CONICET | Buscador de Institutos y Recursos Humanos

Worker honeybees (Apis mellifera) perform different tasks throughout their adult lifespan. While young workers remain inside the nest performing maintenance and brood caring duties, older ones gather resources outside. It has been proposed that the insulin signalling pathway contributes to age related changes in task performance of eusocial insects. Insulin levels are higher in foragers than in food processors and nurses. As transition between tasks implies a differential use of sensory modalities, we wished to evaluate the effect of insulin on olfactory and gustatory sensitivity as well as on appetitive olfactory learning of preforager workers. Bees of known age reared either in the laboratory or in the hive were abdominally injected with 1 μl of insulin or Hepes buffer. Spontaneous responses toward odours, sucrose sensitivity and olfactory learning were tested immediately after insulin injection by examining the proboscis extension response. Insulin injected bees had higher spontaneous odour responses, independently of their age or their rearing environment. Sucrose sensitivity and odour discrimination during olfactory conditioning were differently affected by insulin according to age; whereas insulin injected younger workers increased their gustatory responsiveness and showed diminished learning abilities, older bees showed the opposite behaviour. In sum, insulin improves chemosensory responsiveness in young workers, but impairs their odour discrimination. Thus, the insulin pathway would be readily mature in these young bees, although they are still performing inhive activities. These results show a strong effect of insulin on appetitive behaviour, which reinforces the variable behavioural repertoire found in the honeybee worker caste throughout adulthood.