Pyrenula aurantiothallina
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| Pyrenula aurantiothallina | |
|---|---|
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Eurotiomycetes |
| Order: | Pyrenulales |
| Family: | Pyrenulaceae |
| Genus: | Pyrenula |
| Species: | P. aurantiothallina |
| Binomial name | |
| Pyrenula aurantiothallina C.O.Mendonça, Aptroot & M.Cáceres (2016) | |
 Type locality: Povoado Ouro Verde, Bahia, Brazil | |
Pyrenula aurantiothallina is a crustose (crust-forming), bark-dwelling lichen in the family Pyrenulaceae.[1] It was described as new in 2016 from specimens collected in northeastern Brazil.[2]
It forms a rather thick body (thallus) with a uniformly orange, smooth, dull surface, lacking both pseudocyphellae (tiny pores in the surface) and a visible border zone (prothallus). The algal partner (photobiont) is a trentepohlioid green alga. Its fruiting bodies (perithecia) are partly sunken in the thallus (erumpent), low-conical, and usually 0.7–1.0 mm across, with brown pore-like openings (ostioles) at the apex. The sterile tissue inside the fruiting body (hamathecium) is filled with colorless (hyaline) oil droplets. The asci contain eight ascospores arranged in a single row, which are brown and divided into 4 cells by 3 septa. The spores measure about 19.5–22.5 × 7–8.5 μm, are often slightly pinched at the cross-walls, and have diamond-shaped internal spaces (lumina). Pycnidia (asexual fruiting bodies) were not observed. The thallus gives a purple reaction with potassium hydroxide solution (the K spot test), indicating an anthraquinone pigment; it is UV−, and thin-layer chromatography detected an unidentified anthraquinone.[2]
The species is known from primary forest in Bahia, including the Chapada Diamantina area (type locality near Povoado Ouro Verde–Catolé at about 1,636 m (5,367 ft) elevation), where it grows on smooth bark of trees and branches. Additional collections were reported from the same general locality.[2] It had not been reported from any other Brazilian states as of 2025.[3] The original description compared it with Pyrenula mamillana based on fruiting body and spore characters, separating P. aurantiothallina by its uniformly orange thallus. Other orange-thallus Pyrenula species were noted to differ in ascospore characters.[2]