Investigation of different ontogenetic stages of Raillietiella sp. (Pentastomida: Cephalobaenida). Structure of the foregut and considerations about the feeding process.
The foregut of Raillietiella sp. was investigated ultrastructurally in different ontogenetic stages: the embryo prior to hatching, the first-stage larva, the infective fourth-stage larva from the intermediate host, and juveniles and adults from the definitive host. As early as at the embryo stage the chitinous mouth armature is highly specialized. During postembryogenesis this structure is modified until it reaches its final shape in the juvenile. The most important changes occur during the period of development from the infective larva to the juvenile, which is related to the change from the intermediate to the definitive host; only stages inhabiting the definitive host can use their mouth as a suction pump. Therefore, only juveniles and adults are capable of sucking blood, whereas larvae are dependent on accessible liquid food. The remaining foregut represents a conveyor tube, growing in width toward the midgut. From the juvenile stage onward the transition to the midgut is formed as a cardiac valve.
Thomas
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Zoologisches Institut, Arbeitsgruppe Parasitologie, Kiel, Germany.
Stender-Seidel
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D000818:Animals; D001181:Arthropods / Q000196:embryology / Q000254:growth & development / Q000648:ultrastructure*; D004064:Digestive System; D007814:Larva