Ultrastructural study of the spermatozoon of Taenia taeniaeformis (Batsch, 1786) (Cestoda, Cyclophyllidea, Taeniidae), an intestinal parasite of Felis catus from La Palma (Canary Islands, Spain).

The ultrastructural characters of the mature spermatozoon of Taenia taeniaeformis are described by means of transmission electron microscopy. Materials were obtained from a naturally infected road-killed cat (Felis catus) from La Palma (Canary Islands, Spain). The mature spermatozoon of T. taeniaeformis is a filiform cell, which is tapered at both extremities and lacks mitochondria. It is characterised by the presence of (1) a single spirallised crested body about 140 nm thick, (2) a single axoneme of the 9+'1' pattern of trepaxonematan Platyhelminthes, (3) a twisted (40 degrees ) layer of submembranous cortical microtubules, (4) a periaxonemal sheath surrounding the axoneme, (5) transverse intracytoplasmic walls and (6) a spirallised nucleus encircling the axoneme. The mature spermatozoon of T. taeniaeformis is also characterised by the presence of an apical cone in its anterior extremity and by the disorganisation of the axoneme in its posterior extremity. The ultrastructural characters of the mature spermatozoon of T. taeniaeformis are compared with those of other cestodes studied to date, with particular emphasis on other representatives of the family Taeniidae.