Malformations of the gill filaments of the ruffe Gymnocephalus cernuus (L.) (Pisces) caused by echinostomatid metacercariae.

In parasite surveys of fishes from Lake Balaton and its tributaries in Hungary, infections with metacercariae of a species of the digenean genus Echinochasmus (Trematoda: Echinostomatidae) were found in seven species of fish. In ruffe, Gymnocephalus cernuus, malformations of the gill filaments apparently caused by these infections were observed. These malformations were in the form of bifurcations of the filaments at about their mid-length. At the point where the filaments bifurcate, an Echinochasmus metacercaria was always embedded in the cartilaginous ray of the gill filament. All specimens of the ruffe were found to be infected by these metacercariae, and each ruffe specimen was infected by 30-300 metacercariae. Such a bifurcation was found in all of the ruffe specimens, but, apart from these gill malformations, the metacercariae produced only local changes in the cartilage. In the other six infected fish species, only local signs were observed in the cartilage. Experimental infections of chicks with metacercariae resulted in the finding of the sexual adult (marita) of an unidentified species of Echinochasmus. ITS sequences of the adult and metacercaria corresponded with each other, and also with a cercaria isolated from a gravel snail (Lithoglyphus naticoides), with a 99.5-100% similarity.

Synopsis of the species of Chloromyxum Mingazinni, 1890 (Myxozoa: Myxosporea: Chloromyxidae).

A synopsis of the species of Chloromyxum Mingazinni, 1890 (Myxozoa: Myxosporea: Chloromyxidae) is presented, including 140 nominal species. For each species the most relevant morphological and morphometric characteristics are indicated. Included are data on the site of infection within the host, the original host and the host locality, plus a full bibliography of the original records for these species. A diagrammatic illustration of a spore of each species is also provided.

The evolutionary expansion and host-parasite relationships of the Digenea.

Relevant data on the Digenea extracted from a host-parasite data-base are analysed in relation to host-groups, host-specificity, speciation, radiation and geographical distribution. The classification, evolution, co-evolution, and co-speciation of the group are discussed. Principal components analyses indicated that 119 families formed 11 groups in relation to their vertebrate hosts and the 55 families with molluscan records formed 6 groups in relation to their molluscan hosts. The most prominent host-groups are the Fish and Mammals. Individual digenean families did not exhibit the host combinations Fish+Birds, Fish+Mammals, Herpetiles+Birds and Herpetiles+Mammals. Families with Fish hosts tended to use Prosobranch and, to a lesser extent Bivalve, molluscs, whereas families in Herpetiles, Birds and Mammals tended to use Pulmonates. Families using 3 or 4 mixed vertebrate groups tended to use mixed molluscan groups. Families using Herpetiles as the vertebrate host tend to be the most host-specific and the least speciose, whereas those using 3 to 4 mixed vertebrate groups are the most speciose. In a detailed examination of three zoogonid genera, few indications of co-evolution with their vertebrate hosts were detected, and geographical information from the data-base appeared to shed no light upon the geographical origins of the Digenea. Some of these findings are commented upon in relation to the evolution of the Digenea.

A study of the composition of the sclerites of Gyrodactylus Nordmann, 1832 (Monogenea) using X-ray elemental analysis.

The elemental compositions of the hamuli, marginal hooks and ventral bars were examined following their release from the opisthaptor of the monogenean parasites Gyrodactylus salaris, G. caledoniensis and G. colemanensis. Their compositions were determined using X-ray elemental analysis on an analytical scanning electron microscope, and the variation between each species investigated. Hamuli and marginal hooks exhibited a major peak for sulphur, whilst the ventral bar had high peaks of both sulphur and calcium. The high sulphur content and structure of the hamuli suggest they are composed of a keratin-like protein, while the nature of the ventral bar is less clear. The hamuli of G. colemanensis were differentiated from those of G. caledoniensis by virtue of their calcium fraction. Low levels of several other elements, including vanadium, were also detected in some sclerites. The composition of the hooks of Gyrodactylus and their relationship to the sclerites of monopisthocotyleans and polyopisthocotyleans is commented upon.

The application of chaetotaxy in the discrimination of Gyrodactylus salaris Malmberg, 1957 (Gyrodactylidae: Monogenea) from species of the genus parasitising British salmonids.

The chaetotaxy of argentophilic structures on three species of the monogenean genus Gyrodactylus was investigated in an attempt to distinguish species of this genus. Maps were prepared for Gyrodactylus salaris from Scandinavia and compared with two native species of Gyrodactylus parasitising salmonids in Britain, namely Gyrodactylus derjavini and Gyrodactylus truttae. The maps were subsequently refined and analysed for zones of homology and differentiation. The results demonstrate that G. salaris can be readily distinguished by this technique, which is, therefore, of great potential value in the identification of this notifiable pathogen. The key aggregations of sensilla discriminating G. salaris are, ventrally, the antero-ventral set, the medio-lateral set and the postero-lateral set, and, dorsally, the postero-dorsal set.

A survey of gastrointestinal helminths of the common helmet guinea fowl (Numida meleagris galeata) in Burkina Faso.

Guinea fowls in Burkina Faso (Africa) harbored 13 species of helminth parasites. The two most abundant species were Subulura suctoria and Ascaridia numidae, which comprised 89% of the nematodes. The other nematode species (Gongylonema congolense, Eucoleus annulatus, Synhimantus spiralis, Tetrameres fissispina, and Cyrnea parroti) occurred at low levels. Five species of cestodes and one acanthocephalan were also present. It is likely that guinea fowl act as important reservoir hosts of chicken nematodes.

Diplectanocotyla Yamaguti, 1953 (Monogenea: Diplectanoidea) from Megalops cyprinoides (Broussonet) (Teleostei: Megalopidae) off Peninsular Malaysia.

Two known and two new species of Diplectanocotyla Yamaguti, 1953 (D. gracilis Yamaguti, 1953, D. megalopis Rakotofiringa & Oliver, 1987, D. langkawiensis n. sp. and D. parva n. sp.) were collected from Megalops cyprinoides (Megalopidae) off Langkawi, Kedah and Matang, Perak, Peninsular Malaysia. All four species possess similar types of sclerotised male and female reproductive structures and similar soft anatomical features. The squamodisc sclerites of all four species have spine-like projections with varying degrees of visibility and shapes (sharp-pointed to triangular). In D. megalopis and D. langkawiensis n. sp. the spines are sharp-pointed and distinct on sclerites from rows 5-6 onwards. In D. gracilis and D. parva n. sp. the sclerite spines are triangular, lightly sclerotised and occur on almost all of the sclerites. D. parva n. sp. has comparatively the smallest set of anchors, bars, squamodiscs and squamodisc suckers. The anchors and bars of the other three species are almost similar in overall size, and the main distinguishing feature is the relative lengths of the inner and outer roots of the ventral anchors. In D. gracilis the outer root is very much smaller than the inner root and they are disposed almost at a right angle to each other. In D. megalopis the outer root is usually about half the length of the inner root and the roots are inclined at c.60 degrees to each other. In D. langkawiensis n. sp. the roots are inclined at c.40 degrees degrees and the outer root is of a similar length or only slightly shorter than the inner root. The openings of the two squamodisc suckers of all four Diplectanocotyla species are surrounded by tiny scale-like spines. Bifid tegumental spines are found in the posterior region of all four species, differing only in their extent: in D. parva n. sp. the tegumental spines are only distributed in the peduncular region and not beyond, whilst in the other three species the tegumental spines extend from the posterior level of the testis to the end of the peduncle. An amended diagnosis of Diplectanocotyla and a key to its species are appended.

Cryptic species of Didymobothrium rudolphii (Cestoda: Spathebothriidea) from the sand sole, Solea lascaris, off the Portuguese coast, with an analysis of their molecules, morphology, ultrastructure and phylogeny.

Didymobothrium rudolphii (Cestoda: Spathebothriidea) was collected seasonally from the sand sole, Solea lascaris, off the northern, central and southern areas of the Portuguese coast. Morphological and molecular analyses were conducted in order to examine the possible existence of cryptic species and to facilitate the circumscription of their morphological boundaries. Data were compared between D. rudolphii specimens from each of the 3 geographical areas and 4 seasons, and principal components analysis of 18 morphological characters was used to detect differences. Two distinct genotypes were present with sequence divergences of 1.9% and 2.1% in the large subunit (lsrDNA) and second internal transcribed spacer (ITS-2) of ribosomal DNA (rDNA), respectively. The less common 'central' genotype was present only off the central area from summer to winter, whereas the 'common' genotype was present throughout the year off the northern and southern areas, but only during spring in the central area. No sequence variation was found within each genotype. The presence of 2 distinct genetic entities was supported by morphological analyses, which showed the 'central' genotype specimens to be more slender and elongate, although morphometric ranges overlapped considerably for most characters. Molecular phylogenetic analysis of 4 of the 5 known genera of the Spathebothriidea showed Spathebothrium to be the earliest branching lineage and the 2 genotypes of Didymobothrium formed a sister group to Cyathocephalus. The concordance of genetic differences with variation in host diet according to season and locality could account for sympatric speciation occurring in the central region of the Portuguese coast.

Saturnius minutus n. sp. and S. dimitrovi n. sp. (Digenea: Hemiuridae) from Mugil cephalus L. (Teleostei: Mugilidae), with a multivariate morphological analysis of the Mediterranean species of Saturnius Manter, 1969.

Three species of the bunocotyline genus Saturnius Manter, 1969 are described from the stomach lining of mugilid fishes of the Mediterranean and Black Seas. Two of the species are new: S. minutus n. sp. occurs in Mugil cephalus off the Mediterranean coast of Spain; and S. dimitrovi n. sp., a parasite of M. cephalus off the Bulgarian Black Sea coast and the Spanish Mediterranean coast, was originally described as S. papernai by Dimitrov et al. (1998). In addition, S. papernai Overstreet, 1977 is redescribed from M. cephalus off the Spanish Mediterranean coast and from Liza aurata and L. saliens off the Bulgarian Black Sea coast. The three species are distinguished morphometrically using univariate and multivariate analyses. These results were verified using Linear Discriminant Analysis which correctly allocated all specimens to their species designations based on morphology (i.e. 100% successful classification rate) and assigned almost all specimens to the correct population (locality). The following variables were selected for optimal separation between samples: the length of the forebody, ventral sucker and posterior testis, the length and width of the posteriormost pseudosegment, and the width of the muscular flange at ventral sucker level.

Robinia aurata n. g., n. sp. (Digenea: Hemiuridae) from the mugilid Liza aurata with a molecular confirmation of its position within the Hemiuroidea.

Robinia aurata n. g., n. sp. is described from Liza aurata (Mugilidae), the golden grey mullet, from the Ebro Delta, Spanish Mediterranean. The new genus differs from all other hemiurid genera in the combined possession of muscular flanges and a vestigial ecsoma. Within the Bunocotylinae, which currently accommodates 2 genera, Bunocotyle and Saturnius, the new genus exhibits a unique combination of blind caeca, Juel's organ, post-ovarian bulk of the uterus in the hind-body, and tegumental papillae surrounding the oral and ventral sucker apertures. Furthermore, Robinia n. g. differs from both Bunocotyle and Saturnius in the nature of the muscular extensions around the oral sucker, with the shape of a muscular belt in the latter and numerous muscular papillae in the former. The phylogenetic hypothesis for the Bunocotylinae developed from sequence data analyses based on partial lsrDNA and complete ssrDNA combined (22 species) and V4 domain of the ssrRNA gene (37 species) supports the erection of the new genus and confirms its position within the Hemiuroidea. Both molecular analyses confirmed the monophyly of the Hemiuroidea, its division into 2 major clades and the polyphyly of the Derogenidae, as in previous studies, and suggest that the Gonocercinae (with 2 genera, Gonocerca and Hemipera), may require a distinct familial status. Finally, there was poor support for the distinct status of the Lecithasteridae and Hemiuridae, following previous suggestions based on different sequence data sets. A key to genera of the Bunocotylinae is presented.

Three little known acanthostomine digeneans from Uranoscopus scaber L. in the western Mediterranean.

Three species of acanthostomine digeneans, Anisocoelium capitellatum from the gall-bladder and Anisocladium fallax and A. gracilis from the intestine, are redescribed from the teleost Uranoscopus scaber in the western Mediterranean. The latter two species, which have in the past been confused and synonymised, are distinguished clearly on the basis of morphology, size and site.

Redescriptions of two echinostomes from freshwater fishes, with comments on Singhia Yamaguti, 1958 and Caballerotrema Prudhoe, 1960 (Digenea: Echinostomatidae).

The type-species of Singhia and Caballerotrema (Digenea: Echinostomatidae), parasites of freshwater fishes which have previously been assigned to the subfamily Singhiinae Yamaguti, 1958, are redescribed. One of the specimens of the type-series of Caballerotrema brasiliense Prudhoe, 1960 was identified as C. aruanense Thatcher, 1980. C. arapaimense Thatcher, 1980 is considered a species inquirenda. Himasthla piscicola Stunkard, 1960 is transferred to Caballerotrema as C. piscicola n. comb. The generic diagnoses of Singhia and Caballerotrema are redefined and Singhia is re-allocated to the Echinostomatinae Looss, 1899, the Singhiinae becoming a synonym of the latter.

Metadena phoceae n. sp. (Digenea: Cryptogonimidae), a rectal parasite of the shore rockling Gaidropsarus mediterraneus (Teleostei: Lotidae) in the western Mediterranean.

Metadena phoceae n. sp. is described and figured in detail from the rectum of the shore rockling Gaidropsarus mediterraneus (Lotidae) in the Gulf of Marseilles and off Corsica. It is compared with other cryptogonimids occurring in Mediterranean and Black Sea fishes and is distinguished from its closest relatives, M. depressa (Stossich, 1883) and M. pauli (Vlassenko, 1931), which occur in sparid and sciaenid fishes, respectively, by both morphometrical and biological features. The host-specificity of cryptogonimids occurring in Mediterranean and Black Sea fishes is commented upon.

Hyperparasitism by helminths: new records of cestodes and nematodes in proteocephalid cestodes from South American siluriform fishes.

Proteocephalid cestode hyperparasites are reported from numerous proteocephalids occurring in pimelodid fishes in different regions of Brazil. In addition, three specimens of a nematode hyperparasite are reported from the proteocephalid cestode Choanoscolex abscissus from the pimelodid fish Pseudoplatystoma corruscans in Brazil. Previous records of cestode and nematode hyperparasites of cestodes are listed, and the possible identities of the Brazilian records are discussed.

Molecular systematics in the acanthocephalan genus Echinorhynchus (sensu lato) in northern Europe.

New biological species and high levels of inter- and intraspecific genetic divergence were discovered in an allozyme study of some North European members of the acanthocephalan genus Echinorhynchus (sensu lato), parasites of fish and malacostracan crustaceans. (i) A strong differentiation between the marine E. gadi and the fresh- and brackish-water E. salmonis (genetic identity I congruent to 0) supports a generic distinction between these taxa; however, the subdivision would not entirely concur with the concepts of Echinorhynchus (sensu stricto) and Metechinorhynchus suggested earlier. (ii) Samples of E. gadi from the Baltic, Norwegian and North Seas included three distinct, partially sympatric biological species (spp. I-III; I congruent to 0.5). (iii) E. bothniensis, previously only known from the northern Baltic Sea, represents a complex of freshwater taxa with an intermediate host relationship to the 'glacial relict' Mysis spp. and with a distributional and host analogy to the North American E. leidyi. A population in a northern lake in the Barents Sea basin is closely related to E. bothniensis of the Baltic area, but is probably specifically distinct; the divergence between these populations (I congruent to 0.6) is similar to that between their Mysis host species. (iv) Considerable intraspecific differentiation (FST = 0.25), probably reflecting post-glacial population bottlenecks, was found between Baltic and nearby lacustrine E. bothniensis, and between Atlantic and Baltic E. gadi sp. I.

Cercarial emergence of Ichthyocotylurus erraticus (Rudolphi, 1809), I. variegatus (Creplin, 1825) and Apatemon gracilis (Rudolphi, 1819) (Digenea: Strigeidae): contrasting responses to light:dark cycling.

Many digenean cercariae have been shown to emerge from their molluscan hosts with distinct shedding patterns that have enabled the discrimination of morphologically similar species, or even strains. In this study the cercarial emission patterns of three strigeid species, Ichthyocotylurus erraticus, I. variegatus and Apatemon gracilis, from experimentally infected natural hosts were found to exhibit rhythms that correlated with the light:dark cycle. Both Ichthyocotylurus spp. exhibited a diurnal pattern of release in which cercariae emerged during the light period. Each demonstrated a latent period before the liberation of large numbers of cercariae and yielded similar numbers of cercariae daily. These rhythms offered no means for the discrimination of these two morphologically similar species. A. gracilis cercariae demonstrated a very different circadian rhythm in which the majority emerged at the onset of darkness with no latent period, whereas the cercarial numbers released daily were far greater. Differences could be related to piscine host behaviour.

Dactylogyridean monogeneans of the siluriform fishes of the Old World.

This is a catalogue and discussion of the known dactylogyridean monogenean genera of siluriform fishes of the Old World. Of a total of 38 nominal genera, only 19 are considered valid. Seventeen of these 19 genera are currently in the Ancyrocephalidae (containing the Ancyrocephalinae and Ancylodiscoidinae), whilst the other two (Neocalceostoma and Neocalceostomoides) are in the Neocalceostomatidae. The 17 genera are Anchylodiscus, Ancylodiscoides, Bagrobdella, Bifurcohaptor, Bychowskyella, Chauhanellus, Cornudiscoides, Hamatopeduncularia, Mizelleus, Paraquadriacanthus, Pseudancylodiscoides, Protoancylodiscoides, Quadriacanthus, Schilbetrema, Schilbetrematoides, Synodontella and Thaparocleidus. Clariotrema Long, 1981 and Neobychowskyella Ma, Wang & Li, 1983 are considered synonyms of Bychowskyella Akhmerov, 1952, Anacornuatus Dubey, Gupta & Agarwal, 1992 is considered a synonym of Quadriacanthus Paperna, 1961, Mizellebychowskia Gupta & Sachdeva, 1990 is considered a synonym of Neocalceostoma Tripathi, 1959 and Hargitrema Tripathi, 1959 is treated as a synonym of Hamatopeduncularia Yamaguti, 1953. It is proposed that the Ancylodiscoidinae be raised to family status within the order Dactylogyridea to accommodate these 17 'ancyrocephalid' genera from siluriforms, together with Malayanodiscoides and Notopterodiscoides from notopterids. A key and the diagnostic characteristics of the 19 recognised dactylogyridean genera from catfishes plus two from notopterids, together with a list of species and synonyms, are included. New combinations made in this work are Thaparocleidus avicularia (Chen, 1987) n. comb., T. calyciflorus (Chen, 1987) n. comb., T. choanovagina (Luo & Lang, 1981) n. comb., T. dissimilis (Chen, 1988) n. comb., T. leiocassis (Reichenbach-Klinke, 1959) n. comb., T. meticulosa (Chen, 1987) n. comb., T. parasoti (Zhao & Ma, 1999) n. comb., T. persculpus (Chen, 1987) n. comb., T. valga (Chen, 1987) n. comb. and T. wulingensis (Yao & Wang, 1997) n. comb. [all from Silurodiscoides] and Bychowskyella glyptothoraci (Ma, Wang & Li, 1983) n. comb. [from Neobychowskyella].

Chaetotaxy and armature of Ichthyocotylurus erraticus (Rudolphi, 1809) and I. variegatus (Creplin, 1825) cercariae (Digenea, Strigeidae).

The armature and chaetotaxy of Ichthyocotylurus erraticus (Rudolphi 1809) and I. variegatus (Creplin 1825) cercariae were studied using scanning electron microscopy (SEM) and silver staining of the argentophilic sensilla. This represents the first detailed investigation of the surface structures of cercariae belonging to this genus. Both species exhibited a similar armature, although differences were recorded in the number of spines comprising the pre-oral tuft and the number of rows of spines in the post-oral collar. The number and the distribution of sensilla were found to be identical for both species of cercariae. Four types of sensilla, common to both species, were identified that differed in cilia length and in the structure of the surrounding collar. The distribution of particular sensillary forms was found to be consistent in both species.

A quantitative approach to the evaluation of the morphological variability of two echinostomes, Echinostoma miyagawai Ishii, 1932 and E. revolutum (Frölich, 1802), from Europe.

A comparative morphometric analysis was conducted on two European species of Echinostoma in order to examine the degree of the variability in the metrical characteristics of the adults and to assess their value in discriminating species. Adult E. miyagawai and E. revolutum, obtained experimentally, were compared using univariate and multivariate statistical analyses of 35 and 25 metrical characters, respectively. All subsets of worms of different ages represented homogeneous samples with respect to their morphometric characteristics; however, univariate analyses revealed significant differences in 22 and 23 variables between the corresponding age subsets of the two species, and it was found that the different allometric growth patterns contribute to this. The variables, body width at the posterior border of the ventral sucker, pharynx length and width, ovary length, testes length and width and length of the pre-ovarian region, exhibited isometric or positive allometric growth in E. miyagawai and negative allometry in E. revolutum. A cluster analysis based on 61 specimens and 25 variables separated E. revolutum and E. miyagawai unambiguously, producing an exact ordering of the specimens with respect to their identity and age. A forward stepwise discriminant analysis identified five variables (body width at the posterior border of ventral sucker, head collar width, length of oesophagus, width of ventral sucker and length of the pre-ovarian region) which yielded a 100% accurate classification of the two species. We suggest, therefore, that the morphometric characteristics of the adult worms should be used in studies attempting the identification of species or isolates of Echinostoma spp. More comparative data need to be gathered in order that the species boundaries within the 'revolutum' group be defined more accurately.