Astrothelium intermedium
Astrothelium intermedium is a species of corticolous, crustose lichen in the family Trypetheliaceae. It was formally described in 2008 from material collected on tree bark at Las Cruces Biological Station in Costa Rica, at about elevation. The lichen forms a smooth, glossy, olive-green crust that can spread over patches up to about across, with the fruiting bodies concentrated in low, wart-like lines across the surface. Under the microscope it produces colorless ascospores divided into several compartments.
Taxonomy
It was described as a new species in 2008 by the lichenologists André Aptroot and Robert Lücking, based on material collected on bark at Las Cruces Biological Station in Puntarenas, Costa Rica, at about elevation. In the original description it was characterized as very similar to Trypethelium marcidum, but differing in its astrothelioid ascomata.Description
The lichen forms an olive-green, smooth, glossy thallus that may cover areas up to about across and lacks a . Its perithecia are pear-shaped and measure about 0.2–0.4 × 0.3–0.5 mm; they are oriented vertically to often somewhat off-centre, and usually occur in groups of 2–5 that share common ostioles. The perithecia are immersed in low, wart-like ta that cover about half of the thallus in irregular, net-like lines roughly 3 mm wide and 1–2 cm long. These pseudostromata are covered by the green thallus except at the rounded, ochraceous, slightly raised ostiolar, where one or two tiny black ostioles are visible; each disc is bordered by a narrow ochraceous ring about 0.1 mm wide. Internally, the pseudostromata are pale and consist of fungal hyphae mixed with some bark cells, without pigments or crystals.Microscopically, the perithecial wall is about 10–30 μm thick and is only partly, especially below the hymenium. The tissue between the asci is not oil-filled, and it does not react with iodine ; its filaments are extensively interconnected. Each ascus contains eight colorless ascospores that do not react with iodine and are split into compartments by one main cross-wall and three additional internal partitions, measuring about 29–33 × 12–15 μm. The spore compartments become diamond-shaped, but are more often simply angular, with the end compartments smaller than the central ones.