Cephaleuros Kunze ex E. M. Fries.

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

Cephaleuros Kunze ex E. M. Fries.

Cephaleuros forms heterotrichous to pseudoparenchymatous orange or red macroscopic discs under the cuticle or epidermal cells of leaves, twigs and fruits of tropical and subtropical woody plants. The filament forming cells are cylindrical to irregular in shape and contain discoid to irregular chloroplasts ( Fig. 19 ). Terminal cells of the filaments often produce gametangia. Sporangiophores and setae develop from terminal cells and emerge through the tissue of the host plant ( Suto & Ohtani 2009). Currently, there are 19 taxonomically accepted species and one variety ( Guiry & Guiry 2022). However, most Cephaleuros species appear to be paraphyletic ( Zhu et al. 2017). This genus has a negative impact on agriculture as this semi-parasitic alga causes necrosis on leaves ( Brooks et al. 2015).

Unidentified Cephaleuros species have been isolated from a folicolous lichen Strigula ( Jiang et al. 2020) . Detailed observations of the Strigula life cycle suggest that lichenized Cephaleuros species are also able to live independently, free of the mycobiont. Moreover, lichenization can suppress their reproduction. The mycobiont, on the other hand, will produce pycnidia and perithecia only after the successful colonization of the algal partner ( Ward 1884). A genetic study by Zhu et al. (2017) proves that many closely-related Cephaleuros species exhibit both free-living and lichenized life-styles. In one case, the authors obtained identical strains from two different localities (southern China) and sources: from unidentified folicolous lichen and from a leaf surface ( Zhu et al. 2017).

Figures

Figs 19–30. Lichen photobiont genera (including nonlichenized species) belonging to classes Ulvophyceae and Klebsormidiophyceae. Fig. 19. Cephaleuros virescens (Darienko 2017). Fig. 20. Phycopeltis arundinacea. Fig. 21. Trentepohlia sp. Fig. 22. Blidingia marginata. Fig. 23. Halofilum ramosum (Darienko 2008). Fig. 24. Lithotrichon pulchrum (Darienko 2016b). Fig. 25. Paulbroadya prostrata (Darienko 2016a). Fig. 26. Pseudendoclonium sp. Fig. 27. Rindifilum verrucariae. Fig. 28. Undulifilum symbioticum. Fig. 29. Urospora penicilliformis. Fig. 30. Interfilum terricola. Scale bars: 10 μm (Figs 19, 21-30), 50 μm (Fig. 20).