Megaspora iranica

Megaspora iranica forms a crust-like thallus that spreads across its substrate in patches 5–10 cm wide, sometimes merging into larger mats. The surface is whitish to pale grey and strongly cracked, creating a network of fissures that resemble those of the related species M. rimisorediata. The cracks often contrast with the powdery reproductive granules (soredia), which are greyish because of embedded crystals. The thallus is relatively thin, with a layered structure: a variable upper cortex, a green algal layer containing relatively large algal cells, and a whitish inner medulla. The outer cortex is thickened and crystal-rich, with cell arrangements resembling those in some Teloschistaceae lichens. Along the cracks, dense bands of soredia are produced, each about 40–50 micrometres (μm) across, serving as the main means of vegetative propagation.^[2]

The species also develops small fruiting bodies (apothecia), usually less than 1.5 mm in diameter. These start immersed in the thallus and later become more exposed, with flat to concave discs that may be dusted with a pale coating. Internally, the apothecia contain a spore-bearing layer up to 250 μm tall, supported by branched filaments (paraphyses) and capped by a dull greenish-brown surface layer. Each spore sac (ascus) carries 4–8 colourless ascospores, which are ovoid to broadly ellipsoid and relatively large—typically 32–37 by 17–21 μm. Mature spores often contain conspicuous oil droplets, and in old apothecia they may appear flattened or slightly discoloured. Chemical spot tests on the fruiting bodies show diagnostic colour changes: sections turn brown that intensifies to green or olive with potassium hydroxide solution (K), while the application of nitrite (N) produces a greenish reaction, with some brownish-olive areas shifting to an intense green.^[2]

Megaspora iranica grows on the bark of deciduous trees, with confirmed collections from white mulberry (Morus alba) and Montpellier maple (Acer monspessulanum). It has been recorded from scattered sites in north-eastern Iran and more widely across parts of central Asia.^[2]