Entomoneis sinensis Bing Liu & D.M. Williams, 2022

Long, Ji-Yan, Williams, David M., Liu, Bing, Mo, Wen-Hui & Quan, Si-Jin, 2022, Ultrastructure of three Species of Entomoneis (Bacillariophyta) from Lake Qinghai of China, with reference to the external areola occlusions, PhytoKeys 189, pp. 29-50 : 29

Entomoneis sinensis Bing Liu & D.M. Williams sp. nov.

Figs 1 , 2 , 3 , 4 , 5 , 6 , 7 , 14

Holotype.

Slide BM 81941, the holotype specimen circled on the slide, illustrated here as Fig. 1A ; isotype, slide JIU202101, illustrated here as Fig. 1B .

Type locality.

China. Qinghai Province, Lake Qinghai, a sampling point near the lakeshore, 36°50'34" N, 99°42'39" E, 3210 m a.s.l., collected by Bing Liu, 19 July 2019.

Description.

LM (Fig. 1 ). Frustule panduriform in girdle view (Fig. 1A-F ). Frustule dimensions (n = 41): length 22.6-42.6 μm, width 8.9-14.1 μm at its centre, 14.6-19.8 μm at its widest region. Two distinct 8-shaped loops are present in each frustule (indicated in Fig. 1D-F ), one 8-shaped loop evident in each valve (Fig. 1G-O ). Simple, arcuate junction line discernible in some specimens (indicated in Fig. 1H and I ). Costae and striae invisible under LM. Girdle bands numerous.

SEM, girdle view (Figs 2 - 4 ). Frustule panduriform with low keel (Fig. 2A and B ; Fig. 3A-F , indicated by fused part). Cells having a 5:2 configuration of girdle bands, i.e. five girdle bands associated with the epivalve and two associated with the hypovalve (Fig. 2C-F , labelled in Fig. 2C and D ). Junction line simple, arcuate (Fig. 3A ). Two sides of the keel fused so that subraphe canal connects the cell lumen only near the central ending (Fig. 3B and C , arrow, respectively; see also Fig. 7B , arrow) and distal raphe ending (Fig. 3D , arrow). Short bar-like basal fibulae forming junction line (Fig. 3E and F , three arrows, respectively). Each pars media of valvocopula forming 8-shaped loop that is very distinct under LM (Fig. 4A-D ). Each costa extending from raphe canal to inconspicuous mantle, warts bearing on each costa (Fig. 4E ). Structure of each girdle bands similar, composed of pars exterior, pars media and pars interior (Fig. 4E ). Pars media like a sternum, not located at the mid-line but slightly displaced towards pars interior (Fig. 4G ). Both pars exterior and interior composed of one row of elongate poroids and each elongate poroid consisting of two costae and a hymen strip between them (thus the elongate poroid is n-shaped), with the n-shaped poroid of pars exterior longer than that of pars interior (Fig. 4F and G ).

SEM, valve view (Figs 5 - 7 ). Valve linear-lanceolate, keel Ƨ-shaped (Fig. 5A , Fig. 6A-C ). Costae mostly running from raphe canal to mantle (Fig. 5B ), but some bifurcate (Fig. 5B , arrow), some terminating halfway to mantle (Fig. 5C , short costae). Each stria included between two adjacent costae, composed of one hymen strip (Fig. 5A-F ). This type of hymen strip belonging to Type Two hymen strip, which is a siliceous membrane strip perforated by two rows of elongate (linear) pores next to the transapical costae and two rows of rounded pores between these two rows of linear pores (Fig. 14A and B ). Mantle inconspicuous (Fig. 5B ). Two total rows of separated areolae present along the raphe on both sides of the keel (Fig. 5B , four wavy arrows), but do not extend to the apex (Fig. 5E and F , six arrows, respectively). The hymenes occluding these separated areolae have the same structure as the hymen strip on striae (Fig. 5F , arrows). Stria density 36-43 in 10 μm (n = 7). Two proximal raphe endings slightly dilated and a pore-like structure located at the centre of central nodule (Fig. 6D-F , arrow, respectively). Internally, one cell bearing only one lumen, no sub-compartment present (Fig. 7 ).

Etymology.

Named after China where the species was found (the specific locality is Lake Qinghai).

Ecology and distribution.

Entomoneis sinensis was found on the stone surfaces in Lake Qinghai. The following environmental parameters were measured in the field. Conductivity was 16296.7 ± 86.2 μS /cm, pH was 9.14 ± 0.01 and water temperature was 15.5 ± 0.3°C. According to above data and because Lake Qinghai is a brackish water lake, Entomoneis sinensis should be a brackish water diatom species. So far, E. sinensis is only found in the type locality and is a dominant species.

Figures

Figure 1. A-O Entomoneis sinensis sp. nov., girdle view, LM A-F six frustules showing a size diminution series, note the distinctive 8 - shaped loops (labelled in Figs D-F) G-O nine valves showing a size diminution series, note arcuate junction line (labelled in Figs H and I) A micrograph of holotype specimen B micrograph of isotype specimen. Scale bar: 20 μm.

Figure 2. A-F Entomoneis sinensis sp. nov., girdle view, SEM A, B two frustules, note sigmoid girdle bands C, D central parts from Fig. A and B respectively, note the 5: 2 configuration of girdle bands, i. e. five girdle bands, B 1 (Valvocopula, VC) to B 5, associated with epivalve (EV); two girdle bands, B 1 (Valvocopula, VC) and B 2, associated with hypovalve (HV) E, F two apices from Fig. A. Scale bars: 10 μm (A, B); 2 μm (C-F).

Figure 3. A-F Entomoneis sinensis sp. nov., girdle view, SEM A one broken frustule, note the simple arcuate junction lines B-D details from Fig. A note the fused parts of two sides of the keel and the subraphe canal connecting the cell lumen only near the central (Figs B and C, arrow, respectively) and the distal raphe ending (Fig. D, arrow) E, F details from Fig. A note the short, bar-like basal fibulae (three arrows, respectively). Scale bars: 10 μm (A); 2 μm (B-F).

Figure 4. A-G Entomoneis sinensis sp. nov., SEM A one valve with associated girdle bands, note the 8 - shaped loop formed by the pars media of valvocopula (the pars media indicated by arrowheads and arrows indicating the pars media on the unseen side) B-D two valves with girdle bands further showing the 8 - shaped loop (labelled in Fig. D) E middle part of a valve, note the mantle and the three parts of each girdle bands: parts exterior, pars media and pars interior F detail from Fig. E note the hymen strip occluding the poroid G valvocopula in internal view, note the broader pars exterior than pars interior and sternum-like pars media. Scale bars: 10 μm (A-D); 2 μm (E-G).

Figure 5. A-F Entomoneis sinensis sp. nov., valve external view, SEM A one whole valve showing the Ƨ-shaped keel outline B central part from Fig. A note hymen strips, costae, mantle, warts, forked costa (arrow) and one separated row of rounded areolae at each side of the raphe (wavy arrows) C, D two apices from Fig. A note the short costae (two arrows in Fig. C) and two costae merging into one (arrow in Fig. D) E, F details showing one separated row of rounded areolae terminating before the apex (six arrows, respectively). Scale bars: 10 μm (A); 2 μm (B-F).

Figure 6. A-F Entomoneis sinensis sp. nov., external view, SEM A-C three whole valves, note Ƨ-shaped keel outline D-F three middle parts from Figs A, B and C respectively, note two proximal raphe endings slightly dilated and a pore-like structure at the centre of central nodule (arrows). Scale bars: 10 μm (A-C); 1 μm (D-F).

Figure 7. A-F Entomoneis sinensis sp. nov., valve internal and side views, SEM A one valve showing only one lumen (no sub-compartments present) in a cell (double-headed arrow) B middle part from Fig. A note the canal raphe communicates with the cell interior at the valve centre C, D two apices from Fig. A E, F another valve in side view, note the cell lumen. Scale bars: 10 μm (A, E); 2 μm (B-D, F).

Figure 14. A-F Details of hymen and hymen strip in Entomoneis, SEM A, B details of hymen strip of Type Two from E. sinensis sp. nov., note the two rows of linear pores (Fig. A, two arrows) on either side of the two intermittent rows of rounded pores (Fig. A, wavy arrow) C, D details of hymen strip of Type One from E. qinghainensis sp. nov., note the hymen is finely perforated over both the areolae (Fig. D arrow) and the hymen strips (Fig. D, double-headed arrow) E detail of hymen strip of Type One from E. paludosa, note the hymen is finely perforated over both the areolae and the hymen strips (double-headed arrow) F detail of hymenes from E. triundulata, note the hymenes of the areolae in the girdle bands (two arrows). Scale bars: 600 nm (A-F).