Mycobilimbia subbyssoidea

Mycobilimbia subbyssoidea is a species of crustose lichen in the family Ramalinaceae. This small lichen forms thin, greyish patches with tiny black fruiting bodies up to 1 mm across. It was found growing among dying moss on Heard Island, a remote and largely ice-covered island in the southern Indian Ocean, and remains known only from the original discovery site.

Taxonomy

Mycobilimbia subbyssoidea was described as new to science by Dag Øvstedal in a survey of the lichens of subAntarctic Heard Island. The holotype was collected on Corinth Head at 170 m elevation in 2001 by N.J.M. Gremmen (specimen H-1496, kept at the herbarium of the Australian Antarctic Division, ADT). Earlier, the material had been listed only as Mycobilimbia sp.; subsequent review of the literature—including Southern Hemisphere species treatments—showed it lacked a valid name and warranted formal description.

Description

The thallus is thin and indistinct (described as "evanescent"), greyish, and lacks a protective outer skin (). Its photosynthetic partner is a green alga of the Trebouxia type with cells 6–8 micrometres (μm) across. The fruiting bodies (apothecia) are black, up to about 1 mm in diameter, with a narrow but distinct rim and a flat ; the underside often shows patches of cottony () white tissue.

Internally, the spore-bearing layer (hymenium) is 100–110 ÃŽÂ¼m tall and turns blue with iodine-based reagents (amyloid). Beneath it lie a strongly red-brown layer and a blue-pigmented zone; the pigments intensify slightly in standard spot tests. The asci are of the Biatora-type and the paraphyses are very slender. Ascospores are colourless, with 1–3 cross-walls, typically 30–33 × 5–6 ÃŽÂ¼m, and have pointed ends; no pycnidia were seen. No secondary metabolites were detected, as there was insufficient material for full chemical tests.

Habitat and distribution

The species was found growing among dying moss cushions (moribund bryophytes) and is known only from the type collection on Heard Island. Heard Island is a cold, windy, largely glaciated oceanic island in the southern Indian Ocean.

References