Fungalpedia – Note 2811, Gymnoascaceae
Gymnoascaceae. Baranetzky.
Citation when using this data: Kandemir H et al. 2022 – Fungalpedia.
Index Fungorum, Facesoffungi, MycoBank, GenBank
Classification: Onygenales, Eurotiomycetidae, Eurotiomycetes, Pezizomycotina, Ascomycota, Fungi
Ascocarps in this family are mostly yellowish, greenish, reddish or brownish shades, with a gymnoperidium composed of a loose network of hyaline or pigmented hyphae. Asci globose to ovoid; ascospores are hyaline, yellowish or greenish, spherical, ovoidal or oblate, smooth- and thick walled, sometimes with equatorial grooves and ridges and/or polar thickenings (Currah 1985; Doveri et al. 2012).
Based on the number of described species, Gymnoascaceae is one of the largest families of Onygenales (Solé et al. 2002b). Members of the family are eutrophic and can be found in soil rich in organic matter, various types of dung, and decaying vegetation. Species (e.g., Gymnoascus reessii) have also been isolated from the lungs of wood rats and prairie dogs (Emmons 1954) without any lesions in the lungs, and they have been found to survive mouse passage without causing disease. This survival ability is similar to that of the dimorphic fungus Emmonsia crescens (now known as Emergomyces crescens), which is commonly carried asymptomatically by terrestrial rodents (Jiang et al. 2020). Survival mechanisms in the lung for such environmental pathogens are mostly related to in vitro and in vivo conidial changes (Jiang et al. 2018, 2020), and for Gymnoascaceae members, these mechanisms are not known to exist.
Skin and nail scrapings and animal hair are the main sources of dermatophytes because of their high keratin content (Currah 1985; de Hoog et al. 2017). Members of Gymnoascaceae are frequently found colonizing similar keratinized material shed from humans and other mammals (Currah 1985). Baiting techniques with horse and/or human hair or pieces of hooves have successfully been used for the selective isolation of keratinolytic Gymnoascaceae and the examination of their gymnothecial structures (von Arx 1986; Sharma and Singh 2013).
Osmotolerance might be another trait that enhances the wide distribution of Gymnoascaceae. Sporendonema casei and Sphaerosporium equinum have repeatedly been isolated from cheese, which seems to be their preferred habitat (Ropars et al. 2012; Hermet et al. 2014). According to available records, almost all strains have only been isolated from the rinds of hard cheeses. This habitat lacks moisture, and the relatively high free fatty acid content makes this part highly acidic compared to the interior of the cheese. In addition, the rind has higher levels of crude protein and salt (calcium and phosphorus) (Davies 1938). The ripening process takes place at low temperatures (4‒18 °C), and given the high acid and salt concentrations, these species can be considered xerophilic and halophilic. However, Scaramuzza et al. (2015) showed that S. casei can also be isolated from the air of cheese processing rooms.
Other members of the family Gymnoascaceae show other types of halotolerance, e.g., Gymnoascus halophilus, from lake sediments and can tolerate NaCl concentrations of up to 22.5% (Zhou et al. 2016). Species found under conditions of extreme dryness, such as Gymnoascus desertorum, may possess similar survival factors. Desert soil colonization can also be enhanced by oligotrophism. Possibly due to the wide range of habitat choices of the members of Gymnoascaceae, physiological trends are apparent in this family, suggesting alternative lifestyles, such as eutrophism on animal dung. Temperature relationships seem equally variable: Gymnoascus stercorarius, found in compost, can grow at temperatures up to 50 °C, while Arachniotus ruber, from coyote dung, requires a low temperature of 5 °C for its isolation (Zhou et al. 2016; Currah 1985).
After the description of the family and the genus Gymnoascus in 1872, 20 genera were included in Gymnoascaceae. Species of the genera were reclassified in the family several times by different researchers, mostly using peridium and ascospore morphology as taxonomic criteria (e.g., von Arx 1986; Currah 1985; Apinis 1964). Gymnascella was introduced by Peck (1884) for the single species Gymnascella aurantiaca from old bones in a damp place. The fungus lacked an ascigerous fruitbody, and asci formed clusters between undifferentiated hyphae. Arachniotus Schroeter (1893) was described as having three species that were originally classified in Gymnoascus: G. candidus Eidam, G. aureus Eidam and G. ruber van Tieghem. Arachniotus candidus (Eidam) Schroeter was considered the generic type species. The genus had snow-white or yellowish gymnothecia and thin-walled peridial elements covering the asci in a net-like form, similar to a fragile membrane (Orr et al. 1977a). Pseudoarachniotus Kuehn (1957) was described to separate some Arachniotus species that lacked discrete ascocarps or peridial elements, formation of croziers and lack of conidia on phialides. Type species was indicated as Pseudoarachniotus roseus. However, in describing this genus, Gymnascella was not taken into account. Later, Pseudoarachniotus was used to accommodate species that could not be classified as either Arachniotus or Gymnascella (Orr et al. 1977a). Petalosporus Ghosh, Orr & Kuehn, with the type species Petalosporus nodulosus, was described as having discrete ascocarps, characteristic enlargements at the nodes of smooth hyphae, which comprise a rudimentary peridium and petaloid arrangement of ascospores in asci (Ghosh et al. 1963). Narasimhella Thirum. & Mathur (1966) (type species, N. poonensis) was described for species with well-developed stipitate fruitbodies without peridium; the stipe is composed of upwards growing hyphal bundles, while the irregularly globular, fertile head portion contains groups of asci. Crozier formation was similar to that of Pseudoarachniotus. The genus Plunkettomyces Orr, represented by the type species Plunkettomyces littoralis, has peridial elements that are smooth or coarsely tuberculate, radiating outward from the centrum or the base of the asci (Orr 1977a). Ascospores were lenticular, with a yellow-orange to orange-brown longitudinal band (Orr 1977a). Plunkettomyces littoralis was thought to represent an intermediate between Gymnascella and Pseudoarachniotus. Disarticulatus Orr, with the type species Disarticulatus devroeyi, had yellow-orange to orange gymnothecia, which tended to disarticulate into components with variously shaped, thick-walled cells (Orr 1977a). Ascospores were described as spherical or ellipsoidal, with a slight lateral bulge (Orr 1977a). Disarticulatus was found to be similar to Petalosporus, except for the absence of the petaloid arrangement of ascospores in the asci. Gymnoascoideus was introduced by Orr et al. (1977b) to describe species lacking gymnothecia but having typical elements with branching at right angles, unsharpened at the apices and covered by asexual spores in and around the ascal clusters. Gymnoascoideus shows discrete gymnothecia lacking appendages, and similar to Petalosporus, its ascospores show a petaloid pattern in the asci, but in contrast, they lack lateral bulges. Gymnoascoideus petalosporus was assigned as the type species. Kraurogymnocarpa Udagawa & Uchiyama, represented by Kraurogymnocarpa lenticulospora, was described with yellowish-green ascomata with a disarticulating reticuloperidium, bivalvate ascospores, and weak cellulolytic activity (Udagawa and Uchiyama 1999a). The discrete ascomata have short spines and straight or slightly curved appendages. Mallochia Arx & Samson was introduced to classify Pseudoarachniotus echinulatus into a separate genus (von Arx and Samson 1986). In Mallochia echinulata, similar to Narasimhella, obovate asci develop from croziers. However ascospores in the latter species are bivalvate, with an equatorial furrow surrounded by two rims and covered with blunt spines (von Arx and Samson 1986).
From this summary of genera attributed to Gymnoascaceae on morphological grounds, it appears that a limited set of characters is used in different combinations to define the genera. Many of these fungi have impressive morphologies, which taxonomists acknowledge. However, re-examination of deposited strains or type materials revealed that the morphology may vary within species. For example, de Vroey (1966) examined several strains of Pseudoarachniotus roseus and noted that the presence or absence of discrete ascocarpic elements was variable, and he consequently regarded P. roseus as a synonym of Arachniotus dankaliensis. Similarly, in describing Arachniotus flavoluteus, Kuehn and Orr (1959) observed some ascal clusters that were devoid of peridial elements, as in Pseudoarachniotus. Phylogenetic studies also indicated that species with slight morphological differences may share the same molecular characteristics (Solé et al. 2002b), and vice versa. A Bayesian inference tree of the ITS locus of Gymnoascaceae showed that members of several of the genera mentioned above are not clearly separated into monophyletic groups; no generic substructure can be recognized that matches the current concepts. In contrast, Sporendonema and Sphaerosporium, which have not been associated with Gymnoascaceae, clustered within this amalgamate.
Phylogenetic results in the current study revealed five groups in the family: Group I Gymnascella, Group II Arachniotus, Group III Gymnoascus, Group IV Narasimhella and Group V Gymnoascoideus. Group names were determined by choosing the well-supported branches with high bootstrap values. Type species for each genus in the group were detected. In the case of more than one type species for different genera in the same group, the oldest type species is maintained to name the group.
Type genus: Gymnoascus Baran., Bot. Ztg. 30: 158 (1872).
Other accepted species: Species Fungorum – search Gymnoascaceae.
References
Apinis AE (1964) Revision of British Gymnoascaceae. Mycol Pap 96:1–56
de Vroey C 1966 – Étude mycologique de Gymnoascaceae isolées de lésions cutanées et de la terre en République de Somalie; note préliminaire. Annales de la Société Belge de Médecine Tropicale 46:457–464.
Orr GF 1977a – New Gymnoascaceae. Mycotaxon 6(1):33–42.
Orr GF 1977b – Another genus of the Gymnoascaceae with swollen septa on peridial elements. Mycotaxon 5(1):283–290.
Peck CH (1884) Report of the Botanist, 1882. Annual Report on the New York State Museum of Natural History 35:125–164
Schroeter J 1893 – Die Pilze Schlesiens. Fam. Gymnoascacei. In: Cohn F (ed) Kryptogamenflora von Schlesien 3(2). J.U. Kern’s Verlag, Breslau, pp. 129–2.
Solé M, Cano J, Pitarch LB, Stchigel AM, Guarro J 2002b – Molecular phylogeny of Gymnoascus and related genera. Studies in Mycology 47:141–152.
Thirumalachar MJ, Mathur PN 1966 – Narasimhella, a new genus of the Gymnoascaceae. Sydowia 19:184–186.
von Arx JA (1986) The Ascomycete genus Gymnoascus. Persoonia 13:173–183
von Arx JA 1986 – The Ascomycete genus Gymnoascus. Persoonia 13:173–183.
Entry by
Hazal Kandemir, Center of Expertise in Mycology, Radboud University Medical Center/Canisius Wilhelmina Hospital, Nijmegen, The Netherlands, Division of Medical Mycology, Faculty of Medicine, University of Cukurova, Adana, Turkey
Published online 25 June 2026