Description
Frutidella grows as a thin crust (crustose thallus) that breaks into discrete, tile-like patches ( areoles ) or develops conspicuous wart-like swellings. These swellings are packed with tiny, grain-like outgrowths that resemble miniature isidia; as they age the grains can crumble into a powder of soredia, providing a way for the lichen to spread vegetatively. Thallus colour ranges from greenish and grey to bluish or even nearly black, and a narrow white border ( prothallus ) may or may not be present. The photosynthetic partner is a single-celled green alga of the chlorococcoid type. [4]
The fruiting bodies of Frutidella are small, dome-shaped discs ( biatorine apothecia). They sit directly on the thallus, sometimes half-hidden among the surface granules, and appear bluish black or dusted with a blue-grey frost ( pruina ) when damp. Unlike lichens that recycle thallus tissue to form a rim, these apothecia lack a thalline margin . Instead they are encircled by a true exciple —tightly packed hyphae that radiate like spokes and stay pale or yellowish, never becoming blackened. A crystalline pigment in the surface layer ( epithecium ) lends a bright blue-green sheen that does not react with potassium hydroxide solution. Beneath, the spore-bearing tissue (hymenium) contains slender, sparsely branched threads (paraphyses) and asci of the Lecanora type, each holding eight smooth, colourless, single-celled ascospores. [4]
Asexual reproduction takes place in minute, flask-shaped structures (pycnidia) that have a darkened tip and release very slender, thread-like conidia. Chemical studies using thin-layer chromatography have detected the secondary metabolite compounds sphaerophorin and thiophanic acid in most specimens, with isoarthothelin or asemone present occasionally. [4]
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