Minutisphaera
Minutisphaera Shearer, A.N. Mill. & A. Ferrer, Mycologia 103(2): 415 (2011)
Saprobic on submerged wood. Sexual morph: Ascomata scattered or clustered in groups, erumpent to superficial, uniloculate, globose to subglobose, brown, with central, rounded ostiole surrounded by black hairs. Peridium thin, composed of textura angularis to globulosa cells. Pseudoparaphyses sparse in young ascomata, becoming abundant with age, cellular, hyaline, septate, simple or branched, embedded in a gelatinous matrix. Asci 8-spored, bitunicate, fissitunicate, ovoid to obclavate, lacking a pedicel, rounded at the apex. Ascospores irregularly arranged, clavate, mostly straight, hyaline to pale brown, 1(–3)-septate, constricted at the septum, multiguttulate, asymmetrical, smooth- or rough-walled when mature, with sheath and filamentous appendages (Ferrer et al. 2011). Asexual morph: Undetermined.
Type species: Minutisphaera fimbriatispora Shearer, A.N. Mill. & A. Ferrer
Notes: All species reported within Minutisphaera were collected from freshwater habitats (Ferrer et al. 2011; Raja et al. 2013, 2015; Bao et al. 2019). The ascospores of Minutisphaera are unusual in being asymmetrical and often equipped with a sheath and filamentous appendages (Ferrer et al. 2011; Raja et al. 2015). The shape and size of ascospores and features of appendages and sheaths are used for distinguishing all species within the genus (see key below).
In the analysis of Raja et al. (2015) BLAST search of ITS sequences revealed that two isolates, Pleosporales sp. 39g (JX244063) and Didymosphaeria sp. TS_04_050 (HQ713763), shared 99% similarity with Minutisphaera aspera. Both strains were isolated as fungal endophytes in previous studies (Grünig et al. 2011). Thus, it was hypothesized that members of Minutisphaerales may lead a dual life as saprobes on submerged wood and as fungal endophytes of trees living in close proximity to rivers and streams. However, additional studies are needed to shed light on the dual ecological lifestyle of Minutisphaera spp.
List of freshwater Minutisphaera species
*Minutisphaera aquaticum D.F. Bao, L. Xu & H.Y. Su, Asian Journal of Mycology 2(1): 309 (2019)
*Minutisphaera aspera Raja, Oberlies, Shearer & A.N. Mill, Mycologia 107(4): 854 (2015)
*Minutisphaera fimbriatispora Shearer, A.N. Mill. & A. Ferrer, Mycologia 103(2): 415 (2011)
*Minutisphaera japonica Kaz. Tanaka, Raja & Shearer, Mycologia 105(4): 966, (2013)
*Minutisphaera parafimbriatispora Raja, Oberlies, Shearer & A.N. Mill, Mycologia 107(4): 855 (2015)
Key to freshwater Minutisphaera species
1. Ascospores with sheath, but lacking appendages......................................... 2
1. Ascospores with sheath and appendages...................................................... 4
2. Ascospores with rough-walled…..................................................... M. aspera
2. Ascospores smoth-walled….......................................................................... 3
3. Ascospores broadly fusiform, with acute apex............................... M. japonica
3. Ascospores fusiform to clavate, with rounded apex.................... M. aquaticum
4. Ascospores 24–36 × 6–8 µm….......................................... M. fimbriatispora
4. Ascospores 18–25 × 4–7 µm....................................... M. parafimbriatispora
Fig. 1 Minutisphaera spp. (Material examined: USA, North Carolina: Rockingham County, Piedmont Plateau, Big Beaver Island Creek, Madi- son, on submerged decorticated wood, 26 April 2013, H.A. Raja & N.H. Oberlies, G427-1, ILLS 72340, holotype; ibid., G156-4, ILLS 72342, paratype). a–c M. aspera (G427-1). a Ascoma on wood. b Ascus. c Ascospores. d–f M. parafimbriatispora (G156-4). d Ascoma in culture. e Asci. f Ascospore with gelatinous sheath constricted at the mid-sep- tum. Scale Bars: a = 100 µm, b, c = 20 µm, d = 50 µm, e, f = 10 µm
References
Bao DF, Hyde KD, Luo ZL, Su HY, Nalumpang S (2019) Minutisphaera aquaticum sp. nov. increases the known diversity of Minutisphaeraceae. Asian Journal of Mycology 2:306–314
Ferrer A, Miller AN, Shearer CA (2011) Minutisphaera and Natipusilla: two new genera of freshwater Dothideomycetes. Mycologia 103:411–423
Grünig CR, Queloz V, Sieber TN (2011) Structure of diversity in dark septate endophytes: from species to genes. In: Endophytes of forest trees. Springer, Berlin, pp. 3–30
Raja HA, El-Elimat T, Oberlies NH, Shearer CA, Miller AN, Tanaka K, Hashimoto A, Fournier J (2015) Minutisphaerales (Dothideomycetes, Ascomycota): a new order of freshwater ascomycetes including a new family, Minutisphaeraceae, and two new species from North Carolina, USA. Mycologia 107:845–862
Raja HA, Oberlies NH, Figueroa M, Tanaka K, Hirayama K, Hashimoto A, Miller AN, Zelski SE, Shearer CA (2013) Freshwater ascomycetes: Minutisphaera (Dothideomycetes) revisited, including one new species from Japan. Mycologia 105:959–976
Recent Genus
1Neochlamydotubeufia
Neohelicomyces
Recent Species
Neohelicomyces submersusNeohelicomyces hyalosporus
Neohelicomyces grandisporus