Surirella lacrimula J.D. English 2012

Long, Ji-Yan, Liu, Bing, Rioual, Patrick, Yang, Bin & Zhou, Min, 2023, Ultrastructure of four Surirella taxa (Bacillariophyceae) from Qinghai Province, northwest China, with reference to the characteristics of portulae, Phytotaxa 592 (2), pp. 163-177 : 168

Surirella lacrimula J.D. English 2012 (LM: Figs 55–66 , SEM: Figs 67–77 , 105 )

Observations:— LM: Valve outline ovate with broadly rounded headpole and cuneate footpole ( Figs 55–66 ). Valve dimensions (n = 30): length 24–34 μm, width 10.3–13.1 μm (measured at the widest part of the valve), length/width ratio 2.1–2.6. Valve composed of two distinct portions: central portion and outside portion (indicated in Fig. 59 ). Fibulae evident, spanning c. 1/4 of valve width, not extending to midline, 7–9 in 10 μm. Fibulae parallel at valve middle, radiate approaching apices.

SEM: Valve face flat making CSBs difficult to distinguish as CSBs not elevated from OFCs ( Fig. 67–71 ). Striae multiseriate, composed of 3 or 4 rows of areolae, 30–32 in 10 μm (measured from SEM images, n = 4). Outside openings of areolae slit-like ( Figs 68–71 ). Raphe canal located directly on mantle. Internally, valve composed of two portions: central portion and outside portion (indicated in Fig. 74 ). Wall of raphe canal growing slightly into cell cavity so that the portulae are easily visible ( Figs 72–74 ). Fibulae short, a few bifurcate, spanning c. 1/4 of valve width, not extending to valve midline ( Figs 72–74 ). Raphe continuous at headpole ( Fig. 76 , wavy arrow), but interrupted at footpole ( Fig. 77 , two arrows). One to three portulae occurring between two adjacent fibulae ( Fig. 75 , three arrows; Fig. 105 , three arrows).

Distribution:— S. lacrimula was found in the same site with S. liubingii . From the literature, this species appears to have a global distribution as it has been reported in the USA, France, Argentina, and Iran ( English & Potapova 2012, Bey & Ector 2013, Seeligmann & Maidana 2019, Safiallah et al. 2020).

Figures

FIGURES 55–66. Surirella lacrimula, LM (1000×). 55–66. Twelve different valves showing the size diminution series. Note the ovate valve outline, the recognizable central and outside portions of the valve (labeled in Fig. 59), and the discernible costa-stria bundles (CBSs) within the outside portion. Scale bar = 10 μm (in Fig. 55).

FIGURES67–71. Surirella lacrimula, SEM, externalview.67.A completevalve showing the relativelyflatvalve surface andinconspicuous costa-stria bundles (CSBs). 68, 69. Details of the apices, from Fig. 67. 70, 71. Details of the middle section of the valve, from Fig. 67. Note that over-fibula costae (OFCs) are difficult to distinguish. Scale bars = 5 μm (Fig. 67), 1 μm (Figs 68–71).

FIGURES 72–77. Surirella lacrimula, SEM, internal view. 72–74. Three complete valves, note the slim and short fibulae, some bifurcate (one arrow respectively), and the distinct central portion (indicated by a dotted line in Fig. 74). 75. Details on the middle section from Fig. 72. Note the presence of three portulae between two adjacent fibulae (three arrows) and multiseriate striae. 76. Headpole from Fig. 72, note the continuous raphe (wave arrow). 77. Footpole from Fig. 72, note the interrupted raphe endings (two arrows). Scale bars = 5 μm (Figs 72–74), 1 μm (Figs 75–77).

FIGURES 102–107. Characteristics of the portulae among five Surirella taxa, SEM, internal view. 102, 103. Portula structure of S. liubingii, note the striated internal raphe canal wall (Fig. 102, three arrows) and the presence of only one portula between two adjacent fibulae (Fig.103, three arrows). 104.Portula structure of S. minuta, note the occurrence of only one portula (three arrows). 105–107.Portula structure of S. lacrimula, S. brebissonii var. kuetzingii, and S. tientsinensis, respectively. Note that these three taxa have three portulae between two adjacent fibulae (three arrows respectively) but that a marginal trough-like depression is only produced in S. brebissonii var. kuetzingii (Fig. 106). Scale bars =1 μm (Figs 102–107).