Structure of the Amphilinidea Juvenile and Adult

Adult worms are dorso-ventrally flattened and not divided into a strobila (chain) of proglottids ("segments") as in the eucestodes. They are hermaphroditic, each worm containing one set of male and one set of female reproductive organs (Figs. 1 and 2) (Dubinina, 1982).

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Figure 1. Juvenile Amphilina foliacea. Note uterine and vaginal openings at anterior end, and male gonopore at posterior end (redrawn from Dubinina, 1982).

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Figure 2. Adult Amphilina foliacea with vaginal opening and male gonopore, and various reproductive organs and ducts (redrawn from Dubinina, 1982).

The uterine opening is located at the anterior end and near it are penetration glands which produce histolytic secretion. The main excretory ducts are arranged in various ways. For example, in Amphilina foliacea they form a network (Fig.3A), in Gephyrolina paragonopora two longitudinal ducts are connected by transverse ones (Fig.3B).

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Figure 3. Excretory ducts of Amphilina foliacea (A) and Gephyrolina paragonopora (B) (redrawn from Dubinina, 1982).

Sensory receptors are of several types (Fig.4), although not as many have been demonstrated as in the larva, possibly because of the large size of the worms which makes it difficult to find all the receptor types.

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Figure 4. Sensory receptors of juvenile Austramphilina elongata based on electron-microscopic studies (redrawn from Rohde and Watson, 1990a).

During vitellogenesis (formation of yolk), cytoplasm of small yolk cells gradually increases in volume, and many lipid droplets and shell protein granules are formed which contribute to the formation of the egg shell ( Fig.5).

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Figure 5. Vitellogenesis (yolk formation) in Austramphilina elongata. 1. young yolk cell, 2. maturing yolk cell, 3. yolk. Note the formation of lipid droplets and shell-protein granules (redrawn from Xylander, 1988).

Spermiogenesis is as in other parasitic platyhelminths, i.e., spermatids form clusters connected by a central cytophore, spermatids are transformed to sperm by elongation, and two flagella grow out which fuse with the sperm body in a proximo-distal direction, i.e., beginning near their base. Finally, sperm separate from the cluster (Rohde and Watson, 1986a).

References

Bazitov, A., Lyapkalo, A. and Yukhimenko (1979). [Spermatogenesis of Amphilina japonica (Goto et Ishii, 1936) (Amphilinidea)]. Vestnik Zoologi (Kiew) 1, 50-55 (In Russian).

Coil, W. H. (1987). The oogenotop of Amphilina bipunctata (Cestodaria). Parasitology Research 73, 75-79.

Coil, W. H. (1991). Platyhelminthes: Cestoidea. In "Microscopic Anatomy of Invertebrates, Vol. 3: Platyhelminthes and Nemertinea", (F. W. Harrison and B. J. Bogitsh, eds). Wiley-Liss, New York, pp. 211-283.

Dubinina, M.N. (1982). Parasitic worms of the class Amphilinida (Platyhelminthes). "Nauka", Leningrad (in Russian). (Older references therein).

Rohde, K. (1994). The minor groups of parasitic Platyhelminthes. Advances in Parasitology 33, 145- 234.

Rohde, K. and Watson, N. (1986a). Ultrastructure of spermatogenesis and sperm of Austramphilina elongata (Platyhelminthes, Amphilinidea). Journal of Submicroscopic Cytology 18, 361-374.

Rohde, K. and Watson, N. (1986b). Ultrastructure of the sperm ducts of Austramphilina elongata (Platyhelminthes, Amphilinidea). Zoologischer Anzeiger 217, 23-30.

Rohde, K. and Watson, N. (1989). Ultrastructural studies of larval and juvenile Austramphilina elongata (Platyhelminthes, Amphilinidea); penetration into, and early development in the intermediate host, Cherax destructor. International Journal for Parasitology 19, 529-538.

Rohde, K. and Watson, N. (1990a). Ultrastructural studies of juvenile Austramphilina elongata. Transmission electron-microscopy of sensory receptors. Parasitology Research 76, 336-342.

Rohde, K. and Watson, N. (1990b). Ultrastructural studies of juvenile Austramphilina elongata.: scanning and transmission electron-microscopy of the tegument. International Journal for Parasitology 20, 271-277.

Xylander, W. E. R. (1986). Zur Biologie und Ultrastruktur der Gyrocotylida und Amphilinida sowie ihre Stellung im phylogenetischen System der Plathelminthes. Ph.D. Dissertation thesis, Göttingen.

Xylander, W. E. R. (1988). Ultrastructural studies on the reproductive system of Gyrocotylidea and Amphilinidea (Cestoda). I. Vitellarium, vitellocyte development and vitelloduct in Amphilina foliacea (Rudolphi, 1819). Parasitology Research 74, 363-370.