The development of the tegument and cercomer of the polycephalic larvae (cercoscolices) ofParicterotaenia paradoxa(Rudolphi, 1802) (Cestoda: Dilepididae) at the ultrastructural level

Abstract

SUMMARYThe development of the tegument and cercomer ofParicterotaenia paradoxapolycephalic larvae was examined using electron microscopy. Larvae are formed by budding from the inner surface of the tegument of the degenerating hexacanth embryo. A new secondary tegument formed around the larvae is probably produced from the original hexacanth sub-tegumental cells. Microvilli covering the surface of young larvae are converted directly into microtriches, as the larvae develop, by addition of electron-dense material to the proximal part of the microvillus. Remnants of the original microvillus are visible at the distal surface of each new microthrix, but they eventually degenerate. The cercomer homologue is represented by scattered follicular cells, bearing microvilli, lying just within the containing cyst wall. The continuity of tegumentary tissue from one developmental stage to the next is discussed.

Repair ofHymenolepis diminutaafter complement-mediated damage

“…Microthrix development and emergence during morphogenesis has been studied extensively (Timofeev & Kuperman, 1972;Hulinska, 1980;Hess, 1980;Richards & Arme, 1981MacKinnon & Burt, 1984). We have shown that in H. diminuta microthrix regeneration occurs after complementmediated damage.…”

Utility of complete large and small subunit rRNA genes in resolving the phylogeny of the Neodermata (Platyhelminthes): implications and a review of the cercomer theory

“…Unless a convincing synapomorphy can be found, it seems unlikely that all higher groupings dependent upon ‘cercomers’, beyond the Cestoda (wherein there is also some debate, e.g. Gulyaev, 1996; Mackinnon & Burt, 1984) should be abandoned. In a recent report, Chervy (2002) provides an excellent review of cestode ‘cercomers’, in which the author concludes that ‘presence or absence of a cercomer remains to be determined in several cestode groups’ (p. 17, op.…”

Echinococcus granulosus: changes in the surface ultrastructure during protoscolex formation

“…The microvilli are therefore transitory structures and occur in Echinococcus only during the early stages of protoscolex formation. In other cestode species, however, they occur both on the metacestode and the developing presumptive adult (Mount, 1970;Timofeev & Kuperman, 1972;Lumsden, 1975;Huh'nska, 1980;Lumsden, Voge & Sogandares-Bernal, 1982;Engelkirk & Williams, 1983;Richards & Arme, 1983;MacKinnon & Burt, 1984;Threadgold, 1984). The fully developed protoscolex possesses microtriches on the scolex region and the possibility of the microvilli being the precursors of these structures has to be considered, since Hulmska (1980), (who refers to spineless microtriches) and MacKinnon & Burt (1984) report the transformation of microvilli into microtriches in Taenia hydatigena and Paricterotaenia paradoza respectively.…”