DOI: 10.5061/dryad.pnvx0k6nw
title: The skeletomuscular system of the mesosoma of Formica rufa workers (Hymenoptera: Formicidae)

description: The mesosoma is the power core of the ant, containing critical structural
 and muscular elements for the movement of the head, legs, and metasoma. It
 has been hypothesized that adaptation to ground locomotion and the loss of
 flight led to the substantial rearrangements in the mesosoma in worker
 ants, and that it is likely the ant mesosoma has undergone functional
 modifications as ants diversified into different ecological and behavioral
 niches. Despite this importance, studies on the anatomy of the ant
 mesosoma are still scarce, and we have little understanding of important
 variation across the ant phylogeny. Recent advances in imaging techniques
 have made it possible to digitally dissect small insects, to document the
 anatomy efficiently and in detail, and to visualize these data in 3D. Here
 we document the mesosomal skeletomuscular system of workers of the red
 wood ant Formica rufa Linnaeus, 1761, and use it to establish 3D atlas of
 ant anatomy that will serve as reference work for further studies. We
 discuss and illustrate the configuration of the skeletomuscular components
 and the function of the muscles in interaction with the skeletal elements.
 This anatomical evaluation of a “generalized” ant provides a template for
 future studies of the mesosoma across the radiation of Formicidae, with
 the ultimate objective of synthesizing structural, functional, and
 transformational information to understand the evolution of a crucial body
 region of ants.
description: Most of the data presented
 in the current study is based on adult workers of <i>Formica rufa
 </i>preserved in ethanol (collection code FHG01185: Germany, Hessen,
 Darmstadt, Prinzenberg, 49.836565°, 8.664995°, 240 m, forest edge and open
 area, 20.IV.2016, leg. F. Hita Garcia). Two<i> F. rufa
 </i>specimens (unique specimen identifiers: CASENT0741316 and
 CASENT0741323) were used for µCT-scanning of mesosoma and the middle leg.
 In order to achieve a higher quality scan, the middle leg was detached
 from the body and scanned individually. The specimens were stained in
 iodine solution one week prior to the scanning date.  The µCT-Scanner used was a Zeiss
 Xradia 510 Versa 3D X-ray microscope operated with the Zeiss
 Scout-and-Scan Control System software (version 14.0.14829.38124) at the
 Okinawa Institute of Science and Technology Graduate University, Japan.
 The scanning parameters chosen consisted of a 40 kV (75 μA) / 3 W beam
 strength with 4s exposure time for the thorax and 7s for the leg under a
 4x magnification, which resulted in a voxel size of 2.97 μm and 1.40 μm
 respectively. 3D reconstructions of the resulting scan projection data
 were done with the Zeiss Scout-and-Scan Control System Reconstructor
 (version 14.0.14829.38124) and saved in txm file format. Postprocessing of
 txm raw data was done with Amira 2019.2 software (Visage Imaging GmbH,
 Berlin, Germany) in order to segment individual structures into discrete
 materials. The segmented materials were then exported with the plugin
 script “multiExport” (Engelkes et al. 2018) in Amira 2019.2 as 2D Tiff
 image stacks. VG-Studio 3.4 (Volume Graphics GmbH, Heidelberg, Germany)
 was used to create volume renders out of the Tiff image series.
description: CT scans can be viewed using Fiji (ImageJ) using XRM
 Reader plug-in.