Malmidea sanguineostigma

The thallus of Malmidea sanguineostigma is thin, dull, and grey, featuring numerous hemispherical, corticate warts measuring 0.1–0.2 mm in diameter, each containing a bright red medullary pigment. These warts are typically rounded but occasionally flattened at the apex, without forming soralia. The photobiont partner consists of green algae cells about 7 by 5 μm.^[2]

Apothecia (fruiting bodies) are sessile, ranging from 0.4 to 0.8 mm in diameter, with a flat, smooth, medium-brown disc. The margins of the apothecia are slightly raised, dull, ochraceous to chamois-colored, and occasionally reveal pale yellow medullary tissue. Internally, the hymenium is hyaline (clear), measuring 45–55 μm high, with a pale brownish epihymenium layer (4–6 μm thick). The hypothecium below is hyaline to yellowish-brown, around 35–45 μm thick. Paraphyses (supporting hyphae in the hymenium) are unbranched and slender, about 1 μm wide.^[2]

The asci (spore-bearing structures) are cylindrical and contain eight hyaline, simple (non-septate) ascospores per ascus. Spores are ellipsoid with slightly pointed ends, measuring 10.5–12.5 by 5.5–6.5 μm. Pycnidia (asexual reproductive structures) have not been observed.^[2]

Chemical analysis of M. sanguineostigma revealed a UV-negative thallus with no reactions to standard chemical spot tests (C−, K−, KC−, P−), but its medulla shows a distinctive K+ blood-red reaction and fluoresces orange under UV. Thin-layer chromatography identified the presence of norsolorinic acid in the thallus medulla and xantholepinone pigment in the medulla of the excipulum.^[2]

At the time of its original publication, Malmidea sanguineostigma was known to occur only at its type locality in Sri Lanka. It was collected at an elevation of 1,437 m (4,715 ft) in the Knuckles Conservation Area, near Riverston Tower in the Central Province. Its habitat consists of smooth bark of trees (Elaeocarpus spp.) in primary montane forest.^[2]