Ultrastructure of spermiogenesis and the spermatozoon of Monorchis parvus Looss, 1902 (Digenea, Monorchiidae), a parasite of Diplodus annularis (Pisces, Teleostei)

Abstract

The present paper describes the characteristic ultrastructural features of spermiogenesis and the spermatozoon of Monorchis parvus (Trematoda, Digenea, Monorchiidae). This spermiogenesis is characterized by a flagellar rotation of about 120 degrees and the formation of a novel ultrastructural element: a centriolar extension. It nevertheless follows the general pattern of digeneans. It begins with the formation of a differentiation zone, comprising striated rootlets associated with two centrioles and an intercentriolar body. The mature spermatozoon presents features allowing the distinction between M. parvus and other digenetic trematodes. It possesses an original anterior extremity. The two central elements of the axonemes appear prior to the peripheral doublets. The external ornamentations of the cell membrane are formed parallel to the central elements. Another peculiarity of the male gamete is the presence of two mitochondria. M. parvus, therefore, differs distinctly from other digenetic trematodes.

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

“…This is also the case for T. taeniaeformis. Taking into account the recent observations of flagellar rotations of up to 120°in the Fasciolidae, Dicrocoeliidae, Monorchiidae, Opecoelidae and Allocreadiidae digeneans (Ndiaye et al 2003c;Levron et al 2003Levron et al , 2004Agostini et al 2005;Quilichini et al 2007a, b), and described in the caryophyllidean Wenyonia virilis and in the spathebothriidean C. truncatus (Bruňanská et al 2006, Miquel et al 2008), it appears that there may be a gradual reduction of the rotation angle until there is no rotation, a state that is considered the apomorphic condition of this character (Justine 1998(Justine , 2001.…”

Spermiogenesis and ultrastructure of the spermatozoon of Wardula capitellata (Digenea, Mesometridae), an intestinal parasite of the sparid teleost Sarpa salpa in Senegal

“…This is the case of H. medioplexus, M. parvus, Pronoprymna ventricosa and N. chabaudi (Justine and Mattei 1982, Levron et al 2004a, Quilichini et al 2007d, Kacem et al 2010.…”

“…However, some recent studies have described flagellar rotations greater than 90°. It is the case of Helicometra fasciata, Monorchis parvus, Fasciola hepatica, Dicrocoelium hospes, Nicolla wisniewskii or Crepidostomum metoecus (Ndiaye et al 2003;Levron et al 2003Levron et al , 2004aAgostini et al 2005;Quilichini et al 2007a, b).…”

“…For example, seven electron-dense layers were described in the paramphistomoids Paramphistomum microbothrium, Cotylophoron cotylophorum, Carmyerius endopapillatus, Basidiodiscus ectorchus, Sandonia sudanensis and D. subclavatus (Ashour et al 2007;Seck et al 2007Seck et al , 2008aBakhoum et al 2011a), the allocreadiid C. metoecus (Quilichini et al 2007b), or the opecoelids Opecoeloides furcatus (Miquel et al 2000), and Poracanthium furcatum (Levron et al 2004b). Intercentriolar bodies composed of nine electron-dense layers are described in Cryptocotyle lingua (Rees 1979) and M. parvus (Levron et al 2004a) and others composed of six layers in Deropristis inflata by Foata et al (2007). In W. capitellata the intercentriolar body is composed of six electron-dense layers.…”

“…Thus, these lateral expansions would be a good character for justifying the proximity of these taxa. However, there are different morphologies of lateral expansions in the digeneans such as in H. fasciata, Scaphiostomum palaearcticum or T. acutum (Ndiaye et al 2002, Levron et al 2003, Miquel et al 2006. The presence and variability of lateral expansions in mature spermatozoa of digeneans should be analysed carefully due to their potential phylogenetic interest.…”