Abstract
A new monoraphid diatom genus, Platesiberia gen. nov., is described based on a detailed morphological investigation using light and scanning electron microscopy. The genus is based upon P. rhombicolanceolata Kulikovskiy & Lange-Bertalot and includes Platessa baicalensis Kulikovskiy & Lange-Bertalot, both species previously described from ancient Lake Baikal. Platesiberia gen. nov. is characterized by having biseriate striae on the raphe valves with uniseriate striae on the rapheless valves. Morphology of striae is helpful to distinguish the genus Platesiberia from Platessa and other monoraphid genera, and we provide a comparison of the new Baikalian genus with other freshwater monoraphid groups.
1. Introduction
Over the past 25 years the monoraphid diatoms have been the focus of intense research on their diversity, taxonomy and systematics. Whereas 2–3 generations ago, the freshwater representatives of monoraphid diatoms were treated as two genera, Achnanthes Bory and Cocconeis Ehrenberg [,,], now there are over 14 genera of freshwater monoraphid diatoms that were once considered part of or assignable to Achnanthes sensu lato [,,,,,,,,]. This discovery of diversity amongst the freshwater achnanthioid diatoms, both through recognition of past genera and newly discovered taxa, has been facilitated by observations made with scanning electron microscopes, revealing morphological features and patterns not previously recognized. New species descriptions from the world over have shown many consistencies in the distribution of the features used to diagnose new genera of monoraphid diatoms. However, there have also been some “intermediate” species recognized that might serve to link genera previously recognized as separate [,]. Molecular data have revealed that there have been several different, independent lineages within which the monoraphid condition has evolved [,], while many of the newly created and resurrected genera have been shown to be monophyletic [].
More than 1500 species of diatoms inhabit Lake Baikal [,,,,,,,,,,,,,,,,,,,,,,,]. During a revision of the monoraphid diatoms from Lake Baikal, about 55 new species were described [,,,]. Karayevia Round & Bukhtiyarova 1998, Skabitschewskia Kulikovskiy & Lange-Bertalot 2015, Nupela Vyverman & Compère 1991 and Planothidium Round & Bukhtiyarova 1996 have the greatest diversity of species among the monoraphid diatoms in the world’s oldest lake []. During this revision, many new monoraphid taxa were described from the genera: Eucocconeis P.T. Cleve ex F. Meister 1912, Karayevia, Nupela, Planothidium, Platessa Lange-Bertalot 2004 [], Skabitschewskia, Trifonovia Kulikovskiy & Lange-Bertalot 2012 and Gliwiczia Kulikovskiy, Lange-Bertalot & Witkowski 2013. Two species of the diatom genus, Platessa, P. baicalensis Kulikovskiy & Lange-Bertalot and P. rhombicolanceolata Kulikovskiy & Lange-Bertalot, were described during this revisionary work [].
In the last revision of the genus Platessa Lange-Bertalot, we indicated that eight groups within the genus could be recognized on the basis of morphological features []. Two interesting species previously described and placed in the genus Platessa stood out as a separate group []. This group includes both P. baicalensis and P. rhombicolanceolata [], which are characterized by having biseriate striae on the raphe valve and uniseriate striae in rapheless valves. Most Platessa species have biseriate striae on both valves. In light of this difference, we postulated that the morphology of these species differs from the generitype of Platessa, P. bavarica Lange-Bertalot & Hofmann [] and thus may require an independent genus to accommodate them []. It is interesting that Lake Baikal harbors taxa that do not share important morphological features typical of the generitype.
We have also carefully described all morphological features important for the taxonomy of monoraphid diatoms and postulated striae that are uniseriate, biseriate or multiseriate on the raphe and rapheless valves, as well as combinations of these features, which are important for the taxonomy of this group of diatoms. The same opinion was supported by molecular investigations for species and genera of monoraphid diatoms when possible [,,,,,]. Lange-Bertalot [] proposed Platessa on the basis of morphological features with predominantly biseriate striae in both valves and small, elliptic, flat valves with morphologically similar raphe and rapheless valves; the presence of a stauros-like structure on the rapheless valves; and areolae of both valves occluded by hymenes. Since its original description, Platessa has become a catch-all genus with taxa representing many monoraphid genera with unknown taxonomical positions [,].
The aim of this publication is to provide additional morphological evidence for two monoraphid diatoms, Platessa baicalensis Kulikovskiy & Lange-Bertalot and P. rhombicolanceolata Kulikovskiy & Lange-Bertalot, and, based on the results of this study, to describe the genus Platesiberia gen. nov.
2. Materials and Methods
For this study we used samples from Lake Baikal collected by A.P. Skabitschewsky on 20 July 1965 from bottom deposits surrounding Ushkan’i Islands, obtained from the collection of Galina Khursevich (Minsk, Belarus). For a complete list of samples, please consult Kulikovskiy et al. []. The genus proposed here is based on species present in two samples: sample number 15,645 m—substratum: sand, Ushkan’i Islands 42 m depth, off Bolshoi Ushkan’i Island—and sample number 15,651 m—substratum: sand, Ushkan’i Islands 4 m depth, eastern shore.
The samples were boiled in concentrated hydrogen peroxide (≈37%) to dissolve organic matter. The samples were then washed with deionized water four times at 12 h intervals. After decanting and rinsing with up to 100 mL of deionized water, the suspension was spread onto coverslips and left to dry at room temperature. Permanent diatom slides were mounted in Naphrax®. Light microscopic (LM) observations were performed with a Zeiss Scope A1 microscope equipped with an oil immersion objective (100×, n.a. 1.4, differential interference contrast [DIC]) and Zeiss AxioCam ERc 5s camera. For scanning electron microscopy (SEM), parts of the suspensions were fixed on aluminum stubs after air-drying. The stubs were sputter coated with 50 nm of gold. Valve ultrastructure was examined by means of a JSM-6510LV scanning electron microscope (Institute for Biology of Inland Waters RAS, Borok, Russia).
3. Results
Platesiberia Kulikovskiy, Glushchenko, Genkal & Kociolek gen. nov.
Type species (designated here):Platesiberia rhombicolanceolata (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov.
Description. LM, raphe valves (Figure 1A–H). Valves elliptical to rhombical-lanceolate, ends broadly rounded in longer specimens and somewhat cuneately rounded in shorter specimens. Valves with straight, filiform raphes which are gradually expanded towards the central ends. Axial area more or less widely extended transapically defined by 1–4 irregularly shortened adjacent striae. Striae radiate and biseriate.
Figure 1.
Platesiberia rhombicolanceolata (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov. Slide no. 15645m. Light microscopy, differential interference contrast, size diminution series. (A–H). Raphe valves. (I–P). Rapheless valves. Scale bar = 10 μm.
LM, rapheless valves (Figure 1I–P). Valves elliptical to rhombical-lanceolate, ends broadly rounded in longer and somewhat cuneately rounded in shorter specimens. Axial area widely extended transapically. The central area is almost absent and defined by 1–2 shorter striae. Striae uniseriate.
SEM, raphe valves (Figure 2A–H). Axial area flat, central area expanded on flat valve and organized by elevated interstriae outside. Axial area elevated internally, sternum evident, central area has evident stauros that is defined by highly elevated interstriae between shorter 1–2 striae. Striae biseriate and covered by silica membrane externally. Raphe filiform, distal raphe ends are tear-shaped, extending slightly onto valve mantle and turned in opposite directions externally. Internally, raphe is filiform, distal and central ends are turned to different sides. Central raphe ends are tear-shaped, straight externally and almost straight internally.
Figure 2.
Platesiberia rhombicolanceolata (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov. Scanning electron microscopy. Raphe valves. (A). The whole valve, external view. (B–E). Entire valve, internal views. (F). Central area, internal views. (G,H). Valve ends, internal views. Scale bar (A–C) = 5 μm; (D,E) = 2 μm; (F–H) = 1 μm.
SEM, rapheless valves (Figure 3A–H). Interstriae very prominent, the same width as striae internally. Externally valves are flat, but the central area has elevated interstriae between a few shorter striae. Striae uniseriate. Axial area broad and widened towards the central area. Sternum evident and elevated internally.
Figure 3.
Platesiberia rhombicolanceolata (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov. Scanning electron microscopy. Rapheless valves, internal views. Scale bar (A,B,F,H) = 5 μm; (C–E,G) = 2 μm.
Etymology. Combining epithet refers to the similarity with the genus Platessa and the locality from Eastern Siberia (Lake Baikal).
New combinations:
Platesiberia rhombicolanceolata (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov.
Basionym: Platessa rhombicolanceolata Kulikovskiy & Lange-Bertalot 2015. Lake Baikal: Hotspot of endemic diatoms II. Iconographia Diatomologica. V. 26. pp. 67–68. Figs 75: 11–13.
Platesiberia baicalensis (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov. (see Figure 4).
Figure 4.
Platesiberia baicalensis (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov. Slide no. 15651m. (A–H). Light microscopy, differential interference contrast, size diminution series. (I,J). Scanning electron microscopy. (A–D,I). Raphe valves. (E–H,J). Rapheless valves. Scale bar (A–H) = 10 μm; (J) = 5 μm; (I) = 3 μm.
Basionym: Platessa baicalensis Kulikovskiy & Lange-Bertalot 2015. Lake Baikal: Hotspot of endemic diatoms II. Iconographia Diatomologica. V. 26. pp. 64–65. Figs 75: 1–10.
4. Discussion
Platesiberia gen. nov. is a new genus that is very easily distinguished from other known freshwater monoraphid genera such as Platessa, Achnanthidium, Skabitschewskia, Planothidium, Crenotia, Eucocconeis, Gliwiczia, Lemnicola, Psammothidium, Trifonovia and Platebaikalia (see Table 1 and Table 2) [,]. Our new genus is distinguished from other freshwater monoraphid genera on the basis of striation on both raphe and rapheless valves. Platesiberia gen. nov. is characterized by the presence of biseriate striae on raphe valves and uniseriate striae on rapheless valves, separating it from Platessa as typified by P. bavarica. Our new genus is somewhat similar to the genus Lemnicola on the basis on shape of the valve, which are elliptical or rhombical-elliptical.
However, Lemnicola is very easily distinguished by having areolae that are biseriate on both valves. Skabitschewskia is another genus described from Lake Baikal, but species from this taxon are known from Holarctic. This genus is like Platesiberia gen. nov. valves with uniseriate and biseriate valves, but they occur in opposite placements. In Skabitschewskia, biseriate striae are known in the rapheless valves, and uniseriate striae are found on the raphe valves. Moreover, Skabitschewskia is characterized by the presence of a cavum on the rapheless valves. The cavum is an important morphological feature and is absent in Platesiberia gen. nov. Another genus with a cavum is Planothidium, and this genus is also characterized by having multiseriate striae on both valves [,,].
Another genus having a cavum is Gliwiczia, but unlike the condition seen in Skabitschewskia and Lemnicola, the cavum is present on both the raphe and rapheless valves []. Gliwiczia is characterized by having uniseriate striae on both valves like in other genera without a cavum. These other genera include Trifonovia, Psammothidium, Eucocconeis, Achnanthidium, Gololobovia and Gogorevia [,,].
A very interesting feature of Platesiberia gen. nov. is the presence of a stauros that is evident externally and internally. However, this stauros has distinct interstriae in the central part between shorter striae. This structure is evident in raphe valves but less so in rapheless ones. A stauros, seen in Platesiberica, is also known in the monoraphid genera Gliwiczia, Lemnicola, Gololobovia and Gogorevia [,,,].
The stauros is much more evident in the genus Gogorevia, which is closely related to Lemnicola on the basis molecular data []. We can postulate that a stauros is not common among monoraphid freshwater diatom genera and that the morphology of this structure in the genus Platesiberia gen. nov. is unique. We need more molecular phylogenetic investigations to understand evolution of this feature between monoraphid diatoms. Gogorevia and Lemnicola are phylogenetically close genera, and we can postulate that the stauros arose once in this group.
Table 1.
Comparison of Platesiberia gen. nov. with Platessa and related monoraphid genera.
Table 1.
Comparison of Platesiberia gen. nov. with Platessa and related monoraphid genera.
| Platesiberia gen. nov. | Platessa | Platebaikalia | Gogorevia | |
|---|---|---|---|---|
| Type species | P. rhombicolanceolata (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov. | P. bavarica Lange-Bertalot & Hofmann 2004 | P. elegans Kulikovskiy, Glushchenko & Kociolek | G. renatii Kulikovskiy, Glushchenko, Maltsev & Kociolek |
| Striae in RV | biseriate | biseriate | multiseriate | uniseriate |
| Striae in RLV | uniseriate | biseriate | biseriate | uniseriate |
| Interstriae in RV externally | flat, the same width as striae | flat, equal or broader than striae | flat, more narrow than striae | flat, broader than striae |
| Interstriae in RV internally | very prominent on striae, the same width as striae | flat, equal or broader than striae | very prominent on striae, more narrow than striae | prominent, broader than striae |
| Interstriae in RLV externally | flat, the same width as striae | flat, equal to or broader than striae | flat, equal to or narrower than striae | flat, broader than striae |
| Interstriae in RLV internally | very prominent on striae, the same width as striae | flat, equal to or broader than striae | very prominent, more narrow than striae | prominent, broader than striae |
| Pore occlusions | silica membrane | hymenes | silica membrane | hymenes |
| Distal raphe ends externally | tear-shaped, extending slightly onto valve mantle; turned in opposite directions | linear and straight on valve face | tear-shaped, straight on valve face | deflected to opposite sides, terminating in drop-like pores on the valve face |
| Distal raphe ends internally | in small helictoglossae; curved in the opposite directions | in small helictoglossae; curved in the opposite directions | in small helictoglossa; straight | in small helictoglossae; turned in different directions |
| Central raphe ends externally | tear-shaped, straight | tear-shaped, straight | tear-shaped, straight | tear-shaped, straight |
| Central raphe ends internally | linear, straight, slightly curved in opposite directions | straight; turned in opposite directions | linear, straight, slightly curved in opposite directions | slightly curved in opposite directions |
| Axial area in RV, externally | flat, narrow and linear | flat, narrow and linear | narrow and linear, slightly widened into central area, sternum detected | very narrow, linear, opening rather abruptly to the central area |
| Axial area in RV, internally | enough broad and widened to central area, sternum evident and elevated | flat, narrow and linear | narrow and linear, slightly widened to central area, sternum | slightly raised above the surface of the striae |
| Axial area in RLV, externally | narrow and linear, slightly widened to central area | very broad, flat | narrow and linear, slightly widened to central area, sternum, deep on valve face | flat, narrow sternum is evident |
| Axial area in RLV, internally | broad rhombic sternum | very broad, flat | wide lanceolate, sternum-like prominent on the striae level | flat, narrow sternum is evident |
| Central area in RV externally | bowtie-shaped, narrow, slightly raised | small, circular | flat, moderately transapically enlarged | more or less symmetrical, narrow, rectangular to wedge-shaped fascia reaching in some species the valve margins |
| Central area in RV internally | narrow, bowtie-shaped due to shorter two or three striae, elevated, stauros-like | small, circular | prominent, moderately transapically enlarged | forming a raised stauros |
| Central area in RLV externally | small, flat | absent due to broad axial area | flat, transapically enlarged | asymmetrical, narrow, wedge-shaped fascia reaching in some species the valve margins |
| Central area in RLV internally | small | absent due to broad axial area | prominent, transapically enlarged | more or less expressed, asymmetrical, wedge-shaped |
| References | This investigation, [] | [,] | [,] | [] |
Table 2.
Comparison of Platesiberia gen. nov. with some monoraphid genera.
Table 2.
Comparison of Platesiberia gen. nov. with some monoraphid genera.
| Platesiberia gen. nov. | Gololobovia | Achnanthidium | Skabitschewskia | Gliwiczia | Lemnicola | |
|---|---|---|---|---|---|---|
| Type species | P. rhombicolanceolata (Kulikovskiy & Lange-Bertalot) Kulikovskiy, Glushchenko, Genkal & Kociolek comb. nov. | G. mariae Kulikovskiy, Glushchenko, Genkal & Kociolek sp. nov. | A. microcephalum Kützing 1844 | S. dispersipunctata Kulikovskiy & Lange-Bertalot 2015 | G. tenuis Kulikovskiy, Lange-Bertalot & Witkowski 2013 | L. hungarica (Grunow) Round & Basson 1997 |
| Striae in RV | biseriate | uniseriate | uniseriate | uniseriate | uniseriate | biseriate |
| Striae in RLV | uniseriate | uniseriate | uniseriate | biseriate | uniseriate | biseriate |
| Interstriae in RV externally | flat, the same width as striae | flat, equal to striae | flat, equal or broader than striae | flat, equal to striae | flat, slightly broader than striae | flat, wider than striae |
| Interstriae in RV internally | very prominent on striae, the same width as striae | flat, equal to striae | flat, equal or broader than striae | Prominent, equal to or broader than striae | slightly prominent, slightly broader than striae | slightly raised, narrower than striae |
| Interstriae in RLV externally | flat, the same width as striae | flat, equal to striae | flat, equal to or broader than striae | prominent, equal to or broader than striae | flat, equal to or broader than striae | flat and broader than striae |
| Interstriae in RLV internally | very prominent on striae, the same width as striae | flat, equal to striae | flat, equal to or broader than striae | very prominent (rib-like), connected with sternum, close areolae by silica layer (alveoli), narrower than striae; in some species with reduced striae the interstriae are longer and broader | slightly raised, narrower than striae | evidently raised, narrower than striae |
| Pore occlusions | silica membrane | hymenes | hymenes | silica membrane | silica membrane, below the occlusion a pair of foramina lips | hymenes |
| Distal raphe ends externally | tear-shaped, extending slightly onto valve mantle; turned in opposite directions | curved, terminate to opposite sides of the apices, extending onto valve mantle | straight or slightly curved on valve face or extending slightly going onto valve mantle; turned to the same direction | straight or slightly curved on valve face or extending slightly onto valve mantle; turned in opposite directions | straight and extending slightly onto mantle, slightly deflected in opposite directions | extending onto mantle; curved in opposite directions |
| Distal raphe ends internally | in small helictoglossae; curved in the opposite directions | in small helictoglossae; turned in different directions | in small helictoglossae; turned in different directions | in small helictoglossae; turned in different directions | helictoglossae almost undeveloped; slightly turned in opposite directions | in small helictoglossae; slightly curved in opposite directions |
| Central raphe ends externally | tear-shaped, straight | tear-shaped, slightly curved to the same direction | slim or tear-shaped, straight or slightly curved to the same direction | tear-shaped, straight | tear-shaped, straight | straight and curved to the same direction |
| Central raphe ends internally | linear, straight, slightly curved in opposite directions | linear; tear-shaped, slightly curved in opposite directions | straight or in small hook; turned to the different direction | straight; turned to the different direction | straight; evidently turned in different directions | straight; slightly curved in opposite directions |
| Axial area in RV, externally | flat, narrow and linear | narrow and linear, sternum detected | narrow and linear or widened to form central area | narrow and linear, sternum detected | narrow and linear, sternum detected | linear, narrow, sternum evident |
| Axial area in RV, internally | enough broad and widened to central area, sternum evident and elevated | narrow and linear or widened to central area, sternum evident | narrow and linear or widened to central area, sternum evident | sternum well-developed, narrow and linear | sternum well-developed, narrow and linear | linear, narrow, in well-developed sternum |
| Axial area in RLV, externally | narrow and linear, slightly widened to central area | narrow and linear, deep on valve face | narrow and linear or slightly wider to central area | narrow and linear or slightly wider to central area, in many species deep on valve face | narrow and wider to central area, almost rhombic | flat, linear |
| Axial area in RLV, internally | broad rhombic sternum | has the axial rib elevated near the unequal central area only | narrow and linear or slightly wider to central area | narrow lanceolate, raised on valve face in middle | broad rhombic sternum | linear, well-developed sternum |
| Central area in RV externally | bowtie-shaped, narrow, slightly raised | unequal in width, with the widest side extending to the margin and having no short striae, the opposite, narrower side with short striae evident at the margin | absent or present by fascia, flat | circle or bowtie-shaped, flat or slightly raised in center | stauros elevated, central nodule evidently raised | stauros |
| Central area in RV internally | narrow, bowtie-shaped due to shorter two or three striae, elevated, stauros-like | thickened, is unornamented but not a stauros | absent or present by fascia slightly raised on valve face | circle or bowtie-shaped, raised in center | stauros strongly elevated with cavum on one side | stauros |
| Central area in RLV externally | small, flat | unequal in width, with the widest side extending to the margin and having no short striae, the opposite, narrower side with short striae evident at the margin | absent or present by fascia, flat | flat, fascia in one cavum side of valve | stauros elevated | slightly circle or not evident |
| Central area in RLV internally | small | distinct, thickened, unequal | absent or present by fascia, flat | cavum | stauros strongly elevated with cavum on one side | slightly circular or not evident |
| References | This investigation, [] | [] | [,,,] | [] | [], own data | [,] |
Areolae are closed internally in our new genus Platesiberia gen. nov. by silica cover. Mostly, areolae are covered by hymenes as pore occlusions. SEM did not allow us to observe pore occlusions with hymenes. Hymenes as morphological feature are characterized by a slim silica plate with many tiny pores that are differently shaped []. In Gliwiczia, pore occlusions are presented additionally by a pair of foramina lips below the silica membranes [].
We discussed differences of pore occlusion between monoraphid genera when we described the genus Gololobovia []. We referred to Shi et al. [] who indicated ‘convex hymenes’ and show them to be present in Lemnicola and in our investigation for Gololobovia. This structure covers every areola internally and is found in Lemnicola, Gogorevia and Gololobovia. Further investigation will be important for understanding these peculiarities and needs the combination of morphological analysis with transmission electron microscopy, scanning microscopy with high magnification and molecular phylogenetic investigations. We note here the importance of this work for the future.
We acknowledge here that this work is based on valve morphological features only, and some of these features are only evident with scanning electron microscopy. More recent studies on the delineation and description of taxa take what has been termed a “polyphasic” approach, utilizing a variety of features, morphological and molecular, to characterize new taxa (e.g., [,]). Of course, having a broader understanding of a wider range of features to better understand a taxon, and its phylogenetic relationships, is a highly desirable goal. Due to timing of collections and whether the taxon is extant or extinct help define what can be known at any one time. We also do not have in place yet a formal analysis of relationships and whether each of these freshwater monoraphid genera are monophyletic []. Formal phylogenetic analyses of some monoraphid diatom genera have affirmed, however, that morphologically diagnosable groups of monoraphid diatoms are monophyletic (e.g., []). Further research is necessary to more fully understand the taxon described herein and to assess its systematic position among the freshwater monoraphid diatoms.
This investigation increases our understanding of the diversity of monoraphid freshwater genera that were previously assigned to the old catch-all genus Achnanthes Bory. Description of new genera is related to our investigation of morphology from different monoraphid taxa and combining morphological features together with molecular data for some genera where possible. This work is based on a larger investigation of biodiversity from different poorly studied areas or hotspots of diatoms. Lake Baikal is a unique place, existing for 25–30 million years [], thus allowing a long time for the evolution of diatoms and resulting in very high species diversity. We believe that diversity of monoraphid diatoms in this ancient lake will be investigated in the future more carefully and many new species and possibly new genera will be described. Our previous investigation of monoraphid diatoms [,] from Lake Baikal showed very high diversity between monoraphid and biraphid genera with interesting and shared unusual morphology. It is important for us to combine new morphological information about freshwater diatoms not only from Lake Baikal but also from Southeast Asia, Australia, Africa and South America. These areas have also been poorly studied up till now.
Author Contributions
Conceptualization, M.S.K.; methodology, A.M.G. and M.S.K.; validation, A.M.G., M.S.K. and J.P.K.; investigation, A.M.G., M.S.K. and J.P.K.; resources, M.S.K.; writing—original draft preparation, A.M.G. and M.S.K.; writing—review and editing, A.M.G., M.S.K. and J.P.K.; visualization, M.S.K., I.V.K., S.I.G. and A.M.G.; supervision, M.S.K.; funding acquisition, M.S.K. All authors have read and agreed to the published version of the manuscript.
Funding
Publication is based on research carried out with financial support by Russian Science Foundation (19-14-00320Π) for LM and SEM and by framework of state assignment of the Ministry of Science and Higher Education of the Russian Federation (theme 122042700045-3) for finishing manuscript.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
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