MIDGUT ENDOCRINE CELLS IN Melipona quadrifasciata 683 ULTRASTRUCTURE OF THE MIDGUT ENDOCRINE CELLS

In this study we describe the ultrastructure of the endocrine cells observed in the midgut of M. quadrifasciata anthidioides. This bee has two types of endocrine cells, which are numerous on the posterior midgut re-gion. Cells of the closed type are smaller and have irregular secretory granules with lower electrondensity than those of the open cell type. The open cell type has elongated mitochondria mainly on the basal area, where most of the secretory granules are also found. Besides the secretion granules and mitochondria, endocrine cells in this species have well-developed autophagic vacuoles and Golgi complex elements. Key words: insect midgut, endocrine cells, ultrastructure, secretory granules, stingless bee. RESUMO Ultra-estrutura das células enteroendócrinas do intestino médio de Melipona quadrifasciata anthidioides (Hymenoptera, Apidae) Neste estudo descrevemos a ultra-estrutura das células enteroendócrinas observadas no intestino médio de M. quadrifasciata anthidioides, abelha na qual ocorrem dois tipos de células enteroendócrinas, concentradas na região posterior do intestino médio. As células do tipo fechado são menores e possuem grânulos de secreção menos eletrodensos e menos regulares do que as células do tipo aberto. As células do tipo aberto possue