Decussiphycus sinensis Glushchenko, Maltsev, Mironov, Liu & Kulikovskiy 2025, sp. nov.
Creators: name: Mironov, Andrei
name: Glushchenko, Anton
name: Kezlya, Elena
name: Maltsev, Yevhen
name: Iurmanov, Anton
name: Liu, Yan
name: Kulikovskiy, Maxim
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Plantae
Ochrophyta
Bacillariophyceae
Mastogloiales
Mastogloiaceae
Decussiphycus
Decussiphycus sinensis

description: Decussiphycus sinensis Glushchenko, Maltsev, Mironov, Liu & Kulikovskiy sp. nov.
Figs 2, 3, 4, 5, 6
Holotype.
Slide 09153 in herbarium of MHA, Main Botanical Garden, Russian Academy of Science, Moscow, Russia, represented here by Fig. 4 C.
Isotype.
Slide 08909 in herbarium of MHA, Main Botanical Garden, Russian Academy of Science, Moscow, Russia.
Type.
China. Hainan Province, unnamed stream at the northern slope of Wuzhishan Mountain, biofilms on rocks, 18.9815°N, 109.6854°E, 470 m asl, leg. Y. Liu, 12. 07. 2014. Slide 09153 from oxidized culture strain no. Ca 68, isolated from sample THHN 2014043.
Representative specimens.
Strain Ca 68 (slides 09153); sample THHN 2014043 (slide 08909).
Sequence data.
GenBank accession numbers PV 016799 (strain Ca 68, partial SSU rRNA gene sequence, V 4 region); PV 021297 (strain Ca 68, partial rbcL sequence).
Description.
Live cells (Fig. 2 A – N). Cells solitary. Nucleus located centrally within a cytoplasmic bridge between the central nodules (Fig. 2 A, E, I, white arrows). Each cell contains two chloroplasts of complex configuration, each of which is located at in the apical valve regions (Fig. 2 A, E, I, black arrows). In the valve face view, both of the plastids are invaginated along the apical axis to create a central plastid isthmus. In the girdle view, each chloroplast is H-shaped, with four clearly visible arms that extend along the surface of the valve, in its plane (Fig. 2 M, white arrows). The arms reach the cingulum region. The four lobes can be discerned in valve view as well (Fig. 2 G, white arrows).
LM (Figs 3, 4). The post-initial valve has a linear shape with slightly convex margins and bluntly curved ends; length – 77.5 µm, width – 16.9 µm. Distal raphe ends recurved in opposite directions, terminating to the valve face (Fig. 3 A). Valves linear – elliptical to elliptical with broadly rounded ends. Length 32.1–69.1 µm, width 13.9–18.3 µm. Axial area narrow, linear. Central area transapically oval to circular. Sometimes, a few randomly located areolae, visible with careful focusing, are positioned at the central area (Fig. 3 H, black arrow). Raphe filiform, straight to slightly undulate. Central raphe ends drop-shaped. Distal raphe ends deflected to the valve margin. Striae are decussate, formed by clearly visible areolae forming the right quincunx. Areolae are arranged in multiple rows – a transapical row and two oblique rows which cross each other at angles of 60 ° – 80 °. Transapical striae 21–23 in 10 µm. Occasionally, residual cingula can be found separated from the valve (Fig. 4 L).
SEM, external view (Fig. 5 A – F). Valve face is flat. Central raphe ends slightly tilted to one side and lie in asymmetrical depressions (Fig. 5 C, white arrows). Distal raphe ends oppositely deflected (Fig. 5 A, white arrowheads), bordered by small silica folds (Fig. 5 D, E, white arrowheads). Areolae small, rounded, their diameters are slightly larger near the axial area (Fig. 5 D, E, black arrows) and smaller towards the valve margin (Fig. 5 D, E, white arrows). The apex of the valve is equipped with a single isolated row of areolae, situated behind the distal raphe ends (Fig. 5 D, E, black arrowheads). Cingulum composed of open 3–4 girdle bands (Fig. 5 F). Two rows of areolae are located on each girdle band (Fig. 5 B, black arrowheads). Girdle band areolae are smaller than areolae at the valve and arranged alternately or, sometimes, chaotically. Rarely, one of the rows is interrupted. Notably, each areola in the girdle bands is covered with a layer of silica (Fig. 5 F, black arrowheads).
SEM, internal view (Fig. 6 A – F). The valve margins is shallow (Fig. 6 D, E, black arrows). The striae continue onto the valve margins (Fig. 6 B, D, E, white arrows). The interstriae are slightly raised relatively to the striae. Oblique ribs of the quincunx system are located near the central area. They are more elevated in comparison to the transapical interstriae (Fig. 6 C, black arrowheads). Areolae vary in size, shape, and type of occlusions. Areolae located closer to the sternum are distinguished by a larger diameter, round shape and presence of flat, slightly depressed, rounded silica formations (Fig. 6 D, E, black arrows). Areolae, located near the valve margin are transapically elongated, covered with oval, raised silica caps (“ convex hymene ”, sensu Edlund et al. 2006) (Fig. 6 D, E, white arrows). Transapical areolae density – 18–20 in 10 µm. Raphe slits, straight, lying on the raised sternum. The sternum widens towards the valve apex (Figs 6 D – F). Central raphe ends straight, not expanded (Fig. 6 C, white arrows). Distal raphe ends terminate with well-expressed, horseshoe-shaped helictoglossae (Fig. 6 F, white arrow).
Etymology.
The specific epithet refers to the name of the country where this species was discovered.
Distribution.
So far, the species is known only from the type locality.
Ecology.
The species was located in a mountain stream with temperature of 26.7 ° C, pH = 7.64 and conductivity = 60 µS / cm.
Comments.
Specimens of D. sinensis sp. nov. from wild population were 32.1–69.1 µm long, 13.9–18.3 µm wide, with striae width of 21–23 in 10 µm. Specimens from culture are characterized by smaller valves: 41.5–46.1 µm long, 15.5–17.1 µm wide; striae 22–23 in 10 µm, which corresponds to material from wild population.
description: Published as part of Mironov, Andrei, Glushchenko, Anton, Kezlya, Elena, Maltsev, Yevhen, Iurmanov, Anton, Liu, Yan & Kulikovskiy, Maxim, 2025, Decussiphycus sinensis sp. nov. (Bacillariophyceae, Mastogloiales) – a new species described from China, with comments on phylogenetic position of the genus, pp. 1-19 in PhytoKeys 254 on pages 1-19, DOI: 10.3897/phytokeys.254.142654