Gyalolechia paradoxa

This is a small crustose lichen that grows directly on mosses or as a lichenicolous parasite. The thallus is thin and may be partly embedded in the substrate or sit on its surface, forming a continuous crust or one broken into a network of tiny crack-bounded patches (areoles) about 0.1–0.3 mm wide. It is typically orange to orange-red but may appear whitish, often with small white necrotic spots, and a black prothallus may be present. Apothecia (fruiting bodies) are usually abundant, 0.75–1.3 mm in diameter, with a dark ferruginous-red (rust-coloured) to ferruginous-brown disc and a thin, often tortuous scalloped (crenate) margin. The apothecia range from having a thin thallus-like rim mainly visible underneath zeorine to lacking it almost entirely biatorine, with the thalline exciple mainly developed on the underside and inconspicuous from above.^[2]

Microscopically, the hymenium is about 130 μm high. The upper spore-bearing layer (epihymenium) is rust-red and often covered with a conspicuous layer of granular crystals (epipsamma), while the tissue beneath the spore layer (hypothecium) is brownish and may extend downwards in the centre. Ascospores are colourless and polarilocular, usually fewer than eight per ascus and sometimes poorly developed. They are broadly ellipsoid to more or less spherical (12–19 × 8–13 μm) with septa 4–9 μm wide. Pycnidia are present, and conidia are ellipsoid to rod-shaped (bacilliform), measuring about 2.5–3.5 × 1.5 μm. In standard spot test reactions, the apothecia and thallus react K+ (deep purple) and the apothecia are C+ (red). Chemically, 7-chloroemodin was reported as the major secondary metabolite, with emodin and parietinic acid as minor compounds and traces of fragilin. It can be mistaken for Blastenia ammiospila, but that species has a whitish thallus lacking anthraquinones (and containing atranorin) and has narrower spores. When lichenicolous on Psora rubiformis it may also resemble Caloplaca psoricida, which has more elongate spores and lacks a crenate apothecial margin.^[2]

Gyalolechia paradoxa is known only from its type locality on Medny Island (Commander Islands), where it was collected in tundra on a mountain slope at about 145 m elevation. It occurs on mosses and also as a lichenicolous species on squamules (scale-like lobes) of the terricolous lichen Psora rubiformis. Reported lichen associates at the site included Epilichen scabrosus, Japewia tornoënsis, Lepra dactylina, Ochrolechia frigida, and Pertusaria bryontha.^[2]