Sex and experience related neural and behavioural plasticity in ants

Ants utilise age- and caste-based division of labour, providing an opportunity to investigate behavioural and neural plasticity. Newly eclosed workers perform tasks, such as nursing, and initiate foraging as they mature. Alate males only search for mates and do so exclusively on the wing. In worker ants, age and initial light exposure induce neural changes to the mushroom bodies, higher-order sensory processing regions. However, synaptic neuroplasticity has not been directly linked to the behavioural transition into forager life. In hymenopterans, males demonstrate neuroplasticity associated with initial flights or mating, yet it is unknown how age affects neural circuitry. I documented the navigational behaviour of naïve ants as they exited the nest on consecutive trips. I then compared the structure and organisation of olfactory and visual neuropils within the mushroom bodies with behaviour and foraging experience. Ants leaving the nest for the first time carry out learning walks during which they regularly look back towards the nest. As animals gained experience, their path towards the feeder became increasingly direct. I found no evidence of neuroplasticity among workers with different experience levels. Comparing males that were 2 and 11 days old, I found that the volume and number of synaptic profiles increased in the visual neuropils of mushroom bodies. However, a similar comparison in workers revealed no such differences. I discuss how these differences in neuroplasticity in each caste have evolved to suit their respective lifestyles and ecologies.