Fossil mycoparasite like extant Trichoderma
deutsche Version

fungus hyphae, mainly straightFungus hyphae in Rhynie chert are often surprisingly straight (Fig.1). Hence, wavy or curly hyphae grown along straight ones come as another surprise (Figs.2,3). This phenomenon is known from the thoroughly investigated extant fungus Trichoderma, some of whose species can turn to a parasitic way of life [1]. So it can be assumed that the wavy fossil hyphae most probably are parts of a parasitic fungus with a similar way of nutrient uptake from the host as known from the extant Trichoderma.

Fig.1: Fungus hyphae, or fused bundles thereof,
          of mainly straight aspect. Width of the image 4mm.

Fig.2-5: Irregularly wavy parasitic hyphae grown along straight ones.
          Width of the images 3.2mm, 2.6mm, 1.3mm, 1.3mm.
          Same scale as Fig.1.

wavy fungus hyphae
wavy fungus hyphae

wavy fungus hyphaewavy fungus hyphaeThis fossil evidence is compatible with recent observations on Trichoderma but one fossil structure has been found which indicates that the matter is more complex than a wavy parasite clinging to a straight hypha, as on the left of Fig.5, enlarged in Fig.6. wavy hypha on straight one

  Fig.6 (right): Detail of Fig.5, same sample as Fig.1.
                                                             Width of the image 0.18mm.

 An irregularly wavy hypha is seen connected to a straight one. What has been going on here is far from obvious. According to [1], "Trichoderma coils around or grows along the host hyphae" upon contact but no host hypha is near which could have induced the waviness in Figs.5,6. Perhaps the host hypha has become completely "eaten up" by the parasite, as it is known from Trichoderma species.
The hyphae resembling Trichoderma have been taken from 4 chert samples. Apparently they serve as first fossil evidence of Trichoderma and of the conclusion drawn from genome sequence analysis [2]: "Mycoparasitism is an ancient life style of Trichoderma."
Trichoderma species are commercially grown and successfully used in plant protection [1,2]. This is briefly mentioned in [3] without reference to wavy fossil hyphae.
"T. virens possesses combinations of traits within a single organism that are usually associated with distinct species of symbionts or pathogens" [4]. From the similar aspect of the fossil fungi in these pictures and T. virens in [4] it may be concluded that the ancient species, too, possibly possessed this peculiar combination of traits.

H.-J. Weiss     

[1]  K.E. Borkovich, D.J. Ebbole: Filamentous Fungi. ASM Press 2010, p.676.
[2]  C.P. Kubicek: Comparative genome sequence analysis underscores mycoparasitism as the ancestral life style of Trichoderma. Genome Biol. 2011; 12(4): R40.
[3]  T.N.
Taylor, M. Krings, E.L. Taylor: Fossil Fungi, Elsevier 2015, p.251.
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