Morphology and phylogeny of the parasitic nematode Mooleptus rabuka (Machida, Ogawa & Okiyama, 1982) (Rhabditida, Spirurina: Mooleptinae nom. nov.), with notes on taxonomy of the family Gnathostomatidae.

The nematode Mooleptus rabuka is recorded in the digestive tract of catshark Apristurus fedorovi caught at the Imperial Ridge (Pacific Ocean). Important morphological features such as the number of cephalic and caudal papillae, the position of amphids and the shape of the gubernaculum are detailed in this parasite species. According to the phylogenetic analyses based on the 18S ribosomal RNA gene sequences, M. rabuka forms a lineage, Mooleptinae nom. nov., which is close to the gnathostomatid genus Echinocephalus (maximum likelihood analysis), or else forms a polytomy with this genus and the lineages of Anguillicola + Spiroxys and Tanqua + 'Linstowinema' sp. (Bayesian inference analysis). Overall, our findings do not support the monophyly of the Gnathostomatidae. We elevate spiroxyines to the family status, Spiroxyidae stat. nov., and temporarily consider the Gnathostomatidae to include the following subfamilies: Ancyracanthinae Yorke & Maplestone, 1926, Gnathostomatinae Railliet, 1895 sensu lato and Mooleptinae nom. nov. The name Mooleptinae nom. nov. is suggested instead of the Metaleptinae Moravec & Nagasawa, 2000, which is based on a preoccupied generic name Metaleptus Machida, Ogawa & Okiyama, 1982.

Records of opecoeline species Pseudopecoelus cf. vulgaris and Anomalotrema koiae Gibson & Bray, 1984 (Trematoda, Opecoelidae, Opecoelinae) from fish of the North Pacific, with notes on the phylogeny of the family Opecoelidae.

Opecoelid species Pseudopecoelus cf. vulgaris and Anomalotrema koiae Gibson & Bray, 1984 were found in fish collected in the boreal waters of the North Pacific. Pseudopecoelus cf. vulgaris differs from Pseudopecoelus vulgaris (Manter, 1934) in terms of the egg size. This is the first record of A. koiae in the North Pacific, and the second of Pseudopecoelus cf. vulgaris. Previously, A. koiae was recorded only in North Atlantic fish. Partial sequences of 28S rDNA obtained for these two species and six other previously unsequenced representatives of the family Opecoelidae were analysed together with data from GenBank. Phylogenetic analysis supports the allocation of the six clades of opecoelids - Helicometrinae, Opecoelinae, Opistholebetinae, 'freshwater Plagioporinae', 'marine Plagioporinae B' and 'marine Plagioporinae C', and confirms the paraphyly of the group 'deep-sea Plagioporinae'. Our phylogeny does not support previous hypotheses about the monophyly of opecoelines with a uroproct.

Diversity of the CO1 Gene of Mitochondrial DNA in Representatives of Genus Antimora (Moridae, Gadiformes) in the World Oceans.

The frequency of occurrence of the COI gene of mitochondrial DNA in the Pacific flatnose Antimora microlepis and blue antimora Antimora rostrata (Moridae, Gadiformes) was analyzed in samples collected in different areas of the World Ocean. The revealed maximum haplotype diversity of COI in the blue antimora in the North Atlantics may indicate that this species emerged in this region, from which it widely distributed in the World Ocean. The Pacific flatnose Antimora microlepis originated from Antimora rostrata. Antimora might penetrate into the North Pacific by several routes: through the Panama Strait, along the coast of Antarctica, or through the Indian Ocean along the coast of Australia.

New Data on the Morphology and Phylogenetic Connections of Postlepidapedon Opisthobifurcatum (Trematoda, Lepocreadioidea: Lepidapedidae), a Parasite of Antarctic and Sub-Antarctic Fishes.

The trematode Postlepidapedon opisthobifurcatum (Zdzitowiecki, 1990) is a common intestinal parasite of the gadiform fishes of the Southern Ocean. In this work, we supplement the description of the species with the anatomy of the terminal part of the reproductive system and with molecular data. The male terminal genitalia are characterised by the presence of the external seminal vesicle and cirrus-sac. The external seminal vesicle is surrounded by aciniform groups of outer prostatic cells. Groups of outer prostatic cells and proximal parts of their ducts are associated with a thin-walled membrane that is connected to the proximal edge of the сirrus-sac. The cirrus-sac is claviform, with a long proximal part accommodating the tubular, thin-walled internal seminal vesicle and ducts of outer prostatic cells. The female terminal genitalia are represented by a thick-walled metraterm, which is surrounded by aciniform groups of glandular cells. Phylogenetic analysis based on 28S rDNA partial sequences data placed P. opisthobifurcatum into the monophyletic group Lepidapedidae, including the species Myzoxenus insolens (Crowcroft, 1945), Intusatrium robustum Durio et Manter, 1968, and Postlepidapedon uberis Bray, Cribb et Barker, 1997. However, we were unable to detect direct phylogenetic connections between P. opisthobifurcatum and P. uberis.

[Infection of the pacific saury Cololabis saira by acanthocephalans in the Kuril Islands area].

The Pacific saury Cololabis saira (Brevoort, 1856) is one of the important target species of commercial fisheries. Food manufacturers and consumers encounter problems due to the infection of the saury by acanthocephalans, which are quite difficult to clean out completely during on-board catch processing. Infection of C. saira was not studied on a regular basis, therefore, our knowledge about the parasites of saury is fragmentary. This paper contains infection indices (only acanthocephalans) of the Pacific saury caught in the Kuril Islands area (Russian Exclusive Economic Zone) in 2015.

[METACERCERIAE OF BRACHYPHALLUS CRENARUS RUDOLPHI, 1802 (TREMATODA: HENIURIDAE) IN PLANKTON CRUSTACEANS FROM THE PROSTOR GULF (ITURUP ISLAND, RUSSIA)].

Samples of Zooplankton collected in waters of the Prostor Gulf (Iturup Island) were examined. Metacercariae of Brachyphallus crenatus were found in copepods Pseudocalanus newmani and Acartia longiremis. This is the first record of the second intermediate hosts of this species in the North Pacific.

[COMPARATIVE ANALYSIS OF LIPID METABOLISM INDICES IN SOME PARASITES OF THE WHITE CHARR (SALVELINUS ALBUS) FROM THE LAKE KRINOTSKOE].

Comparative study of lipid metabolism indices (total lipids, separate lipid fractions, level of the lipid peroxidation processes, and antioxidant protection) was carried out in three parasite species collected from the white char in the Lake Kronotskoe: Diphyllobothrium ditremum Crepin, 1825 (Cestoda), Philonema oncorhynchi Kuitunen-Ekbaum, 1933 (Nematoda) H Neoechinorhynchus salmonis Ching, 1984 (Acanthocephala). Acanthocephalans possessed significantly greater levels of total lipids, triacylglycerol, and malondialdehyde; nematodes, of cholesterol and sterol esters; and cestodes, in phospholipids and constants of the substrate oxidation. Dependence between lipid metabolism of helminths and their taxonomic affiliation, morpho-functional features, the stage of the life cycle, and the site of infection in the host are discussed.

[New data on trematodes of Antarctic fish].

Deepwater fishes from the Amundsen Sea, d'Urville Sea, Ross Sea, Cooperation Sea, Weddell Sea, and open waters of the South-West part of the Pacific sector of the Antarctic were examined. Fourteen species of trematodes were found. Muraenolepitrema magnatestis Gaevskaya et Rodjuk, 1988 and Helicometrina sp. were found in the Antarctic for the first time. Muraenolepitrema magnatestis was redescribed and basing on this, diagnosis of the genus Muraenolepitrema was amended. Muraenolepitrema magnatestis possesses the uroproct and glandular cells that are loosely arranged around the external seminal vesicle (without a membranous sac).

[Occurrence of helminths in amphipods Gammarus lacustris Sars, 1863 (Amphipoda: Gammaridae) from Kronotskoe Lake (Kamchatka)].

Metacercariae of Crepidostomum metoecus (prevalence 2.0%), procercoids of Cyathocephalus truncatus (2.9%), and nematodes of the family Cystidicolidae (17.6%) were found in the body cavity of amphipods Gammarus lacustris from the Kronotskoe Lake. The nematodes were presented by Cystidicola farionis (third-stage juvenile) and Ascarophis sp. (adult and fourth-stage juvenile).

[Structure of the glial cells in the nervous system of parasitic and free-living flatworms].

This study is devoted to ultrastructural and immunosytochemical investigation of the nervous system in parasitic and free-living platyhelminthes to learn if glial cells exist in the nervous system of flatworms. We described the ultrastructure of different types of glial cells and the peculiarities of myelinization of gigantic axons; immunoreactivity to the S100b protein is revealed. Comparative analysis of the glia structure of annelids and platods is given; structural, functional, and evolutionary aspects of myelinization of gigantic axons, which are revealed in cestodes, are discussed.