Surirella brebissonii var. kuetzingii Krammer & Lange-Bertalot 1987

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 : 168-170

Surirella brebissonii var. kuetzingii Krammer & Lange-Bertalot 1987 (LM: Figs 78–89 , SEM: Figs 90–101 , 106 )

Observations:— LM: Valve outline ovate to elliptical with broadly rounded headpole and narrowly rounded footpole. Valve dimensions (n = 25): 14–25 μm long, 6.9–8.8 μm wide (measured at widest part of the valve), length/width ratio 1.4–1.6. Valve composed of two portions: central portion and outside portion (indicated in Fig. 83 ). Costa-stria bundles (CSBs) visible, alternated with over-fibula costae (OFCs) from pole to pole. CSBs reaching valve margins. CSBs parallel at valve middle part, radiate approaching apices. Fibulae well-developed, spanning c. 1/4 of valve width, not extending to midline, 6–8 in 10 μm.

SEM: Each CSB often composed of three costae and four striae ( Figs 90–92 ). Striae multiseriate, composed of 3–5 rows of areolae, 23–25 in 10 μm (measured from SEM images, n = 4). Outside openings of areolae slit-like ( Figs 92–95 ). Raphe canal located directly on mantle. Distal raphe endings simple and interrupting at both apices ( Figs 93, 94 , two arrows respectively). Internally, valve composed of two portions: central portion and outside portion (indicated in Fig. 97 ). Wall of raphe canal growing slightly into cell cavity leaving the portulae visible. Fibulae short, spanning c. 1/4 of valve width, not extending to valve midline ( Figs 96–98 ). Raphe continuous at headpole ( Fig. 99 , wavy arrow), but interrupted at footpole ( Fig. 100 , two arrows). Three portulae produced between two adjacent fibulae ( Figs 101 , 106 , three arrows). The areas between the fibulae form marginal trough-like depressions ( Fig. 106 ).

Ecology and distribution:— Epilithic in freshwater river. Surirella brebissonii var. kuetzingi was found in the same sampling site with S. liubingii , for the environmental parameters, see above. It is commonly found in Europe with reports from Germany, France and Poland ( Krammer & Lange-Bertalot 1987, Bey & Ector 2013, Szczepocka et al. 2018).

Figures

FIGURES 78–89. Surirella brebissonii var. kuetzingii, LM (1000×). 78–89. Twelve valves illustrating an incomplete size diminution series for this species. Note the ovate valve outline, the valve composed of a recognizable central portion and an outside portion, and the conspicuous costa-stria bundles (CSBs) within the outside valve portion (labeled in Fig. 83). Scale bar = 10 μm (in Fig. 78).

FIGURES 90–95. Surirella brebissonii var. kuetzingii, SEM, external view. 90, 91. Two complete valves, note the valve composed of a central portion and outside portion (indicated in Fig. 91). 92. Details of the middle section from Fig. 90, note costa-stria bundles (CSBs) alternating with over-fibula costae (OFCs). 93, 94. Details of the headpole (Fig. 93) and footpole (Fig. 94) from Fig. 90. Note the simple, interrupted raphe endings at both poles (two arrows respectively). Scale bars = 5 μm (Figs 90, 91), 1 μm (Figs 92–95).

FIGURES 96–101. Surirella brebissonii var. kuetzingii, SEM, internal view. 96–98. Three complete valves. Note that the valve is composed of two portions: central and outside (labeled in Fig. 97). 99. Headpole from Fig. 96, note the continuous raphe at the apex (wavy arrow). 100. Footpole from Fig. 96, note the raphe interrupted at the apex (two arrows). 101. Detail of the valve margin from Fig. 96, note the slim and short fibulae and the occurrence of three portulae between two adjacent fibulae. Scale bars = 5 μm (Figs 96–98), 1 μm (Figs 99–101).

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).