Ziv E. Lieberman (1), Johan Billen (2), Thomas van de Kamp (3) (4), Brendon E. Boudinot (5)
Journal of Morphology. Volume 283, Issue 6, pages 693-770 (3 April 2022). DOI: https://doi.org/10.1002/jmor.21471

Keywords

Comparative morphology, homology, glands, pregenital segments, ovipositor

Abstract

Recent studies of insect anatomy evince a trend towards a comprehensive and integrative investigation of individual traits and their evolutionary relationships. The abdomen of ants, however, remains critically understudied. To address this shortcoming, we describe the abdominal anatomy of Amblyopone australis Erichson, using a multimodal approach combining manual dissection, histology, and microcomputed tomography. We focus on skeletomusculature, but additionally describe the metapleural and metasomal exocrine glands, and the morphology of the circulatory, digestive, reproductive, and nervous systems. We describe the muscles of the dorsal vessel and the ducts of the venom and Dufour's gland, and characterize the visceral anal musculature. Through comparison with other major ant lineages, apoid wasps, and other hymenopteran outgroups, we provide a first approximation of the complete abdominal skeletomuscular groundplan in Formicidae, with a nomenclatural schema generally applicable to the hexapod abdomen. All skeletal muscles were identifiable with their homologs, while we observe potential apomorphies in the pregenital skeleton and the sting musculature. Specifically, we propose the eighth coxocoxal muscle as an ant synapomorphy; we consider possible transformation series contributing to the distribution of states of the sternal apodemes in ants, Hymenoptera, and Hexapoda; and we address the possibly synapomorphic loss of the seventh sternal–eighth gonapophyseal muscles in the vespiform Aculeata. We homologize the ovipositor muscles across Hymenoptera, and summarize demonstrated and hypothetical muscle functions across the abdomen. We also give a new interpretation of the proximal processes of gonapophyses VIII and the ventromedial processes of gonocoxites IX, and make nomenclatural suggestions in the context of evolutionary anatomy and ontology. Finally, we discuss the utility of techniques applied and emphasize the value of primary anatomical research.

How Our Software Was Used

Segmentation was performed manually to facilitate visualization and quantitative analysis.

Author Affiliation

(1) Department of Entomology and Nematology, University of California, Davis, Davis, California, USA
(2) Department of Biology, Division of Ecology, Evolution and Diversity Conservation, Zoological Institute, University of Leuven, Leuven, Belgium
(3) Institute for Photon Science and Synchrotron Radiation (IPS), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
(4) Laboratory for Applications of Synchrotron Radiation (LAS), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
(5) Friedrich-Schiller-Universität Jena, Institut für Zoologie und Evolutionsforschung, Entomologie Gruppe, Jena, Germany