Morphometric analysis of four species of Eubothrium (Cestoda: Pseudophyllidea) parasites of salmonid fish: an interspecific and intraspecific comparison.

Four species of the genus Eubothrium (E. crassum, E. fragile, E. rugosum and E. salvelini) were subjected to morphometric comparison. Discriminant analysis was conducted utilising 17 characters measured on the scolex and strobila of 101 specimens. Univariate statistics were first used to detect features that were useful for separating individual Eubothrium species and two different host populations of E. salvelini. Subsequent multivariate discriminant analysis, combining all the measured variables, made it possible to separate all four species. A comparison of the four taxa revealed that (1) E. fragile is the most distinct species, possessing a much smaller scolex than the other congeners, and its similarity with the other marine species E. crassum is not proven; (2) the two freshwater taxa, E. rugosum and E. salvelini are the most similar; (3) the characters most suitable for species differentiation are the length of the scolex, the width of the apical disc, the width of the neck and its area, the width of eggs and the number of testes; (4) the width of the apical disc was confirmed to be the most stable character at the intraspecific level (within E. salvelini host populations) and is therefore considered to be a trait of the highest discriminative power in the subset of four Eubothrium species.

The cestode Atractolytocestus huronensis (Caryophyllidea) continues to spread in Europe: new data on the helminth parasite of the common carp.

The caryophyllidean tapeworm Atractolytocestus huronensis Anthony, 1958, originally described from the common carp Cyprinus carpio carpio L. from North America, has recently been introduced into Europe (UK, Hungary). In the present study, the dispersion of the tapeworm in other countries of Central Europe (Slovakia and the Czech Republic) is described, including its first observation in the common carp of the Tisa River, southeastern Slovakia. Because of the transboundary location of the river, there are possible consequences of the rapid distribution of the parasite to other regions throughout the Danube River basin. The parasite has also been found in cultured carp from fishponds in South Bohemia, from where the carp are imported to many European countries. Rapid dissemination of this cestode in Europe indicates its ability to colonise new regions, and represents another example of man-made introduction of potential pathogens of carp and other farmed fish. The morphology of the A. huronensis specimens found is compared with that of specimens from Hungary and North America as well as that of Atractolytocestus sagittatus (Kulakovskaya and Akhmerov, 1965) from the same fish host in eastern Asia.

Host specificity and geographical distribution of Eubothrium in European salmonid fish.

The host specificity and distribution of Eubothrium crassum (Bloch, 1779) and Eubothrium salvelini (Schrank, 1790), morphologically fairly similar pseudophyllidean tapeworms parasitizing salmonid fish, were critically assessed on the basis of morphological and genetic evaluation of extensive material collected from different definitive hosts and geographical regions in Europe. Eubothrium crassum occurs in fish of the genera Salmo, i.e. salmon (S. salar - both freshwater and marine), sea trout (S. trutta trutta), brown trout (S. trutta fario), and lake trout (S. trutta lacustris), and also in Danubian salmon (Hucho hucho) and vendace (Coregonus albula). Eubothrium salvelini parasitizes Arctic char (Salvelinus alpinus) and brook trout (Salvelinus fontinalis) in Europe, and also whitefish (Coregonus wartmanni). Rainbow trout (Oncorhynchus mykiss), which is not a native European fish species, was found to be a suitable definitive host for both Eubothrium species, which may occur simultaneously in the same fish. Previous records of E. crassum in Arctic char and brook trout, and those of E. salvelini in fish of the genus Salmo were most probably misidentifications. Most studies of Eubothrium have involved salmonids from the northern part of Europe, with few records from southern and south-eastern Europe. This study also confirmed the reliability of the morphology of the apical disc for the discrimination of E. crassum and E. salvelini.

Seasonal occurrence of the tapeworm Proteocephalus longicollis and its transmission from copepod intermediate host to fish.

Seasonal occurrence in terms of prevalence, intensity of infection, abundance and density of the tapeworm Proteocephalus longicollis (Zeder, 1800) and its transmission between its intermediate host (Cyclops abyssorum prealpinus) and definitive host (common whitefish, Coregonus lavaretus) in Lake Annecy, an oligotrophic lake in the western part of the Alps, France, were studied in the period of 1998-2000. A copepod Cyclops abyssorum prealpinus (Kiefer, 1939), the dominant species among planktonic crustaceans in the lake, served as the only intermediate host for this parasite. Infection with plerocercoids was higher in adult copepods (predominantly females) than in copepodite stages IV and V. The prevalence rate of 25% found in C. abyssorum prealpinus females in June 1998 represents a unique infection rate of intermediate hosts with fish tapeworms in natural conditions. The final host, the common whitefish Coregonus lavaretus (L.), was heavily infected with P. longicollis throughout the year (prevalence 90%; mean abundance 40.3; maximum intensity of infection more than 500 tapeworms per fish); immature tapeworms predominated in all samples (P<0.01). Transmission of tapeworm larvae from copepods to the common whitefish took place most intensively in summer and autumn, and depended on seasonal changes in the density of the C. abyssorum prealpinus population, infection of this copepod with plerocercoids and their density in the lake. In addition, transmission efficiency also seems to be determined by the longevity of tapeworm larvae in the intermediate host, timing of predation of the fish host and rapid development of the parasite within this host during the summer period. Overall transmission potential of P. longicollis was low, with only about 9% of juvenile specimens reaching maturity in common whitefish.

A molecular study of Eubothrium rugosum (Batsch, 1786) (Cestoda: Pseudophyllidea) using ITS rDNA sequences, with notes on the distribution and intraspecific sequence variation of Eubothrium crassum (Bloch, 1779).

The internal transcribed spacers (ITS-1 and ITS-2) of the ribosomal DNA (rDNA) of fish cestodes of the genus Eubothrium were sequenced. The ITS sequences of Eubothrium rugosum were determined and compared with previously analysed congeneric species, Eubothrium crassum and Eubothrium salvelini. The ITS-1 sequences of E. rugosum and E. crassum were 535 bp long, the length of E. salvelini ITS-1 was 536 bp. The ITS-2 region was found to be 403 bp in E. rugosum and E. crassum, and 401-402 bp in E. salvelini. The ITS-1 region of E. rugosum was closer to E. salvelini (identity 98.9-99.1%) than to E. crassum(97.9-98.1%), while the sequence similarity within the ITS-2 region was almost identical (97.5-98.0% for E. crassum; 97.7-98.3% for E. salvelini). Several restriction enzymes were found to be suitable for the differentiation of the three Eubothrium species by PCR-RFLP. The intraspecific sequence variation of E. crassum from different fish hosts (freshwater and marine) and European regions was very low, 0.2% for ITS-1 and 0.5% for ITS-2. Analysis of the ITS sequences of specimens from rainbow trout from three localities in Scotland revealed that both E. crassum and E. salvelini are present in this fish host.

A comparison of the internal transcribed spacer of the ribosomal DNA for Eubothrium crassum and Eubothrium salvelini (Cestoda: Pseudophyllidea), parasites of salmonid fish.

The internal transcribed spacers (ITS-1 and ITS-2) and 5.8S subunit of the ribosomal RNA gene of Eubothrium crassum and Eubothrium salvelini, cestode parasites of salmonid fish, were sequenced and compared. The lengths and GC contents of the regions sequenced were 1119 bp and 50.1% for E. crassum, and 1117 bp and 50.5% for E. salvelini, respectively. Sequence alignment and comparison of both taxa showed 97.9% similarity. Within the ITS-1 and ITS-2 of both species, the restriction enzymes MspI and Bsh1236I possessed different cleavage sites and could be employed for rapid differentiation of both species of Eubothrium by PCR-RFLP.

Species of Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae), parasites of coregonid and salmonid fishes from North America: taxonomic reappraisal.

A taxonomic study of species of Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae), from coregonid and salmonid fishes in North America, based largely on their type specimens, was carried out. None of the taxa studied possesses obvious autapomorphies that would justify its validity. On the contrary, all species share the following diagnostic features typical of Proteocephalus longicollis (Zeder, 1800) (syn. Proteocephalus exiguus La Rue, 1911), a polymorphic and widely distributed parasite in the Holarctic: (1) a spherical or club-shaped scolex, with sublaterally situated suckers and a vestigial but distinct and relatively large apical sucker; (2) the vagina possessing a well-developed vaginal sphincter and crossing mostly ventrally the proximal part of the cirrus sac; and (3) a long, thick-walled cirrus sac, overlapping vitelline follicles medially by more than its proximal half. Accordingly, Proteocephalus pusillus Ward, 1910; P. laruei Faust, 1920; "P. obtundus" La Rue, 1920 (nomen nudum); P. arcticus Cooper, 1921; P. wickliffi Hunter and Bangham, 1933; P. parallacticus MacLulich, 1943; P. californicus Haderlie, 1950; P. salmonidicola Alexander, 1951; and P. primaverus Neiland, 1952 are considered junior synonyms of P. longicollis.

Species of Proteocephalus Weinland, 1858 (Cestoda: Proteocephalidae) from cyprinid fishes in North America.

A taxonomic study of Proteocephalus species parasitizing cyprinid fishes in North America, namely Proteocephalus ptychocheilus Faust, 1920 and Proteocephalus cobraeformis Haderlie, 1953, has demonstrated their conspecificity with Proteocephalus torulosus (Batsch, 1786), a common parasite of cypriniform fishes (Cyprinidae and Cobitidae) in the Palaearctic Region. Proteocephalus ptychocheilus and P. cobraeformis are considered junior synonyms of P. torulosus.

Scolex morphology of Proteocephalus tapeworms (Cestoda: Proteocephalidae), parasites of freshwater fish in the Palaearctic Region.

The morphology of the scoleces of 11 Proteocephalus species, parasites of freshwater fish in the Palaearctic Region, was compared using light and scanning electron microscopy. The following taxa were evaluated: Proteocephalus ambiguus (Dujardin, 1845); P. cernuae (Gmelin, 1790); P. exiguus La Rue, 1911; P. filicollis (Rudolphi, 1802); P. macrocephalus (Creplin, 1825); P. osculatus (Goeze, 1782); P. percae (Müller, 1780); P. pollanicola Gresson, 1952; P. sagittus (Grimm, 1872); P. thymalli (Annenkova-Chlopina, 1923); and P. torulosus (Batsch, 1786). Some features as overall shape of the scolex, its size, shape and size of an apical sucker were found to be fairly stable and species-specific. The taxa more easily distinguishable from congeners on the basis of their scolex morphology were P. cernuae, P. macrocephalus, P. osculatus, P. percae and P. torulosus. The taxonomic importance of the scolex is discussed.

Neuropeptides and serotonin in the cestode, Proteocephalus exiguus: an immunocytochemical study.

Neuropeptides and serotonin in the cestode, Proteocephalus exiguus: an immunocytochemical study. International Journal for Parasitology 25: 673-682. Neuropeptide F (NPF), RFamide and serotonin (5-HT) immunoreactivities have been detected in the nervous system of P. exiguus procercoids and adults, using an indirect immunocytochemical technique in conjunction with confocal scanning laser microscopy. The peptidergic nervous system of the procercoid is well developed, with two brain ganglia, three pairs of longitudinal nerve cords, transverse ring commissures and nerves in the suckers, all showing NPF-immunostaining. Strong NPF- and RF-immunostaining was observed in the CNS and PNS of the adult worm. The distribution patterns of the two neuropeptides were similar. Immunoreactivity for 5-HT was found only in the CNS.

Morphological and genetic comparison of two Proteocephalus species (Cestoda: Proteocephalidae).

Two Proteocephalus species, P. neglectus La Rue, 1911 and P. exiguus La Rue, 1911, parasites of salmonid and coregonid fishes, were compared morphologically, biometrically, and electrophoretically. The study revealed that the two taxa cannot be differentiated by the morphological criteria used. No fixed allelic difference was found. In all, 12 of 13 enzymes detected by isoelectric focusing exhibited virtually identical isoenzyme profiles in both species. Only in the glutamate oxaloacatate transaminase enzyme locus was a difference observed. The negligible differences in zymograms and morphology, including similar biometric variability of the taxa studied, suggest that the species could be conspecific.