Tremolecia is a small genus of lichen-forming fungi in the family Hymeneliaceae. Its two accepted species form thin crusts on rock and are recognised by their dark, cup-shaped fruiting bodies (apothecia). The better-known species, Tremolecia atrata, is widespread on iron-rich rocks in mountainous and arctic regions.
The genus was circumscribed by the French lichenologist Maurice Choisy in 1953. Choisy characterized Tremolecia by its (centrally raised) or somewhat (brain-like, with wavy folds) apothecia, rather small spores occurring eight per ascus, and very short, straight (asexual spores produced in flask-shaped structures). He also compared the genus with Gyrothecium.
Tremolecia species are crustose lichens, appearing as a thin crust-like growth on its without a protective outer layer (). The âÂÂthe photosynthetic partner in this symbiotic relationshipâÂÂis a single-celled green alga with nearly spherical to completely spherical cells measuring 7âÂÂ14 by 6âÂÂ13 micrometres.
The reproductive structures (ascomata) are cup-shaped fruiting bodies called apothecia. These apothecia are of the type, meaning they have their own distinct margin, and can be either sunken into the lichen surface with a crater-like appearance ( and more or less ) or sitting on top of the surface (sessile). The âÂÂthe tissue forming the rim of the apotheciumâÂÂappears dark brown and opaque when viewed in cross-section.
Inside the reproductive structures, the paraphyses (sterile filaments) are sparsely branched and occasionally fused (), with tips that are not swollen (not ). The asciâÂÂspecialized cells that produce sporesâÂÂare club-shaped and contain eight spores each. They belong to the Tremolecia-type, characterized by a well-developed (thickened apical region) that stains very weakly with iodine (weakly amyloid), has a thin outer cap that does stain with iodine (external amyloid cap), and lacks a central chamber (ocular chamber).
The are (not divided by septa), clear (hyaline), ellipsoid in shape, lack a gelatinous coating (non-), and have thin walls. The asexual reproductive structures (conidiomata) are flask-shaped pycnidia embedded within the lichen body. The asexual spores (conidia) are rod-shaped ().
The genus does not produce any secondary metabolites detectable by standard lichen spot tests.
, Species Fungorum (in the Catalogue of Life), accept two species of Tremolecia:
Another four species transferred into the genus by Hannes Hertel in 1977 (T. lividonigra, T. nivalis, T. similigena, and T. tuberculans) are not currently accepted by Species Fungorum.
Some species that were at one time placed in this genus have since been transferred to other genera: