Astrothelium ultralucens

Astrothelium ultralucens is a species of corticolous (bark-dwelling) lichen in the family Trypetheliaceae. Found in Venezuela, it was formally described as a new species in 2016 by André Aptroot. The type specimen was collected by Harrie Sipman along the Carapo River (Cerro Guaiquinima, Bolivar) at an elevation of 800 m. The lichen has a smooth, somewhat shiny pale greenish grey thallus that covers an area of up to 7 cm. Its ascospores are hyaline, spindle-shaped (fusiform) with three septa and dimensions of 105–130 by 35–42 μm. Astrothelium ultralucens contains lichexanthone, a lichen product that causes the pseudostromata and the thallus to fluoresce yellow when lit with a long-wavelength UV light, although the thallus only weakly.