Megalotremis
Megalotremis Aptroot, Biblthca Lichenol. 44: 124 (1991).
Index Fungorum number: IF 26295; Facesoffungi number: FoF 08077, 16 morphological species (Species Fungorum 2022), 1 species with molecular data.
Lichenized on bark, in tropical regions. Sexual morph: Thallus usually with thin, cartilaginous cortex, rarely ecorticate, greenish grey to white. Photobiont Trentepohlia. Ascomata scattered, usually erumpent, black but at least partly covered by thalline layer, typically carbonaceous, ostiolate, ostiole apical or lateral. Involucrellum present, carbonized. Excipulum dense, consisting of compressed hyphae, appearing prosoplectenchymatous in thin, bleached sections, brown to brown-black. Hamathecium comprising paraphyses, hyaline, straight, branched and anastomosing. Asci (1–)2–8-spored, bitunicate, fissitunicate, cylindrical, short pedicellate, with broad, non-amyloid ocular chamber and fluorescent cap-structures. Ascospores uni-seriate to irregularly arranged, ellipsoid-fusiform, rather large sometimes with the upper cell enlarged, hyaline, uniseptate, with internal, needle-shaped crystals. Asexual morph: Pycnidia rare. Conidia acrogenous, either macro- or microconidia; macroconidia usually aseptate, (globose to) ellipsoid, hyaline; microconidia aseptate, globose to broadly ellipsoid or fusiform, small, hyaline; macro- and/or microconidia in some species aggregated into conglutinate masses sometimes deposited outside the pycnidia. Chemistry: Secondary substances absent (adapted from Hongsanan et al. 2020b).
Type species: Megalotremis verrucosa (Makhija & Patw.) Aptroot
Notes: Megalotremis is characterised by scattered, erumpent ascomata, fissitunicate, cylindrical, short pedicellate asci, ellipsoid-fusiform, hyaline, uniseptate ascospores. Aptroot (1991) placed Megalotremis in Trypetheliaceae based on the endospore thickenings and ‘internal folds’ of the ascospores inferred as crystals. Harris (1995) synonymized Megalotremis under Anisomeridium based on the corticate thalli and pointed out that the second species M. biocellata might be related to Arthopyrenia sensu lato. Megalotremis differs from Anisomeridium in having a corticate thallus and large ascospores with endospore thickenings (Aptroot et al. 2008). Megalotremis also differs from Trypetheliopsis in lacking campylidioid asexual morphs. Hongsanan et al. (2020b) provided an account of the species included under Anisomeridium sensu lato by Harris (1995) based on morphology of thallus, ascospores size and endospore thickenings and provided four combinations, Megalotremis elegans, M. holopolia, M. immersa and M. monospora. Hongsanan et al. (2020b) also considered M. biocellata as a synonym of Constrictolumina malaccitula based on evidences from protologues. Only Megalotremis verrucosa has molecular data in GenBank (LSU, SSU, TEF-1 and mt-SSU). Megalotremis is a distinct genus in Monoblastiaceae.
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