Fungalpedia – Note 665, Paramicrothyrium
Paramicrothyrium H.X. Wu & K.D. Hyde
Citation when using this data: D. S. Marasinghe et al. 2023 (in prep.) – Fungalpedia, Ascomycota.
Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig. 1
Classification: Microthyriaceae, Microthyriales, Dothideomycetidae, Dothideomycetes, Pezizomycotina, Ascomycota, Fungi
Epiphytic and saprobic on leaves. Superficial mycelium indistinct or absent. Sexual morph: Thyriothecia superficial, scattered to gregarious, flattened, circular, dark brown to brown, membranaceous with an irregular ostiole, in section lenticular, basal layer poorly developed. Upper wall comprising radiating parallel angular cells branching at the margin. Peridium comprising two layers, outer layer with cells of textura epidermoidea, inner layer with cells of textura angularis. Hamathecium with or lacking hyaline, filiform pseudoparaphyses. Asci 8-spored, bitunicate, fissitunicate, cylindrical to cylindro-clavate or clavate, apedicellate or short pedicellate. Ascospores 1–2-seriate, fusiform-clavate, 1-septum, hyaline, sometimes ciliate (Wu et al. 2011a). Asexual morph: Pycnothyria superficial, flattened, orbicular, dark brown to black, poorly developed basal layer, with irregular, central ostiole, irregularly rounded at the margin. Upper wall composes of brown cells of textura angularis, radiating in irregular, parallel lines from center to the outer rim. Conidiogenous cells evanescent. Conidia 1-septum, hyaline, cylindrical with obtuse ends, straight or slightly curved, smooth-walled with small guttules (Tennakoon et al. 2023).
Notes: Wu et al. (2011a) introduced Paramicrothyrium with the type species of P. chinensis to accommodate a microthyrium-like taxon. Paramicrothyrium resembles Microthyrium by its flattened, circular, dark brown to brown, ostiolate thyriothecia with radially arranged cells and fusiform to clavate, 1-septum, hyaline ascospores. However, it differs from Microthyrium by having cylindro-clavate asci and the irregular ostiole without a prominent darkened ring (Wu et al. 2011a). Tennakoon et al. (2023) established the asexual morph of Paramicrothyrium bambusae which was collected from dead leaves of Bambusa vulgaris in Thailand (Fig. 1c). The morphology hyaline, cylindrical conidia resembles conidia of Cylindrohyalospora, however, Paramicrothyrium has relatively shorter conidia.
Type species: Paramicrothyrium chinensis H.X. Wu & K.D. Hyde [as ‘chinensis’], Fungal Diversity 51(1): 204 (2011).
Other accepted species: Species Fungorum – search Paramicrothyrium.
Figure 1 – Microthyrium microscopicum. a Thyriothecia. b Development of immature thyriothecia. c Ascus. d Ciliate ascospores. Scale bars are not mentioned. Redrawn from Ellis (1976)
References
Ellis JP 1976 – British Microthyrium species and similar fungi. Trans Br Mycol Soc 67:381–394.
Entry by
Diana Sandamali Marasinghe, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai, 57100, Thailand School of Science, Mae Fah Luang University, Chiang Rai, 57100, Thailand, Mushroom Research Foundation, 128 M.3 Ban Pa Deng T. Pa Pae, A. Mae Taeng, Chiang Mai, 50150, Thailand
Published online 29 August 2023