Oncosphere cyclophyllidean

Hatching of the cyclophyllidean egg involves two processes (a) the rupture of the egg shell (when present) and the passive digestion and/or disruption of the embryophore, (b) activation of the hexacanth embryo to become motile and rupture its enclosing oncospheral membrane. These processes frequently require different stimuli for their initiation. The hatching process has been reviewed by Lethbridge (442), and Ubelaker (888). 

Fig. 8.7. Comparison of the oxygen consumption of eggs and coracidia of a pseudophyllidean (Diphyllobolhrium latum) with the hatched oncospheres of a cyclophyllid (Hymenolepis diminuta). Note that although the pseudophyllidean eggs consume a little oxygen, die hatched coracidia are virtually anaerobic in contrast, hatched cyclophyllidean oncospheres are highly aerobic. (Adapted from Grabiec el at., 1964 Moczon, 19786.)...

Fig. 8.16. Diagrammatic representation of the main features of a cyclophyllidean oncosphere, based on various species, especially Hymenolepis diminuta. (Modified from Davis Roberts, 1983a, copyright 1983. Reprinted by permission of John Wiley Sons, Ltd.)...

The cyclophyllidean oncosphere is well supplied with musculature and the general pattern of muscles appears to be similar in most species. So in both Hymenolepis citelli (which penetrates an invertebrate gut) and E. granulosus (which penetrates a vertebrate gut) there are 16 somatic muscle cells (146, 839). However, E. granulosus has 16 hook muscle cells but H. citelli has only 13. In E. granulosus, the hook muscles have been shown to insert at the collar and base of the hooks and at the basal lamina of the embryonic epithelium. Each pair of hooks has three muscle systems associated with it (a) a protractor system, for hook extensions (b) an abductor system, which draws the hooks together and (c) a retractor system which pulls the hooks into the body (839). 

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