ULTRASTRUCTURE AND HISTOCHEMISTRY OF THE MINERAL CONCRETIONS IN THE MIDGUT OF BEES (HYMENOPTERA, APIDAE)

Mineral concretions in the digestive cells of bees were examined under transmission electron microscope and histochemically. Ultrastructure shows two types of mineral deposits: 1) mineral concretions which are organized in granules with a striking concentrically layered organizat ion of opaque and clear zones and 2) electron dense granules which app ear inside small vacuoles (0.4-0.7 mu m). These two structures are pre sent in the apex of the digestive cells of the posterior midgut. Histo chemical data reveal that mineral concretions are composed of calcium, iron and uric acid or its salts while calcium determination gives a p ositive reaction for electron dense granules. Morphological and chemic al similarities between the mineral concretions of bees and those desc ribed for other insects suggest that they have an important physiologi cal role regulating the composition of the internal environment and to avoid intoxication. Since concretions and granules are structurally d istinct, it is suggested that they are functionally different.