Astrothelium eustomurale
Astrothelium eustomurale is a species of corticolous, crustose lichen in the family Trypetheliaceae. Found in Brazil, it was formally described as a new species in 2016 by lichenologists André Aptroot and Marcela Cáceres. The type specimen was collected by the authors in the Parque Natural Municipal de Porto Velho, in a low-altitude primary rainforest. The lichen has a smooth and somewhat shiny, pale yellowish-grey thallus that lacks a prothallus and covers areas of up to in diameter. The presence of the lichen does not induce the formation of galls in the host. The ascomata are pear-shaped and typically occur in aggregates of two to five, usually immersed in the bark tissue under the and with a whitish-coloured tissue that contrasts with the surrounding thallus. Black pycnidia are abundant on the pseudostromata. The area around and including the ostiole of the ascomata contains lichexanthone, a lichen product that causes these areas to glow yellow when lit with a long-wavelength UV light. The characteristics that distinguish it from other members of Astrothelium include the UV+ yellow nature of the ostiole; and the fused, pseudostromatic ascomata that have a white cover contrasting it with the thallus colour.