An expanded diversity of oomycetes in Carboniferous forests: Reinterpretation of Oochytrium lepidodendri(Renault 1894) from the Esnost chert, Massif Central, France

March 02, 2021

Christine Strullu-Derrien (1,2), Marc Gèze (3,4), Alan R. T. Spencer (2,5), Dario De Franceschi (6), Paul Kenrick (2), Marc-André Selosse (1,7), Andrew H. Knoll (8)
PLOS One, March 2021. DOI: 10.1371/journal.pone.0247849


335–330 million-year-old cherts from the Massif Central, France, contain exceptionally well-preserved remains of an early forest ecosystem, including plants, fungi and other microorganisms. Here we reinvestigate the original material prepared by Renault and Roche from collections of the Muséum National d’Histoire Naturelle, Paris, and present a re-evaluation of Oochytrium lepidodendri (Renault 1894), originally described as a zoosporic fungus. Confocal laser scanning microscopy (CLSM) was used to study the microfossils, enabling us in software to digitally reconstruct them in three-dimensional detail. We reinterpret O. lepidodendri as a pseudofungus and favour placement within the oomycetes, a diverse clade of saprotrophs and both animal and plant parasites. Phylogenetically, O. lepidodendri appears to belong to a group of oomycetes distinct from those previously described from Paleozoic rocks and most likely related to the Peronosporales s.l. This study adds to our knowledge of Paleozoic eukaryotic diversity and reinforces the view that oomycetes were early and diverse constituents of terrestrial biotas, playing similar ecological roles to those they perform in modern ecosystems.

How Our Software Was Used

Dragonfly was used to explore the morphology and internal contents of the microfossils.

Author Affiliation

(1) Institut Systamatique Evolution Biodiversita, Muséum national d’Histoire naturelle, CNRS.
(2) Department of Earth Sciences, The Natural History Museum.
(3) Centre de microscopie et d’imagerie numerique du museum, Muséum National d’Histoire Naturelle.
(4) Departement AVIV, UMR 7245 MCAM Molecules de communication et Adaptation des Micro-organismes, Muséum national d’Histoire naturelle, CNRS.
(5) Department of Earth Science & Engineering, Imperial College London.
(6) Centre de Recherche en Paléontologie Paris, Muséum national d’Histoire naturelle.
(7) Department of Plant Taxonomy and Nature Conservation, University of Gdańsk.
(3) Department of Organismic and Evolutionary Biology, Harvard University.