Antennal sensilla variability among castes and sexes in the leaf-cutter ant Acromyrmex subterraneus subterraneus

Insect antennae play a crucial role in communication, acting as receptors for both chemical and physical cues. This sensory reception is facilitated by specialized cuticular structures known as sensilla, which exhibit diverse morphologies and functions. In ants, caste polymorphism and sexual dimorphism manifest in antennal structure. This study characterized and compared the antennal sensilla across different castes (major and minor workers, and queens) and sexes of the leaf-cutter ant Acromyrmex subterraneus subterraneus, an important agricultural pest, using scanning electron microscopy. The lengths of the scape and pedicel were greater in major workers and queens compared to other classes of individuals (i.e., minor workers and males). Sensillum numbers were significantly higher for these two female classes than for minor workers and tended to be higher than for males. In addition, various types of sensilla were identified, including chaetic types I, II, and III, trichoid I and II, basiconic, ampullaceous, and coeloconic. Chaetic sensilla were found to be the most abundant in all classes of individuals studied. Overall, similar types of sensilla were found in females (major, minor, queen) and males. The differences in the presence, absence, and number of antennal sensilla were analyzed in relation to their functional roles across the studied groups.