In the years 1999-2002, first studies were carried out on the metazoan parasites of Atlantic salmon (Salmo salar L.) recently reintroduced into the Elbe River drainage system, after more than 50 years after the complete extinction of the Elbe salmon population. A total of six helminth species were recorded from salmon smolts from three streams of the Elbe River basin (Kamenice River, Ještědský and Libočanský Brooks) in North Bohemia, Czech Republic, where S. salar fingerlings have been released since 1998: Gyrodactylus truttae Gläser, 1974, Crepidostomum metoecus Braun, 1900, Diplostomum spathaceum (Rudolphi, 1819) metacercariae, Raphidascaris acus (Bloch, 1799) adults and encapsulated larvae, Cystidicoloides ephemeridarum (Linstow, 1872), and Neoechinorhynchus rutili (Müller, 1780). Except for D. spathaceum, all these freshwater parasites have been received from the helminth fauna of the co-habiting brown trout (Salmo trutta fario L.). Due to local ecological conditions, the parasite faunae of both salmon and brown trout exhibited distinct qualitative and quantitative differences in the three localities. The finding of G. truttae on S. salar represents a new host record. Three helminth parasites of marine origin, the cestodes Eubothrium crassum (Bloch, 1779) and Scolex pleuronectis Müller, 1788 plerocercoids, and the nematode Anisakis simplex (Rudolphi, 1809) larvae were found in the single examined adult S. salar from the Kamenice River. New data on the geographical distribution of some nematode parasites of Salmo trutta fario L., Barbatula barbatula (L.) and Anguilla anguilla (L.) are presented.
Based on light and scanning electron microscopical studies, the following nine species of Philometridae (Nematoda: Dracunculoidea) are described from female worms parasitizing marine perciform fishes belonging to six families off the northern coast Australia (near Darwin): Philometra australiensis sp. n. from the swimbladder of the king threadfin Polydactylus macrochir (Günther) (Polynemidae); P. epinepheli Dewi et Palm, 2013 from the operculum of the orange-spotted grouper Epinephelus coioides (Hamilton) (Serranidae); Philometra johnii Moravec et Ali, 2013 from the gonad of the croaker Johnius sp. (Sciaenidae); P. macrochiri sp. n. from the sensory fin of P. macrochir; P. zabidii sp. n. from the ovary of the ninespine batfish Zabidius novemaculeatus (McCulloch) (Ephippidae); Philometra sp. 1 and Philometra sp. 2 from the ovary of the Spanish flag snapper Lutjanus carponotatus (Richardson) (Lutjanidae) and the silver grunt Pomadasys argenteus (Forsskål) (Haemulidae), respectively; Philometroides eleutheronemae Moravec et Manoharan, 2013 from the ovary of the fourfinger threadfin Eleutheronema tetradactylum (Shaw) (Polynemidae); and Spirophilometra endangae Dewi et Palm, 2013 from the pectoral fins of E. coioides. The new species P. australiensis is characterized mainly by the structure of the cephalic end, 14 minute cephalic papillae, absence of caudal projections and body length of gravid female (67 mm), P. macrochiri by the presence of a conspicuously large anterior oesophageal bulb, 14 very small cephalic papillae and the truncated posterior end of body without any caudal projections, whereas P. zabidii is characterized by the presence of distinct caudal projections, the number (14) and larger size and arrangement of cephalic papillae, a poorly developed anterior oesophageal inflation, the body length (114 mm) and the host family (Ephippidae). All above-mentioned species were recorded from Australian waters for the first time.
The following three species of the Philometridae (Nematoda: Dracunculoidea) are described from marine perciform fishes of the Everglades National Park (northern Gulf of Mexico), Florida, USA: Philometra brevispicula sp. n. (male and females) from the subcutaneous tissue of mouth of the gray snapper Lutjanus griseus (Linnaeus) (Lutjanidae), Philometroides grandipapillatus sp. n. (only females) from pectoral fin muscle of the crevalle jack Caranx hippos (Linnaeus) (Carangidae), and Caranginema americanum Moravec, Montoya-Mendoza et Salgado-Maldonado, 2008 (females) from the subcutaneous fascia of trunk muscle in crevalle jack C. hippos. Philometra brevispicula is mainly characterized by small cephalic papillae of the external circle, the absence of oesophageal teeth and the presence of small caudal projections in gravid female, markedly short spicules (45 µm) in male, and by its location in the host. Philometroides grandipapillatus differs from congeners mainly in the shape of the cephalic region (narrow, conspicuously protruding), large cephalic papillae of the external circle and the absence of caudal projections in female, and by the site of infection in the host. Caranginema americanum is for the first time recorded from the northern Gulf of Mexico.
The following four species (only females available) of the Philometridae (Nematoda: Dracunculoidea) were recorded from freshwater fishes of Lake Turkana, northwestern Kenya in 2007-2008: Philometra bagri (Khalil, 1965) from the subcutaneous tissue around the mouth, on gill covers and the fin base of the bayad Bagrus bajad (Forsskål) (Bagridae: Siluriformes), Philometra lati sp. n. from the abdominal cavity of the Nile perch Lates niloticus (Linnaeus) (Latidae: Perciformes), Philometra spiriformis sp. n. from capsules on the inner surface of gill covers of L. niloticus and Afrophilometra hydrocyoni (Fahmy, Mandour et El-Nafar, 1976) comb. n. from the fins of Hydrocynus forskahlii (Cuvier) (Alestidae: Characiformes). The new species P. lati is characterized mainly by the presence of distinct oesophageal teeth, absence of large cephalic lobes and caudal projections, and by a combination of other features. Philometra spiriformis differs from all congeners principally in the spirally coiled body and from individual species by a combination of other morphological features. The already known species P. bagri and A. hydrocyoni are redescribed based on light and scanning electron microscopy; findings of both these species in Kenya represent new geographical records.
A new species of philometrid nematode, Philometroides africanus sp. n., is described from female specimens found encapsulated in gill arches and inner surface of gill covers of the African pike, Hepsetus odoe (Bloch), an endemic freshwater fish in Africa, from the Okavango River and Delta in Botswana. This new nematode is characterised mainly by a markedly small and plump body of gravid females (body length 6-9 mm), a separate anterior oesophageal bulb, a conspicuously small oesophageal gland, presence of four pairs of very small submedian cephalic papillae, and absence of any caudal processes. The prevalence of P. africanus in African pike of the Okavango Delta was 29%, with the intensity 1-8 (mean 3) encapsulated nematodes per fish. The genus Margolisianum Blaylock et Overstreet, 1999 is considered a junior synonym of Philometroides Yamaguti, 1935 and, consequently, its type species is transferred to the latter as Philometroides bulbosus (Blaylock et Overstreet, 1999) comb. n.
Small subunit rRNA sequences were obtained from 38 representatives mainly of the nematode orders Spirurida (Camallanidae, Cystidicolidae, Daniconematidae, Philometridae, Physalopteridae, Rhabdochonidae, Skrjabillanidae) and, in part, Ascaridida (Anisakidae, Cucullanidae, Quimperiidae). The examined nematodes are predominantly parasites of fishes. Their analyses provided well-supported trees allowing the study of phylogenetic relationships among some spirurine nematodes. The present results support the placement of Cucullanidae at the base of the suborder Spirurina and, based on the position of the genus Philonema (subfamily Philoneminae) forming a sister group to Skrjabillanidae (thus Philoneminae should be elevated to Philonemidae), the paraphyly of the Philometridae. Comparison of a large number of sequences of representatives of the latter family supports the paraphyly of the genera Philometra, Philometroides and Dentiphilometra. The validity of the newly included genera Afrophilometra and Caranginema is not supported. These results indicate geographical isolation has not been the cause of speciation in this parasite group and no coevolution with fish hosts is apparent. On the contrary, the group of South-American species of Alinema, Nilonema and Rumai is placed in an independent branch, thus markedly separated from other family members. Molecular data indicate that the skrjabillanid subfamily Esocineminae (represented by Esocinema bohemicum) should be either elevated to the rank of an independent family or Daniconematidae (Mexiconema africanum) should be decreased to Daniconematinae and transferred to the family Skrjabillanidae. Camallanid genera Camallanus and Procamallanus, as well as the subgenera Procamallanus and Spirocamallanus are confirmed to be paraphyletic. Paraphyly has also been found within Filarioidea, Habronematoidea and Thelazioidea and in Cystidicolidae, Physalopteridae and Thelaziidae. The results of the analyses also show that Neoascarophis, Spinitectus and Rhabdochona are monophyletic, in contrast to the paraphyletic genus Ascarophis. They further confirm the independence of two subgenera, Rhabdochona and Globochona, in the genus Rhabdochona. The necessity of further studies of fish-parasitizing representatives of additional nematode families not yet studied by molecular methods, such as Guyanemidae, Lucionematidae or Tetanonematidae, is underscored.
Re-examination of the syntypes of the capillariid nematode Neocapillaria phoxini Yu et Wang, 1994, the type species of Neocapillaria Yu et Wang, 1994, described from the intestine of the freshwater fish Phoxinus lagowskii variegatus Günther (Cyprinidae) from China, confirmed its morphological similarity with species of Freitascapillaria Moravec, 1987, to which it is transferred as Freitascapillaria phoxini (Yu et Wang, 1994) comb. n. Consequently, Neocapillaria Yu et Wang, 1994 (a homonym to Neocapillaria Moravec, 1987) and Sinocapillaria Moravec et Spratt, 1998 become junior synonyms of Freitascapillaria. Skrjabinocapillaria gigantea is transferred to Freitascapillaria as F. gigantea (Wang, 1984) comb. n.
Dracunculus globocephalus Mackin, 1927 (Nematoda: Dracunculoidea) is redescribed from specimens collected from the mesentery of the snapping turtle, Chelydra serpentina (L.), in Louisiana, USA. The use of scanning electron microscopy, applied for the first time in this species, made it possible to study details in the structure of the cephalic end and the arrangement of male caudal papillae that are difficult to observe under the light microscope. This species markedly differs from all other species of Dracunculus in having the spicules greatly unequal in size and shape, in the absence of a gubernaculum, and in the disposition of male caudal papillae. The validity of D. globocephalus is confirmed, but the above mentioned morphological differences are not sufficient for listing it in a separate genus. This is the first record of D. globocephalus in Louisiana.
The cystidicolid nematode Metabronema magnum (Taylor, 1925) is redescribed from specimens collected from the swimbladder of the fish (golden trevally) Gnathanodon speciosus (Forsskål) (Carangidae, Perciformes) off New Caledonia, South Pacific (a new geographical record). The light and scanning electron microscopical examination made it possible to study in detail the morphology of this so far little-known species. Its pseudolabia were found to possess distinct anterior protrusions (protuberances), sublabia are absent, only four cephalic papillae are present, deirids are bifurcated, and the male possesses six pairs of postanal papillae. By its morphology, M. magnum seems to be most similar to species of Salvelinema Trofimenko, 1962, also from the swimbladder of fishes, differing from them mainly in the presence of median wedge-shaped outgrowths in the mouth, lateral alae, the longer spicule on the right side, and a fewer number of pairs of preanal papillae in the male. Since the morphology of M. magnum considerably differs from that of other representatives of the Cystidicolidae, Metabronema in Rasheed's (1966) conception is considered a valid genus.
Two little-known species of Spinitectus (Nematoda: Cystidicolidae) were, for the first time, recorded from fishes of the Lacantún River (Usumacinta River basin) in the Lacandon rain forest, Chiapas, southern Mexico: S. tabascoensis Moravec, García-Magaña et Salgado-Maldonado, 2002 in intestines of Ictalurus furcatus (Valenciennes) (Ictaluridae) (adults and juveniles), Cathorops aguadulce (Meek) and Potamarius nelsoni (Evermann et Goldsborough) (both Ariidae) (in both only juveniles), and S. osorioi Choudhury et Pérez-Ponce de León, 2001 in Atherinella alvarezi (Díaz-Pardo) (Atherinopsidae) (adults in intestine) and Eugerres mexicanus (Steindachner) (Gerreidae) (adults and juveniles in stomach). Eugerres mexicanus, C. aguadulce and P. nelsoni represent new host records. Detailed light and electron microscopical studies of S. tabascoensis revealed some taxonomically important, previously not observed features, such as cuticular spines arranged in four sectors, the cephalic structure, the number (2) of ventral precloacal ridges or the structure of the male caudal end. Therefore, Spinitectus tabascoensis is redescribed. Spinitectus macrospinosus Choudhury et Perryman, 2003, described from ictalurids in Canada and the USA, is considered its junior synonym. Spinitectus tabascoensis seems to be a specific parasite of Ictalurus spp., whereas C. aguadulce and P. nelsoni, as well as some other fishes, serve only as its paratenic hosts. The definitive hosts of S. osorioi are atherinopsid fish (A. alvarezi, Chirostoma spp.), whereas the gerreid E. mexicanus probably serves only as its postcyclic host.