Collemopsidiales » Xanthopyreniaceae

Didymellopsis

Didymellopsis (Sacc.) Clem. & Shear, Gen. fung., Edn 2 (Minneapolis): 66 (1931)

Index Fungorum number: IF 1550; Facesoffungi number: FoF 07656, 6 morphological species (Species Fungorum 2021), molecular data unavailable.

Lichenicolous on host. Sexual morph: Pseudothecia black, usually spherical, rarely pear-shaped, scattered, located on the periphery of the scales of the host or between them, deepened on ½ to completely immersed in tissue or rhizophytes, on the surface only black tips with a rounded outlet. Pseudothecial walls dark brown to brown-black, uniform as in the upper and in the lower parts, consist of 6–8 layers of pseudoparenchymal cells, pigmented amorphously, uniformly in the cell membranes of pseudothecia. Hymenial gelatin from I– to K / I–. Pseudoparaphyses numerous, branched and anastomosing. Asci bitunictae, thickened in the apical parts, with clear "ocular chamber", cylindrical to narrow-club-shaped, with an arrangement of ascospores in one, less often in two rows, I–. Ascospores 2-celled, hyaline, slightly narrowed at the base, without perisporia, the lower cell is slightly narrower than the upper, the tips slightly elongated. Asexual morph: Undetermined (Adapted from Khodosovtsev and Klymenko 2015).

 

Type species: Didymellopsis latitans (Nyl.) Sacc. ex Clem. & Shear

 

Notes: Didymellopsis is characterised by apothecioid, superficial, flattened, discoid or lenticular ascomata, anastomosing, cellular pseudoparaphyses, fissitunicate, cylindrical to clavate, short pedicellate asci and oval to ellipsoid, uniseptate hyaline ascospores. Didymellopsis resembles Rhagadodidymellopsis in having fissitunicate asci, hamathecium of branched and anastomosing, thin interascal filaments and one-septate hyaline ascospores (Grube & Hafellner 1990). Didymellopsis differs from Rhagadodidymellopsis in having non-stromatic perithecioid ascomata, a peridium of rather constant thickness and longer ascospores (Grube & Hafellner 1990). Didymellopsis is also similar to Zwackhiomyces in having apothecioid, superficial ascomata, peridium which is uniform or slightly thicker towards the ostiole but differs in that the former produces ascomata that are at least partially immersed in the host thallus, while species of Zwackhiomyces produce superficial ascomata grouped into a common stroma (Calatayud et al. 2007). Species of Didymellopsis occur on lichens with cyanobacterial photobionts except D. perigena which grows on Catapyrenium squamulosum (Verrucariaceae) probably associated with cyanobacteria nearby the host thallus. Grube and Hafellner (1990) and Vouaux (1913) reported that D. perigena can also occur on Endocarpon, based on a record of Didymella perigena from France. Didymellopsis also resembles Arthopyrenia in having similar asci and ascospores, but they are distinct in that the former has globose or apothecoid and smooth-walled ascomata that grow superficially, mostly occur at the margin of the squamules of the lichen host, while the latter has subglobose to pyriform ascomata that are completely immersed in the host squamules (Fernández-Brime et al. 2020). In this study, we observed two species D. perigena (KHER 11651) and D. pulposi KHER (11994) to illustrate Didymellopsis. Fresh collections are needed as sequence data of Didymellopsis is lacking.

 

 

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