Morpho-functional asymmetry of the olfactory receptors of the honeybee (Apis mellifera)

Lateralization, i.e., the different functional specialisation of the left and right side of the brain, has been documented in many vertebrate species and, recently, in invertebrate species as well. In the Honeybee, Apis mellifera L. (Hymenoptera Apidae), it has been shown that short-term (<1 h) recall of olfactory memories would be possible mainly from the right rather than from the left antenna. Here we confirmed this finding showing that recall of the olfactory memory 1 h after training to associate (−)-linalool, a floral volatile compound, with a sugar reward, as revealed by the bee extending its proboscis when presented with the trained odour, was better when the odour was presented to the right rather than to the left antenna. We then measured the number of sensilla present on the left and right antenna by scanning electron microscopy. Results showed that putative olfactory sensilla (placodea, trichodea, basiconica) were significantly more abundant on the right antenna surface than on the left antenna surface, whereas sensilla not involved in olfaction (campaniformia, coeloconica and chaetica) tended to be more abundant on the left than on the right antenna surface.