Um fóssil de ácaro forético pequeno recuperado por tomografia computadorizada de contraste de fase de raios-X

A minute fossil phoretic mite recovered by phase-contrast X-ray computed tomography

Jason A. Dunlop1,*, Stefan Wirth1, David Penney2, Andrew McNeil3, Robert S. Bradley3, Philip J. Withers3 and Richard F. Preziosi2

Author Affiliations

1Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity, Humboldt University Berlin, 10115 Berlin, Germany

2Faculty of Life Sciences, University of Manchester, Manchester M13 9PF, UK

3Henry Moseley X-ray Imaging Facility, School of Materials, University of Manchester, Manchester M1 7HS, UK

*Author for correspondence (jason.dunlop@mfn-berlin.de).

Abstract

High-resolution phase-contrast X-ray computed tomography (CT) reveals the phoretic deutonymph of a fossil astigmatid mite (Acariformes: Astigmata) attached to a spider's carapace (Araneae: Dysderidae) in Eocene (44–49 Myr ago) Baltic amber. Details of appendages and a sucker plate were resolved, and the resulting three-dimensional model demonstrates the potential of tomography to recover morphological characters of systematic significance from even the tiniest amber inclusions without the need for a synchrotron. Astigmatids have an extremely sparse palaeontological record. We confirm one of the few convincing fossils, potentially the oldest record of Histiostomatidae. At 176 µm long, we believe this to be the smallest arthropod in amber to be CT-scanned as a complete body fossil, extending the boundaries for what can be recovered using this technique. We also demonstrate a minimum age for the evolution of phoretic behaviour among their deutonymphs, an ecological trait used by extant species to disperse into favourable environments. The occurrence of the fossil on a spider is noteworthy, as modern histiostomatids tend to favour other arthropods as carriers.

Acariformes, Astigmata, Histiostomatidae, Acaridae, amber, Eocene

Received September 23, 2011.

Accepted October 18, 2011.

This journal is © 2011 The Royal Society

+++++

FREE PDF GRATIS

DATA SUPPLEMENT/DADOS SUPLEMENTARES