Fungalpedia – Note 2420, Jahnula
Jahnula. Kirschst.
Citation when using this data: Dong W et al. 2020 – Fungalpedia, Ascomycota.
Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig 1
Classification: Aliquandostipitaceae, Jahnulales, Incertae sedis, Dothideomycetes, Pezizomycotina, Ascomycota, Fungi
Saprobic on submerged wood. Sexual morph: Ascomata semi-immersed to erumpent, become superficial with base remaining immersed, solitary or clustered in small groups, globose to subglobose, unilocular, brown to dark brown, membranous, with a stalk-like strand or stoloniferous hyphae attached to the substratum, or covered by sparse hair-like projections, with ostiolate papilla. Peridium variable in thickness, comprising a few layers of relatively large, thin-walled, light brown cells of textura angularis. Pseudoparaphyses cellular, persistent, filiform or hypha-like, hyaline, sparsely septate. Asci 8-spored, bitunicate, fissitunicate, mostly cylindrical, short-pedicellate, with an ocular chamber and sometimes with a faint ring. Ascospores mostly uniseriate, ellipsoid-fusiform, apical cell slightly larger, both cells tapering with rounded ends, reddish brown or dark brown, l-septate, straight or curved (definition sensu stricto from Hawksworth (1984), Hyde and Goh (1999b) and Raja and Shearer (2006)). Asexual morph: Undetermined.
Notes: Jahnula is undoubtedly polyphyletic (Hyde et al. 2013, 2017, 2019; Huang et al. 2018) and Jahnula sensu stricto was mentioned in Huang et al. (2018), and Hyde et al. (2013). Hyde et al. (2013) suggested that taxonomic changes are needed for taxa in Jahnula sensu lato, but more jahnula-like species need to be collected and sequenced. We accept three species,
J. aquatica, J. granulosa K.D. Hyde & S.W. Wong and J. rostrata Raja & Shearer in Jahnula sensu stricto, which have been collected from freshwater habitats (listed below). These three species share common characters in having dark ascomata with few appendages attached to the base, and ellipsoid-fusiform, brown, l-septate ascospores with wider apical cell (Hawksworth 1984; Hyde and Wong 1999; Raja and Shearer 2006). Asci of J. aquatica are cylindrical, those of J. granulosa are obclavate and those of J. rostrata are clavate. Jahnula aquatica has smooth-walled ascospores without a sheath, while J. granulosa has granular-walled ascospores with a thin mucilaginous sheath. Jahnula rostrata is similar to J. granulosa by rough-walled ascospores, but differs in having an irregularly striated pattern. These three species formed a well-supported and stable clade in previous publications (Huang et al. 2018; Hyde et al. 2019).
The type species, Jahnula aquatica commonly occurs in freshwater habitats as listed below. The lectotype of J. aquatica was examined, illustrated and described by Hawksworth (1984). Jahnula aquatica is characterized by ascomata attached to the substratum by subiculum-like hyphae, peridium uneven in thickness, cylindrical asci, elongate-ellipsoid to very broadly fusiform, reddish brown, smooth, moderately thick-walled ascospores without a distinct gelatinous sheath (Hawksworth 1984). The sequences of two isolates R68-1 and R68-2 (not type) were obtained by Raja and Shearer (2006), recognized and used for current phylogenetic analyses (Suetrong et al. 2011a; Huang et al. 2018; Hyde et al. 2019).
Xylomyces chlamydosporus Goos et al. was considered to be the asexual state of Jahnula aquatica based on fusiform chlamydospores produced in culture (Sivichai et al. 2011). However, the phylogenetic analyses did not support this conclusion because J. aquatica and
X. chlamydosporus scattered in different clades within Jahnulales (Campbell et al. 2007; Suetrong et al. 2011a).
We introduce two new genera Neojahnula and Pseudojahnula to accommodate two known species Jahnula australiensis K.D. Hyde and J. potamophila K.D. Hyde & S.W. Wong, respectively. Seven species, i.e. J. bipolaris, J. guttulaspora, J. queenslandica, J. seychellensis, J. submersa, J. sunyatsenii and J. thailandensis, which are phylogenetically distant from J. aquatica, are transferred to Ascagilis K.D. Hyde. Nine species, i.e. J. apiospora, J. appendiculata, J. bipileata, J. dianchia, J. morakotii, J. poonythii, J. purpurea, J. sangamonensis and J. systyla, are placed in Jahnula sensu lato. For convenience and practicality, we have excluded Jahnula systyla K.D. Hyde & S.W. Wong from the key, because we believe it may be phylogenetically related to Aliquandostipite.
Type species: Jahnula aquatica (Kirschst.) Kirschst.
Other accepted species: Species Fungorum – search Jahnula.
Figure 1 – Jahnula aquatica (Material examined: USA, Illinois, Salt Fork Association Lake (SFA Lake), a manmade private lake, on submerged, decorticated wood, 15 October 2002, HAR, R68-1). a Squash mount of ascoma. b Ascus. c Pseudoparaphyses. d, e Ascospores. Scale bars: a = 100 µm, b, c, e = 20 µm, d = 10 µm
References
Entry by
Wei Dong, Faculty of Agriculture and Food, Kunming University of Science and Technology, Kunming 650500, China, Department of Entomology and Plant Pathology, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand, Innovative Agriculture Research Center, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand, Center of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai 57100, Thailand, Institute of Plant Health, Zhongkai University of Agriculture and Engineering, Haizhu District, Guangzhou 510225, China
Published online 21 May 2026