The honeybee is one of the few organisms that can deposit iron minerals intracellularly. Numerous iron granules are formed in the trophocytes, which are located in the abdomen, beginning on the second day after eclosion. The sequential events of iron deposition in honeybees have been determined and the special features of this biomineralization system are (1) that iron deposition vesicles (IDVs) enlarge by fusing with one another; (2) that dense particles (approx. 7.5 nm in diameter) are the basic building blocks in the formation of iron granules; and (3) that a cloudy layer just beneath the membrane of IDVs may play an important role in the formation of the dense particles. The iron granules seem to be randomly distributed in the trophocytes of the worker and drone. In the queen, however, they are clustered and peripherally located. This distinct difference in the iron granule distribution between members of the hive suggests that these iron granules may have some biological functions. A detailed analysis of total iron content during the life cycle of honeybees has shown that iron granules in the adult worker contain approximately 1 % of the total iron content and also account for approximately 3 % of the increase in iron content that occurs between the newly eclosed worker stage and the adult worker stage.

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