl. 7/figs 18, 19). Nevertheless, the authors report them in their description of this species.

In morphology of Eunotia the characters suitable for the species identification are quite restricted. Besides, the frustule ultrastructure is poorly studied even for the species which were investigated with SEM, in particularly, raphe system. For many species there is still no data on the slits form, central pores etc. In the meantime, among key diagnostic characters for the Eunotia species identification more than half include the ones which refer to the peculiarity of raphe system (Table 1). For instance, central raphe pores usually have a different shape on the inner and outer valve surfaces, however their shape on inner surface is uniform within the genera and some taxa of higher rank of taxonomy while the shape of central pores on the outer valve surface has the species rank of taxonomy (Bukhtiyarova and Pomazkina 2013).

Thus, careful application of suggested terms in future is necessary when describing new Eunotia taxa and will be helpful in correct identification of the known species.

Species of Eunotia prefer acidic, dystrophic or oligotrophic freshwater habitats, mostly of low conductivity and usually inhabit in epiphytic or epilithic hydrotopes (Alles et al. 1991, Metzeltin and Lange-Bertalot 1998, Siver et al. 2006, Cantonati and Lange-Bertalot 2011, Pavlov and Levkov 2013, Bahls et al. 2018). In Ukraine 32 species and eight varieties of Eunotia were known until this study and now 9 more species are reported for the first time. Thus, the total number of Eunotia species in Ukraine is 41, which is only 7% of the species in this genus worldwide. This is indirect evidence of insufficient investigation of the wetlands in Ukraine where Eunotia has high species richness. The findings in the present study include five species widely distributed in the world flora on most continents and seven rare species that are known from several locations, among the latter are E. genuflexa, E. jarensis and E. ruzickae, which are probably European endemics. At present, in the Cheremsky Nature Reserve, 20 species have been recorded, which is the largest number of Eunotia species in any region of Ukraine. In total 19 Eunotia species were recorded in this study together with the ones which were not identified to the species level. Given the large number of poorly studied oligotrophic lakes and bogs in the country, especially in Ukrainian Polissya, it is possible to predict the future discovery of many more Eunotia species from Ukraine.

Acknowledgement

This research has been carried out under the scientific project Nº 0117U004321 of the National Academy of Sciences of Ukraine. The author is extremely grateful to Dr Loren Bahls for his kind help with English language corrections and for his many valuable comments, to every reviewer and the editor Dr Kalina Manoylov for their careful patient work with the manuscript and for many suggestions which significantly improved final version of this paper.

References

Agardh CA (1830) Conspectus criticus diatomacearum. Part 1. Literis Berlingianus, Lundae [Lund], 1–16.

Alles E, Nörpel-Schempp M, Lange-Bertalot H (1991) Zur Systematik und Ökologie charakteristischer Eunotia-Arten (Bacillariophyceae) in elektrolytarmen Bachoberläufen. Nova Hedwigia 53(1–2): 171–213.

Bahls L (2012) Eunotia tetraodon. In Diatoms of North America. https://diatoms.org/species/eunotia_tetraodon [Retrieved April 05, 2019]

Bahls L, Boynton B, Johnston B (2018) Atlas of diatoms (Bacillariophyta) from diverse habitats in remote regions of western Canada. PhytoKeys 105: 1–186. https://doi.org/10.3897/phytokeys.105.23806

Bąk M, Witkowski A, Zelazna-Wieczorek J, Wojtal AZ, Szczepocka E, Szulc K, Szulc B (2012) Klucz do Oznaczania okrzemek w fitobentosie na potrzeby oceny stanu ekologicznego wod powierzchniowych w Polsce. Biblioteka Monitoringu Srodowiska, Warszawa, 452 pp.

Berg A (1939) Some new species and forms of the diatom genus Eunotia Ehrenberg 1837. Botaniska Notiser: 423–462.

Bílý J, Marvan P (1962) Eunotia ruzickae spec. nova. Preslia 34: 293.

Bory JBGM (1822) Bacillariées. Dictionnaire Classique d’Histoire naturelle 2: 127–129.

Bukhtiyarova LN (2008) Preliminary data on diatoms from Cheremsky Natural Reserve, Ukrainian Polissya. In: Likhoshway Ye (Ed.) Proceedings of the Nineteenth International Diatom Symposium. Biopress Ltd., Bristol, 23.

Bukhtiyarova LN (2009a) Frustule functions and functional morphology of Bacillariophyta. Algologia 19(3): 321–331.

Bukhtiyarova LN (2009b) New for Ukraine taxa of the genus Pinnularia Eherenb. (Bacillariophyta) from Ukrainian Polissya. In: Budz MD (Ed.) Preservation and reproduction of biodiversity of protected areas. Materials of the International Scientific and Practical Conference devoted to the 10th anniversary of Rivne Nature Reserve. June 11–13, 2009, Sarny. Rivnenska drukarnya, Rivne, 128–132.

Bukhtiyarova LN (2015) Classification of uniserial striae in Bacillariophyta with bipolar frustule. Algologia 25(2): 198–210. https://doi.org/10.15407/alg25.02.198

Bukhtiyarova LN (2019) Functional morphology of the diatom frustule in systematics of Bacillariophyta. In: Tsarenko PM (Ed.) VI International Conference “Advances in modern phycology”, 15–17 May 2019, Kyiv, Ukraine. National Academy of Sciences of Ukraine, Kyiv, 24–26.

Bukhtiyarova LN, Pomazkina GV (2013) Bacillariophyta of Lake Baikal. Vol. 1. Genera Baikalia, Slavia, Navigeia, Placogeia, Grachevia, Goldfishia, Nadiya, Cymbelgeia. LigaPres, Lviv, 184 pp.

Bukhtiyarova LN, Round FE (1996) Revision of the genus Achnanthes sensu lato. Psammothidium a new genus based on Achnanthidium marginulatum. Diatom Research 11(1): 1–30. https://doi.org/10.1080/0269249X.1996.9705361

Burliga AL, Kociolek JP, Salomoni SE, Figueiredo D (2013) A new genus and species in the diatom family Eunotiaceae Kützing (Bacillariophyceae) from the Amazonian hydrographic region, Brazil. Phytotaxa 79(2): 47–57. https://doi.org/10.11646/phytotaxa.79.2.1

Cantonati M, Lange-Bertalot H (2011) Diatom monitors of close-to-pristine, very-low alkalinity habitats: Three new Eunotia species from springs in Nature Parks of the south-eastern Alps. Journal of Limnology 70(2): 209–221. https://doi.org/10.4081/jlimnol.2011.209

Costa LF (2015) Taxonomia e ecologia de Eunotia (Bacillariophyceae) em represas das regiões Sul e Sudeste do Estado de São Paulo. Dissertação (Mestrado). Instituto de Botânica da Secretaria de Estado do Meio Ambiente, São Paulo, 349 pp.

Costa LF, Wetzel CE, Lange-Bertalot H, Ector L, Bicudo DC (2017) Taxonomy and ecology of Eunotia species (Bacillariophyta) in south eastern Brazilian reservoirs. Bibliotheca Diatomologica 64. J. Cramer In Borntraeger Science Publishers, Stuttgart, 302 pp.

Diatoms of North America (2019) Diatoms of North America. https://diatoms.org/glossary/raphe

Ector L, Wetzel CE, Novais MH, Guillard D (2015) Atlas des diatomées des rivières des Pays de la Loire et de la Bretagne. DREAL Pays de la Loire, Nantes, 649 pp.

Ehrenberg CG (1838) Die Infusionsthierchen als vollkommene Organismen. Ein Blick in das tiefere organische Leben der Natur. Verlag von Leopold Voss, Leipzig, 547 pp. https://doi.org/10.5962/bhl.title.58475

Ehrenberg CG (1843) Verbreitung und Einfluss des mikroskopischen Lebens in Süd-und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1841: 291–466.

Furey PC (2012) Eunotia paludosa. Diatoms of North America. https://diatoms.org/species/eunotia_paludosa [Retrieved April 08, 2019]

Furey PC, Lowe RL, Johansen JR (2011) Eunotia Ehrenberg (Bacillariophyta) of the Great Smoky Mountains National Park, USA. Bibliotheca Diatomologica 56: 1–133.

Genkal SI, Komulaynen SF (2015) Novyye dannyye k flore Bacillariophyta rek yuzhnogo (pomorskogo) poberezh’ya Belogo morya (Respublika Kareliya) [New data on the flora of Bacillariophyta in rivers of the southern (Pomorsky) coast of the White Sea (the Republic of Karelia)]. Inland water biology 2: 5–13. [In Russsian] https://doi.org/10.7868/S0320965215020072

Gogorev RM, Chudaev DA, Stepanova VA, Kulikovskiy MS (2018) Russkiy i angliyskiy terminologicheskiy slovar’ po morfologii diatomovykh vodorosley [Russian and English terminological glossary on morphology of diatoms]. Novosti sistematiki nizshikh rastenii 52(2): 265–309. [In Russian] https://doi.org/10.31111/nsnr/2018.52.2.265

Gregory W (1854) Notice of the new forms and varieties of known forms occurring in the diatomaceous earth of Mull with remarks on the classification of the Diatomaceae. The Quarterly Journal of Microscopical Science 2: 90–100.

Grunow A (1860) Über neue oder ungenügend gekannte Algen. Erste Folge, Diatomeen, Familie Naviculaceen. Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wein 10: 503–582.

Grunow A (1862) Die Österreichischen Diatomaceen nebst Anschluss einiger neuen Arten von andern Lokalitäten und einer kritischen Uebersicht der bisher bekannten Gattungen und Arten. Epithemieae, Meridioneae, Diatomeae, Entopyleae, Surirelleae, Amphipleureae. Verhandlungen der kaiserlich-königlichen zoologisch-botanischen Gesellschaft in Wien 12(1): 315–472. https://doi.org/10.5962/bhl.title.64361

Guiry MD, Guiry GM (2019) AlgaeBase. National University of Ireland, Galway. http://www.algaebase.org

Hamilton PB, Siver PA (2010) A morphological investigation of Eunotia fennica (Bacillariophyceae) from a freshwater acidic pond in Newfoundland, Canada. Proceedings. Academy of Natural Sciences of Philadelphia 160(1): 89–98. https://doi.org/10.1635/053.160.0110

Hustedt F (1930) Bacillariophyta (Diatomeae) Zweite Auflage. In: Pascher A (Ed.) Die Süsswasser-Flora Mitteleuropas. Heft 10. [i]-vii, [1]. Verlag von Gustav Fischer, Jena, 466 pp.

Hustedt F (1949) Süsswasser-Diatomeen. In: Exploration du Parc National Albert, Mission H. Damas (1935–1936) 8. Institut des Parcs Nationaux Du Congo Belge, Brussels, 1–199.

Jüttner I, Bennion H, Carter C, Cox EJ, Ector L, Flower R, Jones V, Kelly MG, Mann DG, Sayer C, Turner JA, Williams DM (2019) Eunotia intermedia (Krasske) Nörpel et Lange-Bertalot in Lange-Bertalot; 1993; 32. Freshwater Diatom Flora of Britain and Ireland. Amgueddfa Cymru – National Museum Wales. https://naturalhistory.museumwales.ac.uk/diatoms/browsespecies.php?-recid=2913 [Accessed: 7 April 2019]

Konischuk VV, Didukh YaP (2004) Kartohrafichnyy ta ordynatsiynyy analiz ekolohichnykh faktoriv Cheremsʹkoho pryrodnoho zapovidnyka [The cartographic and ordination analysis of the ecological factors of the Cheremsky Nature Reserve]. Ukrainian Botanical Journal 61(3): 47–60. [In Ukrainian]

Konishchuk VV (2005) Klasyfikatsiya ekosystem Cheremsʹkoho pryrodnoho zapovidnyka z vykorystannyam kartohrafichnoho metodu [The classification of the Cheremsky Nature Reserve ecosystems using a mapping method]. Ukrainian Phytosociological Collection, Series C 1(23): 61–76. [in Ukrainian]

Krammer K (1992) Pinnularia. Eine Monographie der europäischen Taxa. Bibliotheca Diatomologica 26: 1–353.

Krammer K (2000) The genus Pinnularia. In: Lange-Bertalot H (Ed.) Diatoms of Europe Vol. 1. ARG Gantner Verlag KG, Ruggell, 1–703.

Krammer K, Lange-Bertalot H (1991) Bacillariophyceae 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. In: Ettl H, et al. (Eds) Suesswasserflora von Mitteleuropa 2(3). VEB Gustav Fisher Verlag, Jena, 1–576.

Kulikovskiy MS, Lange-Bertalot H, Genkal SI, Witkowski A (2010a) Eunotia (Bacillariophyta) in the holarctic: New species from the Russian arctic. Polish Botanical Journal 55(1): 93–107.

Kulikovskiy MS, Lange-Bertalot H, Witkowski A, Dorofeyuk NI, Genkal SI (2010b) Diatom assemblages from sphagnum bogs of the world. I. Nur bog in northern Mongolia. In: Lange-Bertalot H, Kociolek P (Eds) Bibliotheca Diatomologica 55. J. Cramer, Stuttgart, 1–326.

Kulikovskiy M, Glushchenko AM, Kuznetsova IV, Genka SI (2016) Opredelitel’ diatomovykh vodorosley Rossii [The identification book of the diatoms from Russia]. Filigran, Yaroslavl, 804 pp. [in Russian]

Kützing FT (1844) Die Kieselschaligen Bacillarien oder Diatomeen. Zu finden bei W. Köhne Nordhausen, 1–152. https://doi.org/10.5962/bhl.title.64360

Kützing FT (1849) Species algarum. FA Brockhaus, Lipsiae [Leipzig], 922 pp.

Lange-Bertalot H (1993) 85 neue Taxa und über 100 weitere neu definierte Taxa ergänzend zur Süsswasserflora von Mitteleuropa Vol. 2/1–4. Bibliotheca Diatomologica 27. Cramer, Berlin, Stuttgart, 454 pp.

Lange-Bertalot H, Metzeltin D (1996) Indicators of oligotrophy – 800 taxa representative of three ecologically distinct lake types: Carbonate buffered – Oligodystrophic – weakly buffered soft water. In: Lange-Bertalot H (Ed.) Iconographia Diatomologica. Annotated Diatom Micrographs 2. Ecology, Diversity, Taxonomy. Koeltz Scientific Books, Königstein, 1–390.

Lange-Bertalot H, Metzeltin D, Witkowski A (1996) Hippodonta gen. nov. Umschreibung und Begründung einer neuer Gattung der Naviculaceae. Iconographia Diatomologica 4: 247–275.

Lange-Bertalot H, Cavacini P, Tagliaventi N, Alfinito S (2003) Diatoms of Sardinia. Rare and 76 new species in rock pools and other ephemeral waters. In: Lange-Bertalot H (Ed.) Iconographia Diatomologica 12. ARG Gantner Verlag KG, Ruggell, 1–438.

Lange-Bertalot H, Bąk M, Witkowski A, Tagliaventi N (2011) Eunotia and some related genera. In: Lange-Bertalot H (Ed.) Diatoms of Europe. Diatoms of the European inland waters and comparable habitats. 6. ARG Gantner Verlag KG, Ruggell, 1–747.

Lewis FW (1864) On some new and singular intermediate forms of Diatomaceae. Proceedings. Academy of Natural Sciences of Philadelphia 15: 336–346.

Malakhov Yu, Kryvosheia O, Tsarenko P (2017) Microalgae of protected lakes of Northwestern Ukraine. Polish Botanical Journal 62(1): 61–76. https://doi.org/10.1515/pbj-2017-0008

Marra RC, Tremarin PI, Algarte VM, Ludwig TV (2016) Epiphytic diatoms (Diatomeae) from Piraquara II urban reservoir, Paraná state. Biota Neotropica 16(4): 1–20. e20160200. https://doi.org/10.1590/1676-0611-BN-2016-0200

Mayama S (1997) Eunotia nymanniana Grunow and related taxa. Diatom 13: 31–37.

Mayama S, Kawashima A (1998) New combinations for some taxa of Navicula and Stauroneis and an avowed substitute for a taxon of E.notia. Diatom 14: 69–71.

Metzeltin D, Lange-Bertalot H (1998) Tropical diatoms of South America I: About 700 predominantly rarely known or new taxa representative of the neotropical flora. In: Lange-Bertalot H (Ed.) Iconographia Diatomologica 5. Koeltz Scientific Books, Königstein, 695 pp.

Mimura T, Ohtsuka T (2016) Diatoms of Yamamuro Moor, a sphagnum moor situated in the warm-temperate zone in Shiga Prefecture, central Japan. Diatom 32: 24–32. https://doi.org/10.11464/diatom.32.24

Noga T (2019) Valuable habitats of protected areas in southern Poland – a source of rare and poorly known diatom species. Acta Societatis Botanicorum Poloniae 88(1): 1–20. DOI: 10.5586/asbp.3595 https://doi.org/10.5586/asbp.3595

Ohtsuka T (2002) Checklist and illustration of diatoms in the Hii River. Diatom 18: 23–56.

Ortiz-Lerín R, Cambra J (2007) Distribution and taxonomic notes of Eunotia Ehrenberg 1837 (Bacillariophyceae) in rivers and streams of Northern Spain. Limnetica 26(2): 415–434.

Palamar’-Mordvintseva GM, Tsarenko PM, Wasser SP (1998) K voprosu o sostavlenii «krasnykh spiskov» vodorosley Ukrainy [On the question of the compilation of the “red lists” of algae of the Ukraine]. Algologia 8(4): 341–350. [In Russian]

Pavlov A, Levkov Z (2013) Diversity and distribution of taxa in the genus Eunotia Ehrenberg (Bacillariophyta) in Macedonia. Phytotaxa 86(1): 1–117. https://doi.org/10.11646/phytotaxa.86.1.1

Potapova MG, Hamilton PB, Kopyrina LI, Sosina NK (2014) New and rare diatom (Bacillariophyta) species from a mountain lake in Eastern Siberia. Phytotaxa 156(3): 100–116. https://doi.org/10.11646/phytotaxa.156.3.2

Rivera-Rondón CA, Catalan J (2017) Diatom diversity in the lakes of the Pyrenees: An iconographic reference. Limnetica 36(1): 127–395. https://doi.org/10.23818/limn.36.10

Round FE, Crawford RM, Mann DG (1990) The Diatoms. Biology and morphology of the genera. Cambridge University Press, Cambridge, 747 pp.

Simonsen R (1987) Atlas and Catalogue of the Diatom Types of Friedrich Hustedt 1. J. Cramer, Berlin, Stuttgart, 1–525.

Siver PA, Hamilton PB, Morales EA (2006) Two new planktic species of Eunotia (Bacillariophyceae) from freshwater water bodies in North Carolina, U.S.A. Algological Studies 119(1): 1–16. https://doi.org/10.1127/1864-1318/2006/0119-0001

Smith W (1856) A synopsis of the British Diatomaceae with remarks on their structure, functions and distribution and instructions for collecting and preserving specimens. Vol. 2. John van Voorst, London, 107 pp.

Taylor JC, Harding WR, Archibald CGM (2007) An Illustrated Guide to Some Common Diatom Species from South Africa. WRC Report TT 282/07. Water Research Commission, Pretoria.

Topachevsky OV, Oksiyuk OP (1960) Diatomovi vodorosti – Bacillariophyta (Diatomeae). In: Topachevsky OV (Ed.) Vyznachnyk prisnovodnyh vodorostey Ukrainskoi RSR T. 11. Naukova dumka, Kyiv, 1–412.

Van Heurck H (1881) Synopsis des Diatomées de Belgique. Atlas. Ducaju, Cie., Anvers. Pls 31–77.

Wasser SP, Kondrat’eva NV, Masyuk NP et al. (1989) Vodorosli – Spravochnik [Algae – Reference Book]. Naukova dumka, Kiev, 605 pp. [In Russian]

Werum M, Lange-Bertalot H (2004) Diatoms in springs from Central Europe and elsewhere under the influence of hydrologeology and anthropogenic impacts. Iconographia Diatomologica 13. ARG Gantner, Ruggell, 3–417.

1 detection limit

2 Species epithet ' dorofeyukiae' is corrected by M. Gury (in Guiry and Guiry 2019), the author’s epithet was ' dorofeyukae'

3 current geographic names are added to this paper