Ultrastructural study of neurosecretory cells in the nervous system in the cestode (Taenia hydatigena)

The neurosecretory cells in nervous system of the Taenia hydatigena was studied light- and electron-microscopically. On the basis of the cytological structure they were divided into two types: type I neurosecretory cells, which containing large dense-cored vesicles, small elongated mitochondria and a large amount of free ribosomes, were located mainly in the central and peripheral nervous system; type II neurosecretory cells were characterized by their moderate amount of free ribosomes, endoplasmic reticulum which contacted with the membranes of perikarya, large ovoid mitochondria, large dense-cored vesicles and their localization in the musculature near serve profiles. The synaptic and nonsynaptic contacts i.e. omega figure and exocytosis release sites were seen in the neuropile, musculature and excretory ducts. The present findings suggest that neurosecretory cells in nervous system may play an important integrative roles of both neuronal and endocrine in the flatworm.