Chloroidium viscosum (Chodat) Darienko & Pröschold 2018

Darienko, Tatyana, Lukešová, Alena & Pröschold, Thomas, 2018, The polyphasic approach revealed new species of Chloroidium (Trebouxiophyceae, Chlorophyta), Phytotaxa 372 (1), pp. 51-66 : 62

Chloroidium viscosum (Chodat) Darienko & Pröschold comb. nov.

Basionym: Chlorella viscosa Chodat, 1913 , Monographies d‘algues en cultures pure, p. 105, Fig. 97 (lectotype designated here).

Emended Diagnosis: Young cells are ellipsoidal to broadly ellipsoidal, 4.1 × 2.8–5.6 × 5.0 μm. Cell wall is thin and smooth. Chloroplast is parietal and band-shaped with a smooth even margin, sometimes slightly removed from the cell wall. Pyrenoid is not distinct, naked, without a starch sheath, and becomes suffiently visible after staining with Lugol solution.

Mature vegetative cells ellipsoidal to almost spherical, 6.3 × 5.0–8.8 × 6.9 μm. Chloroplast is parietal, band-shaped, sometimes with a slightly wavy margin, and often removed from the cell wall. Cell wall of mature vegetative cells becomes slightly thicker in comparison with young cells. Nucleus is single, not distinct. Old cells are spherical, 9.4–10.0 μm in diameter. Chloroplast belt-like with a wavy margin, removed from the cell wall and similar to that of Heterochlorella luteoviridis .

Reproduction is done by autospores of equal and unequal size. Autosporangia with equally sized autospores usually contain 32 spores, while autosporangia with unequally sized contain 2–8 spores. Autosporangia are spherical, 7.5 to 12.0 μm in size. Large autospores have the same size as mature vegetative cells. Liberation of autospores happens via the rupturing of the sporangia. Often one autospore remains in the sporangial cell wall and develops into a mature vegetative cell.

Differs from the morphologically similar species Heterochlorella luteoviridis by the presence of a naked pyrenoid and absence of cytoplasm vacuolization. Differs from other species of Chloroidium by spherical cell shape and CBCs in its ITS-2.

Type locality: Photobiont of Woessia fusarioides , on trunk of Quercus , collected near Tatzmannsdorf, Burgenland, Austria ( Tschermak-Woess, 1988).

Epitype (designated here): The strain SAG 56.87 is cryopreserved in a metabolically inactive state at the SAG, Göttingen, Germany.

Iconotype (in support of the holotype designated here): Fig. 6H–M in this study.

The second strain MG-2 was isolated in 2010 from free-living biofilm collected from the bark of tree of Fagus sylvatica in Vienna Forest. Note: The strain SAG 2338, designated as authentic strain of Chlorella viscosa , differed in its morphology and does not fit the original description provided by Chodat (1913). Our sequence (acc. no. MH 551524) demonstrated that this strain is identical to C. vulgaris .

Figures

FIGURE 6. Morphology and phenotypic plasticity of the new Chloroidium species. A.–G. C. antarcticum; H.–M. C. viscosum; N.–V. C. arboriculum; scale bar = 10 μm.