Small intestinal flukes of the genus Metagonimus (Digenea: Heterophyidae) in Europe and the Middle East: A review of parasites with zoonotic potential.

The heterophyid trematode Metagonimus romanicus (Ciurea, 1915) (Digenea) is redescribed on the basis of type material from domestic dogs (Canis familiaris) in Romania, vouchers from experimentally infected cats (Felis catus) and adults recovered from golden hamsters (Mesocricetus auratus) infected with metacercariae from scales of chub (Squalius cephalus) and common nase (Chondrostoma nasus) (Cypriniformes: Leuciscidae) in Hungary. This trematode, endemic to Europe and neighbouring regions (northwestern Türkiye), was previously misidentified as M. yokogawai (Katsurada, 1912), a zoonotic parasite of humans in East Asia. However, the two species differ considerably both genetically and morphologically, e.g., in the position of the ventral sucker, the presence of the prepharynx, the anterior extent of the vitelline follicles and the posterior extent of the uterus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), described from domestic cats and dogs in Israel, is a valid species distributed in the Middle East and Transcaucasia, which is also confirmed by molecular data. It differs from all Metagonimus species, including M. romanicus, in having symmetrical testes instead of the oblique testes of the other congeners. The zoonotic significance of M. romanicus and M. ciureanus is unclear, but appears to be low in Europe, mainly because raw or undercooked, whole fish with scales are generally not consumed. Accidental infection of fishermen by metacercariae in the scales when cleaning fish is more likely, but has never been reported. Remains of cyprinoids with scales infected with metacercariae of Metagonimus spp. can be an important natural source of infection for dogs, cats, and other carnivores, which can serve as a reservoir for these parasites.

Title: Petits trématodes intestinaux du genre Metagonimus (Digenea : Heterophyidae) en Europe et au Moyen-Orient : revue de parasites à potentiel zoonotique. Abstract: Le trématode Heterophyidae Metagonimus romanicus (Ciurea, 1915) (Digenea) est redécrit sur la base de matériel type provenant de chiens domestiques (Canis familiaris) en Roumanie, de vouchers issus de chats (Felis catus) infectés expérimentalement et d'adultes collectés chez des hamsters dorés (Mesocricetus auratus) infectés par des métacercaires provenant d'écailles de chevesne commun (Squalius cephalus) et de nase commun (Chondrostoma nasus) (Cypriniformes : Leuciscidae) de Hongrie. Ce trématode, endémique d'Europe et des régions voisines (nord-ouest de la Turquie), avait été précédemment identifié à tort comme étant M. yokogawai (Katsurada, 1912), un parasite zoonotique des humains en Asie de l'Est. Cependant, les deux espèces diffèrent considérablement sur le plan génétique et morphologique, par exemple par la position de la ventouse ventrale, la présence du prépharynx, l'étendue antérieure des follicules vitellins et l'étendue postérieure de l'utérus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), décrite chez des chats et des chiens domestiques en Israël, est une espèce valide répartie au Moyen-Orient et en Transcaucasie, ce qui est également confirmé par des données moléculaires. Cette espèce diffère de toutes les espèces de Metagonimus, y compris M. romanicus, par ses testicules symétriques au lieu des testicules obliques des autres congénères. L'importance zoonotique de M. romanicus et M. ciureanus n'est pas claire, mais semble faible en Europe, principalement parce que les poissons n'y sont généralement pas consommés crus ou insuffisamment cuits et entiers avec les écailles. L'infection accidentelle des pêcheurs par des métacercaires présents dans les écailles lors du nettoyage du poisson est plus probable mais n'a jamais été signalée. Les restes de poissons cyprinoïdes avec les écailles, infectés par des métacercaires de Metagonimus spp. peuvent être une source naturelle importante d'infection pour les chiens, les chats et autres carnivores, qui peuvent servir de réservoir à ces parasites.

Human diphyllobothriosis in Taiwan: A review of cases and molecular evidence of Dibothriocephalus nihonkaiensis.

Diphyllobothriosis is an infectious disease caused by the consumption of raw freshwater or marine fish containing larvae of broad tapeworms (Diphyllobothriidae). In the present study, we critically reviewed all cases of human diphyllobothriosis reported from Taiwan, including unpublished reports from hospitals in Taipei. Genotyping based on mitochondrial DNA marker (cox1) confirmed that two of the recent cases were caused by Dibothriocephalus nihonkaiensis, which is not native to Taiwan and was probably imported with Pacific salmon infected with larvae of D. nihonkaiensis. The causative species previously reported in Taiwan could not be definitively confirmed. However, considering the distribution of Dibothriocephalus latus, which is not endemic in Taiwan, past cases diagnosed as D. latus are questionable.

Zoonotic Marine Nematode Infection of Fish Products in Landlocked Country, Slovakia.

Fish products in Slovakia have been heavily infected with Anisakis spp. larvae, which causes human anisakiasis. We found larvae in all tested samples of frozen Atlantic herring. Anisakid allergen t-Ani s7 testing revealed 2 positive cases in humans, signaling need for health authorities to closely monitor zoonotic marine parasites, even in inland areas.

Hooking the scientific community on thorny-headed worms: interesting and exciting facts, knowledge gaps and perspectives for research directions on Acanthocephala.

Although interest in Acanthocephala seems to have reached only a small community of researchers worldwide, we show in this opinion article that this group of parasites is composed of excellent model organisms for studying key questions in parasite molecular biology and cytogenetics, evolutionary ecology, and ecotoxicology. Their shared ancestry with free-living rotifers makes them an ideal group to explore the origins of the parasitic lifestyle and evolutionary drivers of host shifts and environmental transitions. They also provide useful features in the quest to decipher the proximate mechanisms of parasite-induced phenotypic alterations and better understand the evolution of behavioral manipulation. From an applied perspective, acanthocephalans' ability to accumulate contaminants offers useful opportunities to monitor the impacts - and evaluate the possible mitigation - of anthropogenic pollutants on aquatic fauna and develop the environmental parasitology framework. However, exploring these exciting research avenues will require connecting fragmentary knowledge by enlarging the taxonomic coverage of molecular and phenotypic data. In this opinion paper, we highlight the needs and opportunities of research on Acanthocephala in three main directions: (i) integrative taxonomy (including non-molecular tools) and phylogeny-based comparative analysis; (ii) ecology and evolution of life cycles, transmission strategies and host ranges; and (iii) environmental issues related to global changes, including ecotoxicology. In each section, the most promising ideas and developments are presented based on selected case studies, with the goal that the present and future generations of parasitologists further explore and increase knowledge of Acanthocephala.

Title: Accrocher la communauté scientifique à des vers à la tête pleine d'épines : faits intéressants et passionnants, lacunes dans les connaissances et perspectives pour des orientations de recherche sur les Acanthocéphales. Abstract: Bien que l'intérêt pour les acanthocéphales semble n'avoir atteint qu'un petit nombre de chercheurs dans le monde, nous montrons dans cet article que ce groupe de parasites est composé d'excellents organismes modèles pour étudier les questions en suspens en biologie moléculaire et cytogénétique, écologie évolutive et écotoxicologie. Leur ascendance partagée avec les rotifères en fait un groupe idéal pour explorer les origines du mode de vie parasitaire et les moteurs évolutifs des changements d'hôtes et des transitions environnementales. Ils présentent également des caractéristiques intéressantes pour l'étude des mécanismes proximaux sous-tendant les altérations phénotypiques induites par les parasites, et ainsi mieux comprendre l'évolution de la manipulation comportementale. D'un point de vue appliqué, la capacité des acanthocéphales à accumuler les contaminants offre des opportunités utiles pour surveiller les impacts - et évaluer les possibilités d'atténuation - des pollutions anthropiques sur la faune aquatique et développer le domaine de la parasitologie environnementale. Cependant, l'exploration de ces pistes de recherche passionnantes nécessitera de relier des connaissances fragmentaires en élargissant la couverture taxonomique des données moléculaires et phénotypiques. Dans cet article, nous présentons l'état actuel de la recherche sur les acanthocéphales selon trois axes principaux : (i) la taxonomie intégrative (y compris les outils non-moléculaires) et la phylogénie à des fins d'analyse comparative ; (ii) l'écologie et l'évolution des cycles de vie, des stratégies d'exploitation des hôtes et de transmission ; (iii) les questions environnementales liées aux changements globaux, y compris l'écotoxicologie. Dans chaque section, nous soulignons les besoins et les opportunités, en espérant que cela incitera une nouvelle génération de parasitologues à s'intéresser aux acanthocéphales.

An examination of nervous system revealed unexpected immunoreactivity of both secretory apparatus and excretory canals in plerocercoids of two broad tapeworms (Cestoda: Diphyllobothriidea).

Dibothriocephalus ditremus and Dibothriocephalus latus are diphyllobothriidean tapeworms autochthonous to Europe. Their larval stages (plerocercoids) may seriously alter health of their intermediate fish hosts (D. ditremus) or cause intestinal diphyllobothriosis of the final human host (D. latus). Despite numerous data on the internal structure of broad tapeworms, many aspects of the morphology and physiology related to host­parasite co-existence remain unclear for these 2 species. The main objective of this work was to elucidate functional morphology of the frontal part (scolex) of plerocercoids, which is crucial for their establishment in fish tissues and for an early attachment in final hosts. The whole-mount specimens were labelled with different antibodies and examined by confocal microscope to capture their complex 3-dimensional microanatomy. Both species exhibited similar general pattern of immunofluorescent signal, although some differences were observed. In the nervous system, FMRF amide-like immunoreactivity (IR) occurred in the bi-lobed brain, 2 main nerve cords and surrounding nerve plexuses. Differences between the species were found in the structure of the brain commissures and the size of the sensilla. Synapsin IR examined in D. ditremus occurred mainly around FMRF amide-like IR brain lobes and main cords. The unexpected finding was an occurrence of FMRF amide-like IR in terminal reservoirs of secretory gland ducts and excretory canals, which has not been observed previously in any tapeworm species. This may indicate that secretory/excretory products, which play a key role in host­parasite relationships, are likely to contain FMRF amide-related peptide/s.

A fish-parasite sentinel system in an assessment of the spatial distribution of polychlorinated biphenyls.

The spatial distribution of polychlorinated biphenyls (PCBs), in the Zemplínska Sírava water reservoir and adjacent tributaries in the Bodrog River Basin were investigated using a fish-parasite sentinel system. PCB concentrations were detected in various fish matrices (dorsal and abdominal muscles, liver and intestine) of the Wels catfish (Silurus glanis) and its intestinal cestode Glanitaenia osculata. PCB concentrations in the fish from the water reservoir, located closest to the chemical plant, the primary source of the PCB pollution, were the highest. The analysis of these contaminants in catfish matrices showed the highest concentrations in the abdominal muscle, followed by the dorsal muscle, liver and intestine. Concentrations of ∑PCBs exceeding the limits for food set by European regulations were measured in the muscle tissue of catfish at all sites, even in the Bodrog River, 60 km away from the primary source of contamination, posing a significant risk to humans in the Zemplín region. For the first time, the ability of cestode G. osculata to accumulate higher amounts of PCBs compared to fish matrices has been demonstrated. Due to the enormous ability of the parasites to accumulate PCBs, we recommend this approach for alternative biomonitoring of PCBs in contaminated aquatic environments.

Acanthocephalans of marine and freshwater fishes from Taiwan with description of a new species.

During an ichthyoparasitological survey in 2017-2019, six species of acanthocephalans were found among Taiwan's freshwater (Cypriniformes: Xenocyprididae, Cyprinidae) and marine fishes (Scombriformes: Scombridae, Trichiuridae; Anabantiformes: Channidae; Carangaria/misc: Latidae): Micracanthorhynchina dakusuiensis (Harada, 1938), Rhadinorhynchus laterospinosus Amin, Heckmann et Ha, 2011, Pallisentis rexus Wongkham et Whitfield, 1999, Longicollum sp., Bolbosoma vasculosum (Rudolphi, 1819), and one new species, Micracanthorynchina brevelemniscus sp. n. All species are morphologically characterised and illustrated using light and scanning electron microscopy. The finding of R. laterospinosus, P. rexus and B. vasculosum is the first record for these species in Taiwan. Micracanthorhynchina brevelemniscus is similar to Micracanthorhynchina motomurai (Harada, 1935) and M. dakusuiensis in proboscis armature but differs from M. motomurai by larger eggs (53-59 × 15-16 µm vs 40 × 16 µm) and by the number of cement glands (6 vs 4) and from M. dakusuiensis by shorter body length (2.2-2.9 mm vs 4.0 mm in males and 2.9-4.1 mm vs 7.6 mm in females), by the location of the organs of the male reproductive system (from level of the posterior third of the proboscis receptacle in M. brevelemniscus vs in the posterior half of the trunk in M. dakusuiensis), and by length of lemnisci (lemnisci shorter than the proboscis receptacle vs lemnisci longer than the proboscis receptacle). Phylogenetic analyses of almost complete 18S rRNA gene revealed paraphyly of the family Rhadinorhynchidae suggested in previous studies. Micracanthorhynchina dakusuiensis and M. brevelemniscus formed a strongly supported cluster, which formed the earliest diverging branch to the rest of the rhadinorhynchids and transvenids.

New cytogenetic data on Caryophyllaeus laticeps and Paracaryophyllaeus gotoi, parasites of evolutionary interest.

Caryophyllideans are intestinal parasites of freshwater fishes, occupying a basal position among the 'true' tapeworms. We performed detailed cytogenetic analyses of the well-known caryophyllidean species Caryophyllaeus laticeps. For comparison, we also examined for the first time the chromosomes of Paracaryophyllaeus gotoi, a specific parasite of loaches in China. Both species showed a diploid chromosome number of 2n = 20, n = 10m. Chromomycin A3 (CMA3)/diamidino-2-phenylindole (DAPI) staining performed for the first time in the class Cestoda revealed CMA3+/DAPI− bands in the pericentromeric regions of the short arms of chromosome pair no. 7 in the karyotype of C. laticeps. Fluorescence in situ hybridization with the 18S rDNA probe confirmed the presence of a single cluster of major rDNA near the centromere on a pair of small chromosomes in both species. These findings support the hypothesis that the ancestral state in the family Caryophyllaeidae is a single interstitial cluster of major rDNA genes and thus one nucleolar organizer region per haploid genome. Our results, which we presented together with literature data plotted on a phylogenetic tree, show stability of caryophyllidean karyotypes at the genus level, but showed differences between genera without a clear phylogenetic signal. The data allowed us to at least formulate a hypothesis about the ancestral haploid chromosome number of n = 10 for the family Caryophyllaeidae and possibly for the sister family Capingentidae. In addition, we compared two populations of C. laticeps from water bodies with different levels of polychlorinated biphenyl contamination, showing a slightly increased incidence of chromosomal abnormalities at the contaminated site.

Impact of Sainfoin (Onobrychis viciifolia) Pellets on Parasitological Status, Antibody Responses, and Antioxidant Parameters in Lambs Infected with Haemonchus contortus.

Our study analyzed the parasitological status, antibody responses, and antioxidant parameters of lambs experimentally infected with a gastrointestinal nematode during the consumption of sainfoin pellets (SFPs) for 14 d. Twenty-four lambs infected with Haemonchus contortus were separated into two groups: untreated animals (control) and animals treated with SFPs (600 g dry matter/d). SFP treatment began on day (D) 30 post-infection. The number of eggs per gram (EPG) of feces was quantified on D18, D23, D26, D30, D33, D37, D40, and D44. The mean reductions in EPG on D40 and D44 were 33.6 and 36.7%, respectively. The number of abomasal worms was lower for the SFP than the control group (p < 0.05). SFP treatment did not significantly affect either the total or the local antibody response (p > 0.05). The blood activity of glutathione peroxidase was affected by the treatment (p < 0.022). Adult worms were selected for scanning electron microscopy after necropsy, but surface structures of adult H. contortus females did not differ between the groups. The treatment of lambs with SFPs directly affected the dynamics of infection, probably indirectly by mobilizing the antioxidant defensive system and antibody response thus improving animal resistance.

Hazardous pollutants in the environment: Fish host-parasite interactions and bioaccumulation of polychlorinated biphenyls.

The present paper reports on the interrelationships of fish, parasites and the bioaccumulation of hazardous organic compounds in the Zemplínska Sírava water reservoir in eastern Slovakia, which is heavily polluted with polychlorinated biphenyls (PCBs). The concentrations of these contaminants were measured in various fish matrices (dorsal and abdominal muscle tissues, hepatopancreas, intestine wall and adipose tissue) of the freshwater bream, Abramis brama (Cyprinidae), and in its intestinal parasite Caryophyllaeus laticeps (Cestoda), which was used for the first time as a model for a PCB bioaccumulation study. Regarding the fish, the highest concentrations of PCBs were found in the intestine, followed by hepatopancreas and muscle tissues. The amounts of PCBs were higher in abdominal muscles than in their dorsal parts. Concentrations of ∑PCBs above the limits set by European regulations were detected in both muscle parts in the fish, confirming the persistent unfavorable conditions in this locality and high risk for biota and humans. Based on bioconcentration factor values (BCFs), PCBs reached much higher levels in cestodes compared to bream matrices. Some significant differences in PCB amounts between infected and uninfected bream were determined. Fulton's condition factor (CF) significantly differed in infected and non-infected fish (p ˂ 0.05), with CF values surprisingly lower in fish free of parasites compared to parasitized fish, which suggests a "mutualistic" relationship between the parasite and its host.

Hidden diversity of the most basal tapeworms (Cestoda, Gyrocotylidea), the enigmatic parasites of holocephalans (Chimaeriformes).

Gyrocotylideans are evolutionary ancient parasitic flatworms, and like their hosts-a relict group of holocephalan fishes (Chimaeriformes)-they are considered to be "living fossils" of a vanished past. However, the species diversity, host associations and biogeography of these most basal tapeworms are poorly known. Herein, we provide evidence of a conspicuous contrast between the genetic and morphological data based on an examination of newly collected and properly processed Gyrocotyle specimens (hologenophores) isolated from holocephalans off Taiwan and Argentina. Our molecular data, inferred from three genes (COI, 28S rRNA, 18S rRNA), showed unexpected genetic interrelationships among isolates of the genus Gyrocotyle, because each of the four genotypes from Taiwan clustered with isolates of distinct gyrocotylideans from the North Atlantic. Three genotypes of Gyrocotyle from Taiwan were morphologically almost indistinguishable from each other but represented distinct genetic lineages; a single specimen of Gyrocotyle sp. genotype 4 exhibited a clear genetic and morphological distinctness, though its formal description as a new species would be premature. Additionally, specimens of Gyrocotyle rugosa Diesing, 1850, from the type host Callorhinchus callorynchus from Argentina, provided the first genetic data on the type species of the genus and enabled us to characterise it, which is necessary for future taxonomic studies. The finding of some specimens of Gyrocotyle sp. genotype 3 in Chimaera phantasma, and another one in C. cf. argiloba, together with the putative conspecificity of an unidentified gyrocotylidean from Callorhinchus milii off Australia and G. rugosa from C. callorynchus off Argentina, represent evidence that one gyrocotylidean species may parasitise more than one holocephalan host species. Existing taxonomic problems and conflicts between morphological and molecular data on species of Gyrocotyle can only be resolved if hologenophores from type hosts and localities of nominal taxa are properly characterised genetically and morphologically.

Crossing barriers of zoogeographical regions: Molecular evidence of vicariance of the only cestode parasite of loaches (Cobitidae) in the Indomalayan region, Paracaryophyllaeus lepidocephali (Cestoda: Caryophyllidea), and its redescription.

Tapeworms of the genus Paracaryophyllaeus Kulakovskaya, 1961 (Cestoda: Caryophyllidea) are specific parasites of loaches (Cypriniformes: Cobitoidea) and occur almost exclusively in the Palaearctic region. The only exception and example of vicariance over the borders of two zoogeographical regions is Paracaryophyllaeus lepidocephali (Kundu, 1985), an insufficiently known species described from the Indomalayan region, with uncertain generic allocation. In the present paper, the species is redescribed based on new material collected from the type host, Lepidocephalichthys guntea, in West Bengal, India. Molecular data reveal this species as a member of Paracaryophyllaeus, within which it is the most closely related to P. cf. gotoi from Misgurnus anguillicaudatus in China and Japan on the basis of large subunit of ribosomal nuclear DNA (28S rDNA). Generic position of P. lepidocephali examined herein is also confirmed by morphology including cross sections, in particular, by a small, cylindrical body, medullary testes with testicular fields crossing the anterior margin of the cirrus sac, medullary vitelline follicles, with some follicles paramuscular, a shallow common genital atrium, short vagina and uterus not extending anteriorly beyond the cirrus sac. It differs from all Palaearctic congeners but Paracaryophyllaeus vladkae Scholz, Oros and Aydogdu, 2014 by the testicular field crossing the anterior margin of the cirrus sac. It differs from P. vladkae by more anterior position of the first vitelline follicles compared to the first testes. This species is a unique example of a fish tapeworm crossing the borders of the Palaearctic and Indomalayan zoogeographical regions.

Tapeworms (Cestoda) of Ictalurid Catfishes (Siluriformes) in North America: Redescription of Type Species of Two Genera and Proposal of Essexiellinae n. Subfam.

Ictalurid catfishes (Siluriformes) in North America harbor proteocephalid tapeworms of the subfamily Corallobothriinae. Type species of 2 of 3 genera of these tapeworms from ictalurids are redescribed, based on museum and newly collected material. Essexiella fimbriata (Essex, 1928) is typified mainly by a wide, umbrella-shaped scolex with a metascolex formed by numerous folds of tissue, anteriorly directed suckers without sphincters, vitellarium bent inwards posteriorly, "flower-shaped" uterus (with anterior, lateral, and posterior diverticula), and a conspicuously pre-equatorial genital atrium. Verified host records of this cestode are only from 3 species of Ictalurus Rafinesque, 1820. Megathylacoides giganteum (Essex, 1928), which seems to be specific to the channel catfish (Ictalurus punctatus), possesses a globular scolex, with a weakly developed metascolex formed by tissue folds posterior to the suckers, anterolaterally directed suckers with large semilunar sphincters, proglottids that are widest at the level of the genital atrium at the anterior third of the proglottid, and uterine diverticula that do not reach the vitelline follicles laterally. A new subfamily, Essexiellinae Scholz and Barcák, is proposed to accommodate species of EssexiellaScholz, de Chambrier, Mariaux and Kuchta, 2011 (type genus), MegathylacoidesJones, Kerley and Sneed, 1956, and CorallotaeniaFreze, 1965 from ictalurid catfishes in the Nearctic Region. These tapeworms possess a metascolex, medullary genital organs, uterus lined with numerous chromophilic cells, pre-equatorial genital atrium, and uterine development of type 2. The new subfamily was monophyletic in all molecular phylogenetic analyses, being most closely related to 3 Neotropical proteocephalids from the redtail catfish, Phractocephalus hemioliopterus (Bloch and Schneider, 1801), but distant from all remaining proteocephalid tapeworms from freshwater fishes in North America.

Multidisciplinary approach in study of the zoonotic Anisakis larval infection in the blue mackerel (Scomber australasicus) and the largehead hairtail (Trichiurus lepturus) in Northern Taiwan.

BACKGROUND: Anisakid larvae are the food-borne pathogen highly prevalent among numerous marine fishes. Accidental consumption of infected raw or poorly cooked fish fillets may cause anisakiasis. METHODS: This study used the multidisciplinary approach to investigate the occurrence of Anisakis nematodes in commonly consumed fish species, Scomber australasicus and Trichiurus lepturus purchased in Taipei Xinyi traditional fish market. RESULTS: All the Anisakis larvae collected herein were identified morphologically as Anisakis type I or Anisakis type II. The prevalence and the mean intensity of Anisakis larvae collected from S. australasicus was 80.77%, 26.8 (10-32) and 100%, 49.0 (27-70) for T. lepturus. Using molecular analysis, 83.33% (180/216) were identified as Anisakis pegreffii, 6.05% (13/216) as Ascaris typica, 1.85% (4/216) as Ascaris physeteris and 8.80% (19/216) as hybrid genotype (A. pegreffii + Anisakis simplex) in S. australasicus. In T. lepturus, 86.31% (290/336) were identified as A. pegreffii, 2.38% (8/336) as A. typica, and 11.31% (38/336) as hybrid genotype (A. pegreffii + A. simplex [s.s]). The molecular phylogenetic analysis shows two cluster clades, one group includes A. pegreffii complex and the other include Ascaris paggiae, Ascaris brevispiculata, and A. physeteris. CONCLUSION: Thus, A. pegreffii is the most abundant species and may be the potential causes of human infection.

A new species of Clinostomum Leidy, 1856 in East Asia based on genomic and morphological data.

Metacercariae of Clinostomum Leidy, 1856 are frequently encountered in freshwater fish. In 2015, a provisional species of Clinostomum in People's Republic of China (PRC) was distinguished from C. complanatum (Rudolphi, 1819) in Europe based on divergent cytochrome c oxidase I (CO1). However, in subsequent studies in East Asia, the same divergent CO1 genotype was identified as C. complanatum. These matching sequences suggest that either the provisional East Asian species was incorrectly distinguished from C. complanatum in 2015 or that C. complanatum in East Asia was misidentified in later studies. We tested these alternatives by sequencing the mitochondrial genome of C. complanatum in Italy, which was 5.7% divergent from a previously published sequence from Clinostomum in PRC, including differences in 80 of 3390 (2.4%) translated amino acids. Partial CO1 sequences of specimens from PRC and those from Italy, Romania, and Turkey also each formed reciprocally monophyletic clades. Partial CO1 from the East Asian clade varied by mean 3.6% (range 2.4-4.8%) from C. complanatum from Italy, Romania, and Turkey; mean intra-clade CO1 variation was 0.3% (range 0-1.9%). Metacercariae from Europe and East Asia display significant morphometric variation, and data from the literature suggest morphological differences in the genital complex of adults. Although sequences of nuclear rDNA did not differ between isolates from the west and East Asia, taken together, these results lead us to describe a new species of Clinostomum.

Complex insight on microanatomy of larval "human broad tapeworm" Dibothriocephalus latus (Cestoda: Diphyllobothriidea).

BACKGROUND: In Europe, the tapeworm Dibothriocephalus latus (syn. Diphyllobothrium latum) is a well-known etiological agent of human diphyllobothriosis, which spreads by the consumption of raw fish flesh infected by plerocercoids (tapeworm's larval stage). However, the process of parasite establishment in both intermediate and definitive hosts is poorly understood. This study was targeted mainly on the scolex (anterior part) of the plerocercoid of this species, which facilitates penetration of the parasite in intermediate paratenic fish hosts, and subsequently its attachment to the intestine of the definitive host. METHODS: Plerocercoids were isolated from the musculature of European perch (Perca fluviatilis) caught in Italian alpine lakes. Parasites were examined using confocal microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Immunofluorescence tagging was held on whole mount larvae. RESULTS: The organisation of the central and peripheral nervous system was captured in D. latus plerocercoids, including the ultrastructure of the nerve cells possessing large dense neurosecretory granules. Two types of nerve fibres run from the body surface toward the nerve plexus located in the parenchyma on each side of bothria. One type of these fibres was found to be serotoninergic and possessed large subtegumental nerve cell bodies. A well-developed gland apparatus, found throughout the plerocercoid parenchyma, produced heterogeneous granules with lucent core packed in a dense layer. Three different types of microtriches occurred on the scolex and body surface of plerocercoids of D. latus: (i) uncinate spinitriches; (ii) coniform spinitriches; and (iii) capilliform filitriches. Non-ciliated sensory receptors were observed between the distal cytoplasm of the tegument and the underlying musculature. CONCLUSIONS: Confocal laser scanning microscopy and electron microscopy (SEM and TEM) showed the detailed microanatomy of the nervous system in the scolex of plerocercoids, and also several differences in the larval stages compared with adult D. latus. These features, i.e. well-developed glandular system and massive hook-shaped uncinate spinitriches, are thus probably required for plerocercoids inhabiting fish hosts and also for their post-infection attachment in the human intestine.

A synoptic review of Caryophyllaeus Gmelin, 1790 (Cestoda: Caryophyllidea), parasites of cyprinid fishes.

Tapeworms of the genus Caryophyllaeus Gmelin, 1790 (Caryophyllidea: Caryophyllaeidae), common parasites of cyprinid fishes, are reviewed and taxonomic status of 42 nominal taxa that have been placed in the genus during its long history is clarified. The following seven species occurring in the Palaearctic Region are recognised as valid: C. laticeps (Pallas, 1781), C. auriculatus (Kulakovskaya, 1961), C. balticus (Szidat, 1941) comb. n. (syn. Khawia baltica Szidat, 1941), C. brachycollis Janiszewska, 1953, C. fimbriceps Annenkova-Chlopina, 1919, C. syrdarjensis Skrjabin, 1913, and newly described Caryophyllaeus chondrostomi sp. n. (= C. laticeps morphotype 4 of Bazsalovicsová et al., 2014) from common nase, Chondrostoma nasus (Linnaeus), found in Austria and Slovakia. The new species differs by the paramuscular or cortical position of preovarian vitelline follicles, a large, robust body (up to 64 mm long), conspicuously long vas deferens, flabellate scolex with small wrinkles on the anterior margin, and anteriormost testes located in a relatively short distance from the anterior extremity. Caryophyllaeus kashmirenses Mehra, 1930 and Caryophyllaeus prussicus (Szidat, 1937) comb. n. are considered to be species inquirendae, C. truncatus von Siebold in Baird, 1853 and C. tuba von Siebold in Baird, 1853 are nomina nuda. Data on the morphology, host spectra, distribution and known life-cycles of valid species are provided. Phylogenetic interrelations of four species of the genus including its type species and newly described C. chondrostomi were assessed based on an analysis of sequences of lsrDNA and cox1. A key to identification of all valid species of Caryophyllaeus is also provided.

The occurrence of the common European fish cestode Caryophyllaeus laticeps (Pallas, 1781) in the River Irtysh, China: a morphological characterization and molecular data.

The cestode Caryophyllaeus laticeps (Pallas, 1781) is a highly polymorphic species with several morphotypes, and belongs to the most widespread species of monozoic tapeworm (Cestoda: Caryophyllidea) found in the Palaearctic zoogeographic region with a wide range of cyprinid fish hosts. This paper provides the first reliable evidence about the occurrence of C. laticeps in northern China that is based on detailed morphological characteristics and mitochondrial cox1 sequences. C. laticeps was found in freshwater bream Abramis brama (L.), in the River Irtysh, with the prevalence of 40% and mean intensity of infection 8. The tapeworms were rather similar in their morphological characters to the morphotype 1 of C. laticeps which is typified by the possession of a slender body with a flabellate wide scolex, narrow neck, robust, long and clearly visible vas deferens, large, and almost spherical cirrus-sac containing well-developed internal seminal vesicle and the first vitelline follicles and first testes beginning far from anterior margin of the body. Subsequent molecular analysis confirmed the morphological identification of the species. Our results show that the studied specimens were firmly clustered into the C. laticeps clade and formed a monophyletic group with C. laticeps morphotype 1 and 2 from Europe and Russia. In China, C. laticeps is a non-indigenous fish parasite, which has the most probably been introduced into the Irtysh River basin with its typical host inhabiting Russia.

Asian fish tapeworm, Khawia japonensis (Yamaguti, 1934), has expanded its European invasive range.

The invasive fish tapeworm, Khawia japonensis (Yamaguti, 1934) originally described in Japan, is reported for the first time in Slovakia. The tapeworm was found in farmed common carp (Cyprinus carpio L.) from East-Slovakian breeding fish pond. This finding is registered 4 years after the first announcement of this parasite in Europe (Po River Basin in Italy) in 2010 and increases its distribution area within this continent. Morphological characterization of K. japonensis supplemented with DNA sequences of cox1 and ribosomal lsrDNA genes is provided. Specimens from Slovakia phenotypically corresponded with those from feral and farmed carps from China, Vietnam, and Italy. Moreover, 100 and 98.7% identity of partial ribosomal lsrDNA gene and mitochondrial cox1 genes, respectively, were detected with K. japonensis from Japan. The invasive and pathogenic potential of K. japonensis in commercial breeding fisheries and its possible further spread in natural habitats is difficult to estimate for now. As yet, K. japonensis appears to be without a major impact on commercial breeding fisheries, but calls for more attention to the problem of biological invasions.

Morphological polymorphism in tapeworms: redescription of Caryophyllaeus laticeps (Pallas, 1781) (Cestoda: Caryophyllidea) and characterisation of its morphotypes from different fish hosts.

Recent morphological and molecular data have shown that one of the most common parasites of freshwater fish in the Palaearctic Region, the cestode Caryophyllaeus laticeps (Pallas, 1781) (Eucestoda: Caryophyllidea), is highly polymorphic. Five distinct morphotypes of C. laticeps, largely corresponding to different fish hosts and representing separate, yet closely related genetic lineages, have been recognised and they are characterised in the present paper. Morphotype 1 from breams, Abramis brama (L.) (type-host) and Ballerus spp., corresponds to the original Taenia laticeps Pallas, 1781 and its neotype (paragenophore ex A. brama in Russia) is designated. This morphotype is characterised by a slender body and flabellate scolex. Morphotype 2 was found in the Macedonian vimba Vimba melanops (Heckel) and the vimba bream V. vimba (L.); it is typified by a more robust body, with most anterior extent of the vitelline follicles near the scolex and the cirrus-sac situated more anteriorly than in other morphotypes. Morphotype 3 is represented by worms from the common carp Cyprinus carpio L. that possess a cuneicrispitate scolex (having the form of a wedge with shallow indentations on anterior margin). Morphotype 4 from the common nase Chondrostoma nasus (L.) has a large, robust body and a wide scolex with numerous superficial grooves (wrinkles) in its anterior part. Morphotype 5 is represented by worms from the white-eye bream Ballerus sapa (Pallas); its typical characteristics are a festoon-like anterior margin of the scolex, the absence of vitelline follicles posterior to the cirrus-sac and the absence of a well-developed internal seminal vesicle. Discriminant analysis of 15 morphometric variables readily separated Morphotypes 3, 4 and 5 and confirmed the key discriminating power of traits related to the reproductive system, especially the terminal reproductive organs. Morphological polymorphism and the genetic divergence of different morphotypes of C. laticeps correspond to its wide spectrum of fish definitive hosts and a large distribution area that includes Europe, most of Palaearctic Asia and northern Africa.