Insulin effects on honeybee appetitive behaviour

Abstract

Worker honeybees (Apis mellifera) carry out multiple tasks throughout their adult lifespan. It has been suggested that the insulin/insulin-like signalling pathway participates in regulating behavioural maturation in eusocial insects. Insulin signalling increases as the honeybee worker transitions from nurse to food processor to forager. As behavioural shifts require differential usage of sensory modalities, our aim was to assess insulin effects on olfactory and gustatory responsiveness as well as on olfactory learning in preforaging honeybee workers of different ages. Adults were reared in the laboratory or in the hive. Immediately after being injected with insulin or vehicle (control), and focusing on the proboscis extension response, bees were tested for their spontaneous response to odours, sucrose responsiveness and ability to discriminate odours through olfactory conditioning. Bees injected with insulin have higher spontaneous odour responses. Sucrose responsiveness and odour discrimination are differentially affected by treatment according to age: whereas insulin increases gustatory responsiveness and diminishes learning abilities of younger workers, it has the opposite effect on older bees. In summary, insulin can improve chemosensory responsiveness in young workers, but also worsens their learning abilities to discriminate odours. The insulin signalling pathway is responsive in young workers, although they are not yet initiating outdoor activities. Our results show strong age-dependent effects of insulin on appetitive behaviour, which uncover differences in insulin signalling regulation throughout the honeybee worker's adulthood.

The short neuropeptide F regulates appetitive but not aversive responsiveness in a social insect

“…Experiment 3: the effect of sNPF on appetitive olfactory responsiveness After the topical application and while the bees were still cold-narcotized, they were harnessed individually in vertical tubes. Appetitive olfactory responsiveness was then quantified by measuring PER to linalool and 2-phenlyethanol, two floral odorants known for eliciting spontaneous PER (Gon ˜alons et al, 2016;Laloi et al, 2001;Nouvian et al, 2015;Sandoz et al, 1995). Odorants were obtained from Sigma-Aldrich.…”

Support for the reproductive ground plan hypothesis in a solitary bee: links between sucrose response and reproductive status

“…The sucrose response of each bee was tested following established protocols [2,14], with the exception that we targeted our stimulation to the gustatory sensilla on the mouthparts (i.e. the galea on the maxillae and the labial palps) while they were folded against the head in the resting position (see fig.…”

Assessment of Appetitive Behavior in Honey Bee Dance Followers

“…Odor discrimination were tested in bees from scent pre-exposed hives H3 and H4 (H3: N F = 51, N NF = 49; H4: N F = 29, N NF = 30) under PER conditioning procedure. Global Discrimination Index (DI) was defined for each bee as the number of trial pairs the bee succeeded in discriminating between the two odors, in other words, if it extended its proboscis towards the CS+ but not to the CS− (Mengoni Goñalons et al, 2016 ). No difference was found during the acquisition between the two behavioral groups of bees (Figure 3A , Supplementary Table S3; ACQ H3+H4 ~Trial+1|Bee).…”

“…For instance, individualized bees that followed dances showed a wide age range (i.e., from 9 to 32 days old; Balbuena et al, 2012 ). Likewise, a recent study evaluated the sucrose responsiveness of hive bees captured from the dance floor or delivery area within an age interval of 2–15 days old (Mengoni Goñalons et al, 2016 ). No age-dependent relationship was found for the sucrose responsiveness measured at the per setup in that study.…”