Cestoda

Tapeworms are obligate internal parasites (endoparasites) of vertebrates and belong to the group called flatworms (Platyhelminthes). Majority of them are parasites of intestinal system and most species of approximatelly 5000 known to science can be found in sharks and fishes. They can reach 30 metres in length and are hold in place in guts by a tiny rostellum („the head“) with hooks. Tapeworms do not have digestion system, instead they receive nutrients by their entire body surface directly from their host and causing it by that harm. Tapeworms have complex life cycles that may include several hosts, quite often from a different group of animals. They are usually hermaphrodites, it means that one animal has both male´s and female´s reproductive cells. Teminal body segments are almost completely filled with fertilised eggs. Tapeworms gradually loose them so the segments leave their hosts´ bodies together with faeces. Eggs then have to wait to be eaten by a suitable host species to start another lifecycle.