Ultrastructure of spermatogenesis of Taenia taeniaeformis (Batsch, 1786) (Cestoda, Cyclophyllidea, Taeniidae) and comparison of spermatological characters in the family Taeniidae Ludwig, 1886

Abstract

The ultrastructure of spermatogenesis of Taenia taeniaeformis is described for the first time by means of transmission electron microscopy (TEM). Mature testes contain all stages of spermatogenesis; primary spermatogonia are usually situated at the periphery and mature spermatozoa in the centre of testes. The general process is similar to that described in other cestodes. Six incomplete, synchronic cytokineses occur: four mitotic and two meiotic cell divisions. All these divisions occur simultaneously, resulting in a rosette cluster of four tertiary spermatogonia, then eight quaternary spermatogonia, and subsequently sixteen primary spermatocytes. All of these enter into a growth period and their enlarged nuclei move to the periphery of cells of the rosettes. The first meiotic division forms thirty-two secondary spermatocytes and after the second meiotic division, there are sixty-four spermatids. Spermiogenesis in T. taeniaeformis corresponds to the Bâ and Marchand's Type 3 and begins with the formation of a differentiation zone in the form of a conical projection of cytoplasm delimited by a ring of arching membranes and surrounded by submembranous cortical microtubules. Within this area, there are two centrioles, orthogonally disposed, and vestigial striated rootlets. Only one of the centrioles develops a flagellum that grows externally to the cytoplasmic extension. Posteriorly, a flagellar rotation inferior to 90º occurs and the flagellum becomes parallel to the cytoplasmic extension. Later, the two processes fuse during the so-called proximodistal fusion. The nucleus elongates and moves into the cytoplasmic extension. In the final stage of spermiogenesis, a single crested body appears at the base of the differentiating spermatozoon. Finally, the ring of arching membranes constricts and the young spermatozoon detaches from the residual cytoplasm. Ultrastructural aspects of spermatogenesis are compared with that of other cestodes studied to date, particularly of the family Taeniidae.

Ultrastructure of spermiogenesis and mature spermatozoon of Triaenorhina rectangula (Cestoda: Cyclophyllidea: Paruterinidae)

“…The presence of slight flagellar rotation during spermiogenesis confirms relationships with Anonchotaenia globata (see ), metadilepidids (see Yoneva et al 2006a), taeniids (Ndiaye et al 2003a, Miquel et al 2009a) and catenotaeniids (Hidalgo et al 2000).…”

“…The previously described spermiogenesis in the paruterinid A. globata (see ), as well as in the catenotaeniid Catenotaenia pusilla (see Hidalgo et al 2000) and the taeniids Taenia parva (see Ndiaye et al 2003a) and T. taeniaeformis (see Miquel et al 2009a), exhibits slight flagellar rotation. In the other examined cyclophyllideans, in which spermiogenesis is also of Type III, i.e.…”

“…The presence of numerous vestigial roots jointed with one centriole has been observed in anoplocephalids Anoplocephaloides dentata (see , Gallegoides arfaai (see Miquel et al 2005a) and Mosgovoyia ctenoides (see Eira et al 2006), dipylidiid Dipylidium caninum (see Miquel et al , 2005b, paruterinid Anonchotaenia globata (see ), metadilepidid Skrjabinoporus merops (see Yoneva et al 2006a) and taeniid Taenia taeniaeformis (see Miquel et al 2009a). Miquel et al (2005a) considered the vestigial roots as degenerated typical striated roots, which have undergone a progressive reduction in the cyclophyllideans towards their absence in more evolved cestodes.…”

“…The comparison of the spermiological characters of T. rectangula with those of the taeniids Taenia hydatigena (see Featherston 1971), T. mustelae (see Miquel et al 2000), T. parva (see Ndiaye et al 2003a), T. crassiceps (see Willms et al 2004) and T. taeniaeformis (see Miquel et al 2009a, c) and the metadilepidid Skrjabinoporus merops (see Yoneva et al 2006a) reveals the same ultrastructural organisation. All these species exhibit similarities in spermiogenesis, i.e.…”

Spermiogenesis and spermatozoon of the liver fluke Mediogonimus jourdanei (Microphalloidea: Prosthogonimidae), a parasite of Myodes glareolus (Rodentia: Cricetidae)

“…the importance of this flagellar rotation resides in the comparison between trematodes and cestodes. in fact, in the cestodes the flagellar rotation decreases from 90° until 0° in some cyclophyllideans (see Miquel et al 2009). Nevertheless, some cestodes present a flagellar rotation greater than 90° (Bruňanská et al 2006, Miquel et al 2008).…”