A comprehensive characterization of opsin distribution across the visual system in the three castes of the honeybee

Honeybees see the world through photoreceptors in their compound eyes and ocelli, which express four opsins: UVOP (UV-sensitive), BLOP (blue-sensitive), and LOP1/LOP2 (both green-sensitive). Here, we provide the first comparative mapping of opsin RNA across the three bee castes: workers, drones, and queens. In all castes, <i>Lop1</i> was exclusive to the compound eyes, while <i>Lop2</i> was confined to the ocelli, which also contained <i>Uvop</i> photoreceptors. Queens and workers exhibited three ommatidial types in their compound eyes, with six <i>Lop1</i> photoreceptors, alongside either one <i>Uvop</i> and one <i>Blop</i>, two <i>Uvop</i> or two <i>Blop</i> photoreceptors. Drones shared the same ommatidial types ventrally, but the upper two-thirds of their compound eyes exhibited only two ommatidial types: one with one <i>Uvop</i> and seven <i>Blop</i> photoreceptors, the other with two <i>Uvop</i> and six <i>Blop</i> photoreceptors. Our findings reveal unknown caste-specific adaptations in bee vision, enhancing understanding of the evolutionary diversity of insect visual systems.