Symbiochloris Škaloud, Friedl, A. Beck & Dal Grande.

Veselá, Veronika, Malavasi, Veronica & Škaloud, Pavel, 2024, A synopsis of green-algal lichen symbionts with an emphasis on their free-living lifestyle, Phycologia 63 (3), pp. 317-338 : 327

Symbiochloris Škaloud, Friedl, A. Beck & Dal Grande.

Symbiochloris is characterized by spherical, ellipsoidal, or irregular cell shape with a smooth and thin cell wall ( Fig. 16 ). Young cells have a single parietal chloroplast with lobes. In mature cells the chloroplast is reticulate, the lobes are never arranged in parallel (unlike in the genus Dictyochloropsis ) and a pyrenoid is absent. Asexual reproduction occurs either by zoospores or by two types of immobile cells, aplanospores and autospores ( Škaloud et al. 2016). The genus was established to differentiate between two morphologically similar lineages, both including species described under the genus Dictyochloropsis ( Škaloud et al. 2007; Dal Grande et al. 2014) and is closely related to the Watanabeales ( Škaloud et al. 2016; Li et al. 2021).

Currently, the genus Symbiochloris has ten accepted species ( Guiry & Guiry 2022) most of which (except of S. irregularis and S. tropica that are only known as free-living species; Škaloud et al. 2016) enter lichen symbiotic associations with a plethora of fungal families (e. g. Peršoh et al. 2004; Škaloud et al. 2016). Recent sequencing of leaves in tropical forest revealed many Symbiochloris sequences ( Zhu et al. 2018).

In the literature dealing with the diversity of free-living algae, S. reticulata was the most frequently observed species. Its occurrence has been recorded on tree bark (beech, ash, maple, alder; Štifterová & Neustupa 2015, 2017), in soil and in moss ( Škaloud 2009). Other records of this species come from granite rocks in the Teteriv River Valley, Ukraine, where it formed macroscopic growths (Mikhailyuk 2008) and from the Great Smoky Mountains National Park, USA ( Johansen et al. 2007; Khaybullina et al. 2010).

Another species, S. symbiontica , was discovered during environmental sequencing of soil in the Alps ( Stewart et al. 2021). Morphological confirmations of the same species come from wood and bark of trees of a lowland tropical forest nature reserve, Singapore ( Neustupa & Škaloud 2010), granite rocks in the Pivdennyi Bug River valley, Ukraine ( Mikhailyuk et al. 2003) and soil ( Andreyeva 2004, 2005, 2009; Andreyeva & Chaplygina 2006, 2007). Moreover, other species of the genus Symbiochloris ( S. ellipsoidea , S. gelatinosa , S. pauciautosporica ) have been observed in soil of north-eastern Russia ( Andreyeva 2005, 2009; Andreyeva & Chaplygina 2006). Additionally, S. handae was observed in soil mountain environments of the Alps ( Stewart et al. 2021).

Figures

Figs 1–18. Lichen photobiont genera (including nonlichenized species) belonging to classes Trebouxiophyceae and Chlorophyceae. Fig. 1. Asterochloris lobophora. Fig. 10. Prasiola crispa. Fig. 2. Myrmecia incisa. Fig. 11. Pseudochlorella pringsheimii. Fig. 3. Trebouxia impressa. Fig. 12. Stichococcus sp. Fig. 4. Vulcanochloris symbiontica. Fig. 13. Auxenochlorella protothecoides. Fig. 5. Chloroidium saccharophilum. Fig. 14. Apatococcus sp. Fig. 6. Jaagichlorella luteoviridis. Fig. 15. Leptosira sp. Fig. 7. Coccomyxa sp. Fig. 16. Symbiochloris tschermakiae. Fig. 8. Elliptochloris subsphaerica. Fig. 17. Uvulifera verrucariae (Lorenz 2016). Fig. 9. Diplosphaera chodatii. Fig. 18. Bracteacoccus. sp. Scale bars: 10 μm (Figs 1-9, 11-18), 200 μm (Fig. 10).