Spermatological characteristics of Sclerodistomoides pacificus (Digenea, Sclerodistomoididae) a parasite of the flying fish Cheilopogon pinnatibarbatus (Teleostei, Exocoetidae).

Sclerodistomoides pacificus is the only species described now in Sclerodistomoididae. We present in this paper the first ultrastructural data of the mature spermatozoon of a species from the genus Sclerodistomoides. Adult specimens of S. pacificus (Digenea: Hemiuroidea: Sclerodistomoididae), were parasites of the gall-bladder of the teleost fish Cheilopogon pinnatibarbatus captured in the Atlantic Ocean, near Dakar (Senegal). The male gamete is a filiform cell which exhibits a similar ultrastructural organization to that reported in most species belonging to the Hemiuroidea with two axonemes of the 9 + '1' pattern of trepaxonematans, a nucleus, a mitochondrion, external ornamentation of the plasma membrane not associated with cortical microtubules and located in the anterior region of the spermatozoon, and parallel cortical microtubules disposed in one side of the spermatozoon. However, the present study allowed describing for the first time a moniliform mitochondrion in the Hemiuroidea. The presence of a moniliform mitochondrion and the absence of filamentous external ornamentation described in other Hemiuridae: Lecithochirium microstomum, L. musculus and Hemiurus appendiculatus are a good tool for phylogenetic purposes in the Hemiuroidea. Moreover, spermatological organisation and model are discussed in context with those of previous studies in the Hemiuroidea.

Advances in Spermatological Characters in the Digenea: Review and Proposal of Spermatozoa Models and Their Phylogenetic Importance.

The wide biodiversity and economic importance of digeneans have motivated a great deal of research in the last decade, focussing on their phylogenetic positions. Molecular research was instrumental for our understanding of phylogeny in the Digenea, but spermatological studies have also provided many results, which are potentially useful for phylogeny; however, the complete spermatological data set has never been reviewed in a whole phylogenetic perspective. Spermatological data are now available for more than 100 species, belonging to 15 superfamilies and 46 families. In this paper, we try to summarize the current knowledge about sperm structure in the digeneans and propose a classification of digenean spermatozoa into five basic models. The main ultrastructural characters used are (1) the type of axoneme, (2) the lateral expansion, (3) the association 'external ornamentation of the plasma membrane + cortical microtubules', (4) the field of cortical microtubules and its number, (5) the location of the external ornamentation, (6) the location of the maximum number of cortical microtubules and (7) the number of mitochondria. We also outline the most interesting features for phylogenetic inference and their possible value in the context of digenean systematics, phylogeny and evolution. Associations between sperm models and superfamilies were found as follows: Type 1 in the Schistosomatoidea; Type 2 in the Hemiuroidea; Type 3 in the Opecoeloidea, Lepocreadioidea, Haploporoidea and Opisthorchioidea; Type 4 in the Gorgoderoidea, Microphalloidea, Plagiorchioidea and Gymnophalloidea; Type 5 in the Echinostomatoidea, Microscaphidioidea, Paramphistomoidea, Pronocephaloidea and Brachylaimoidea.

Spermatozoon ultrastructure in two monorchiid digeneans.

Spermatological characteristics of species from two monorchiid genera, Opisthomonorchis and Paramonorcheides, have been investigated, for the first time, by means of transmission electron microscopy. The ultrastructural study reveals that the mature spermatozoon of Opisthomonorchis dinema and Paramonorcheides selaris share several characters such as the presence of two axonemes of different lengths showing the 9+"1" pattern of the Trepaxonemata, a nucleus, two mitochondria, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies, granules of glycogen and similar morphologies of the anterior and posterior extremities. The slight differences between the male gamete of O. dinema and P. selaris are the length of the first axoneme and the position of the second mitochondrion. This study also elucidates the general morphology of the spermatozoon in all monorchiid species described so far, which corresponds to a unique spermatozoon type. Other interesting finds concern the spermatological similarities between monorchiid spermatozoa and the mature spermatozoon reported in the apocreadiid Neoapocreadium chabaudi. These similarities allow us to suggest a close phylogenetical relationship between the Monorchiidae and the Apocreadiidae, although more studies are needed, especially in the unexplored taxa.

First spermatological study in the Atractotrematidae (Digenea, Haploporoidea): the case of Atractotrema sigani, intestinal parasite of Siganus lineatus.

The ultrastructural organization of the mature spermatozoon of the digenean Atractotrema sigani (from Siganus lineatus off New Caledonia) was investigated by transmission electron microscopy. The male gamete of A. sigani exhibits the general morphology described in digeneans with the presence of two axonemes of different lengths showing the 9 + "1" pattern of the Trepaxonemata, a nucleus, two mitochondria, two bundles of parallel cortical microtubules, external ornamentation, spine-like bodies and granules of glycogen. However, the mature spermatozoon of A. sigani has some specific characters such as the morphology of its anterior region and the submembranous electron-dense material. Although similar structures have been reported in some digenean species, the presence of a submembranous electron-dense material describing a complete ring is reported here for the first time in the mature spermatozoon of A. sigani. In addition, sperm characteristics are compared between the Haploporoidea and their supposed close superfamilies, and possible phylogenetic implications of these findings for the Digenea are discussed.

Ultrastructural study of sperm cells in Acanthocolpidae: the case of Stephanostomum murielae and Stephanostomoides tenuis (Digenea).

The mature spermatozoa of Stephanostomum murielae and Stephanostomoides tenuis are described by transmission electron microscopy. They present several ultrastructural features previously reported in other digeneans. Their spermatozoa possess two axonemes of different length showing the 9 + '1' trepaxonematan pattern, four attachment zones, two mitochondria (with an anterior moniliform one in S. murielae), a nucleus, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies and granules of glycogen. The main differences between the mature spermatozoon of S. murielae and S. tenuis are the maximum number of cortical microtubules, the morphology of the anterior spermatozoon extremity and the anterior mitochondrion. This study is the first concerning members of the family Acanthocolpidae. The main ultrastructural characteristics discussed are the morphology of the anterior and posterior spermatozoon extremities, antero-lateral electron dense material, external ornamentations, spine-like bodies and number and morphology of mitochondria. In addition, the phylogenetic significance of all these ultrastructural features is discussed and compared to molecular results in order to highlight the complex relationships in the Digenea.

Neomultitestis aspidogastriformis Bray and Cribb, 2003 (Digenea, Lepocreadiidae): mature spermatozoon and sperm morphologies in the Lepocreadioidea.

Spermatological characteristics are described for the first time in the genus Neomultitestis Machida, 1982, belonging to the family Lepocreadiidae Odhner, 1905. Adult Neomultitestis aspidogastriformis were collected from the digestive tract of Platax teira, caught off New Caledonia. The mature spermatozoon of N. aspidogastriformis is described by transmission electron microscopy (TEM). It includes two axonemes with 9 + "1" pattern of Trepaxonemata, an antero-lateral electron-dense material, attachment zones, two mitochondria, a nucleus, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies, and granules of glycogen. Certain ultrastructural characteristics of the spermatozoon, especially the antero-lateral electron-dense material, are shared by N. aspidogastriformis and all species of the superfamily Lepocreadioidea studied so far. The antero-lateral electron-dense material, present in different families of lepocreadioids, supports the monophyletic status of the superfamily. We also list several ultrastructural characteristics which characterize the mature spermatozoon of the Lepocreadioidea.

Ultrastructural characters of the spermatozoon of the digenean Hypocreadium caputvadum Kacem et al., 2011 (Lepocreadioidea: Lepocreadiidae), an intestinal parasite of Balistes capriscus in Tunisia.

The ultrastructural organization of the spermatozoon of the digenean Hypocreadium caputvadum (Lepocreadioidea: Lepocreadiidae) is described. Live digeneans were collected from Balistes capriscus (Teleostei: Balistidae) from the Gulf of Gabès, Tunisia (Eastern Mediterranean Sea). The mature spermatozoon of H. caputvadum shows several ultrastructural characters such as two axonemes of different lengths exhibiting the classical 9+"1" trepaxonematan pattern, a nucleus, two mitochondria, granules of glycogen, external ornamentation of the plasma membrane and two bundles of parallel cortical microtubules. Moreover, in the anterior extremity, the second axoneme is partly surrounded by a discontinuous and submembranous layer of electron-dense material. Our study provides new data on the spermatozoon of H. caputvadum in order to improve the understanding of phylogenetic relationships in the Digenea, particularly in the superfamily Lepocreadioidea. In this context, the electron-dense material surrounding one of the axonemes in the anterior spermatozoon extremity constitutes the unique distinguishing ultrastructural character of lepocreadioideans, and it is present in spermatozoa of lepocreadiids, aephnidiogenids and gyliauchenids.

Ultrastructure of the spermatozoon of the digenean Lecithocladium excisum (Rudolphi, 1819) (Hemiuroidea: Hemiuridae), a parasite of marine teleosts in Senegal.

The present study describes the ultrastructure of the mature spermatozoon of Lecithocladium excisum (Rudolphi, 1819) (Digenea: Hemiuroidea: Hemiuridae) from the stomach of the marine teleost Scomber japonicus Houttuyn (Scombridae) captured in the Atlantic Ocean, off Dakar (Senegal). The ultrastructural organization of the spermatozoon of L. excisum follows the general model described in most digeneans. It presents two axonemes of the 9+'1' pattern of the Trepaxonemata, nucleus, mitochondrion and parallel cortical microtubules, among other characters. However, some particularities of the spermatozoon of L. excisum are (i) the presence of a membranous ornamentation not associated with cortical microtubules in its anterior extremity, (ii) the presence of a very reduced number of cortical microtubules located only in the ventral side of the spermatozoon and (iii) the absence of several structures described in most digeneans such as spine-like bodies and cytoplasmic expansions.

Spermiogenesis and the spermatozoon ultrastructure of Robphildollfusium fractum (Digenea: Gyliauchenidae), an intestinal parasite of Sarpa salpa (Pisces: Teleostei).

Spermiogenesis in Robphildollfusium fractum begins with the formation of a differentiation zone containing: two centrioles, each bearing striated rootlets, nucleus, several mitochondria and an intercentriolar body constituted by seven electron-dense layers. The two centrioles originate two free flagella growing orthogonally to the median cytoplasmic process. Later, the free flagella rotate and undergo proximodistal fusion with the median cytoplasmic process. Nuclear and mitochondrial migrations occur before this proximodistal fusion. Finally, the young spermatozoon detaches from the residual cytoplasm after the constriction of the ring of arched membranes. The spermatozoon of R. fractum exhibits two axonemes of different length of the 9+'1' trepaxonematan pattern, nucleus, two mitochondria, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies and granules of glycogen. Additionally, a shorter axoneme, which does not reach the nuclear region, the presence of an electron-dense material in the anterior spermatozoon extremity and the morphologies of both spermatozoon extremities characterize the mature sperm of R. fractum.

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

The spermiogenesis process in Wardula capitellata begins with the formation of a differentiation zone containing two centrioles associated with striated rootlets and an intercentriolar body. Each centriole develops into a free flagellum orthogonal to a median cytoplasmic process. Later these flagella rotate and become parallel to the median cytoplasmic process, which already exhibits two electron-dense areas and spinelike bodies before its proximodistal fusion with the flagella. The final stage of the spermiogenesis is characterized by the constriction of the ring of arched membranes, giving rise to the young spermatozoon, which detaches from the residual cytoplasm. The mature spermatozoon of W. capitellata presents most of the classical characters reported in digenean spermatozoa such as two axonemes of different lengths of the 9 + "1" trepaxonematan pattern, nucleus, mitochondrion, two bundles of parallel cortical microtubules and granules of glycogen. However, some peculiarities such as two lateral expansions accompanied by external ornamentation of the plasma membrane and spinelike bodies characterize the mature sperm. Moreover, a new spermatological character is described for the first time, the so-called cytoplasmic ornamented buttons.

Parasite fauna of rodents (Murinae) from El Hierro (Canary Islands, Spain): a multidisciplinary approach.

The parasite fauna (protozoa, helminths and insects) of the two most widespread Murinae rodents in El Hierro (Canary Islands, Spain), the black rat (Rattus rattus) and the house mouse (Mus musculus domesticus) was studied. Faunistic, ecological, ecotoxicological data, as well as information on the biology of some nematode parasites of R. rattus are provided. The present work is unprecedented in the Canary Islands, and provides the first data on the parasite biodiversity in Murinae from the archipelago. Concerning to parasitofaunas stands out: a) impoverishment of biodiversity of helminths respect of which have the same hosts in other islands; b) increasing the number of species of Siphonaptera, even compared with flea species that parasitize the same hosts from continental biotopes.

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

Spermatological characters of the liver fluke Mediogonimus jourdanei Mas-Coma et Rocamora, 1978 were studied by means of transmission and scanning electron microscopy. Spermiogenesis begins with the formation of the differentiation zone containing two centrioles associated with striated rootlets and an intercentriolar body. These two centrioles originate two free flagella that undergo a 90 degrees rotation before fusing with the median cytoplasmic process. Both nuclear and mitochondrial migrations toward the median cytoplasmic process occur before the proximodistal fusion of flagella. Finally, the constriction of the ring of arched membranes gives rise to the young spermatozoon. The mature sperm of M. jourdanei measures about 260 microm and presents two axonemes of different lengths with the typical pattern of the Trepaxonemata, two bundles of parallel cortical microtubules, one mitochondrion, a nucleus and granules of glycogen. An analysis of all the microphalloidean species studied to date emphasised some differences in certain characters found in Maritrema linguilla Jägerskiöld, 1908 and Ganeo tigrinum Mehra et Negi, 1928 in comparison to those in the remaining microphalloideans. The presence and variability of such ultrastructural characters according to family, superfamily or order have led several authors to propose their use in the analysis of trematode relationships and phylogeny. Therefore, apart from producing new data on the family Prosthogonimidae, the present study also compares the spermatological organization of M jourdanei with other available ultrastructural studies focusing on the Microphalloidea.

Ultrastructural study of vitellogenesis in Maritrema feliui (Digenea, Microphallidae).

During vitellogenesis in the microphallid trematode Maritrema feliui, we distinguished four stages: (I) a stem cell stage of the gonial type; (II) an early differentiation stage with the main cell activity concentrated on the initiation of protein synthetic activity and the beginning of shell globule formation; (III) an advanced differentiation stage concentrated on a rapid intensification of protein synthetic activity, the progressive fusion of individual shell globules into large shell globule clusters and the formation of saturated lipid droplets and a small amount of ß-glycogen particles in the peripheral cytoplasm, considered as a store of nutritive reserves for the developing embryos; and (IV) the mature vitellocyte. Early vitellocyte maturation is characterised by: (1) an increase in cell volume; (2) extensive development of large, labyrinth-like cisternae of GER that produce proteinaceous granules; (3) the development of Golgi complexes engaged in packaging this material; and (4) a continuous enlargement of proteinaceous granules within vacuoles and their transformation into shell globule clusters composed of the heterogeneous material observed during vitellocyte cytodifferentiation. Mature vitelline cells are very rich in two types of cell inclusions accumulated in large amounts in their cytoplasm: (1) shell globule clusters, which play an important role in eggshell formation; and (2) a few osmiophobic lipid droplets of a saturated nature that undoubtedly represent nutritive reserves for the developing embryos. In addition, there are small numbers of ß-glycogen particles in the peripheral cytoplasm of mature vitellocytes of this species. The general pattern and ultrastructure of vitellogenesis in M. feliui greatly resembles those observed in another microphallid trematode, Maritrema linguilla, in other digeneans and in some lower cestodes. Quantitative and qualitative variations in lipids (saturated and unsaturated) and glycogen (α-glycogen rosettes and ß-glycogen particles) during platyhelminth vitellogenesis between the different species of trematodes and some lower cestodes are identified and discussed.

Spermatological characters of the digenean Rubenstrema exasperatum (Rudolphi, 1819) (Plagiorchioidea, Omphalometridae).

We present the first ultrastructural description of spermiogenesis and of the spermatozoon of Rubenstrema exasperatum (Omphalometridae), an intestinal parasite of Sorex araneus (Soricidae). Spermiogenesis begins with the formation of the differentiation zone delimited at the base by the ring of the arched membranes and bordered by cortical microtubules. This area contains two centrioles associated with striated rootlets and with an intercentriolar body. It also contains the nucleus and numerous mitochondria. The intercentriolar body is made up of seven electron-dense layers. The two centrioles give rise to two free flagella that grow orthogonally to the median cytoplasmic process. Additionally, flagellar rotation is followed by the proximodistal fusion of the flagella with the median cytoplasmic process, while the nucleus and mitochondria migrate along the spermatid. The constriction of the ring of arched membranes gives rise to the young spermatozoon. The mature spermatozoon of R. exasperatum shows several ultrastructural characters found in digenean spermatozoa such as two axonemes, mitochondrion, two bundles of parallel cortical microtubules, nucleus, and granules of glycogen. External ornamentation of the plasma membrane and spinelike bodies are also present in the spermatozoon of this species. In the present study, we produced additional spermatological data concerning a previously unexplored family, and we also compare our data to the existent ultrastructural descriptions within the Digenea in order to assess the use of several characters proposed as phylogenetic tools.