metacestode
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[:life-stage/id "WBls:0000716"] :life-stage/definition The larval stages of a tapeworm, beginning with the metamorphosis of the oncosphere and ending with the first evidence of sexuality in the adult worm. Includes the procercoid and plerocercoid stages of pseudophyllid cestodes, and the cysticercus, cysticercoid, coenurus, and hydatid stages of cyclophyllidean cestodes.
protoscolex stage
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[:life-stage/id "WBls:0000715"] :life-stage/definition An infective larval stage of cestodes which develops from the hydatid cyst. The stage begins when a clustering of cells emerge from the germinal layer of hydatid cysts. The buds elongate and the cells at their bases seem to diminish in number. Very early on a furrow appears in the elongated buds, delimiting anterior (scolex) and caudal (body) regions. Hooks are the first fully-differentiated structures formed at the apical region of the nascent scolex. A cone can later be seen at the center of the hooks, the body is expanded and a structured neck is evident between the scolex and the body. During protoscolex development this parasitic form remains attached to the germinative layer through a stalk. When fully differentiated, the stalk is cut off and the infective protoscolex is now free in the hydatid fluid. This stage ends when the protoscolex attaches, via the scolex, to the host intestinal tissue and begins to develop into a adult.