Abstract (eng)
Spectral heterogeneity seems to be a common design of the insect compound eye. In honeybee workers of Apis mellifera, three photoreceptor types - with absorption maximum in the UV, blue and green range of wavelength spectrum - are distributed heterogeneously in the ommatidia. The three known types of ommatidia each contain six green receptors and either two UV, two blue or one UV and one blue receptor. The spectral quality of the short ninth cell at the base of the ommatidium remains unclear. The spectral heterogeneity in drones’ eyes has not yet been examined on the cellular level. Based on morphological, physiological and molecular biological data, it is known that the eye is divided in two distinct areas, which are used in different contexts. Likewise, in the dorsal rim area (DRA), a region used for polarization vision in both sexes, there is strong evidence that the photoreceptor distribution differs from the main retina.
The sex-specific differences of photoreceptor distribution in different eye areas of workers and drones were examined with immunohistochemical, molecular biological and ultrastructural techniques. In the main retina of workers, the three known ommatidia types were found. The same three types were found in the ventral area of the drone’s eye. In the dorsal area three new ommatidia types with respect to the number of UV-receptors (none, one or two) were identified. Additionally, they contain, in contrast to the known types, blue receptors in all ommatidia while green receptors are absent. It can be assumed that these dorsal modifications are adaptations for mating behavior. Additionally, there is evidence that the DRA of both sexes contains more UV receptors in each ommatidium than in the main retina.