Chloroidium arboriculum 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 arboriculum Darienko & Pröschold sp. nov.

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

Mature vegetative cells are ellipsoidal to almost spherical, 5.3 × 5.0–8.3 × 8.5 μm. Chloroplast is parietal, band-shaped, sometimes with a slightly wavy margin, and often removed from the cell wall. Cell walls of mature vegetative cells sometimes become granulated. Nucleus is single and not distinct. Old cells are spherical, 9.2–10.0 μm in diameter. Chloroplast is belt-like with a wavy margin, and is removed from the cell wall. Hollow spaces that could also be contrasted using the Lugol solution are also sometimes present in the cells.

Reproduction occurs by autospores of equal and unequal size. Autosporangia with equally sized autospores usually contain 4–8 spores. Autosporangia are spherical, 7.2 to 10.8 μm in size. Liberation of autospores occurs via the rupturing of sporangia.

Compared to morphologically similar Parachloroidium laureanum , P. lobatum differs by chloroplasts often being slightly removed from the cell wall and differences in its ITS-2 sequences. It is distinguished from Chloroidium viscosum only by changes in the ITS-2 sequences.

Type locality: Vienna Forest, bark of tree, free-living biofilm on Fagus sylvatica , near Vienna, Austria.

Holotype (designated here): The strain MG-3 is cryopreserved in a metabolically inactive state at the SAG, Göttingen , Germany.

Iconotype (in support of the lectotype designated here): Fig. 6N–V in this study.

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.