Class Cestoidea
Basics: Cestoidea flatworms are the most highly specialized , and all of the species of this class reside in the digestive system. Tapeworms lack pigments as adults so they usually look white with yellow or gray shades and can be 1mm to 25 m in lenth. Since tape worms lack mouths and a digestive tract they receive nutrients through their body wall , and they are divided into proglottid units that hold reproductive structures inside of them. Like most endoparasites tape worms live in stable environments based on the host homeostasis which they invade.
Subclass Cestodaria: These endoparasites in the intestine and coelom of primitive fishes, they posses some digenetic trematode features in that both reproductive system is present in each animal. Bear suckers have similar body structures to cestodes due to their lack of digestive systems, multiple larval stages, and parenchymal muscles.
Subclass Eucestoda: Almost all cestodes belong to this class and are the true tape worms,They are the ultimate degree of specialization of any parasitic animal. These worms are divided into three regions , The scolex contains circular sucks and a rostellum to hook on to the intestinal wall of the host. The scolex narrows to form the neck and transverse constrictions give way to third body region called the strobila. These structures have proglottids attached to them which function in reproduction. The old proglottids move up the neck area as new ones are produced by the strobila, as the proglottids mature and start to produce eggs become gravid. The outer body wall tapeworms consists of a tegument similar to trematodes , It helps them absorb nutrients sinse the tape worms don't have digestive systems, and they absorb their host enzymes to help them digest it. The bodies of these tape worms are very simplistic, They have a pair nerve cords that arise from nerve masses in the scolex and extend the strobila length.
Tapeworms are monoecious , and most of their physiology is about producing large numbers of eggs. Each proglottids contain male and female productive organs, The testes deliver sperm through ducts to a copulatory organ called a cirrus. The mall system of a proglottid matures before the female part so it finds another proglottid from the same or a different tape worm. Ovaries in each proglottid produce eggs, then stored sperm fertlizes the eggs as the move through the oviduct, Vitelline cells from gland are poored onto the eggs in the ootype. The mehlis glands surround the ootype to help shape the egg capsule. As the eggs accumulate they can be released from the proglottids when they start to degenerate and can be released through the human feces or in the host intestines