RESUMO
FMRFamide-like immunoreactive cells have been identified in almost all insect species studied. However, the functions of this peptide are still unknown, although several studies have suggested that FMRFamide may play a role in controlling peristalsis, digestion, development and reproduction in insects. Differences in the number, morphology, and distribution of FMRFamide-like cells have been observed among insects. Social bees are characterized by the presence of well-defined castes, each with a different behavior, energy demand and nutrient consumption. In this work, we used immunofluorescence to assess the number, morphology,and distribution of FMRFamide-like immunoreactive cells in different castes of the bee Melipona quadrifasciata anthidioides. These immunoreactive cells were observed only in the posterior region of the midgut, whereas FMRFamide-immunoreactive nerve fibers were more abundant in the fore-and hind-midgut boudary . However, htere were no differences in the number and distribution of FMRFamide-like cells among the castes. This localization of immunoreactivity may indicate that the nervous system controls the passage of food through the cardiac and pyloric valves, while the passge of food through the midgut is controlled by midgut endocrine cells. The number, morphology and distribution of midgut FMRFamide-like cells were not influencend by behavior, feeding habits, cast, or sex in this species.