Tapeworms are the most highly specialised flatworms. Adults parasitise the guts of vertebrates. The head or scolex bears attachment organs and is embedded in the wall of the gut. Tapeworms themselves have no guts. They absorb nutrients directly form the host’s gut through their tegument. The neck region protrudes into the lumen of the gut and buds off a chain (a strobila) of segments or proglottids, each with a set of male and female gonads. Mature proglottids usually release eggs, which pass out in the faeces and are then picked up by an intermediate host. The eggs hatch into a small hooked, hexacanth larva, which develops into a resting, often also proliferative stage, in the tissues of the host. The nature of this stage varies from species to species. The life cycle is completed when the flesh of the intermediate host is eaten by the definitive host in which the adult tapeworm develops
Right: Taenia saginata, the beef tapeworm
Below: Scolices of Diphyllobothrium latum, the broad fish tapeworm, and Taenia solium, the pork tapeworm.