Rhizophydites matryoshkaegen. et sp. nov. (Fossil Chytridiomycota) on Spores of the Early Land PlantHorneophyton lignierifrom the Lower Devonian Rhynie Chert

Abstract

Premise of research. As our understanding of the importance of fungi in ecosystems today increases, we are still in the early stages of appreciating their roles in the past. The famous Early Devonian Rhynie chert contains a remarkable diversity of fungal fossils and copious evidence of fungal interactions; however, only relatively few of them have been described.Methodology. Thin sections of the chert were studied at high magnification in transmitted light. Images of fossils were captured digitally and processed in Adobe Photoshop.Pivotal results. A distinct eucarpic, monocentric chytrid (Chytridiomycota), Rhizophydites matryoshkae gen. et sp. nov., occurs on partially degraded in situ spores of the early land plant Horneophyton lignieri. Zoosporangia are epibiotic, usually spheroidal and less than 30 mm in diameter, and inoperculate, and they possess one to four discharge papillae or short tubes. Small bodies present within and outside many of the zoosporangia are suggestive of encysted zoospores and germinating zoospore cysts. Several specimens comprise two or more successive generations of zoosporangia occurring one inside another, a feature that allows for a direct comparison of the fossils with modern Rhizophydium (Rhizophydiales).Conclusions. The discovery of R. matryoshkae interacting with the spores of H. lignieri expands our knowledge of the biological relationships that define complexity in early continental ecosystems and provides a new calibration point that can be used to align molecular clock estimates with fossil evidence in the discussion of chytrid evolution.

Entophysalis in the Rhynie chert (Lower Devonian, Scotland): implications for cyanobacterial evolution

“…Images obtained were processed in the Leica Application Suite v. 4.0 software with additional enhancement of brightness and contrast in Adobe Photoshop (for details of microscopy and image optimisation, refer to Krings et al . 2021). Cell unit diameters were measured with the freeware ImageJ software ().…”

“…The section was studied (a) in Edinburgh, using a Leica DM2700 P petrographic microscope (configured for Koehler illumination with a 100× oil-immersion objective), and photographed in transmitted light with a Leica DFC 420c camera and (b) in Munich, using a Leica DM LB2 microscope with a Jenoptik Gryphax Naos camera. Images obtained were processed in the Leica Application Suite v. 4.0 software with additional enhancement of brightness and contrast in Adobe Photoshop (for details of microscopy and image optimisation, refer to Krings et al 2021). Cell unit diameters were measured with the freeware ImageJ software (https://imagej.…”

An early snapshot of plant–herbivore interactions: Psilophyton diakanthon sp. nov. from the Early Devonian of Gaspé (Quebec, Canada)

“…In most plants, reduction of water loss is achieved most effectively by dense trichomes, which tend to be less robust and are usually slender, filamentous, and less energetically expensive to produce, even at high densities. A role of the spines in climbing is equally unlikely, given their consistent upward orientation and morphological dissimilarity with spinescent emergences that represent climbing adaptations (e.g., Krings et al, 2021), and considering the scarcity of other plants large enough to provide climbing support among the coeval vegetation. On the other hand, attachment between neighboring individuals, or between ramets, in semi-self-supporting plants does not require emergences that have regular morphologies and, indeed, is best achieved through emergences that have irregular shapes.…”

Fossils of parasitic fungi

“…Rhizophydites matryoshkae is a monocentric chytrid from the Rhynie chert that parasitizes spores of the land plant Horneophyton lignieri (Fig. 1C; Krings et al ., 2021). Zoosporangia are epibiotic, inoperculate, and possess 1-4 discharge papillae or short tubes.…”