Mikuláš Oros

Spermatozoa of tapeworms (Platyhelminthes, Eucestoda): advances in ultrastructural and phylogenetic studies.

New data on spermiogenesis and the ultrastructure of spermatozoa of ‘true’ tapeworms (Eucestoda) are summarized. Since 2001, more than 50 species belonging to most orders of the Eucestoda have been studied or reinvestigated, particularly members of the Caryophyllidea, Spathebothriidea, Diphyllobothriidea, Bothriocephalidea, Trypanorhyncha, Tetraphyllidea, Proteocephalidea, and Cyclophyllidea. A new classification of spermatozoa of eucestodes into seven basic types is proposed and a key to their identification is given. For the first time, a phylogenetic tree inferred from spermatological characters is provided. New information obtained in the last decade has made it possible to fill numerous gaps in the character data matrix, enabling us to carry out a more reliable analysis of the evolution of ultrastructural characters of sperm and spermiogenesis in eucestodes. The tree is broadly congruent with those based on morphological and molecular data, indicating that convergent evolution of sperm characters in cestodes may not be as common as in other invertebrate taxa. The main gaps in the current knowledge of spermatological characters are mapped and topics for future research are outlined, with special emphasis on those characters that might provide additional information about the evolution of tapeworms and their spermatozoa. Future studies should be focused on representatives of those major groups (families and orders) in which molecular data indicate paraphyly or polyphyly (e.g. ‘Tetraphyllidea’ and Trypanorhyncha) and on those that have a key phylogenetic position among eucestodes (e.g. Diphyllidea, ‘Tetraphyllidea’, Lecanicephalidea, Nippotaeniidea).

Re-establishment of the fish parasite fauna in the Tisa River system (Slovakia) after a catastrophic pollution event

An extensive survey of helminth parasites in 1,316 freshwater fish representing 31 species from two aquatic ecosystems in southeastern Slovakia characterized by different level of environmental pollution was carried out. The helminth species diversity was compared between the Tisa River, heavily polluted with cyanides and heavy metals after a series of ecological disasters in 2000, and the less anthropogenically influenced Latorica River. A parasitological survey found 31 gastrointestinal helminths: Trematoda (11 species), Cestoda (14), Acanthocephala (3) and Nematoda (3). As many as 70 host−parasite combinations have been found. Twenty of them (28.6%) represent new host−parasite finding records for the territory of Slovakia. The component communities were species-poor in both rivers, with high dominance of one to three helminth species. Even though the fish communities were qualitatively similar (ICS = 81%) and the number of fish examined was approximately the same (676 and 640) in both localities, the helminth species richness and diversity of host−parasite combinations were two times lower in the more polluted Tisa River. The helminth communities were also much less abundant in the Tisa River. Based on the Czekanowski−Sørensen similarity index (ICS = 48.8%) and the Percentage similarity index (PI = 19.5%), the helminth communities were qualitatively and quantitatively different in the two rivers. The remarkable lack of species diversity in the Tisa River can be explained by the negative impact of residual contamination of the Tisa river bottom on certain freshwater invertebrates (bivalves and prosobranch mollusks, copepods and amphipods) which serve as obligatory intermediate hosts for the helminths. Four species, the aspidogastrean Aspidogaster limacoides Diesing, 1835, the acanthocephalan Pomphorhynchus tereticollis (Rudolphi, 1809) tapeworms Atractolytocestus huronensis Anthony, 1958 and Khawia sinensis Hsü, 1935 are recorded in Slovakia for the first time.

Phylogenetic relationships of the monozoic tapeworms (Eucestoda: Caryophyllidea) inferred from morphological characters

Phylogenetic relationships of all genera of the order Caryophyllidea, possibly the earliest branching group of true tapeworms (Platyhelminthes: Eucestoda) and the only one that is monozoic, have been assessed for the first time. Results of this cladistic analysis, inferred from 30 unweighted morphological characters, are only partly congruent with the existing classification, which consists of four families based on the position of the inner longitudinal muscles in relation to the internal genital organs. Whereas all but five genera of the Caryophyllaeidae form a monophyletic clade, members of the Capingentidae are split, occurring within six unrelated groups. The Lytocestidae is also paraphyletic, as some genera appear in four unrelated clades. Archigetes appears in a derived clade, indicating that its direct (monoxenous) life-cycle involving only tubificid oligochaetes is secondarily derived and not plesiomorphic among the Eucestoda, as postulated by some authors.

Tapeworm Khawia sinensis: review of the introduction and subsequent decline of a pathogen of carp, Cyprinus carpio.

The Asian tapeworm Khawia sinensis Hsü, 1935 (Cestoda: Caryophyllidea) is a large-sized (body length up to 11.5 cm) monozoic (unsegmented) parasite of common carp (Cyprinus carpio L.) that may cause mortality of young fish (fry). Since the 1960s, this cestode successfully colonized a large part of Europe, including the British Isles, North America and Japan. However, a review of published records provides evidence that the tapeworm K. sinensis, invasive parasite of carp, has become less common during the last two decades. Decline of K. sinensis may have been related to the recent introduction of another invasive tapeworm, the caryophyllidean Atractolytocestus huronensis Anthony, 1958 to Europe. Other factors that may have caused that K. sinensis is much less common than previously are also briefly discussed. A comparison of K. sinensis from feral and cultured carp, published to date, with those recently found for the first time in wild populations of carp in Slovakia did not reveal any marked differences in their morphology or measurements.

Ultrastructure of spermiogenesis and mature spermatozoon of Breviscolex orientalis (Cestoda: Caryophyllidea).

Spermiogenesis and spermatozoon ultrastructure of the caryophyllidean cestode Breviscolex orientalis Kulakovskaya, 1962, first member of the family Capingentidae studied, a parasite of cyprinid fish Abbottina rivularis, are described using transmission electron microscopy. Spermiogenesis in B. orientalis follows the Type II pattern described by Bâ and Marchand (Mém Mus Natl Hist Nat 166:87–95, 1995) for cestodes. It begins with the formation of a zone of differentiation containing a large nucleus and a pair of centrioles. The centrioles are separated from one another by an intercentriolar body composed of three electron-dense layers. Each centriole is associated with typical striated roots. At the beginning of the spermiogenesis, an electron-dense material is observed in the apical region of the differentiation zone. During the initial stage of spermiogenesis, one of the centrioles gives rise to a free flagellum, which then rotates and undergoes proximodistal fusion with the cytoplasmic protrusion of the differentiation zone. The mature spermatozoon of B. orientalis corresponds to the Type III pattern described by Levron et al. (Biol Rev 85:523–543, 2010). It is characterized by the absence of mitochondrion and crested body. Five regions of the mature spermatozoon are differentiated. The main ultrastructural characteristics are: one axoneme of 9 + “1” trepaxonematan pattern, cortical microtubules and nucleus. The comparison of the spermiogenesis of B. orientalis with those of the other caryophyllidean species demonstrates some variation within the order relative to the presence and morphology of the intercentriolar body, the presence of slight rotation of the flagellar bud and a complete proximodistal fusion of the free flagellum with a cytoplasmic protrusion.

Bothriocephalidean tapeworms (Cestoda) of freshwater fish in Africa, including erection of Kirstenella n. gen. and description of Tetracampos martinae n. sp.

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Tapeworms (Cestoda: Caryophyllidea), Parasites of Clarias batrachus (Pisces: Siluriformes) in the Indomalayan Region

Abstract Revision of monozoic cestodes (Caryophyllidea) parasitic in commercially important walking catfish Clarias batrachus (L.) in tropical Asia (Indomalayan zoogeographical region) was carried out, based on the evaluation of newly collected material from India, Indonesia, and Thailand, as well as a study of type specimens. Instead of the 59 nominal taxa of 15 genera from 3 caryophyllidean families previously described, only 8 species of the Lytocestidae are considered to be valid: Bovienia indica (Niyogi, Gupta and Agarwal, 1982) n. comb.; Bovienia raipurensis (Satpute and Agarwal, 1980) Mackiewicz, 1994; Bovienia serialis (Bovien, 1926) Fuhrmann, 1931; Djombangia penetrans Bovien, 1926; Lucknowia microcephala (Bovien, 1926) n. comb.; Lytocestus indicus (Moghe, 1925) Woodland 1926; Pseudocaryophyllaeus ritai Gupta and Singh, 1983; and Pseudocaryophyllaeus tenuicollis (Bovien, 1926) n. comb. All valid species are redescribed and SEM photomicrographs of their scolices and photomicrographs of their eggs are provided for the first time. Crescentovitus Murhar, 1963, Heeradevina Srivastav and Khare, 2005, Pseudobatrachus Pathak and Srivastav, 2005, Pseudobilobulata Srivastav and Lohia, 2002, Pseudoclariasis Pathak, 2002, and Pseudoinverta Pathak, 2002 are invalidated and 50 nominal species are newly synonymized, including 4 species described from other fish hosts. Taxonomic status of the remaining caryophyllidean taxa reported from C. batrachus (at least 6 taxa) could not be clarified because of the unavailability of their original descriptions. A key to identification of caryophyllidean tapeworms parasitic in C. batrachus is provided. To avoid current inflation of descriptions of invalid taxa, researchers are strongly encouraged to work only with well-fixed material; damaged, decomposed, or strongly flattened specimens should not be used for taxonomic studies, and type specimens must always be deposited in internationally recognized collections.

Vitellogenesis in the cestode Atractolytocestus huronensis Anthony, 1958 (Caryophyllidea: Lytocestidae).

Vitellogenesis in the parthenogenetic caryophyllidean tapeworm Atractolytocestus huronensis Anthony, 1958, parasitizing the carp Cyprinus carpio L., has been examined using light (LM) and transmission electron microscopy and cytochemical staining with periodic acid–thiosemicarbazide–silver proteinate for glycogen. It was found that formation of vitellocytes shares the same basic patterns in lower tapeworms with parthenogenetic and normal reproduction. Each vitelline follicle of A. huronensis consists of vitellocytes at various stages of development and an interstitial tissue. Projections of the interstitial tissue surround each vitellocyte and extend as a cytoplasmic sheath on the follicular periphery. In contrary to other Eucestoda, interstitial tissue of A. huronensis includes numerous electron-dense vesicles of various sizes. Maturing and mature vitellocytes contain vitelline material in the form of single small shell globules, which may gradually fuse and give rise to the large shell globule clusters. Shell globule clusters are of two types in A. huronensis. Additional vitelline material is represented by single “lamellar” granules and glycogen in the cytoplasm of mature vitellocytes. The ultrastructural features of vitellogenesis and/or vitellocyte in A. huronensis are compared with that in other caryophyllideans and/or Neodermata.

A chromosome study and localization of 18S rDNA in Khawia saurogobii (Cestoda: Caryophyllidea)

This paper reports results of the first cytogenetic study carried out on a recently described monozoic tapeworm, Khawia saurogobii Xi et al., 2009, from the Chinese lizard gudgeon (Saurogobio dabryi). The karyotype of this species is composed of eight pairs of metacentric and telocentric chromosomes (2n = 16;