Ultrastructure of the cirrus pouch of Cylindrotaenia hickmani (Jones, 1985) (Cestoda, Nematotaeniidae)

The cirrus pouch of Cylindrotaenia hickmani was examined by transmission electron microscopy. The cirrus pouch is a complex organ consisting of muscular, nervous and epithelial tissues. Muscles forming the cirrus pouch wall contain large myocytons that merge with myofibrils. Muscles supplying the gonadoducts within the pouch consist of small myocytons which are connected to associated myofibrils by elongate processes. Discrete neuromuscular junctions are commonly seen in both muscles. Two cells, thought to be neurons, are present in the pouch. The abundance of nervous tissue in the pouch is suggestive of a high level of neural control of the activity of that organ. The cirrus is lined by filamentous, hook-like and blade-like microtriches. Ciliated sensory receptors are found among the microtriches lining the cirrus. Epithelial cytons associated with proximal regions of the cirrus produce a material which is secreted from the syncytial cytoplasm of the cirrus. Intercellular junctions, resembling gap junctions, are common among the cells associated with the cirrus. The complexity of the cirrus pouch of C. hickmani suggests that this organ may prove valuable for studies on neuromuscular physiology and cellular interactions in cestodes.