Milospium graphideorum (Nyl.) D. Hawksw.

Non-lichenized lichenicolous fungus parasitic on crustose Trentepohlia lichens.

    Unlichenized lichenicolous fungus thriving on numerous species of crustose lichens. No visible thallus, mimicks the host thallus aspect. At the beginning of infestation, development of minute brown-black spots, typically evolving into brown-black to blackish patches: sporodochia. Sporodochia round, flat at first, then slightly convex and cushion-shaped, 0.3-0.6 mm diam., scattered or merging, sometimes partially on-line. Development of conidiophors on sporodochia, with the production of conidia, unicellular, brown-black, pyriform, clusters forming (2-6), one side of the cell wall more or less thickenned and crescent-shaped, 8-12 x 8-10 µm. This species (more probably this group of species) is a parasite of a large number of crustose lichens growing on barks or rocks. At the beginning of infestation, it seems limited to small patches on the thallus of the host species, then it covers the whole thallus surface and deeply changes its aspect and metabolism. The resulting aspect is highly variable as a function of hosts and it is not surprising that many different names have been used to described this organism. Changes are not limited to hosts but also depend on the infestation stages, and this species initially was mistakenly described as lichenized. As a result, this very common species has been confusing for a long time.

 The parasitized hosts belong to the genera: Dirina, Schismatomma, Lecanactis, Lecanographa, Opegrapha, Arthonia, Sporodophoron, Dendrographa, Zwackhia,... see for example:  Milospium graphideorum parasite de Lecanographa lyncea et Milospium graphideorum parasite de Dirina massiliensis forma sorediata.

Cf. Milospium deslooveri whose conidia are septate and spirally coiled.