Characterization of the first-order visual interneurons in the visual system of the bumblebee (Bombus terrestris)

The bumblebee (Bombus terrestris) has become a common model animal in the study of various aspects of vision and visually guided behavior. Although the bumblebee visual system has been studied to some extent, little is known about the functional role of the first visual neuropil, the lamina. In this work, we provide an anatomical and electrophysiological description of the first-order visual interneurons, lamina monopolar cells (LMCs), of the bumblebee. Using intracellular recording coupled with dye injection, we found that bumblebee LMCs morphologically resemble those found in the honeybee, although only the LMC type L1 cells could be morphologically matched directly between the species. LMCs could also be classified on the basis of their light response properties as spiking or non-spiking. We also show that some bumblebee LMCs can produce spikes during responses to stimulation with naturalistic light contrasts, a property unusual for these neurons.