Changes in the structure and pigmentation of the eyes of honeybee (Apis mellifera L.) queens with the "limao" mutation

This study describes the ultrastructural differences between the compound e yes of ch(li)/ch(li) and Ch/ch(li) honeybee queens. Heterozygous "limao" be es had an almost normal ultrastructural organization of the ommatidia, but there were some alterations, including small vacuoles in the crystalline co nes and a loss of pigment by primary pigmentary cells. In homozygous bees m any ommatidia had very deformed crystalline cones and there were some bipar tite rhabdoma. There was a reduction in the amount of pigment in the primar y and secondary pigmentary cells and receptor cells (retinulae) of mutant e yes. However, the eyes of both heterozygous and homozygous queens had the s ame type of pigment granules. Certain membrane-limited structures containin g pigment granules and electron-dense material appeared to be of lysosomal nature. Since these structures occurred in the retinular cells of mutant ey es, they were considered to be multivesicular bodies responsible for the re duction in rhabdom volume in the presence of light, as a type of adaptation to brightness. The reduction of pigment in the pigmentary and retinular ce lls and the morphological changes seen in the rhabdom of the ommatidia may originate visual deficiencies, which could explain the behavioral modificat ions reported for Apis mellifera queens with mutant eye color.