Astrothelium longisporum

Astrothelium longisporum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae. It occurs in the Atlantic Forest of Brazil.

Taxonomy
The lichen was formally described in 2016 by the lichenologists André Aptroot, Jeanne dos Reis Silva, and Marcela Eugenia da Silva Cáceres. The type specimen was collected in Poço Redondo, Serra da Guia, Sergipe state. It is differentiated from the otherwise similar Astrothelium megaspermum by its eccentric and the count of  per.

Description
Astrothelium longisporum is recognised by its, somewhat , and somewhat shiny thallus. The thallus is continuous, covering areas up to 6 cm in diameter and approximately 0.2 mm thick. It is pale olive-green and surrounded by a black about 0.3 mm wide. This species does not induce gall formation on the host bark. The are roughly spherical, measuring 0.8–1.2 mm in diameter, and are single in hemispherical warts covered by the thallus. The wall of the ascomata is and up to about 50 μm thick. are eccentric, flat, and black, surrounded by an irregular whitish spot of approximately 0.5 mm. The  does not have oil globules interspersed. Asci contain eight, which are hyaline, , , and measure 200–230 by 30–40 μm. These ascospores do not have a distinctly thickened median septum, with ends that are rounded and not surrounded by a gelatinous layer. have not been observed in this species.

The surface of the thallus is UV− and the thallus medulla is K−; the decorticated ascoma surface is also UV−. Thin-layer chromatography, a technique used to identify chemical substances, did not detect any secondary metabolites in this lichen.

Habitat and distribution
Astrothelium longisporum is found on smooth bark of trees in the Atlantic Forest and is known to occur only in Brazil.