Eco-Evolutionary Trends in Sensillar Architecture Across three distinct lineages of Anochetus, the trap jaw ants

Abstract Antennal sensilla are critical sensory structures in ants, mediating chemical, tactile, and environmental perception. The study provides a comprehensive and comparative analysis of antennal sensillar morphology and distribution across three Anochetus species— Anochetus myops , A. graeffei , and A. obscurior which belong to three distinct species groups ( longifossatus , graeffei , and sedilloti , respectively). Using scanning electron microscopy and morphometric analysis, we quantified and mapped the types and abundance of sensilla on the apical antennal segments, while correlating these with size of eye. Results reveal clear interspecific variation in both sensillar complexity and density. A. myops , a small-eyed member of the longifossatus group, exhibited the least sensillar diversity and a pronounced apical protuberance studded with a pair of sensilla placodea, reported for the first time in ants. A. graeffei manifests intermediate complexity, with expanded sensillar arrangements. In contrast, A. obscurior , with large eyes displays the highest number and diversity of sensilla types, including novel trichoid forms and multiple coeloconic variants. Our findings highlight functional morphological diversification of antennal sensory systems in Anochetus and suggest a correlation of sensillar complexity in ecological and evolutionary contexts.