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| Rugososporomyces lavoisierae Strullu-Derrien & Schornack, in Strullu-Derrien, Wightman, McDonnell, Evans, Fercoq, Kenrick, Ferrari et Schornack, 2025. |
Mycorrhizal associations between fungi and plants are a fundamental aspect of terrestrial ecosystems. Mycorrhizas occur in c. 85% of extant plants, yet their geological record remains sparse. Rare fossil evidence from early terrestrial environments offers crucial insights into these ancient symbioses, but visualizing fossil fungi at the microscale within plant tissues is challenging.
Here, we combine confocal laser scanning microscopy and fluorescence lifetime imaging microscopy (FLIM) to investigate a newly identified fungus and cellular structures of a 407-Myr-old plant from the Windyfield Chert, a stratigraphically distinct fossiliferous unit from Rhynie (Scotland). We also applied Raman spectroscopy to investigate the carbon framework of both fungal and plant tissues.
This integrative approach revealed fungal structures in unprecedented detail. The fungus, Rugososporomyces lavoisierae gen. nov., sp. nov., exhibits features resembling extant Glomeromycotina arbuscular mycorrhizal fungi. This is the first record of mycorrhizas from the Windyfield Chert. FLIM further distinguished features at the subcellular level, while Raman spectroscopy showed that fungal arbuscules and vesicles of the plant water-conducting cells underwent geological alterations, resulting in a similar chemical composition.
These findings expand our understanding of ancient and extremely rare plant–fungal symbioses and highlight the potential of confocal-FLIM for advancing palaeobotanical research.
Keywords: AM mycorrhizas, confocal scanning laser microscopy, Devonian, fluorescence lifetime imaging microscopy, fossil record, plant symbioic fingus, Raman Spectroscopy, 3D imaging
A morphologically distinct endomycorrhizal fungus colonizing the plant Aglaophyton majus
Systematics
Kingdom – Fungi R.T. Moore.
Phylum – Mucoromycota Doweld, emend. Spatafora & Stajich.
Subphylum – Glomeromycotina (C. Walker and A. Schüßler) Spatafora & Stajich, subphylum and stat. nov.
Class – Glomeromycetes Caval.-Sm.
Order – Incertae sedis – Strullu-Derrien & Schornack.
Genus – Rugososporomyces Strullu-Derrien & Schornack gen. nov.
Etymology – Rugoso refers to the nature of the spore wall; sporo is from the Greek spora meaning spore; myces is the Latin word for fungus.
Genus diagnosis – Fungus with aseptate intercellular hyphae with H branching, spores, vesicles and intracellular arbuscules. Differs from other fungi in the Rhynie Chert in the following ways: spore wall possibly bilayered, with a relatively thick, rugose wall; smaller diameter of the branching hyphae; hyphae terminating in a spore are either smaller or larger than other hyphae; the ratio of spore diameter to hyphal width is smaller; the spores are comparatively either smaller or larger.
Species – Rugososporomyces lavoisierae Strullu-Derrien & Schornack sp. nov.
Etymology – In honor of Marie-Anne Paulze de Lavoisier (1758–1836), who was a collaborator of her husband, Antoine Laurent de Lavoisier and was his laboratory assistant. The scientific collaboration of this husband-wife team is perhaps unique among the giants of respiratory physiology (West, 2013). Together, they pioneered Physiology and established the basis of modern Chemistry, two areas relevant to our study.
Species diagnosis – Branched hyphae 3.5–6.5 μm in diameter; unbranched hyphae 7 μm in diameter when terminating in a spore and 4 μm in diameter when terminating in a vesicle; basal stalk of the arbuscules 3.5 μm in diameter. Spores globose, up to 74 μm in diameter, with a 3.1 μm thick rugose and possibly bilayered wall. Subtending hypha closed by a septum. Vesicles range from globose (up to 39 μm in diameter) to elongate (41 μm wide, 50 μm long).
Holotype – specimens in slide no. NMS G.2022.11.48.1 at the National Museum of Scotland, Edinburgh. Fig. 1.
Locality – Rhynie, North-West of Aberdeen (Scotland): Windyfield Cherts Unit (Rice & Ashcroft, 2004).
Age – Lower Devonian (407.1 ± 2.2 Ma) (Mark et al., 2011).
Christine Strullu-Derrien, Raymond Wightman, Liam Patrick McDonnell, Gareth Evans, Frédéric A. Fercoq, Paul Kenrick, Andrea C. Ferrari and Sebastian Schornack. 2025. An arbuscular mycorrhiza from the 407-million-year-old Windyfield Chert identified through advanced fluorescence and Raman imaging. New Phytologist. DOI: doi.org/10.1111/nph.70655 [12 November 2025]
