Mallomonas tyleri E.S. Gusev, Shkurina, Hoan Tran & Martynenko, 2025

Gusev, Evgeniy S., Shkurina, Nataliya A., Tran, Hoan & Martynenko, Nikita A., 2025, Revision of the Mallomonas splendens species clade (Chrysophyceae, Synurales) based on morphological and molecular data, Phytotaxa 708 (3), pp. 241-259 : 251-252

Mallomonas tyleri E.S. Gusev, Shkurina, Hoan Tran & Martynenko sp. nov. ( Figs 19–26 )

Cells are ellipsoidal, 19–25 × 8–14 µm, covered with three types of scales (anterior, body and posterior), and with up to four bristles on each end of the cell. All types of scales are thick, with an internal reticulation of closely-spaced meshes and externally covered with papillae. Body scales are rhomboidal, slightly asymmetric, 4.5–5.7 × 3.0–3.8 µm. The V-rib is absent. The posterior rim is wide, encircles approximately half of the scale perimeter. Posterior and anterior flanges are narrow and smooth. The shield is thick and raised above the flanges. Anterior scales are oval, 4.0–5.1 × 5.8–7.4 µm, with a curved zigzag-like rib, narrow posterior rim and wide posterior flange. Posterior scales are suboval, 5.8–6.8 × 4.3–5.2 µm, with an asymmetrically placed dome, and a curved posterior submarginal rib along the posterior rim. Bristles are straight or slightly curved, 9.0–18.5 µm, with a flattened foot, an open slit on the shaft, terminates with small teeth. Stomatocysts unknown.

Holotype: — Portion of a single gathering of cells on SEM stub 62_I_1, deposited at the Herbarium of the Steppe Institute of the Ural Branch of the Russian Academy of Sciences , Orenburg ( ORIS). Material from the irrigation channel in Dak Lua village, Cat Tien National Park, Dong Nai Province, Vietnam, collected by N.A. Martynenko, 29 February 2020.

Type locality: — Vietnam: irrigation channel, Dak Lua village, Cat Tien National Park, Dong Nai Province, Latitude/Longitude: N11° 31.058’ E107° 21.598’.

Genbank accession numbers for the reference strain (VNG2002): PV771129 (nuclear SSU rDNA), PV780776 (rbc L cpDNA) and PV779675 (nuclear ITS rDNA).

Etymology:—The epithet is in honor of the well-known specialist in limnology and phycology Peter A. Tyler.

Distribution and ecology:—In addition to the type locality, this species has been observed in three more localities in Vietnam ( Tables 1, 2). Strains of this species have also been isolated from South Korea and Australia ( Siver et al. 2015). Mallomonas tyleri was found at quite narrow ranges of environmental parameters: pH from 5.5 to 6.7, specific conductance from 47 to 231 µS cm-1, and temperature 27–28 ºC ( Tables 1, 2). This species prefers acidic conditions.

Since M. splendens f. arnhemensis can be clearly differentiated from M. splendens in having circular or ellipsoidal depression in the angle of the V-rib, we propose to raise it to a species rank:

Figures

FIGURES 19–26. Mallomonas tyleri sp. nov. (strain VNG2002) studied using TEM and SEM. Figure 19. Body scale, TEM. Figures 20–21. Body scales, SEM. Figure 22. Posterior scale, SEM. Figure 23. Posterior scale, TEM. Figure 24. Whole cell with bristles, SEM. Figure 25. Bristle, TEM. Figure 26. Bristle, SEM. Scale bars: Figures 20–22: 1 μm; Figures 19, 23: 2 μm; Figures 25–26: 5 μm; Figure 24: 10 μm.