Rostellar apparatus of Fernandezia spinosissima (von Linstow, 1894) (Cestoda, Cyclophyllidea, Davaineidae): microanatomy and fine structure

The rostellar apparatus of Fernandezia spinosissima is examined by light an d transmission electron microscopy. It is described as composed of rostellu m, pseudoproboscis, and two groups of glandular syncytia, one in the rostel lum and the other inwards to the rostellum and the pseudoproboscis. The ros tellum is a discoid cushion with muscular walls. There are numerous thin ve rtical muscular fibres and glandular syncytia inside it. Its tegument has s lender microtriches. Peripherally, the rostellum is encircled by thin muscl e fibres that protrude anteriorly between rostellar hooks and group posteri orly to form retractors. The rostellar hook guards are associated with a co mplicated network of muscles and nerves. The pseudoproboscis is a thick-wal led ring around the apical part of the scolex adjacent to the rostellum. It s tegument has microtriches with modified spines that are interpreted as ac cessory spines. The walls of the pseudoproboscis possess a loose structure of parallel muscular fibres and glandular processes. The glandular syncytia , interpreted as modified tegumental perikarya, have basophilic cytoplasm a nd stain positively for protein and carbohydrate. They form cellular proces ses, which protrude to reach to the tegument. These results provide structu ral details characterising one of the rostellar types recognized in the ord er Cyclophyllidea, i.e. the davaineid rostellar apparatus.