Witkowskia famintsinii Mironov, Glushchenko & Kulikovskiy, 2024

Mironov, Andrei, Glushchenko, Anton & Kulikovskiy, Maxim, 2024, Description of Witkowskia famintsinii sp. nov. (Cymbellales, Bacillariophyceae) with morphological investigation of Witkowskia strigosa comb. et stat. nov., Phytotaxa 670 (1), pp. 31-42 : 37

Witkowskia famintsinii Mironov, Glushchenko & Kulikovskiy sp. nov. ( Figs29–55 ); Fig. 30 represents the holotype.

LM ( Figs 29–43 ):— Valves apically and transapically symmetric.Outlines elliptic-lanceolate, becoming broadly elliptic in smaller valves. Apices mostly subrostrate, practically unprotracted in smaller specimen. Valve dimensions (n=25): length 9–15 μm, width 4.5–5.5 μm. Axial area narrow. Linear; central area unexpressed. Raphe straight, filiform, with moderately expanded proximal ends. Striae predominantly radiate, becoming linear in the central portion of the valve. Striae density 19–21 in 10 μm around the central nodule, circa 23 in 10 μm near the apices. Areolae unresolvable in LM. Apparently, all valves equipped with a single stigmoid, which is discernible in LM with careful focusing.

SEM, external view ( Figs 44–49 ). Proximal raphe ends expanded, with shallow grooves and translucent inner fissures ( Figs 46–47 , black arrows); both of the distal ends unilaterally deflected, equipped with recurvatures ( Figs 48–49 , black arrows). Striae uniseriate, composed of more or less circular areolae. Areolae density 40–42 in 10 μm throughout the valve. Virgae broader than striae, narrowing towards the apices ( Figs 46, 49 , white arrows). Striae extending onto the valve mantle ( Figs 46–49 , white arrowheads). Central nodule bearing a single stigmoid with a small round opening. ( Figs 46–47 , black arrowheads).

SEM, internal view ( Figs 50–55 ). Proximal raphe ends practically not expanded, gradually deepening ( Figs 52– 53 , black arrows); distal ends straight, terminating with small helictoglossae ( Figs 54–55 , black arrows). Raphosternum raising inconspicuous.Areolae arranged in single rows; areolar openings round to rectangular (transapically elongated), occluded by tectula ( Figs 52, 54–55 , white arrows). Tectula with 4, less often 5 or 6 small outgrowths. Vimines thin, equipped with stubs or, rarely, struts ( Figs 52–55 , white arrowheads). Apices equipped with shallow subpolar areolae on each valve side ( Fig. 54 , black arrowheads). Internally, stigmoid represented by a rectangular angled opening ( Figs 52–53 , black arrowheads).

Type:— Vietnam, Lào Cai Province, Sa Pa , Mư ờng Hoa River (22 o 15.415’N, 103 o 8.883’E) ; leg. M.S. Kulikovskiy, coll. date 10.05.201 5. Slide no. 02079 (in collection of Maxim Kulikovskiy at the Herbarium of the Institute of Plant Physiology Russian Academy of Sciences, Moscow, Russia) ; holotype specimen illustrated in Fig. 30

Etymology:— The species name is dedicated to A.S. Famintsin (1835–1918), a prominent Russian botanist and phycologist, pioneer of plant physiology in Russia.

Distribution:— As yet known only from the type locality.

Ecology:— The species was discovered in a sample of periphyton from the waterfall of slightly alkaline pH (7.5), temperature—18.4 °C and low electrical conductivity (128 μS/cm).

Figures

FIGURES 29–43. Witkowskia famintsinii sp. nov., LM, DIC, size diminution series. Type material, slide 02079. Scale bar = 10 μm. Fig. 30 represents the holotype.

FIGURES 44–49. Witkowskia famintsinii sp. nov., SEM, type material, slide no. 02079. External valve surface. 44–45. The entire valve. 46–47. Details of the central area, note expanded proximal raphe ends (46–47, black arrows); a single stigmoid (46–47, black arrowheads); virgae broader than striae (46–47, white arrows); areolae at the valve mantle (46–47, white arrowheads). 48–49. Details of the apices, note the distal raphe ends with recurvatures (48–49, black arrows); virgae narrowing towards the apices (49, white arrows); areolae at the valve mantle (48–49, white arrowheads). Scale bars = 2 µm (Figs 44–45), 1 µm (Figs 46–47), 0.5 µm (Figs 48–49).

FIGURES 50–55. Witkowskia famintsinii sp. nov., SEM, type material, slide no. 02079. Internal valve surface. 50–51. The entire valve. 52–53. Details of the central area, note the gradually deepening proximal raphe ends (52–53, black arrows); small angled opening of stigmoid (52–53, black arrowheads); areolae occluded by tectula (52, white arrows) and separated by thin vimines (52–53, white arrowheads). 54–55. Details of the apices, note the distal raphe ends terminating with small helictoglossae (54–55, black arrows); subpolar areolae on each valve side (54–55, black arrowheads); areolae occluded by tectula (54–55, white arrows); vimines with stubs (54–55, white arrowheads). Scale bars = 2 µm (Figs 50–51), 0,5 µm (Figs 52–55).