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, Lop1 was exclusive to the compound eyes, while Lop2 was confined to the ocelli, which also contained Uvop photoreceptors. Queens and workers exhibited three ommatidial types in their compound eyes, with six Lop1 photoreceptors, alongside either one Uvop and one Blop, two Uvop or two Blop 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 Uvop and seven Blop photoreceptors, the other with two Uvop and six Blop photoreceptors. Our findings reveal unknown caste-specific adaptations in bee vision, enhancing understanding of the evolutionary diversity of insect visual systems.