{'fraction_non_alphanumeric': 0.0478805560322636, 'fraction_numerical': 0.03869915908700875, 'mean_word_length': 4.7956240676280455, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Three new freshwater species of the genus Achnanthidium (Bacillariophyta, Achnanthidiaceae) from Taiping Lake, China

We describe three new Achnanthidium species, A. lacustre sp. nov., A. sublanceolatum sp. nov., and A. taipingensis sp. nov., from Taiping Lake, Anhui Province (China) based on light and scanning electron microscopy. A. lacustre sp. nov. belongs to the “A. minutissimum complex” of the genus, based on it having straight external distal raphe fissures and round to elliptical areolae. Both A. sublanceolatum sp. nov., and A. taipingensis sp. nov. belong to the “A. pyrenaicum complex” of the genus, based on them having transpically–elongated areolae and deflected external distal raphe fissures. All three species are sufficiently different from other similar species based on valve outline, shape of the axial and center areas, and striae density. These three new species are all observed in benthic collections from Taiping Lake.


Introduction
The genus Achnanthidium is known from freshwaters, and species of this genus are widely distributed in various types freshwater habitats and can be common and abundant in those habitats (Karthick et al. 2017;Liu et al. 2016;Pinseel et al. 2015;Novais et al. 2011;Potapova & Ponader 2004;Kobayasi et al. 2006). Achnanthidium species can occur across a broad range of trophic conditions, from oligotrophic to eutrophic waters (Karthick et al. 2017;Ponader & Potapova 2007). This genus was initially described by Kützing (1844) as a subgenus of Achnanthes, and the species Achnanthes microcephalum Kützing was the type species (Pérès et al. 2014;Kingston 2003). Later, Achnanthidium was elevated to the level of genus by Round et al. (1990) and Round & Bukhtiyarova (1996). Because the size of many Achnanthidium is small, and there may be few identification characteristics evident as viewed with the light microscopy (LM), and the variability of diagnostic features often overlap, this genus may be challenging to study in terms of species recognition (Karthick et al. 2017;Marquardt et al. 2017;Ponader & Potapova 2007).
The genus Achnanthidium has been subdivided into three subgroups, the "Achnanthidium minutissimum complex", "A. pyrenaicum complex" and the "A. exiguum complex" (Karthick et al. 2017;Pérès et al. 2014;Wojtal et al. 2011;Wojtal et al. 2010). The A. minutissimum complex has straight external distal raphe ends and, usually, linear to linear-lanceolate valve shapes, striae density increasing towards the apices and round external areolar openings (Pinseel et al. 2015;Compère & Van De Vijver 2011). Members of A. pyrenaicum complex have external distal raphe ends that are deflected or hooked to one side of the valve and slit-like areolar openings (Pinseel et al. 2015;Jüttner et al. 2011;Round & Bukhtiyarova 1996). Members of the A. exiguum complex have external distal raphe ends curved in opposite directions.
Presently, the number of species of the genus Achnanthidium is greater than 200 (Marquardt et al. 2017;Kociolek et al. 2018). Only a limited number of new Achnanthidium species have been described from China (e.g. Liu et al. 2016;Yu et al. 2018, accepted). During a survey of the freshwater diatoms from Taiping Lake, in the framework of water quality monitoring, three unknown Achnanthidium species were encountered. The purpose of this present is to document and formally describe those species with light microscopy (LM) and scanning electron microscopy (SEM), and to compare the new species with morphologically similar taxa.

Material and Methods
For this study we used samples that were collected from Taiping Lake (30ᵒ14 '-30ᵒ28'N, 117ᵒ55'-1118ᵒ12'E), located in the District of Huangshan Mountain, Southern Anhui Province, China, in May 2018. Taiping Lake is the largest artificial reservoir lake in Anhui province. In the field, several water chemistry characteristics were recorded, including: pH, temperature, dissolved oxygen, salinity, total dissolved solids (TDS), and conductivity. These were all measured using a YSIPro Plus multiparameter meter (YSI, Ohio, USA). Diatom samples were collected from natural substrates, including stones, or from navigation buoys, by clean toothbrushes, and the samples were placed in a bottle and preserved with formalin (4% final concentration).
In the laboratory, diatom samples were cleaned with concentrated nitric acid using the Microwave Accelerated Reaction System (Model MARS, CEM Corporation, Charlotte, USA) (Parr et al. 2004), with a pre-programmed digestion scheme (temperature, 180℃) (You et al. 2015;Yu et al. 2017). Next, samples were alternately centrifuged for 5 min at 3500 rpm (TDZ5-WS, Luyi Corporation, Shanghai, China) and washed six times using distilled water until the pH of the sample was close to neutral. Finally, the cleaned samples were kept in 95% ethanol. Cleaned diatom frustules were made mounted in Naphrax for light microscopy (LM) or air-dried onto cover slips and mounted onto alloy stubs for observation with the scanning electron microscope (SEM). LM studies were made with an Olympus BX-53 microscope fitted with DIC optics and a 100× oil immersion objectives (1.4 numerical aperture). SEM examination was made using a Hitachi SU8010 (1-2 kV, WD less than 6 mm) (Tokyo, Japan). Images were compiled with Adobe Photoshop CS6. Morphological terminology follows Round et al. (1990). All of the diatom samples and permanent slides are housed in the Biology Department Diatom Herbarium, Shanghai Normal University (SHTU). Isotype material and slides has been deposited in the Kociolek Collection at the University of Colorado, Boulder (COLO).  (Figs 1-20), frustules are bent in girdle view with a concave raphe valve and a convex rapheless valve. Frustules are heterovalvar, monorpahid. Valves are irregularly linear-lanceolate in shape, with bluntly rounded apices. Valve length 20-23 µm, breadth 3.0-3.5 µm (n=200). Both valves possess a linear axial area which widens slightly towards the central area. On the raphe valve, central area is a small oval in shape forming an elliptical fascia. Striae are radiate along the whole valve, and the middle striae are more distantly placed than others. Striae number 27-29 in 10 µm at the center, up to 28-32 in 10 µm near the apices on the raphe valve. On the rapheless valve, striae are radiate throughout the entire valve, becoming denser towards the valve apices, 26-29 in 10 µm in the middle and 28-30 in 10 µm near the apices. Individual areolae are not visible in LM.

SEM observations of both valves show the valve face:
mantle junction bordered by a narrow hyaline area (Figs 90,98), and the mantle has single row of linear areolae (Figs 100,102). On the exterior of the raphe valve, the raphe is filiform and straight (Fig 90), proximal raphe ends are straight, and simple (Fig 92), and the distal raphe ends are straight and extend on the valve mantle (Fig. 93). Striae are uniseriate, comprised of 2-3 round to oblong areolae in the center of the valve (Fig 93), and 1-3 large, irregularly-round or transapically elongate areolae elsewhere (Fig 93). Some striae have one slitlike areolae on the valve mantle . Areolar occlusions are positioned within the opening and can be seen from the exterior (Fig 96). Internally, the raphe terminates distally as elevated helictoglossae (Figs 91,94), and the proximal raphe endings are short, deflected in opposite directions (Figs 91,95). Areolae are large round to oblong in shape and the openings are occluded with fine hymenate structures that include small openings around the periphery (Fig 97).
On the external of the rapheless valve, the axial area is linear, widening slightly towards the central area (Fig 98). Striae are uniseriate, comprised of 4-5 round to transapically elongate areolae in the middle part of the valve (Figs 98, 102), and 1-3 irregularly round or transapically elongate areolae at the ends (Fig 100). Some striae have one slit-like areola on the valve mantle (Figs 100, 102). The areolae are occluded with fine hymen structure that can be seen externally (Fig 104). Internally, areolae are round to transapically-elongate, occluded on valve face and mantle, and the occlusions are comprised of a fine hymenate structure (Figs 99,101,103,105).
linear-lanceolate, widening slightly towards the central area. Striae nearly parallel, 20-23 in 10 µm at the middle portion, 36-42 in 10 µm near the apices, on the raphe valve. The rapheless valve is convex, with narrow linear-lanceolate axial area weakly expanded at the middle portion of the valve. Striae are nearly parallel, 21-24 in 10 µm in the center, and 30-36 in 10 µm near the apices. Areolae are not visible in LM.
In the SEM, both valves have a narrow hyaline area at the valve face: mantle junction (Figs 106, 115). Raphe valve: Externally, the raphe is filiform and straight (Fig 106), distal raphe ends are deflected to the same side at an angle of nearly 90°, and the proximal raphe ends are straight and teardrop-shaped (Figs 106,108,110). Striae are uniseriate, containing 3-4 transapically-oriented areolae in the middle portion of the valve, and 1-2 long narrow areolae at the apices (Figs 108,110,(112)(113). Valve mantle with a single row of linear areolae extended around the apices with small interruption at the ends ( Ecology: Collected in two samples (TPH-201805008; TPH-201805011) on navigation mark. pH 8.5, water temperature 25.5 ℃, Salinity 0.05‰, TDS 69.6 mg.l -1 , Conductivity 108 µs.cm -1 ). Distribution: So far, the new species is only known from the two samples localities.
In the SEM, the frustule is slightly bent ventrally in girdle view (Fig.139). On the both valves, the valve mantle has a single row of linear areolae (Figs 139,141), but there is a small depression on one side of the raphe (Figs 126-127) that is absent at the apices of rapheless valveS (Figs 142-143). Externally, the raphe is filiform, straight (Fig 124), and has distal raphe ends deflected to the same side. On the side of the deflection there is a depression near the distal raphe ends . The proximal raphe ends are straight and teardrop-shaped (Figs 128-130). Areolae are small, round to transapically-oriented, the uniserate striae are composed of 1-5, usually 4-5, areolae in the middle portion of the valve (Figs 128-130), and 1-4 areolae at the apex (Figs 126-127). Internally, distal raphe ends terminate in raised helictoglossae (Figs 131,133), while the proximal raphe ends are very weakly deflected in opposite directions (Figs 131, 135).

Discussion
The three new species possess characters that support their assignment to the genus Achnanthidium, including, having small linear-lanceolate to lanceolate elliptic valves, shallow V-shaped valve in girdle view, uniseriate striae, a fine raphe and straight or deflected external distal raphe fissures Ponader & Potapova 2007).
A. lacustre belongs to the "A. minutissimum complex" based on its possession of straight external distal raphe fissures, while A. sublanceolatum and A. taipingensis belong to the "Achnanthidium pyrenaicum complex" based on them having deflected external distal raphe fissures.
This paper represents the first published treatment of diatoms from Taiping Lake, Southern Anhui Province, China. The three new Achnanthidium species were abundant in the samples studied, and there are some other monoraphid species that co-occur with these new species. The co-occurring monoraphid taxa include, Achnanthidium caledonicum Lange-Bertalot, A. pyrenaicum (Hustedt) Kobayasi, A. rivulare Potapova et Ponader and A. duthiei (Sreen.) Edlund. We will continue to study the diatom diversity of the Taiping Lake.