Project A.23

Olfactory Receptor Neurons expressing a single Odorant Receptor send projections to a single glomerulus in the antennal lobe, which consists of a fixed number of glomeruli. In T. longispinosus, glomeruli count varies within and across colonies, suggesting plasticity in the olfactory organization. This study explores how task specialization, age, and colony size, relate to variation in anatomy. In my PhD, I aim to understand the evolutionary basis of olfactory organization in social insects.

Ants rely on chemical communication to drive collective behavior with specialized tasks assigned to different worker castes, such as foraging and nursing. Ants can detect pheromones and other chemical cues due to their expanded odorant receptor repertoires. Odorant (chemosensory) receptors are capable of converting chemical cues (smells) into neuronal signals that are processed in the brain. This is carried out through an established olfactory system, where Olfactory Receptor Neurons (ORN) expressing a single Odorant Receptor (OR) send projections from the antennae to a single glomerulus in the antennal lobe (AL). The AL is the primary olfactory processing center in the brain and consists of a fixed number of glomeruli. This canonical one-OR:one-ORN:one-glomerulus organization is largely conserved across both invertebrates and vertebrates, but deviations from this paradigm exist in some species.

Temnothorax longispinosus age-dependent division of labour, but this task allocation is flexible, and workers can switch tasks depending on the requirements of the colony. Previous work from our group has shown that the genomes of most Temnothorax ants encode ~420 OR genes and that OR subfamilies are differentially expressed between nurses and foragers.

According to the 1:1:1 model, the number of glomeruli should correspond to the number of OR genes. However, preliminary data reveal discrepancies between glomeruli and OR gene numbers, along with variation in glomeruli counts within- and across-colonies. This raises the question of whether task specialization and colony factors influence AL anatomy in T. longispinosus.

This study aims to investigate the basis of this anatomical variation by examining the relationship between worker behavior, task allocation, and variation in AL structure in T. longispinosus. By integrating video monitoring to track colony behavior, immunohistochemistry to visualize brain structures, and image processing software to quantify glomeruli numbers and AL morphology, I will investigate potential factors like colony size, worker age, and division of labour, that may contribute to variation. Through this approach, I seek to determine the organizational logic of the olfactory system, advancing our understanding of the evolution of olfactory organization in insects, especially eusocial insects.