Proglottids are continually being produced by the neck region of the scolex, as long as the scolex is attached and alive.Mature proglottids are essentially bags of eggs, each of which is infective to the proper intermediate host. They are released and leave the host in feces, or migrate outwards as independent motile proglottids. The number of proglottids forming the tapeworm ranges from three to four thousand. Their layout comes in two forms: craspedote, meaning any given proglottid is overlapped by the previous proglottid, or acraspedote, indicating the proglottids do not overlap. Reproduction
Cestodes are exclusively hermaphrodites, with both male and female reproductive systems in each body. The reproductive system includes one or more testes, cirri, vas deferens, and seminal vesicles as male organs, and a single lobed or unlobed ovary with the connecting oviduct and uterus as female organs. The common external opening for both male and female reproductive systems is known as the genital pore, which is situated at the surface opening of the cup-shaped atrium. Though they are sexually hermaphroditic and cross-fertilization is the norm, self-fertilization sometimes occurs and makes possible the reproduction of a worm when it is the only individual in its hosts gut. During copulation, the cirri of one individual connect with those of the other through the genital pore, and then spermatozoa are exchanged. Life cycle
Cestodes are parasites of vertebrates, with each species infecting a single definitive host or group of closely related host species.
The tegument also protects the parasite from the hosts digestive enzymes and allows it to transfer molecules back to the host.The body form of adult eucestodes is simple, with a scolex, or grasping head, adapted for attachment to the definitive host, a short neck, and a strobila, or segmented trunk formed of proglottids, which makes up the worms body. Members of the subclass Cestodaria, the Amphilinidea and Gyrocotylidea, are wormlike but not divided into proglottids. Amphilinids have a muscular proboscis at the front end; Gyrocotylids have a sucker or proboscis which they can pull inside or push outside at the front end, and a holdfast rosette at the posterior end.The Cestodaria have 10 larval hooks while Eucestoda have 6 larval hooks. Scolex
The scolex, which attaches to the intestine of the definitive host, is often minute in comparison with the proglottids. It is typically a four-sided knob, armed with suckers or hooks or both. In some species, the scolex is dominated by bothria, or "sucking grooves" that function like suction cups. Cyclophyllid cestodes can be identified by the presence of four suckers on their scolices. Other species have ruffled or leaflike scolices, and there may be other structures to aid attachment.In the larval stage the scolex is similarly shaped and is known as the protoscoleces. Body systems
Circular and longitudinal muscles lie under the neodermis, beneath which further longitudinal, dorso-ventral and transverse muscles surround the central parenchyma. Protonephridial cells drain into the parenchyma.