Arthonia pannariae
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| Arthonia pannariae | |
|---|---|
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Arthoniomycetes |
| Order: | Arthoniales |
| Family: | Arthoniaceae |
| Genus: | Arthonia |
| Species: | A. pannariae |
| Binomial name | |
| Arthonia pannariae Zhurb. & Grube (2010) | |
Arthonia pannariae is a species of lichen-dwelling fungus in the family Arthoniaceae.[1] It was described in 2010 from material collected in northern Norway, with additional specimens known from arctic Russia and Greenland. The fungus infects soil-dwelling lichens of the family Pannariaceae, where it colonizes the spore-producing tissues of the host's fruiting bodies, often visibly bleaching or destroying them. Its known distribution spans the northern Holarctic, mainly in tundra and polar desert environments, though a 2025 report extended the range to Papua New Guinea.
Arthonia pannariae was described as a new species in 2010 by Mikhail Zhurbenko and Martin Grube, based on material collected in northern Norway and compared with additional specimens from arctic Russia and Greenland. The type specimen was collected in Troms county (Skibotndalen Valley, between Luhcajavri and Stuoraoaivi) at 700 m elevation, growing mainly on the hymenium of Protopannaria pezizoides apothecia. The specific epithet pannariae refers to the Pannariaceae, the family of the host lichens.[2]
The authors placed the species in the Arthonia radiata group, and compared it most closely with Arthonia clemens and A. vagans var. lecanorina. They separated A. pannariae from A. clemens in the strict sense (sensu stricto) by its more often pigmented hymenium, longer asci (typically 33–43 × 12–16 μm), narrower ascospores (typically 9.5–12.5 × 3.5–4.5 μm), and by its host choice (Protopannaria and Psoroma rather than lichens such as Rhizoplaca). In discussing host associations, they suggested that a broad concept of A. clemens likely merges multiple host-specific taxa, and that A. clemens sensu stricto may be restricted to Rhizoplaca.[2]
Description
Arthonia pannariae grows as colourless, branching hyphae that form a dense network within the host's hymenium. Its fruiting bodies are black (sometimes with a brown tinge), dull to slightly glossy, and may occur singly but more often merge into crowded, composite apothecia up to 2 mm across; these range from moderately convex to lumpy and warted (tuberculate). Microscopically, the uppermost layer of the spore-bearing region (epihymenium) is distinct and grey-olive to brown-olive, about 10 μm tall, while the spore-bearing layer itself (hymenium) is 40–50 μm tall and ranges from pale olive-brown (especially near the top) to nearly colourless. The subhymenium is indistinct, and the underlying hypothecium may reach 150 μm in height. In iodine-based tests the hymenial tissues show diagnostic colour reactions, staining red in iodine and blue after pretreatment with KOH.[2]
The paraphyses are mostly unbranched in their lower portions but become more branched and wavy above, with pigmented, slightly to strongly swollen upper cells that lack a distinct pigment cap. The asci are club-shaped (clavate), often with a short stalk, and consistently contain eight spores. The asci typically measure 33–43 × 12–16 μm, though extremes of roughly 28–48 × 11–20 μm have been recorded. The ascospores are colourless (hyaline), smooth, and divided by a single cross-wall (1-septate), often with a gently "sole-shaped" outline in which the upper cell is the broader of the two. They typically measure 9.5–12.5 × 3.5–4.5 μm, with occasional extremes of about 7.5–15.0 × 3.0–5.0 μm, and lack a gelatinous sheath. No asexual reproductive stage (anamorph) has been reported.[2]