The ant abdomen: Skeletomusculature and soft tissue anatomy of the Amblyopone australis worker

The ant abdomen is a complex tagma with numerous ancestral and derived morphological and functional traits. Despite the significance of the abdomen in prey capture, communication, reproduction, digestion, and distribution, as well as its many sources of phylogenetic signal, it has been critically understudied. Other tagmata and specific body regions have recently received highly detailed descriptive and comparative work, but the abdomen has remained mostly uncharacterized. An approach which is both holistic in scale and anatomical in detail is required to fill our gap in understanding homology, variation, and mechanical and physiological functions of abdominal characters. Here, I present the main results of our recently published study addressing this lacuna, focusing on the worker Amblyopone australis (Hymenoptera: Formicidae: Amblyoponinae). To achieve comprehensive description at various scales, we employ a multimodal synthesis of manual dissection, histology, and synchrotron micro-computed tomography. We describe the complete skeletomuscular system, the metapleural and metasomal exocrine glands, and the gross anatomy of the reproductive, nervous, digestive, and cardiac organs. Through outgroup comparison with other ants and aculeates, we infer the groundplan of ant abdominal segments for the first time; we homologize the ovipositor muscles across Hymenoptera; we identify skeletomuscular synapomorphies of ants and vespiform aculeates; and we provide the first standardized nomenclature for the skeletal muscles. We additionally submit a new anatomical interpretation of the female genital appendages, review muscular function, identify foci for future research, and emphasize the importance of primary anatomical investigation and reproducibility in the era of digital imaging technologies.