Cyclophyllideans

Cyclophyllideans are the largest and most common order of tapeworms, belonging to the class Cestoda. These endoparasitic flatworms are characterized by a scolex, or head, which typically bears four prominent suckers. Some species also possess a rostellum, a retractable structure often armed with hooks, which aids in attachment to the host's intestinal wall. The body of a cyclophyllidean is segmented into proglottids, which develop sequentially from the scolex. Each mature proglottid contains both male and female reproductive organs, making them hermaphroditic. Reproduction occurs through self-fertilization or cross-fertilization between proglottids. Fertilized eggs are released within the proglottid, which then detaches from the strobila (the main body of the tapeworm) and is expelled in the host's feces. Cyclophyllideans require at least one intermediate host to complete their life cycle. The eggs are ingested by an intermediate host, where they develop into larval stages, often cysticercus or strobilocercus. These larval stages are infective to the definitive host, usually a vertebrate, which becomes infected by consuming raw or undercooked meat containing the larvae. Examples of medically and economically important cyclophyllideans include Taenia species (e.g., pork tapeworm, beef tapeworm) and Echinococcus species.