The chemosensory system of the clonal raider ant larva

Ant larvae, blind and immobile, heavily rely on parents for care including feeding, grooming, and transportation. Despite this dependency, larvae play a crucial role in colony organization by influencing adult behavior and physiology. Although adult ants have been extensively studied, knowledge about the sensory modalities utilized by larvae remains limited.

This study offers a molecular and circuit-level investigation of the chemosensory system in clonal raider ant larvae. Using scanning electron microscopy and confocal imaging, the research reveals that dome sensilla in the maxillary and labial palps are connected to odorant receptor (OR) neurons. Additionally, a larger population of ionotropic receptor (IR) neurons innervate various papilla sensilla on the larval head, such as the antennae, labrum, maxillary palps, galeae, labial palps, and ventral labium.

The results suggest that IRs, which can serve multiple functions including taste, olfaction, temperature, and humidity sensing, are the primary chemosensory modality in ant larvae. To examine the central brain projections of OR- and IR-expressing neurons, the study employed transgenic lines that label these neurons with fluorescence.

Findings indicate that OR- and IR-expressing neurons in the labium and maxilla form projections through the subesophageal ganglion to the deutocerebrum, while IR-expressing neurons from the labrum project to the tritocerebrum and those from the antenna project to the posterior deutocerebrum. The findings establish a structural and molecular foundation for further exploration of larval chemosensation in ants.