Shogo Nomura1, Naoko Ichikawa2, Tetsuhiko Sasaki3, and Masami Sasaki3. (1) Graduate School of Agriculture, Tamagawa University, Tokyo, 194-8610, Japan, (2) Faculty of Education, Tamagawa University, Tokyo, 194-8610, Japan, (3) Honeybee Science Research Center, Tamagawa University, Tokyo, 194-8610, Japan
Learning and Memory in honeybees are important for their social life. In the present study, we investigated the development of learning capability in the honeybee, Apis mellifera. First, we examined the development of learning capability along with aging of adult bees. The capability of associative learning, with an odor as the conditioned stimulus, was assayed using the proboscis extension reflex. Under the given conditions, the learning rate increased gradually from emergence. Second, we examined the effect of stimuli in colonies on the development of learning capability by comparing the bees kept in an isolated environment to those kept in a colony. The isolated bees showed significantly lower rates of learning than those in the colony, suggestion the importance of the colony environment for the development of brain function. Considering that the queen bee of the colony is known to affect the physiology of worker bees, a mimic of the queen substance was provided the isolated bees. However, the learning capability of the isolated bees was not recovered, suggesting that social stimuli from other worker bees are important for the acquisition of learning capability. Finally, we investigated the expression of three genes, IP3R, PKC and CaMK2, in mushroom bodies, which are the insect brain centers involved in learning and memory. These three genes are known to be expressed in mushroom bodies and are expected to be involved in memory formation. Real time quantification PCR demonstrated that the expression levels of the three genes were significantly higher in old foragers than in young bees. This expression pattern seems to be consistent with the fact that the task of foraging requires complex learning and information processing. No significant difference in gene expression was found between the bees raised in a colony and those kept in an isolated environment.
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