Gomphonema lepskayae Glushchenko, Mironov, Kezlya & Kulikovskiy sp. nov. (Figs 25 –47)

LM description (Figs 25–40):— Valves nearly naviculoid in shape, barely dorsiventral and weakly heteropolar. Valve apices broadly rounded, mostly unprotracted. Headpole sometimes moderately truncate. Valve dimensions (n=39): length 8.4–15.7 μm, width 2.8–4.0 μm. Raphe more or less lateral or slightly undulate (visible with careful focusing). Raphe ends barely resolvable. Axial area narrow, linear to weakly lanceolate. Central area small, nearly rectangular, formed by 1–3 shortened striae on each side. A single isolated pore (stigmoid sensu Krammer 1982, Cox & Van de Vijver 2024) is located beside the central nodule. Striae mostly parallel in the central part of the valve, becoming weakly radiate towards the apices, 15–16/10μm. Areolae undiscernible in LM.

SEM, external valve surface (Figs 41, 43, 45):— Moderate undulation of the raphe is evident. Proximal raphe ends expanded, round, slightly dislocated towards the isolated pore (Figs 41, 43, black arrows). Distal raphe fissures slender, unilaterally curved, terminating at the valve margin (Figs 41, 43, white arrows). At the footpole, raphe fissure divides the APF into two equal parts (Fig. 45, black arrow). APF is comprised of small, round porelli (Fig. 45, white arrows). Striae clearly uniseriate. Areolae occluded by typical unilateral foricula, i.e., areolar openings C-shaped (Fig. 45, black arrowheads). External opening of the stigmoid is round, exceeding areolae in size (Figs 41, 43, black arrowheads).

SEM, internal view (Figs 42, 44, 46 –47):— Proximal raphe ends hook-shaped, located at the raised central nodule (Figs 42, 44, 47, black arrows). Distal raphe fissures terminating with helictoglossae (Figs 42, 44, 46, white arrows). Pseudosepta present at each valve pole, more profound at the headpole, narrow at the footpole (Fig. 46, asterisk). Footpole APF small, equally bisected, constructed by the rows of porelli with lenticular occlusions (Fig. 46, black arrows). Openings of areolae in striae small, each with a unilateral reniform outgrowth attached to the wall, i.e., occluded by unilateral foricula (Fig. 46, black arrowheads). Areolar openings located in grooves, forming foraminal rows. The rows become narrower towards the axial area. Vimines well-defined, practically equal in width to the foraminal rows (Fig. 47, white arrows). Inner opening of the stigmoid is relatively small, round or slightly elongated in transapical direction (Figs 42, 44, 47, black arrowheads).

Type:— RUSSIA. Kamchatka Territory, Karaginsky district: Limnokren spring, periphyton (57°33’57.78”N; 160°50’4.49”E); leg. Z. V. Krivova, collection date 04.09.2024. Slide 09862 (from sample O-1), holotype specimen illustrated in Fig. 25. Deposited in Diatom Herbarium (HD) of Laboratory of Molecular Systematics of Aquatic Plants, K.A. Timiryazev Institute of Plant Physiology RAS, Moscow, Russia.

Representative materials:— Slides 09873, 09874, 09875 deposited in Diatom Herbarium (HD) of Laboratory of Molecular Systematics of Aquatic Plants, K.A. Timiryazev Institute of Plant Physiology RAS, Moscow, Russia.

Etymology:— The new species is named after Dr. Ekaterina Viktorovna Lepskaya, Russian algologist, researcher of freshwater and marine ecosystems of Kamchatka.

Ecology:— Found in periphyton from watercourses of slightly alkaline pH (7.87–8.24) and low electrical conductivity (10–100 μS/cm), at temperatures of 6.3–13.7°C.

Distribution: — Kamchatka Peninsula: Limnokren spring, type locality (sample O-1, slide 09862), Pravaya Ozernaya River (sample O-15, slide 09873), Ozernaya River (sample O-16, slide 09874; sample O-L, slide 09875); Bering Island, as “ Gomphonema sp. 2 ” (Potapova 2014).

Comments:— The new species is typical for the diatom communities in several waterbodies studied herein. It was registered in Limnokren spring and rivers Ozernaya and Pravaya Ozernaya. Previously, the species was illustrated as “ Gomphonema sp. 2 ” by Potapova (2014: figs 343, 345) in the study devoted to the diatom flora of Bering Island, Russia. Thus, it can be assumed that Gomphonema lepskayae sp. nov. is distributed beyond its type locality and is widespread in the aquatic ecosystems of Kamchatka Peninsula and adjacent regions.