Insulin effects on honeybee appetitive behavior

MENGONI CAROLINA; GIRAUD MARIE; DE BRITO SANCHEZ GABRIELA; FARINA WALTER M.

JOURNAL OF EXPERIMENTAL BIOLOGY

COMPANY OF BIOLOGISTS LTD

Lugar: Cambridge; Año: 2016 p. 3003 - 3008

0022-0949

Worker honeybees (Apis mellifera L.) perform different tasks throughout their adult lifespan. It has been proposed that the insulin/insulin-like signalling pathway contributes to age related changes in task performance of eusocial insects. Insulin levels increase as the honeybee worker ages from nurse to food processor to forager. As transition between tasks implies a differential use of sensory modalities, we wished to evaluate the effect of insulin signalling on olfactory and gustatory responsiveness as well as on appetitive olfactory learning in preforaging honeybee workers. Adults of known age reared either in the laboratory or in the hive were abdominally injected with 1 µl of insulin or Hepes buffer (control). Immediately after, and focussing on the proboscis extension response, spontaneous response toward odours, sucrose responsiveness and olfactory learning were tested. Insulin injected bees have higher spontaneous odour responses, independently of the environment they were reared in or their age. Sucrose responsiveness and odour discrimination during PER conditioning are affected by insulin differently according to age; whereas insulin increases gustatory responsiveness and diminishes learning abilities of younger workers, it has the opposite effect on older bees. As a summary, insulin can improve chemosensory responsiveness in young workers, but also worsens their learning abilities to discriminate odours. Thus, the insulin signalling pathway would be readily mature in young workers, although they are not yet initiating outdoor activities. These results show a strong effect of insulin signalling on appetitive behaviour, which reinforces the variable behavioural repertoire found in the honeybee worker caste throughout adulthood.