Jahnula aquatica
Anamorph: not known.
Teleomorph: stromata absent. Ascomata 250-400 (-500) µm diam., arising singly or in small clusters, ± superficial but sometimes immersed in surface silt, attached to the substratum by subiculum-like hyphae, subglobose to broadly obpyriform, the base often slightly immersed, black. Ostiole papilliform, scarcely projecting. Peridium variable in thickness, mainly 30-80 µm thick, often thickest in the upper parts, not carbonaceous, unchanged in potassium hydroxide, composed of several layers of reddish brown subglobose to polyhedral cells that are moderately thick-walled and very variable in size, the outermost 20-30 µm diam. with slightly verruculose walls, the inner becoming radially compressed, less deeply pigmented, mainly 15-20 µm long and 4-8 µm wide; base of the peridium continuous, similar to the sides. Periphyses absent. Interascal tissue of trabeculate pseudoparaphyses 1.5-2.5 µm diam., persistent, filiform, branched and anastomosing, rarely septate, not reacting with iodine. Asci arising from the base of the ascomatal cavity, 180-220 x 18-22 um, cylindrical, fairly long-stalked, fissitunicate, with an ocular chamber visible when young, when mature with a short apical cylinder or broad rectangular indentation, possibly with some annular apical apparatus not reacting with iodine, 8-spored. Ascospores ± uniseriately arranged, (30-)33-36 (-41) x (11-)14-16.5 µm, elongate-ellipsoidal to broadly fusiform, the apices usually acute to obtuse with one or both apical regions sometimes slightly attenuated, 1-septate, often slightly inaequilateral, usually slightly constricted at the septum, reddish brown, thick-walled, usually with numerous small guttules, smooth, without a distinct gelatinous sheath when mature.
Not formally assessed, but the species has only been recorded from two sites in GB&I. Its habitat is under-surveyed and populations may be vulnerable to various threats including pollution and variation in water level.
In GB&I, recorded from VC3 S Devon and VC17 Surrey.
On rotten submerged decorticated wood, presumably saprobic.