Comparative morphological study of the venom glands of the centipede Cryptops iheringi, Otostigmus pradoi and Scolopendra viridicornis

Centipedes are widely distributed over all the continents. As they are well adapted to urban areas they can often cause accidents to humans by injecting venom produced in the glands located inside their maxillipeds. The fine morphology of the centipede venom glands is practically unknown. This present study is the first comparative report on the histology, histochemistry and ultrastructure of the venom glands of the centipede species responsible for the majority of accidents to humans in Brazil: Scolopendra viridicornis, Cryptops iheringi and Otostigmus pradoi. In all species the glands are basically composed of columnar secretory cells radially disposed side by side, individually opening through pores in a central chitinous duct. Each secretory cell is covered by striated muscular fibres. The secretion has the form of small PAS positive granules and large hyaline secretory bromophenol blue positive vacuoles, indicating the presence of neutral polysaccharides and protein. The secretion is conducted through the secretory cell necks to the pores, which open into the central chitinous duct. The results indicate a great similarity both in morphology and primary chemical composition of the venom among the studied species, except for the size of the glands, which is proportional to the body dimensions of each species.