Pink-eyed Shingle Lichen

Vahliella saubinetii forms a thin crust made up of tiny, scale-like lobes (squamules) that are bluish grey to grey-brown and lack any frost-like surface bloom (epruinose). The squamules have finely scalloped margins and are usually 0.2–0.3 mm across, though they occasionally reach 0.5 mm or shrink to as little as 0.1 mm. Internally, the thallus is heteromerous (built in distinct layers): a brickwork-like upper cortex(paraplectenchyma), a loose white medulla that grades into anchoring hyphae (rhizohyphae), and no lower cortex. The photosynthetic partner (photobiont) is a cyanobacterium of the genus Nostoc, with cells clustered in packets. Sexual fruiting bodies (apothecia) are common, 0.3–1.2 mm wide, and sit directly on the thallus surface (sessile). The disc is flat to slightly convex and pale brown-orange to pink-brown, bordered by a paler, persistent rim of fungal tissue (a thin proper margin). Microscopically, the surface film over the disc (epithecium) is brownish, while the spore-bearing layer (hymenium) is colourless to pale yellow-brown and stains blue with iodine (I+). The simple paraphyses (sterile filaments among the spore sacs) are about 2 μm thick and broaden to club-shaped tips. Beneath the hymenium, the supporting tissue (hypothecium) is colourless. The asci (spore sacs) are club-shaped to nearly cylindrical, each containing eight ascospores. …