Intermediate host patterns of acanthocephalans in the Weser river system: co-invasion vs host capture.

Anthropogenic interference is a major driver of ecological change in freshwater ecosystems. Pollution and the introduction of new species not only alter macrozoobenthic community structures, but can also affect their respective parasite communities. The ecology of the Weser river system experienced a drastic decline in biodiversity over the past century due to salinization caused by the local potash industry. As a response, the amphipod Gammarus tigrinus was released into the Werra in 1957. A few decades after the introduction and subsequent spread of this North American species, its natural acanthocephalan Paratenuisentis ambiguus was recorded in the Weser in 1988, where it had captured the European eel Anguilla anguilla as a novel host. To assess the recent ecological changes in the acanthocephalan parasite community, we investigated gammarids and eel in the Weser river system. In addition to P. ambiguus, 3 Pomphorhynchus species and Polymorphus cf. minutus were discovered. The introduced G. tigrinus serves as a novel intermediate host for the acanthocephalans Pomphorhynchus tereticollis and P. cf. minutus in the tributary Werra. Pomphorhynchus laevis is persistent in the tributary Fulda in its indigenous host Gammarus pulex. Pomphorhynchus bosniacus colonized the Weser with its Ponto-Caspian intermediate host Dikerogammarus villosus. This study highlights the anthropogenically driven changes in ecology and evolution in the Weser river system. Based on morphological and phylogenetic identification, the shifts in distribution and host usage described here for the first time contribute to the puzzling taxonomy of the genus Pomphorhynchus in times of ecological globalization.

Cryptic species and their utilization of indigenous and non-indigenous intermediate hosts in the acanthocephalan Polymorphus minutus sensu lato (Polymorphidae).

The bird-infecting acanthocephalan Polymorphus minutus has been suggested to comprise different lineages or even cryptic species using different intermediate hosts. To clarify this open question, we investigated Polymorphus cf. minutus cystacanths originating from amphipod intermediate hosts from 27 sites in Germany and France. Parasites and hosts were identified using integrated datasets (COI and/or morphology for hosts and COI + ITS1-5.8S-ITS2 for parasites).Mitochondrial and nuclear data (ITS1) strongly support the existence of three cryptic species in Polymorphus cf. minutus (type 1-3). These three types reveal a high degree of intermediate host specificity, with Polymorphus type 1 only encountered in Gammarus fossarum type B, Polymorphus type 2 in Echinogammarus sp. and Echinogammarus berilloni, and Polymorphus type 3 in Gammarus pulex and Gammarus roeselii. Our results point to a so far neglected cryptic diversity of the genus Polymorphus in Central Europe. Furthermore, Polymorphus type 2 is most likely a non-native parasite in Germany that co-invaded with E. berilloni from the Mediterranean area. Potentially, type 3 originates from South-East Europe and migrated to Germany by G. roeselii, where it might have captured G. pulex as an intermediate host. Therefore, our findings can be seen in the context of ecological globalization in terms of the anthropogenic displacement of intermediate hosts and its impact on the genetic divergence of the parasites.

Evolutionary anatomy of the muscular apparatus involved in the anchoring of Acanthocephala to the intestinal wall of their vertebrate hosts.

Different conceptions exist regarding structure, function, and evolution of the muscles that move the acanthocephalan presoma, including the proboscis, i.e., the usually hooked hold-fast anchoring these endoparasites to the intestinal wall of their vertebrate definitive hosts. In order to clarify the unresolved issues, we carried out a light microscopic analysis of series of semi-thin sections and whole mounts representing the three traditional acanthocephalan classes: Archiacanthocephala (Macracanthorhynchus hirudinaceus), Eoacanthocephala (Paratenuisentis ambiguus, Tenuisentis niloticus), and Palaeacanthocephala (Acanthocephalus anguillae, Echinorhynchus truttae, Pomphorhynchus laevis, Corynosoma sp.). Combining our data with published light, transmission electron, and scanning electron microscopic data, we demonstrate that receptacle protrusor and proboscis receptacle in Archi- and Eoacanthocephala are homologous to the outer and inner wall of the proboscis receptacle in Palaeacanthocephala. Besides the proboscis receptacle and a "surrounding muscle," the last common ancestor of Acanthocephala presumably possessed a proboscis retractor, receptacle retractor, neck retractor (continuous with lemnisci compressors), and retinacula. These muscles most probably evolved in the acanthocephalan stem line. Moreover, the last common ancestor of Acanthocephala presumably possessed only a single layer of muscular cords under the presomal tegument while the metasomal body wall had circular and longitudinal strands. Two lateral receptacle flexors (also lateral receptacle protrusors), an apical muscle plate (surrounding one or two apical sensory organs), a midventral longitudinal muscle, and the differentiation of longitudinal body wall musculature at the base of the proboscis probably emerged within Archiacanthocephala. All muscles have a common organization principle: a peripheral layer of contractile filaments encloses the cytoplasm.

Transcriptome analyses of Anguillicola crassus from native and novel hosts.

Anguillicola crassus is a swim bladder nematode of eels. The parasite is native to the Asian eel Anguilla japonica, but was introduced to Europe and the European eel Anguilla anguilla in the early 1980s. A Taiwanese source has been proposed for this introduction. In the new host in the recipient area, the parasite appears to be more pathogenic. As a reason for these differences, genetically fixed differences in infectivity and development between Taiwanese and European A.crassus have been described and disentangled from plasticity induced by different host environments. To explore whether transcriptional regulation is involved in these lifecycle differences, we have analysed a "common garden", cross infection experiment, using deep-sequencing transcriptomics. Surprisingly, in the face of clear phenotypic differences in life history traits, we identified no significant differences in gene expression between parasite populations or between experimental host species. From 120,000 SNPs identified in the transcriptome data we found that European A. crassus were not a genetic subset of the Taiwanese nematodes sampled. The loci that have the major contribution to the European-Taiwanese population differentiation show an enrichment of synonymous and non-coding polymorphism. This argues against positive selection in population differentiation. However, genes involved in protein processing in the endoplasmatic reticulum membrane and genes bearing secretion signal sequences were enriched in the set of genes most differentiated between European and Taiwanese A. crassus. These genes could be a source for the phenotypically visible genetically fixed differences between European and Taiwanese A. crassus.

Redescription of Heliconema africanum (Linstow, 1899) n. comb. (Nematoda: Physalopteridae), a nematode parasite of freshwater eels (Anguilla spp.) in South Africa.

The little-known nematode species Heliconema africanum (Linstow, 1899) n. comb. (Physalopteridae) is redescribed based on light and scanning electron microscopical examinations of specimens collected from the stomach of the African longfin eel Anguilla mossambica (Peters) in the Nahoon River, Eastern Cape Province, South Africa. This species, previously misidentified as Heliconema longissimum (Ortlepp, 1922), is a common parasite of eels in South Africa. The systematic status of H. longissimum, a species originally described from unidentified Australian snakes, is unclear and probably several morphologically closely related species have been included under this name.

Evolutionary divergence of the swim bladder nematode Anguillicola crassus after colonization of a novel host, Anguilla anguilla.

BACKGROUND: Anguillicola crassus, a swim bladder nematode naturally parasitizing the Japanese eel, was introduced about 30 years ago from East Asia into Europe where it colonized almost all populations of the European eel. We conducted a common garden experiment under a reciprocal transfer design infecting both European and Japanese eels with populations of A. crassus from Germany, Poland and Taiwan. We tested, whether differences in infectivity, developmental dynamics and reproductive output between the European and Asian parasite populations occur while harboured in the specimens of native and colonized eel host, and if these differences are genetically based or are plastic responses to the new environment. RESULTS: Under common garden conditions an evolutionary change in the both European parasite populations of A. crassus compared with their Taiwanese conspecifics was observed for infectivity and developmental dynamics, but not for reproductive output. When infecting the European eel, current European populations of the parasite were less infective and developed faster than their Taiwanese conspecifics. In the reciprocally infected Japanese eel the genetically induced differences between the parasite strains were less apparent than in the European eel but higher infectivity, faster development and higher larval mortality of the European parasite populations could be inferred. CONCLUSIONS: The differences in infectivity and developmental dynamics between European and Taiwanese populations of A. crassus found in our study suggest rapid genetic divergence of this parasite after a successful host switch in Europe.

The transcriptome of the invasive eel swimbladder nematode parasite Anguillicola crassus.

BACKGROUND: Anguillicola crassus is an economically and ecologically important parasitic nematode of eels. The native range of A. crassus is in East Asia, where it infects Anguilla japonica, the Japanese eel. A. crassus was introduced into European eels, Anguilla anguilla, 30 years ago. The parasite is more pathogenic in its new host than in its native one, and is thought to threaten the endangered An. anguilla across its range. The molecular bases for the increased pathogenicity of the nematodes in their new hosts is not known. RESULTS: A reference transcriptome was assembled for A. crassus from Roche 454 pyrosequencing data. Raw reads (756,363 total) from nematodes from An. japonica and An. anguilla hosts were filtered for likely host contaminants and ribosomal RNAs. The remaining 353,055 reads were assembled into 11,372 contigs of a high confidence assembly (spanning 6.6 Mb) and an additional 21,153 singletons and contigs of a lower confidence assembly (spanning an additional 6.2 Mb). Roughly 55% of the high confidence assembly contigs were annotated with domain- or protein sequence similarity derived functional information. Sequences conserved only in nematodes, or unique to A. crassus were more likely to have secretory signal peptides. Thousands of high quality single nucleotide polymorphisms were identified, and coding polymorphism was correlated with differential expression between individual nematodes. Transcripts identified as being under positive selection were enriched in peptidases. Enzymes involved in energy metabolism were enriched in the set of genes differentially expressed between European and Asian A. crassus. CONCLUSIONS: The reference transcriptome of A. crassus is of high quality, and will serve as a basis for future work on the invasion biology of this important parasite. The polymorphisms identified will provide a key tool set for analysis of population structure and identification of genes likely to be involved in increased pathogenicity in European eel hosts. The identification of peptidases under positive selection is a first step in this programme.

Human contact influences the foraging behaviour and parasite community in long-tailed macaques.

Human­wildlife interactions have reached unprecedented levels, and humans are influencing the earth's ecosystems more rapidly and extensively than ever before. This situation is cause for serious concern, especially since disease interactions between wildlife and humans have been recognized as major conservation threats. In this study, long-tailed macaques, Macaca fascicularis, from 2 forest parks located in north-eastern Thailand were investigated to determine the influence of habitat modification by humans on helminth parasite associations in non-human primates. Macaque populations with contact to anthropogenically modified environments were compared with sylvatic groups in nearby natural environments. In order to test for human­non-human primate transmission of parasites, the local human populations were also examined. Humans were infected with a number of potentially pathogenic parasites, including Opisthorchis viverrini and Strongyloides stercoralis. However, eggs of these helminths were not detected in macaque feces. Thus, no direct parasite transfer from humans to non-human primates could be confirmed. However, macaque groups with more frequent contact with human modified habitats, and a higher portion of human-provided food in their diet, had significantly higher prevalences and intensities of Strongyloides fuelleborni and of an intestinal fluke (probably Haplorchis sp.) than sylvatic groups. Positive correlations were found between the time foraging on the ground and infection with S. fuelleborni, and the amount of human-provided food and intestinal fluke infection. Human alteration of habitat and associated modifications in nonhuman primate behaviour are likely to play a role in determining the occurrence, prevalence and intensity of zoonotic helminth infection of wild non-human primates.

Detection of Rickettsia helvetica in ticks collected from European hedgehogs (Erinaceus europaeus, Linnaeus, 1758).

The role of wild mammals in the dissemination and maintenance of Rickettsia in nature is still under investigation. European hedgehogs (Erinaceus europaeus) are often heavily infested by tick and flea species that are known to harbor and transmit different Rickettsia spp. We investigated ixodid ticks sampled from European hedgehogs for the presence of Rickettsia. A total of 471 Ixodes ricinus and 755 I. hexagonus were collected from 26 German and 7 British European hedgehogs. These were tested by a genus-specific real-time PCR assay targeting the citrate synthase gene (gltA). The rickettsia minimum infection rate was 11.7% with an increase detected with each parasitic tick stage. No significant difference in Rickettsia prevalence in the 2 Ixodes species was detected. Using sequencing of partial ompB, Rickettsia helvetica was the only species identified. More than half of the hedgehogs carried Rickettsia-positive ticks. In addition, tissue samples from 2/5 hedgehogs (where tissue DNA was available) were PCR-positive. These results show that European hedgehogs are exposed to R. helvetica via infected ticks and might be involved in the natural transmission cycle of this Rickettsia species.

The phylogenetics of Anguillicolidae (Nematoda: Anguillicoloidea), swimbladder parasites of eels.

BACKGROUND: Anguillicolidae Yamaguti, 1935 is a family of parasitic nematode infecting fresh-water eels of the genus Anguilla, comprising five species in the genera Anguillicola and Anguillicoloides. Anguillicoloides crassus is of particular importance, as it has recently spread from its endemic range in the Eastern Pacific to Europe and North America, where it poses a significant threat to new, naïve hosts such as the economic important eel species Anguilla anguilla and Anguilla rostrata. The Anguillicolidae are therefore all potentially invasive taxa, but the relationships of the described species remain unclear. Anguillicolidae is part of Spirurina, a diverse clade made up of only animal parasites, but placement of the family within Spirurina is based on limited data. RESULTS: We generated an extensive DNA sequence dataset from three loci (the 5' one-third of the nuclear small subunit ribosomal RNA, the D2-D3 region of the nuclear large subunit ribosomal RNA and the 5' half of the mitochondrial cytochrome c oxidase I gene) for the five species of Anguillicolidae and used this to investigate specific and generic boundaries within the family, and the relationship of Anguillicolidae to other spirurine nematodes. Neither nuclear nor mitochondrial sequences supported monophyly of Anguillicoloides. Genetic diversity within the African species Anguillicoloides papernai was suggestive of cryptic taxa, as was the finding of distinct lineages of Anguillicoloides novaezelandiae in New Zealand and Tasmania. Phylogenetic analysis of the Spirurina grouped the Anguillicolidae together with members of the Gnathostomatidae and Seuratidae. CONCLUSIONS: The Anguillicolidae is part of a complex radiation of parasitic nematodes of vertebrates with wide host diversity (chondrichthyes, teleosts, squamates and mammals), most closely related to other marine vertebrate parasites that also have complex life cycles. Molecular analyses do not support the recent division of Anguillicolidae into two genera. The described species may hide cryptic taxa, identified here by DNA taxonomy, and this DNA barcoding approach may assist in tracking species invasions. The propensity for host switching, and thus the potential for invasive behaviour, is found in A. crassus, A. novaezelandiae and A. papernai, and thus may be common to the group.

Occurrence of different Borrelia burgdorferi sensu lato genospecies including B. afzelii, B. bavariensis, and B. spielmanii in hedgehogs (Erinaceus spp.) in Europe.

In order to determine whether European hedgehogs (Erinaceus europaeus and E. roumanicus) play a role in the epidemiological cycle of Borrelia burgdorferi sensu lato in Central Europe and Great Britain, tissue samples of hedgehogs from Germany (n=211), Austria (n=4), the Czech Republic (n=22), and the U.K. (n=32) were tested for the presence of these tick-borne pathogens. PCR for amplification of the B. burgdorferi s.l.-specific 5S-23S intergenic spacer region as well as the outer surface protein A (ospA) gene were used. B. burgdorferi s.l. DNA was detected in 35 of the 259 E. europaeus and in 2 of 10 E. roumanicus. B. burgdorferi prevalences in E. europaeus ranged from 0% (U.K.) to 37.5% (Czech Republic), for E. roumanicus from 0% (Czech Republic) to 50.0% (Austria). Sequencing revealed the occurrence of 3 different B. burgdorferi genospecies in E. europaeus: B. afzelii was the dominant genospecies, followed by B. bavariensis (previously B. garinii OspA serotype 4) and B. spielmanii, the latter was detected for the first time in Hamburg (Germany). B. afzelii and B. bavariensis were also found in E. roumanicus. Our results suggest that hedgehogs modulate the epidemiology of certain species of the B. burgdorferi s.l. complex, potentially affecting the distribution and abundance of individual B. burgdorferi s.l. genospecies in various habitats. We hypothesise that juvenile or individuals with low immune competence in particular, have a high reservoir potential for the 3 genospecies identified here.

The European hedgehog (Erinaceus europaeus)--a suitable reservoir for variants of Anaplasma phagocytophilum?

The European hedgehog (Erinaceus europaeus) is a common insectivore in most parts of Europe and is frequently infested by the ticks Ixodes ricinus and I. hexagonus. I. ricinus ticks have been found infected with Anaplasma phagocytophilum, an obligate intracellular bacterium, but little is known about the potential of the hedgehog as a reservoir host. In this study, the infection with A. phagocytophilum and the genetic variants involved were investigated in a captive hedgehog population which was kept in a fenced, natural grass and bush garden habitat, and also in its ticks. Additionally hedgehogs from hedgehog caretaking stations were investigated. EDTA blood and ticks were collected from the captive hedgehog population once a month from March to October 2007 and in March and April 2008. All 3 developmental stages of I. ricinus and I. hexagonus occurred on the hedgehogs. After DNA extraction, the samples were screened for A. phagocytophilum with a real-time PCR, and selected samples were further investigated with a nested PCR targeting the partial 16S rRNA gene, followed by sequencing. One hundred thirty-six out of 220 hedgehog blood samples (61.8%) from altogether 48 individuals, 413 out of 563 I. ricinus samples and 90 out of 338 I. hexagonus samples were PCR-positive. Thirty-two hedgehogs were positive more than once, most frequently twice or 3 times, but also up to 9 times. Sequencing of the partial 16S rRNA gene resulted in 6 variants, but one variant ('A') was the most frequent which appeared in 93.8% of the positive hedgehogs. This variant (equaling Frankonia II, GenBank AF136712) has recently been reported from human, equine, and canine granulocytic anaplasmosis cases and thus, its specific association with hedgehogs is an important finding in the epidemiology of A. phagocytophilum in Europe. The high infection rate of both hedgehogs and ticks with A. phagocytophilum and the simultaneous infestation with 2 tick species of all developmental stages suggest that the hedgehog may be a suitable reservoir for at least some variants of A. phagocytophilum.

Quantifying differences in parasite numbers between samples of hosts.

An important question in many parasitological studies is the assessment of differences in parasite numbers between samples of hosts. This is not always an easy problem with which to deal. While almost everyone will agree that the main task consists in deciding whether the values in one sample tend to be higher than the values of another sample, there is considerable disagreement about what higher (or lower) should mean. In most cases, dissimilarity measures are differences between mean values, medians, geometric means, prevalence rates, relative effects, and more. In general, different measures can lead to different conclusions. However, a debate as to which measure is superior is fruitless; it depends on goals and circumstances of the respective study. In our opinion, it is more important to identify situations in which most of the above measures coincide, and, hence, one can confidently claim that the values in one sample are higher than in another. This is the case when one sample is stochastically larger than a second. Roughly speaking, a random variable X is stochastically larger than a second random variable Y, when X assumes large values with a higher probability than Y. In this paper, we review this concept using distributional and data examples, and we propose the use of graphical tools for detecting stochastic dominance. Our method provides a relatively easy, visual way of fully justifying general statements that the number of parasites in one sample is larger than in another.

Molecular detection of Anaplasma phagocytophilum in the European hedgehog (Erinaceus europaeus) and its ticks.

The European hedgehog (Erinaceus europaeus) is a common wild mammal in Central Europe that shares habitats with humans in urban, peri-urban, and rural areas. Thus, this species may play a role in human contact with zoonotic diseases. Here we report the presence of the pathogen Anaplasma phagocytophilum in hedgehogs and their ticks in Germany.

The avian acanthocephalan Plagiorhynchus cylindraceus (Palaeacanthocephala) parasitizing the European hedgehog (Erinaceus europaeus) in Europe and New Zealand.

The palaeacanthocephalan Plagiorhynchus cylindraceus is a common intestinal parasite of passerine birds, which can also occur parenterally or in the intestinal tract of mammals, often as an invading species in many countries worldwide. In this survey, introduced hedgehogs (Erinaceus europaeus, n = 183) killed in New Zealand during a biocontrol campaign and conspecifics (n = 174) that had died in hedgehog rehabilitation centers in Germany and Britain were examined for this parasite. In New Zealand, P. cylindraceus is recorded for the first time here, in the vicinity of Auckland. In Europe, prevalences ranged from 4.2% up to 47.6%, while in New Zealand, only 1.6% (Auckland 7.9%). Most of the worms occurred inside the peritoneal cavity where they had partly degenerated. Since hedgehogs are seldom preyed upon in continental Europe but often become traffic victims, we hypothesize that the worms inside them, whether extra- or intraperitoneally, contribute to the abundance and persistence of the parasite by being ingested by scavenging birds. Accordingly, we consider P. cylindraceus as a "modern parasite" taking advantage of two aspects of global change: anthropogenic promoted transmission (road kills) and the transcontinental spread of infected intermediate and/or final hosts caused by humans.

Massive encapsulation of larval Anguillicoloides crassus in the intestinal wall of Japanese eels.

BACKGROUND: Within the last 25 years, after the introduction of the swimbladder nematode Anguillicoloides crassus from East-Asia to Europe, a body of work has aggregated on the host parasite interactions in the acquired host Anguilla anguilla. Despite the emerging evolutionary interest there is still a lack of knowledge about host parasite relations of A. crassus in its natural host Anguilla japonica. We examined the Anguillicoloides infections of wild-caught Japanese eels as well as from aquacultured specimens in Taiwan with respect to the fate of migratory L3 larvae and performed infection experiments with Japanese eels. RESULTS: Inside the intestinal wall of cultured eels, where the infective pressure was higher than among wild eels, we found large numbers of granuloma-like cysts. In a few eels these cysts contained nematodes still recognizable as L3 larvae of A. crassus, while in most cases the content of these capsules was degraded to amorphous matter. Occurrence of these objects was correlated with the number of encapsulated larvae in the swimbladder wall. We were able to show, that the cysts contained disintegrated L3 larvae by amplification and subsequent sequencing of large subunit ribosomal rRNA. Furthermore we identified repeated infections with high doses of larvae as prerequisites for the processes of encapsulation in infection experiments. CONCLUSION: Under high infective pressure a large percentage of L3 larvae of A. crassus coming from the gut lumen are eliminated by the natural host within its intestinal tissue. It is possible to reproduce this condition in infection experiments. We provide a fast, easy and reliable PCR-based method for identification of encapsulated swimbladder parasites.

Population structure of the parasitic nematode Anguillicola crassus, an invader of declining North Atlantic eel stocks.

Probably half of all animal species exhibit a parasitic lifestyle and numerous parasites have recently expanded their distribution and host ranges due to anthropogenic activities. Here, we report on the population genetic structure of the invasive nematode Anguillicola crassus, a parasite in freshwater eels, which recently spread from Asia to Europe and North America. Samples were collected from the newly colonized naive host species Anguilla anguilla (Europe) and Anguilla rostrata (North America), and from indigenous Anguilla japonica in Taiwan and Japan. Using seven microsatellite loci and one mitochondrial marker, we show that the parasite's population structure in Europe mirrors the zoogeographic Boreal-Lusitanian break along the English Channel. Both the north-to-south decline of nuclear allelic diversity and the loss of private alleles in the same direction are consistent with a significant isolation-by-distance pattern based on rho(ST) values. In combination with the specific topology of the distance tree among nematode populations, our data suggest that Europe was invaded only once from Taiwan, and that subsequently, genetic diversity was lost due to random drift. On the contrary, the North American sample shares distinct nuclear and mitochondrial signatures with Japanese specimens. We propose that the genetic structure in Europe was shaped by long-range anthropogenic eel host transfers in the north and a single dispersal event into the southwest. The genetically distinct Brittany sample at the edge of the Boreal-Lusitanian boundary is indicative of natural dispersal of fish hosts since recruitment occurs naturally there and invertebrate host dissemination is interrupted due to oceanic currents.

Parasite communities in eels of the Island of Reunion (Indian Ocean): a lesson in parasite introduction.

Eel populations from the small rivers on the Island of Reunion (French Overseas Department in the Indian Ocean) were investigated with respect to the occurrence and abundance of helminths during the autumn of 2005. The native species Anguilla marmorata (n = 80), Anguilla bicolor (n = 23), and Anguilla mossambica (n = 15) were studied. Six species of helminths were identified, four of them having a definitely nonnative status. Furthermore, unidentified intra-intestinal juvenile cestodes and extra-intestinal encapsulated anisakid nematode larvae were present in a few eels. We found that the invasive swim bladder nematode Anguillicoloides (Anguillicola) crassus had been introduced into the island. Six specimens were collected, four from A. marmorata, one from A. bicolor and one from A. mossambica. The maximum intensity of infection was two worms. The other helminths also showed a low abundance. These species were the monogenean gill worms Pseudodactylogyrus anguillae and Pseudodactylogyrus bini and the intestinal parasites Bothriocephalus claviceps (Cestodes), Paraquimperia africana (Nematodes), and the acanthocephalan Acanthocephalus reunionensis Warner, Sasal, and Taraschewski, 2007. The latter species, found as intra-intestinal immatures, is thought to utilize amphibians as required hosts; its status, introduced or native, could not be determined. P. africana was described from A. mossambica in South Africa and has not been recorded outside Africa. The other species are known from populations of European and American eels. However, A. crassus and the two Pseudodactylogyrus species originate from East Asia, where they are indigenous parasites of Anguilla japonica. Both an assignment test based on seven specific microsatellite loci and subsequent sequencing of mitochondrial haplotypes of a partial fragment of cytochrome c oxidase 1 strongly suggest that the A. crassus may originated around the Baltic Sea. According to the results presented here, populations of the indigenous eel species from Reunion can be considered to harbor extremely isolationist alien parasite communities. Our findings support the hypothesis that during the present time of global biological change, invasion by a nonnative species into a target island is more likely to reflect the political affiliation of the colonized environment and the pathways of trade and tourism than geographic proximity between donor and recipient areas or other natural circumstances.

Do eel parasites reflect the local crustacean community? A case study from the Rhine River system.

In 2003, the parasite fauna of 197 European eels Anguilla anguilla, captured at three different locations (Laufenburg, Karlsruhe and Beneeden Leeuwen) in the River Rhine, was analysed. The eels harboured a total of 18 species, among them the protozoa (Myxidium giardi, Myxobolus kotlani and Trypanosoma granulosum), acanthocephalans (Acanthocephalus anguillae, Acanthocephalus lucii, Echinorhynchus truttae, Pomphorhynchus laevis), nematodes (Paraquimperia tenerrima, Pseudocapillaria tomentosa, Camallanus lacustris, Raphidascaris acus, Spinitectus inermis and Anguillicola crassus), cestodes (Bothriocephalus claviceps and Proteocephalus macrocephalus) and monogeneans (Pseudodactylogyrus sp.). The parasite fauna at the different locations is discussed with respect to the crustacean fauna present at these locations. The investigation shows that changes in the composition of the crustacean fauna, due to the anthropogenic breakdown of a biogeographic barrier, are reflected in the composition of the intestinal eel parasite fauna.