Bryoparasitic Pezizales

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Octospora bicarpa Döbbeler, Büschlen & Eckstein
Ascomycete.org 13(2): 85 (2021)
MycoBank: MB 838886

Type: Switzerland, Lucerne, Werthenstein, hiking path from Staldigstrasse towards the alp, in a drainage ditch on the edge of forest, 47.03146°N, 8.10094°E, 910 m a.s.l., on Lewinskya speciosa growing on the bark of a living Sambucus nigra, 2020-Nov-07, A. Büschlen #1 (both morphs; holotypus ZT Myc 64623)

Octospora bicarpa Octospora bicarpa
1: Octospora bicarpa, apothecia on shoot of Lewinskya speciosa, holotype, image by A. Büschlen 2: Octospora bicarpa, spores in water, Switzerland, Badi, A. Büschlen, 2021-Feb-05, image by A. Büschlen
Apothecia: 450–800 µm diam., 400 µm high, turbinate or disc-like with a short stipe, at first margin bent inwards, later with a plane or slightly deepened disk, light to dark orange, rarely yellowish, felty on the outside, rim inconspicuous
Excipulum: seen from the outside with longitudinally arranged, straight or waved, 5–7(–8) µm thick hyphae (textura porrecta) containing numerous yellowish droplets, cell walls moderately thickened
Paraphyses: filiform, hardly ramified in the lower part, 2–2.5(–3) µm wide, end cells straight, not or hardly widened
Asci: cylindrical, less often claviform, (115-)125-150(-157) x (14-)15-17(-18) µm, 8-spored (but often only with 6 or rarely 4 spores, degenerating spores recognizable), spores arranged uniseriately to sometimes apically biseriately, discharged asci much longer than mature ones
Ascospores: ellipsoidal, colourless, (15-)16-19(-20) x (9-)10-12 µm, with 1(2) large, light yellowish oil-bodies 5-8(-9) µm diam., epispore delicately rough
Host: Lewinskya speciosa (Orthotrichum speciosum)
Infectious structures: infects the stem and leaf cells, appressoria seen from above elliptical, apically sometimes extended, (in CB) 20–27 µm long, 10–13 µm wide, 10–15 µm high, 1-or 2- (rarely 3-)celled, sessile or stiped, with 1–3 µm thick walls, 2-celled appressoria with a wider distal cell and a smaller, often claviform proximal cell, the distinction between a stipitate, 1-celled appressorium and a sessile 2-celled is sometimes impossible
Conidiomata: sporodochia-like, reduced, of varying size and shape, almost colourless to light brown, with an uneven surface, consisting of a few-layered basal stroma of large cells and condiophores, less than 100 to ca. 300 µm long, 90–120(–140) µm high, shape strongly determined by the colonized microsite
Conidia: dry, numerous, colourless, globose to subglobose, (13-)16-21(-25) x (14-)16-20(-21) µm (without hilum), wall 0.5-1.5(-2) µm thick, hilum slightly prominent, 1-1.5 µm long, 2-2.5 µm wide, not always recognizable, epispore delicately warty or spiny, cyanophilous, cytoplasm of mature conidia often does not react with cotton blue
Habitat: on the epiphytic moss Lewinskya speciosa (Orthotrichum speciosum)
Distribution: Switzerland

References:
  • Döbbeler P., Büschlen A. & Eckstein J. 2021. Octospora bicarpa sp. nov. (Pezizales), the first species of the bryophilous genus Octospora Hedw. with ameroconidia. - Ascomycete.org 13: 85–91. DOI
Images:
Octospora bicarpa Octospora bicarpa
3: Octospora bicarpa, conidioma whith conidia in leaf axil of Lewinskya speciosa stained with cotton blue, Switzerland, Unterägeri, A. Büschlen 2020-Nov-27, image by A. Büschlen 4: Octospora bicarpa, conidia stained with cotton blue, Switzerland, Unterägeri, A. Büschlen 2020-Nov-27, image by A. Büschlen

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