Fossil mycoparasite like extant Trichoderma (3)
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Since the mycoparasite Trichoderma, which is of agricultural relevance, has never been found as a fossil [1], it seems appropriate to present more pictures from the Rhynie chert, in addition to the previously presented ones [2], of a Lower Devonian fungus similar to the extant parasite.
parasite hyphaparasite hyphae
Fig.1 (left): Undulating hypha grown in water, possibly contacting a thinner one, all silicified together with the bottom below.
Image width 2mm.

Fig.2: Irregularly curled branching hypha; straight branching hypha above.
Image width 1.5mm.

Fungus hyphae seen in the Rhynie chert are most often unexpectedly straight, a feature apparently not only due to growing in water but to some not yet known reason. Hence, a few wavy hyphae among lots of (partially) straight ones are conspicuous. Undulating hyphae growing along straight ones did not arouse attention as fossils [3] until the striking similarity to the extant parasitic fungus Trichoderma was noticed in 2017 [2]. Their aspect may vary between wavy in a more or less regular way as in Fig.1, curly as in Figs.2-4, or fuzzy with small wavy and curly components as in Figs.5,6.
parasite hypha parasite hyphaparasite hyphaeparasite hyphae

Figs.3,4 (left): Curly hyphae beset with microbes seen as tiny dark dots. Image widths 0.6mm, 0.5mm.

Figs.5,6: Hyphae of fuzzy aspect with wavy or curly parts.
Image widths 0.6mm, 0.8mm.

All pictures of same scale. Taken by J. Gardavsky.

The straight hyphae which the parasite had preyed upon are most often no more seen, probably owing to decay.
Several details not related to parasitism are also offered by Fig.1. It provides a rare view not only of the water where the fungi had grown but also of the soil beneath with mineral debris and organic residues. Two of the mineral grains on the left can be identified as stacks of mica platelets. The black objects are most probably Aglaophyton spores. The dark layer seems to be dead microbes. A cross-section of a twice coated hypha is seen in the water on the right.

Sample: Rh2/4, obtained from Shanks in 1998, cut into 4 parts, Part2 returned. Part1 (slab, given to J. Gardavsky): Figs.2,3,6; Part3 (slab, in the own collection): Figs.1,4,5.

H.-J. Weiss     2019

[1]  C.P. Kubicek: Comparative genome sequence analysis underscores mycoparasitism as the ancestral life style of Trichoderma. Genome Biol. 2011; 12(4): R40.
[2]  H.-J. Weiss:, Rhynie Chert News 109, 111.
[3]  T.N. Taylor, M. Krings, E.L. Taylor: Fossil Fungi, Elsevier 2015, p.251.

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