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

Podunay, Yulia, Martynenko, Nikita, Shkurina, Nataliya, Tran, Hoan & Gusev, Evgeniy, 2025, Two new Mallomonas species (Synurales, Chrysophyceae) from section Torquatae: Mallomonas sagittifera and Mallomonas trifonovae, Phytotaxa 710 (1), pp. 91-104 : 97

Mallomonas trifonovae Podunay, Martynenko, Shkurina, Hoan Tran & E.S. Gusev sp. nov. ( Figs 17–27 )

Three types of scales have been observed: apical domed collar scales, domeless body scales and small rear scales with spines. The body scales are rhomboidal, 2.1–3.6 × 1.4–3.1 μm. Shield and anterior flange are ornamented with numerous papillae. Anterior flange is slightly raised above the shield and usually have 2–3 rows of papillae along each side. Anterior submarginal rib is not developed. The shield is patterned with densely spaced papillae, with or without internal reticulation in form of polygonal mesh. Posterior submarginal rib is well developed. At the distal end of each arm of the posterior submarginal rib, another short rib may develop on the outer side. There is one rimmed pore in the angle of the posterior submarginal rib, located in a pit lacking secondary siliceous layer. Posterior rim is smooth. Posterior flange is narrow and smooth. The collar scales are asymmetrical, elongate, 3.2–4.0 × 1.5–2.4 μm. Ornamentation on the shield and flanges is the same as found on the body scales. The posterior submarginal rib on the “dorsal” side is well developed, connected with the dome. An additional short submarginal rib (anterior) departs from the dome on the “ventral” side. There are up to three rimmed pores are located in the angle of the posterior submarginal rib. The dome on the collar scales is large and ornamented with papillae and ribs. The rear scales are 1.3–2.1 × 0.9–2.0 μm, similar in structure and outline to the body scales, and each scale bearing a spine. Bristles are 5.2–7.9 µm long, curved, smooth. Cysts were not observed.

Holotype (here designated): Portion of a single gathering of cells on SEM stub 64_I_1 deposited at the Herbarium of the Steppe Institute of the Ural Branch of the Russian Academy of Sciences , Orenburg ( ORIS). Material from swamp Bau Thai in Cat Tien National Park, Dong Nai Province, Vietnam, collected by E.S. Gusev on the 6 th of May, 2018. The strain was isolated by Yu.A. Podunay. Figure 25 represents scales from the type specimen.

Type Locality: Swamp Bau Thai in Cat Tien National Park, Dong Nai Province, Vietnam. Latitude/Longitude: N11°30.382’ E107°21.616’.

Genbank accession numbers for the reference strain ( 8_18): PV791368 (nuclear SSU rDNA), PV780785 ( rbc L cpDNA) and PV791369 (nuclear ITS rDNA).

Etymology: the species epithet is in honor of scientist Irina S. Trifonova ( Russia), a well-known expert in algae for her contribution to the study of chrysophytes.

Distribution: In addition to the type locality, this species has been observed in three more localities in Vietnam ( Table 1). Mallomonas trifonovae was found under the following environmental parameters: pH from 5.2 to 6.2, specific conductance from 27 to 242 µS cm-1, and temperature 26–37 ºC ( Table 1).

Figures

FIGURES 17–27. Mallomonas trifonovae sp. nov. (strain 8_18) studied using TEM and SEM. Figures 17–19. Body scales with internal reticulation, TEM.Figures 20–21. Body scales without internal reticulation, TEM.Figure 22. Two rear scales, TEM.Figures 23–24. Collar scales, TEM. Figure 25. Group of scales, SEM. Figure 26. Bristle, TEM. Figure 27. Collar scales with bristle, SEM. Scale bars: Figures 25, 27: 1 μm; Figures 17–24, 26: 2 μm.