E.B.G. Jones, Systema Ascomycetum 10: 8. 1991.


Sordariomycetes, Subclass Hypocreomycetidae






Iwilsoniella E.B.G. Jones, Systema Ascomycetum 10: 8 (1991)

Type and marine species

Iwilsoniella rotunda E.B.G. Jones, Systema Ascomycetum 10: 8. 1991.

Index Fungorum Number: 128203                         Faceoffungi Number: N/A

Saprobic on wood, sexual morph: Ascomata: 250-400 µm high x 200-230 µm diam., subglobose, dark brown, membranous, superficial or immersed, solitary or gregarious, ostiolate, papillate. Peridium: 10-24 µm thick, composed of two types of cells, outer layer of rectangular, thick-walled and melanized cells, inner layer of thin-walled, pseudoparenchymatous cells. Necks: (100-)250-300 x 50-60 µm, periphyses absent. Asci: 55-75 x 20-28 µm, thin-walled, unitunicate, 8-spored, clavate, deliquescing early, pedicellate. Catenophyses: absent. Ascospores: 12-18 µm, hyaline, round, thin-walled, 1-celled, not appendaged. Asexual morph: Undermined.

Description from Jones (1991)


Key references:

Hyde KD, Moss ST, Jones EBG (1989). Attachment studies in marine fungi. Biofouling 1: 287– 298.

Jones EBG (1991). Iwilsoniella rotunda, a new pyrenomycete genus and species from wood in a water cooling tower. Systema Ascomycetum. 10: 7–12.

Jones EBG (1994). Fungal adhesion. Mycological Research 98: 961-981.

Sakayaroj J, Pang KL, Jones EBG (2011). Multi-gene phylogeny of the Halosphaeriaceae: its ordinal status, relationships between genera and morphological character evolution. Fungal Divers. 46: 87–109.

Type & Location:
Other Specimens:
Saprobic on wood in a water-cooling tower run on brackish to full seawater.
Pertinent Literature:
Description from Jones (1991)
NOTES: Iwilsoniella rotunda was initially found on wood test blocks exposed in a water cooling tower at Stella North Power Station, UK, run on seawater and has been widely used in further studies on ascospore dispersal and attachment (Hyde et al. 1989). In that study the fungus was referred to as Ascomycete “A” and showed that its ascospores were easily detached when subjected to shear stress (Hyde et al. 1989). Iwilsoniella rotunda as a marine fungus is unusual in that it does not have elaborate ascospores appendages (Jones 1994) and resembles the those of other marine ascomycetes e.g. Anisostagma, Moana and Thalassogena. The lack of periphyses and catenophyses in Iwilsoniella distinguish it from Anisostagma. The lack of ascospore appendage discriminates it from Moana which has strap-like uncoiling appendages. The deliquescing asci without apical structures in Iwilsoniella differentiate it from Thalassogena. Although Iwilsoniella lacks appendages the spore wall has membranous material which appears to peel off the spore wall (Hyde et al. 1989, Jones 1991). The species is known only from the original site Northumberland, United Kingdom. There are no cultures or sequence data available for Iwilsoniella rotunda and the species needs to be recollected to confirm its placement in the Halosphaeriaceae (Sakayaroj et al. 2011).


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