Spermatozoon ultrastructure of Thysanotaenia congolensis (Cyclophyllidea, Anoplocephalidae, Inermicapsiferinae): phylogenetic implications

Abstract

The mature spermatozoon of Thysanotaenia congolensis, an intestinal parasite of black rat Rattus rattus from Cape Verde, is described by means of transmission electron microscopy. The ultrastructural organization of the sperm cell of T. congolensis follows Levron et al.'s type VII of the Eucestoda. It corresponds to a uniflagellate spermatozoon that presents crested bodies, periaxonemal sheath and intracytoplasmic walls, spiralled cortical microtubules and nucleus spiralled around the axoneme. These characteristics are also present in the spermatozoa of other inermicapsiferines and differ from the characters found in species belonging to the remaining subfamilies of anoplocephalids, namely Anoplocephalinae, Linstowiinae and Thysanosomatinae. Several authors consider the family Anoplocephalidae as a polyphyletic group, and its relationships with the Davaineidae are a matter of controversy. The phylogenetic implications of spermatological ultrastructural features present in inermicapsiferines and in the remaining anoplocephalids are discussed, and the available data on anoplocephalids are compared to similar results in davaineids in order to contribute to a better knowledge of relationships between these cyclophyllidean families.

Spermatological Characterization of the Cestode Meggittina gerbilli (Cyclophyllidea: Catenotaeniidae), a Parasite of Gerbils, Gerbillus gerbillus and Gerbillus campestris (Rodentia: Muridae) in Tunisia

“…Crest-like bodies are helical cordons that are present in the anterior extremity of the spermatozoon of most cestodes. The number of crest-like bodies varies between 1 and 12 [ 21 , 32 , 72 , 84 ], although only 1 or 2 crest-like bodies have commonly been found in the species studied so far, including M. gerbilli , with two crest-like bodies. However, some species exhibit a higher number, particularly those belonging to the Cyclophyllidean family Hymenolepididae.…”

“…However, species of the cyclophyllidean family Mesocestoididae possess parallel cortical microtubules in the spermatozoon [ 89 , 90 ]. In the remaining cyclophyllideans, the cortical microtubules in the spermatozoon are twisted at an angle between 10 and 60° [ 32 , 72 , 84 ]. In the Catenotaeniidae, this angle varies between 30 and 40° (see Table 1 ), similar to numerous species of other cyclophyllidean families [ 32 , 72 , 84 ].…”

“…Thus, sperm cells with two axonemes are present in the orders Diphyllobothriidea, Spathebothriidea, Haplobothriidea, Onchoproteocephalidea, and Trypanorhyncha [21][22][23][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60]. Contrarily, spermatozoa with one axoneme are present in the orders Caryophyllidea, Cyclophyllidea, Lecanicephalidea, Nippotaeniidea, Phyllobothriidea, and Tetrabothiidea [21][22][23][26][27][28][29][30][31][32][61][62][63][64][65][66][67][68][69][70][71][72]. In the order Diphyllidea, there are some discrepancies between the spermiogenesis process and the resulting spermatozoa.…”

“…These species are the Onchoproteocephalidea Nomimoscolex sp. (with three crest-like bodies) [85], the Anoplocephalidae Aporina delafondi (with five) and Sudarikovina taterae (with seven) [86,87], and the Hymenolepididae Cladogynia serrata and Rodentolepis microstoma (with six), Echinocotyle dolosa and Rodentolepis straminea (with eight), Hymenolepis sulcata and Rodentolepis myoxi (with nine), Rodentolepis fraterna (with 10), and Rodentolepis nana (with 12) [88]. On the other hand, crest-like bodies are absent in cestodes of the orders Amphilinidea, Gyrocotylidea, Caryophyllidea, Diphyllobothriidea, Haplobothriidea, Spathebothriidea, and Trypanorhyncha [21][22][23].…”

“…In the Cestoda, there are numerous ultrastructural studies describing spermiogenesis and/or the spermatozoon, particularly in the order Cyclophyllidea [ 23 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. However, in the Catenotaeniidae family, ultrastructural aspects of spermiogenesis and/or the spermatozoon have only been studied in two species, namely Catenotaenia pusilla (Goeze, 1782) (Catenotaeniinae Spassky, 1950) and Skrjabinotaenia lobata (Baer, 1925) (Skrjabinotaeniinae) [ 33 , 34 ].…”