Pyrenula sanguineomeandrata

Pyrenula sanguineomeandrata was described in 2018 by André Aptroot and Joel Mercado-Díaz from material collected in Puerto Rico. It is taxonomically notable as only the second species of Pyrenula known to have a red-pigmented . This pigmentation, which reacts with potassium hydroxide (KOH) to produce an orange colour, is chemically and structurally distinct from that found in the similar species P. rubroinspersa, which has a green KOH reaction and likely contains isohypocrellinic acid. ==Description==

This corticolous (bark-dwelling) lichen forms a thin, smooth, ochraceous (yellowish-brown) thallus up to 0.1 mm thick. The surface is marked with a distinctive (net-like) or linear pattern of dark red pigmentation. No pseudocyphellae or crystalline deposits are present. The is a green alga of the genus Trentepohlia. The ascomata are (flask-shaped), simple, and scattered across the thallus. They are (pear-shaped) and deeply immersed in the bark, with only the apical ostiole (the spore-release pore) visible at the surface. Each ascoma measures 0.2–0.4 mm in diameter and has a dark to reddish-brown ostiole. The wall is black and evenly , lacking internal crystals. The is densely inspersed with dark red oil droplets, a distinctive feature of the species. The asci are cylindrically club-shaped and contain eight irregularly arranged spores. Ascospores are dark brown, 3-septate, and broadly (spindle-shaped) with pointed ends. They measure 25–29 × 10–12 μm. The internal are diamond-shaped and are separated from the end wall by an layer. Asexual reproductive structures (pycnidia) are absent. Chemically, the thallus contains red anthraquinone pigments that fluoresce red under ultraviolet light and react purple with KOH. The red pigment in the hamathecium similarly reacts KOH+ (orange), indicating a distinct chemical composition. ==Habitat and distribution==

Pyrenula sanguineomeandrata is known only from its type locality in the submontane evergreen forest of the Maricao State Forest in Puerto Rico, where it was found at around elevation. It grows on bark in wet forest conditions and is considered a rare and localised species. ==See also==