Mallomonas pseudopustula E. S. Gusev, Ignatenko, Lituanas, Gumapac & Martynenko, 2025

Gusev, Evgeniy S., Ignatenko, Marina E., Lituanas, Chris Rey, Gumapac, Kyla Rose, Martynenko, Nikita A. & Efeykin, Boris D., 2025, Diversity of silica-scaled chrysophytes (Chrysophyceae) from Mindanao Island (Philippines) with the description of Mallomonas pseudopustula sp. nov., PhytoKeys 268, pp. 81-102 : 81-102

Mallomonas pseudopustula E. S. Gusev, Ignatenko, Lituanas, Gumapac & Martynenko sp. nov.

Fig. 2

Description.

Scales oval, 5.8–7.1 × 4.1–4.6 µm. A wide posterior rim (0.6–1.1 µm) encircles approximately one-half of the scale’s perimeter on its posterior part. The anterior part of the scale is bordered by a narrow, trough-shaped hyaline belt along a narrow, thickened edge. A thick secondary siliceous layer with an internal reticulation pattern of rounded mesh covers most of the scale surface, typically from two-thirds to four-fifths of it. This area contains numerous base plate pores and papillae on the surface of the secondary silica layer. In the proximal part of the scale, the secondary silica layer is significantly thinner and is absent around a large rimmed pore located centrally in this area. This central rimmed pore is surrounded by a “ cloud ” of small pores. Additional pores penetrate the entire proximal part of the scale, where the secondary siliceous layer is thinner. These pores are smaller in size than those in the distal part of the scale covered with the thick secondary layer.

Cysts and bristles were not observed.

Type.

Philippines • Mindanao Island, Bukidnon, Don Carlos, Barangay Pinamaloy, Lake Pinamaloy ; 7°40.436'N, 125°00.063'E; 21 June 2025; E. S. Gusev leg. Holotype. Portion of a single gathering of cells on SEM stub 70_I_1, deposited at the Herbarium of the Steppe Institute of the Ural Branch of the Russian Academy of Sciences, Orenburg ( ORIS). Fig. 2 A is a representative scale from the type specimen .

Etymology.

Epithet “ pseudopustula ” is derived from the species Mallomonas pustula E. S. Gusev, Safronova, Podunay, Hoan Tran & Martynenko and Greek “pseudo” (= false).

Distribution and ecology.

In addition to the type locality, this species has been observed in the Fullbright Pond (Bukidnon, Maramag, Musuan, CMU Campus, 7°51.410'N, 125°2.998'E) and a water pool (Misamis Oriental, Gingoog City, Barangay Lunotan, 8°42.263'N, 125°00.923'E). This species has also been previously recorded in Vietnam, Dong Nai Province ( Gusev et al. 2022 a, fig. 4 f, p. 210 as Mallomonas sp. 1 ). Mallomonas pseudopustula sp. nov. was found under the following environmental conditions: pH 6.6 to 7.3, specific conductance of 49 to 169 µS cm - 1 and a temperature range of 28 to 31 ° C (Table 1 ).

Figures

Figure 2. Mallomonas pseudopustula sp. nov. A – D, G, H. Surface view of the scale; E, F. Undersurface view of the scale; Arrows indicate: (a) Posterior rim; (b) Hyaline belt; (c) Thick secondary layer with papillae and pores; (d) Large central rimmed pore in the proximal part of the scale surrounded by a “ cloud ” of small pores; (e) Pores in the proximal part of the scale; (f) Pores in the distal part of the scale; A – F. SEM; G, H. TEM. Scale bars: 5 µm (G); 2 µm (A – F, H).