I was wondering if someone could help with this aquatic fungus, found on a deciduous branch in a stream in Sweden. Perithecia immersed, elongated, with a more or less elongated neck. It has two-celled spores, hyaline when they are inside the asci, but brown, 4-celled and finely warty when senescent, 24-28 x 9-10 µm. Hamathecial filaments are cylindrical as well. The photos I send are taken from dead material.

Looking at the available literature I have, I wonder if it might conform to Lentithecium fluviatile, but the spores did not have any sheath when I looked at it fresh (I only used water) and the perithecia seem more elongated like in some Lophiotrema. Any other possibility?

Thank you in advance!

Cheers,

Ibai.

Yannick Mourgues, 13-06-2015 21:09

Re : Aquatic Pleosporales (Lentithecium?)

Hello.
It reminds me more L. aquaticum then L. fluviatile.
The wood around ascomata seems to be dark-grey colored. Spores dimensions fits well : 25-30x8-12um in Zhang & Co. : http://www.fungaldiversity.org/fdp/sfdp/FD38-13.pdf
They are broadly fusiform with rounded ends, hyaline, 2-celled and four celled with age, constricted at the septum, they should have four refractive guttules before beeing dried.
You should check the presence or not of gel sheat in Indian ink. Not easy to see. Impossible to see in water only, I think.
We have here in France many recolts of Lentithecium cf. aquaticum lacking sheat around spores. Is it possible for you to send me a part of your recolt ?
Yannick

Jacques Fournier, 26-06-2015 14:58

Re : Aquatic Pleosporales (Lentithecium?)

Hi Ibai,
clearly L. aquaticum. The sheath around the ascospores is most often visible in water but it stains readily in aqueous nigrosin (photo attached).
The brown verrucose senescent ascospores are rarely encountered and may be misleading.
Cheers,
Jacques

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