[Postembryonic development of cestodes of the genus Aploparaksis Clerc, 1903 (Hymenolepididae) with a diplocyst type of cysticercoid].

The formation of cysticercoids of the diplocyst type in three species of cestodes of the genus Aploparaksis: A. bulbocirrus Deblock et Rausch, 1968, A. furcigera (Rud., 1819) and A. groenlandica (Krabbe, 1869) at the experimental infection of oligochaetes (Lumbriculus sp.) is described. The development of diplocysts is characterized by two invaginations. The first invagination occurs at an early developmental stage when non-differentiated anterior part of the larval body submerges into the external cyst which is formed by the walls of the primary cavity displaced toward the hind end. The second invagination of the fully formed scolex and neck into the cavity of the internal cyst completes the formation of the diplocysts.