Mallomonas gemina (Dürrschmidt & Croome) E.S. Gusev 2024

Gusev, Evgeniy S., Podunay, Yulia A., Martynenko, Nikita A., Tran, Hoan & Kuzmin, Denis V., 2024, Mallomonas gemina comb. et stat. nov. (Synurales, Chrysophyceae) - a new combination based on molecular studies, Phytotaxa 665 (3), pp. 221-232 : 226-228

Mallomonas gemina (Dürrschmidt & Croome) E.S. Gusev comb. et stat. nov. ( Figs. 11–19 )

Basionym: Mallomonas favosa f. gemina Dürrschmidt & Croome 1985 . Nordic Journal of Botany 5, 289, Figs. 22–24.

Cells are armoured with apical domed collar scales, domeless body scales and small rear scales with short spines. The body scales are rhomboidal and slightly asymmetrical, 2.9–4.3 × 1.7–3.3 μm, with a shield, posterior and anterior submarginal ribs, anterior and posterior flanges, and a posterior rim. The shield is patterned with a reticulated meshwork, creating a dense system of irregular, polygonal apertures and scattered, delicate papillae on the surface. The anterior submarginal rib is raised above the shield, with struts radiating to the anterior flange and the shield. There is a papilla at the distal end of each strut on the side of the anterior flange. The anterior flange is narrow, with struts radiating from the anterior submarginal rib. The posterior submarginal rib is smooth and fused with the arms of the anterior submarginal rib. There is a distinct row of small pits located on the shield along the posterior submarginal rib. There are usually 6–14 pits, rarely fewer. Each pit contains a small, rimmed pore. The posterior rim is wide, smooth and encircles half of the scale. The posterior flange is narrow and smooth. The collar scales are 3.4–4.8 × 2.0–3.4 μm, asymmetrical, elongate and have a broadly rounded, proximal end and narrower distal end, with a well-developed dome. The shield of the collar scales has a meshwork pattern similar to the body scales. The dome is oval in outline, with reticulation and a sharply pointed peak at the apex. There are several rimmed base plate pores in the angle of the posterior submarginal rib. The rear scales are similar in structure to the body scales, but more asymmetrical, bearing small spines and smaller in size, 1.7–2.9 × 1.1–1.9 μm. Bristles are 6.1–8.8 μm in length, curved, smooth and pointed. Cysts are not observed.

Reference strain: Representative living and fixed strain 12_18 and DNA sample deposited at the Collection of the A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences.

Genbank accession numbers for reference strain (strain 12_18): PQ308596 (nuclear SSU rDNA), PQ300137 (rbcL cpDNA) and PQ308599 (nuclear ITS rDNA).

Genbank accession numbers for other strain (strain 2_18): PQ308595 (nuclear SSU rDNA), PQ300136 (rbcL cpDNA) and PQ308598 (nuclear ITS rDNA).

Figures

FIGURES 11–19. Mallomonas gemina comb. et stat. nov. (strain 12_18), SEM and TEM. Figures 11–12. Body scales, SEM. Figure 13. Body scale, undersurface view, SEM. Figure 14. Collar scale, SEM.Figures 15–16. Body scales, TEM.Figure 17. Collar scale with bristle, TEM. Figure 18. Group of scales and bristles, TEM. Figure 19. Bristle, SEM. Scale bars: Figures 11–14, 19: 1 μm; Figures 15–17: 2 μm; Figure 18: 5 μm.