From egg to adult: a developmental table of the ant Monomorium pharaonis

Abstract Ants exhibit remarkable phenotypic diversity and, with over approximately 16,000 species across 6 continents, represent one of the most evolutionarily and ecologically successful groups of animals. All ants are eusocial with a reproductive division of labor between morphologically and/or behaviourally distinct castes within a single species. This has made ants an ideal system to study core questions of eco-evo-devo (ecological evolutionary developmental biology) by highlighting the role of developmental plasticity, epigenetics, ancestral developmental potentials, modularity, and major evolutionary transitions in the evolutionary process. Yet, despite their importance for eco-evo-devo, no complete ontological series for an ant has been published to date. We therefore present the first developmental table in ants, from egg to adult, for the Myrmicine ant Monomorium pharaonis. We identified and characterized 17 embryonic stages, 3 larval instars, and prepupal/pupal development. We found that the majority of landmarks identified during embryogenesis in the fruitfly Drosophila melanogaster are conserved in M. pharaonis. Furthermore, we can morphologically discriminate reproductive larvae (queen and male-destined larvae) from one another after the 1st larval instar. Finally, this ontological series of M. pharaonis will serve as a blueprint for the generation of future ant developmental tables, which is key to understanding how the remarkable diversity in ants evolved.