Astrothelium parathelioides
Astrothelium parathelioides is a species of corticolous crustose lichen in the family Trypetheliaceae. This species was described in 2022 from specimens collected in the Amazon rainforest of Brazil and is distinguished by its unusual fruiting bodies that open sideways rather than at the top, along with ascospores that have a distinctly thickened middle partition.
Taxonomy
Astrothelium parathelioides was described as new to science by André Aptroot and Bruno Barbosa from material collected on tree bark in primary rainforest at the Cristalino Reserve, Mato Grosso, Brazil. The specific epithet refers to the species' "parathelioid" fruiting bodies: perithecia whose pore opens on the side rather than at the top. In overall appearance it resembles A. medioincrassatum, but that species has compound fruiting bodies with several pores fused together, whereas A. parathelioides has solitary perithecia with a single lateral pore and ascospores with a conspicuously thickened middle septum.Description
This is a corticolous species. The lichen body is slightly glossy and pale ocher, forming patches up to about 4 cm across and only to about 0.1 mm thick; it lacks a contrasting border. The sexual fruiting bodies are perithecia: small, pear-shaped structures mostly embedded in the thallus and sometimes breaking through the surface, 0.5–0.8 mm in diameter. They occur singly. Each perithecium has one black ostiole positioned on the side, which is the tiny pore where spores are released. The internal, non-spore tissue is clear rather than filled with oil droplets or granules.Asci contain eight ascospores. The spores are hyaline, long-ellipsoid, and divided by 9–13 internal cross-walls ; the central septum is distinctly thickened. Ascospore size is 101–124 × 25–30 μm, they do not react with iodine, and no gelatinous sheath is present. Asexual structures appear as small black, erupting dots scattered among the perithecia, but their spores were not observed.
Spot tests on the thallus are negative and there is no ultraviolet fluorescence. Thin-layer chromatography did not detect secondary metabolites.