Lichenostigma
From Wikipedia, the free encyclopedia
| Lichenostigma | |
|---|---|
 | |
| Lichenostigma cosmopolites | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Arthoniomycetes |
| Order: | Lichenostigmatales |
| Family: | Phaeococcomycetaceae |
| Genus: | Lichenostigma Hafellner (1983) |
| Type species | |
| Lichenostigma maureri Hafellner (1983) | |
| Synonyms[1] | |
| |
Lichenostigma is a genus of fungi in the family Phaeococcomycetaceae.[2] It includes several species which are lichenicolous (i.e. parasitic on lichens).[3] The genus was circumscribed in 1983 by the Austrian mycologist Josef Hafellner, with Lichenostigma maureri assigned as the type species.[4]
Lichenostigma is a lichen-dwelling (lichenicolous) fungus that forms no independent thallus and shows little, if any, surface mycelium of its own. Its reproductive structures (ascostromata) appear scattered across the host lichen as dark brown to blackish swellings. When young these bodies are roughly spherical, but they often become elongate with age and may develop a shallow central depression; very old specimens can even mimic the lirellae of script lichens. The stromatic wall is made of thick-walled, budding cells: the outer layers are dark brown and frequently display a warted or mosaic-like texture, whereas the internal cells remain pale. At maturity the stromata break down irregularly, releasing their ascospores.[5]
Unlike many ascomycetes, Lichenostigma lacks a well-defined hymenial cavity and any hamathecium. The asci—usually four to eight per stroma—develop directly among the stromatic cells without discrete locules. They are nearly shperical to broadly ellipsoidal, sit almost sessile on the stroma, and have a very thickened apex with a distinct ocular chamber; although structurally fissitunicate, they often deliquesce as they ripen. The ascospores are initially colourless, sometimes showing a faint blue staining reaction to potassium iodide in the outer wall, but they may darken to brown when over-mature. Each spore is one-septate, ellipsoidal to elongate, and ends in either rounded or slightly pointed tips.[5]
Asexual reproduction is common and takes place in pycnidial structures that are macroscopically indistinguishable from the ascostromata. These conidiomata produce no conidiophores; instead, pale- to medium-brown conidiogenous cells arise directly from the stromatic tissue. Each cell repeatedly buds off multicellular, brown conidia that resemble miniature cell clusters—ellipsoidal overall and initially smooth, though they can become warted or spiny in very old material.[5]
