Astrothelium megatropicum

Species of lichen

Astrothelium megatropicum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae. Found in Guyana, it was formally described as a new species in 2016 by Dutch lichenologist André Aptroot. The type specimen was collected by Harrie Sipman near Paramakatoi village at an altitude of 800 metres (2,600 ft); there, it was found growing on smooth tree bark. The lichen has a smooth and somewhat shiny, pale ochraceous-green thallus with a cortex and a thin black prothallus line. It covers areas of up to 7 cm (2.8 in) in diameter. The presence of the lichen does not induce the formation of galls in the host plant. No lichen products were detected from collected specimens using thin-layer chromatography. The combination of characteristics of the lichen that distinguish it from others in Astrothelium are its uneven to verrucose thallus; its confluent ascomata, which are erumpent to prominent and exposed, with gently to steeply sloping sides; and the dimensions of its ascospores. The spores, which have three septa and diamond-shaped cavities, are the longest 3-septate ascospores in the Trypetheliaceae.

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