Comparative analysis of brain and brain component size in different honeybee species

Bees of the genus Apis are major crop pollinators and economically highly important. Much research has been done on the pollination biology, navigation, communication, learning and memory and sensory biology of European honeybees, Apis mellifera, but much less is known about other species in the genus Apis. Here we compare the brain size and composition of Apis mellifera and the three Asian honeybee species, Apis florea, Apis cerana and Apis dorsata. We measured the volumes of the brains and distinct brain components and compare them to body size measures (head width and body weight) of the respective Apis species. As is the case in most animal taxa in general, body size allometrically correlated with brain size. Interestingly, A.dorsata featured a relatively smaller brain compared to their body weight. We did not find significant differences in the relative volume of the central brain components in the four species. However, the relative volume of the distalmost neuropil of the optic lobe (the lamina) was significantly larger in A. dorsata, while the other two major components of the optic lobe, the medulla and lobula, were relatively smaller compared to other Apis species. On the other hand A.mellifera had significantly larger antennal lobes compared to other Apis species.  Our data suggests that there is a trade-off between the  size of visual and olfactory centers in A.dorsata and A.mellifera. Likewise, our data also suggests that A.dorsata exhibit a trade-off between visual sensitivity and acuity.