title: A Carboniferous Mite on an Insect Reveals the Antiquity of an Inconspicuous Interaction.
abstract: Symbiosis [1], understood as prolonged interspecific association, is as ancient as the eukaryotic cell [2, 3]. A variety of such associations have been reported in the continental fossil record, albeit sporadically. As for mites, which as a group have been present since the Devonian (ca. 390 mya) [4, 5] and are involved in a tremendous variety of modern-day symbioses, reported associations are limited to a few amber-preserved cases [6-11], with the earliest instance in the Cretaceous (ca. 85 mya) [11]. As a consequence, the antiquity and origin of associations involving small-sized mites and larger animals are poorly understood. Here we report, recovered from the Carboniferous Xiaheyan locality (ca. 320 mya), an oribatid mite located on the thorax of an extinct relative of grasshoppers, crickets, and katydids [12]. The mite was investigated using several methods, including phase-contrast tomography. The detailed morphological data allowed the placement of the mite in a new family within Mixonomata, whose fossil record is thus extended by ca. 250 Ma. Specimen and abundance distribution data derived from the fossil insect sample indicate that specimens from the corresponding excavation site were buried rapidly and were sub-autochthonous, indicating a syn vivo association. Moreover, the mite is located in a sequestered position on the insect. The observed interaction best fits the definition for phoresy, in which the benefit is transport and protection for the mite. This discovery demonstrates that this association, a trait shared by representatives of the most speciose mite taxa, arose very early during mite evolution.
authors.affiliation: Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P, UMR 7207), Sorbonne Universités, MNHN, CNRS, UPMC-Paris6, Muséum National d'Histoire Naturelle, 57 Rue Cuvier, CP 38, 75005 Paris, France.
authors.forename: Ninon
authors.initials: N
authors.lastname: Robin
authors.affiliation: Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P, UMR 7207), Sorbonne Universités, MNHN, CNRS, UPMC-Paris6, Muséum National d'Histoire Naturelle, 57 Rue Cuvier, CP 38, 75005 Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Béthoux
authors.affiliation: Arthropoda Laboratory, Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya Ulitsa 123, Moscow 117647, Russia.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Sidorchuk
authors.affiliation: College of Life Science, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing 100048, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Cui
authors.affiliation: College of Life Science, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing 100048, China.
authors.forename: Yingnan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P, UMR 7207), Sorbonne Universités, MNHN, CNRS, UPMC-Paris6, Muséum National d'Histoire Naturelle, 57 Rue Cuvier, CP 38, 75005 Paris, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Germain
authors.affiliation: Synchrotron SOLEIL, BP 48 Saint-Aubin, 91192 Gif-sur-Yvette, France.
authors.forename: Andrew
authors.initials: A
authors.lastname: King
authors.affiliation: IPANEMA, CNRS, Ministère de la Culture et de la Communication, Université de Versailles, USR 3461, Université Paris-Saclay, 91192 Gif-sur-Yvette, France.
authors.forename: Felisa
authors.initials: F
authors.lastname: Berenguer
authors.affiliation: College of Life Science, Capital Normal University, 105 Xisanhuanbeilu, Haidian District, Beijing 100048, China. Electronic address: rendong@mail.cnu.edu.cn.
authors.forename: Dong
authors.initials: D
authors.lastname: Ren
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002681:China; D005580:Fossils / Q000033:anatomy & histology; D007313:Insecta / Q000033:anatomy & histology / Q000502:physiology*; D008925:Mites / Q000033:anatomy & histology / Q000145:classification* / Q000502:physiology*; D010802:Phylogeny; D013559:Symbiosis
keywords: Archaeorthoptera; Carboniferous; Ningxia; fossil mite; phoresy; symbiosis