The most common and probably the most variable Placynthium species, which associates with filamentous cyanobacteria of the family Rivulariaceae. It forms a conspicuously dark thallus, almost black when moist, obviously finely structured and cracked into areoles when dry. Granulose to coralloid isidia, sometimes replaced by adventive lobules, form on its surface. Dark lecideine apothecia, which contain blue-green and purple pigments and 3-septate cylindrical spores, are usually present but may also be missing. A blue, indigo-coloured fimbriate prothallus is the most prominent characteristic of the species.
The species grows on various calcareous substrates, both natural and anthropogenic, from lowlands to mountains. Ecologically, it is very plastic and may even grow under water in water currents of high mountains, forming the conspicuous form P. nigrum f. crustaceum with thin thallus and no vegetative propagules (Thüs & Schultz 2009) which, however, has not been documented in the Czech Republic yet. In the country, it is abundant in karst areas and is very rare in siliceous areas.
Literature: Thüs H. & Schultz M. (2009): Fungi: Lichens Pt. 1 (Süßwasserflora Von Mitteleuropa / Freshwater Flora of Central Europe). – Spektrum Akademischer Verlag, Heidelberg.
taxonomic classification:Ascomycota → Lecanoromycetes → Peltigerales → Placynthiaceae → Placynthium
Red List (Liška & Palice 2010):NT – near threatened
Occurrence in the Czech Republic
All records: 131, confirmed 68. One click on a selected square displays particular record(s), including their source(s).