Spermiogenesis of Bothriocephalus scorpii (Cestoda, Pseudophyllidea) includes an orthogonal development of two flagella, followed by a flagellar rotation and a proximo-distal fusion with the median cytoplasmic process. The fusion occurs at the level of four attachment zones. The presence of dense material in the apical region of the differentiation zone in the early stage of spermiogenesis appears to be a characteristic feature for the Pseudophyllidea. The mature spermatozoon possesses two axonemes of 9+"1" pattern of the Trepaxonemata, nucleus, cortical microtubules, electron-dense granules and crested body. The anterior part of the gamete exhibits a centriole surrounded by electron-dense tubular structures arranged as incomplete spiral. When the crested body disappears, the electron-dense tubular structures are arranged into a ring encircling the axoneme. The electron-dense tubular structures and their arrangement appear to be a specific feature for the clade "Bothriocephalidea". The organization of the posterior extremity of the gamete with the nucleus is described for the first time in the Pseudophyllidea.

Institute of Parasitology Academy of Sciences of the Czech Republic Branisovská 31 370 05 Ceské Budejovice Czech Republic

References provided by Crossref.org

Ultrastructure and Cytochemistry of the Mature Spermatozoon of Khawia Armeniaca (Cholodkovsky, 1915) (Caryophyllidea: Lytocestidae), a Parasite of Capoeta Capoeta Sevangi (De Filippi, 1865) (Teleostei, Cyprinidae)

New data on spermiogenesis and trepaxonematan axoneme in basal tapeworms (Cestoda, Caryophyllidea, Lytocestidae) parasitizing cyprinid fishes

First ultrastructural and cytochemical data on the spermatozoon and its differentiation in progenetic and adult Archigetes sieboldi Leuckart, 1878 (Cestoda, Caryophyllidea, Caryophyllaeidae)

Ultrastructural, cytochemistry and electron tomography analysis of Caryophyllaeides fennica (Schneider, 1902) (Cestoda: Lytocestidae) reveals novel spermatology characteristics in the Eucestoda

Spermatological characters of bothriocephalideans (Cestoda) inferred from an ultrastructural study on Oncodiscus sauridae and Senga sp

Spermatozoon ultrastructure of the pseudophyllidean cestode Paraechinophallus japonicus, a parasite of deep-sea fish Psenopsis anomala (Perciformes, Centrolophidae)

Spermiogenesis in the caryophyllidean cestode Khawia armeniaca (Cholodkovski, 1915)