Ultrastructure of the spermatozoon of the diphyllobothriidean cestode Cephalochlamys namaquensis (Cohn, 1906).

This contribution provides the first ultrastructural and cytochemical data on the mature spermatozoon of a diphyllobothriidean cestode belonging to the family Cephalochlamydidae. The mature spermatozoon of Cephalochlamys namaquensis (Cohn, 1906), a parasite of the African clawed frog, Xenopus laevis (Daudin, 1802), from southern California, USA, has been examined using transmission electron microscopy and cytochemical staining with periodic acid-thiosemicarbazide-silver proteinate for glycogen. The male gamete is a filiform cell tapered at both extremities. Its moderately electron-dense cytoplasm possesses two parallel axonemes of unequal lengths with a 9 + "1" trepaxonematan pattern, a nucleus, parallel cortical microtubules, four electron-dense plaques/attachment zones, and electron-dense granules of glycogen. The crested body is absent. The anterior extremity of the cell exhibits a centriole surrounded by a semiarc of four parallel cortical microtubules. The number of cortical microtubules reaches its maximum (up to 37) at the beginning of the anucleated two-axoneme region II of the spermatozoon. In contrast to other diphyllobothriideans, a small membranous element appears in the anucleated region II. In addition, the nucleus is surrounded by a few cortical microtubules in region V. The distal extremity of the mature spermatozoon exhibits only one nucleus. Variations of spermatozoa ultrastructural characters within diphyllobothriideans as well as other Eucestoda are discussed.