Minutisphaerales » Minutisphaeraceae

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