FINE-STRUCTURE AND CYTOCHEMISTRY OF THE DORSAL VESSEL OF PANSTRONGYLUS-MEGISTUS (BURMEISTER, 1835) (HEMIPTERA, REDUVIIDAE)

The microanatomy of the dorsal vessel of the triatomine Panstrongylus megistus is here analyzed by transmission electron microscopy. The org an is delimited by a circular layer of striated muscle. The muscle cel ls are externally covered by a thick basement membrane and are bound t o it by means of hemidesmosomes. Internally, the muscle layer is cover ed by a thin basal lamina. Pericardial cells are found inside and outs ide the vessel. They are enveloped by a lamellar basement membrane and form clusters of two or more cells kept together through interdigitat ions and septate desmosomes. The cytoplasm of the pericardial cells is rich in free ribosomes and contains a large number of granules. Cytoc hemical analysis showed that the granules contain basic proteins, lipo proteins and acid phosphatase activity. Inside the vessel, between the layers of pericardial cells and muscle cells, a discontinues layer of endothelial-like cells was found. Some of these cells present long cy toplasmic projections, and are rich in ribosomes and glycogen particle s, as well as in cytoplasmic granules containing basic proteins, acid phosphatase activity and microtubular structures disposed in a regular array. These cells present high endocytic activity, as evaluated by t he uptake of gold-labeled probes.