Scanning electron microscopy examinations of trematode specimens belonging to Crepidostomum farionis (O.F. Müller, 1784) and C. metoecus Braun, 1900, collected from brown trout, Salmo trutta fario L., in the Czech Republic, made it possible to study their surface morphology including details not described previously. The tegument of both species bears numerous characteristic papillae around the oral sucker (in C. metoecus also around the ventral sucker) and the ventral and dorsal surfaces of the forebody, exhibiting a high degree of variability in numbers and arrangement, with tegumental bosses forming lateral fields on the forebody and minute sensory receptors with submerged cilia scattered on the surface of the dorsal part of the oral sucker. In addition to marked differences in the size, shape and position of the oral muscular lobes, both species distinctly differ in the number of genital pores: two separate pores in C. farionis and a single pore in C. metoecus.
The nematode Philometra rubra (Leidy, 1856) (Philometridae) is redescribed from subgravid females found in the abdominal cavity of the fish Morone saxatilis (Walbaum) from South Carolina, USA in November 2008. The species is characterized by the presence of 14 cephalic papillae arranged in two circles, a relatively long oesophagus with a distinct anterior inflation, and well-developed papilla-like caudal projections. Cephalic papillae of the external circle differ from those in other congeners in that the dorso-lateral and ventro-lateral papillae are large, dome-shaped, whereas the dorso-dorsal and ventro-ventral papillae are small.
The male of the gonad-infecting nematode Philometra filiformis (Stossich, 1896) (Philometridae) is for the first time described, based on specimens from the ovary of the marine fish Pagellus erythrinus (Linnaeus) from the Tyrrhenian Sea off Sicily, Italy. It is mainly characterized by the testis extending anteriorly nearly to the anterior end of body, the oesophagus without a usual anterior inflation, the absence of a dorsal barb or distinct transverse lamellae on the tip of the gubernaculum, the measurements of the spicules and the gubernaculum, and a fairly long body.
Two species of mayfly nymphs, Habroleptoides modesta (Hagen) and Habrophlebia lauta (Eaton) (Ephemeroptera: Leptophlebiidae), were found as suitable experimental intermediate hosts of the fish nematode Rhabdochona denudata (Dujardin, 1845) (Rhabdochonidae), an intestinal parasite of Palaearctic cyprinids. The parasite's eggs were obtained from nematode gravid females parasitizing the European chub, Leuciscus cephalus (L.), of the Rokytná River, Czech Republic. At the water temperature of 9°C, the eggs of R. denudata were ingested by the intermediate host and the hatched, toothed (with a minute cephalic boring tooth) first-stage larvae about 200 µm long penetrated into the body cavity of the mayfly. There the larvae grew and moulted twice (on 16-18 and 30-35 days p.i.) before attaining the third stage, which is already infective for the fish definitive host. Infective larvae of this stage were about 1.5 mm long and their morphology resembled that of adults except for the vestibule structure; they became encapsulated as in those of other congeneric species.
Based on light and scanning electron microscopical studies, the following five species of the Philometridae (Nematoda: Dracunculoidea) are described from female specimens collected from marine fishes off the southwestern coast of Java, Indonesia: Philometra lobotidis sp. n. from the abdominal cavity of the Atlantic tripletail Lobotes surinamensis (Bloch) (Lobotidae, Perciformes); Philometra javaensis sp. n. from the abdominal cavity of the immaculate puffer Arothron immaculatus (Bloch et Schneider) (Tetraodontidae, Tetraodontiformes); Philometra psettoditis sp. n. from the musculature of the Indian spiny turbot Psettodes erumei (Bloch et Schneider) (Psettodidae, Pleuronectiformes); Philometroides indonesiensis sp. n. from the musculature of the hound needlefish Tylosurus crocodilus crocodilus (Péron et Lesueur) (Belonidae, Beloniformes); and Philometroides trichiuri sp. n. from the dorsal fin of the largehead hairtail Trichiurus lepturus Linnaeus (type host) and the savalai hairtail Lepturacanthus savala (Cuvier) (both Trichiuridae, Perciformes). All these new species are distinguished from their congeners parasitizing marine fishes by morphological (mainly the shape and structure of the cephalic and caudal ends and of the oesophagus) and biometrical features. Besides previously known Philometra pellucida (Jägerskiöld, 1893) and Philometra ocularis Moravec, Ogawa, Suzuki, Miyazaki et Donai, 2002, they are the only nominal philometrid species recorded from Indonesian waters.
The nematode Goezia spinulosa (Diesing, 1839) (Raphidascarididae) is redescribed based on specimens found in the stomach and intestine of the naturally infected arapaima Arapaima gigas (Schinz) from the Mexiana Island, Amazon River Delta, Brazil. Light and electron microscopy examinations revealed some previously unreported or inaccurately described morphological features in the species, such as the position of the excretory pore, phasmids in the male or the number (4) of postanal papillae. The morphology of G. spinulosa is compared with that of other four congeneric species parasitizing freshwater fishes in South America. This nematode seems to be one of the most pathogenic parasites of A. gigas in the Mexiana Island, which are responsible for a high mortality of cultured arapaima fingerlings. Apparently, the source of G. spinulosa infection for arapaima fingerlings cultured in tanks was the infected plankton collected in the localities inhabited by wild arapaimas. Therefore, control measures should include the sterilisation of the plankton before its use as food for fish. A rare infection of Eustrongylides sp. larvae (Dioctophymatidae) in arapaima fingerlings was also found (new host record); the larvae were inside swellings on the body surface.
Based on light and scanning electron microscopical studies, the following five gonad-infecting species of the Philometridae (Nematoda: Dracunculoidea) are described from marine perciform fishes off the eastern coast of India (Bay of Bengal): Philometra sphyraenae sp. n. (males and females) from the pickhandle barracuda Sphyraena jello Cuvier (Sphyraenidae), Philometra gerrei sp. n. (males and females) from the whipfin silver-biddy Gerres filamentosus Cuvier (Gerreidae), Philometra otolithi sp. n. (single female) from the tigertooth croaker Otolithes ruber (Bloch et Schneider) (Sciaenidae), Philometra sp. (females) from the Belanger's croaker Johnius belangerii (Cuvier) (Sciaenidae), and Philometroides eleutheronemae sp. n. (females) from the fourfinger threadfin Eleutheronema tetradactylum (Shaw) (Polynemidae). All new species are distinguished from their congeners parasitizing gonads of marine fishes by morphological (mainly the gubernaculum structure in males and the shape and structure of the cephalic and caudal ends and of the oesophagus in females) and biometrical features. Philometra rajani Mukherjee, 1963 is considered a species inquirenda.
Previously undescribed third-stage larvae of two species of Spirurida were found in the haemocoel of the stalk-eyed mud crab Macrophthalmus hirtipes (Heller) (Ocypodidae) in New Zealand. Examinations by light and scanning electron microscopy showed that the larger larvae (about 7 mm long) belonged to a species of Ascarophis van Beneden, 1871 (Cystidicolidae), the genus including parasites of fishes, whereas the smaller larvae (about 4-5 mm long) belonged to the Acuariidae, a family with species parasitic as adults mostly in aquatic birds. In a sample of 82 specimens of M. hirtipes collected in July 2002 from Papanui Inlet, on Otago Peninsula, South Island, 74 crabs (90.2%) were infected with larval nematodes with an intensity of 1-18 (mean 4.6) nematodes per crab; no distinction between nematode species was made in these estimates, although juvenile Acuariidae greatly outnumbered larval Ascarophis. Apparently, crabs play a role as intermediate hosts of these nematode species. This is the first record of larval representatives of Cystidicolidae and Acuariidae from invertebrates in the Australasian Region.