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DNA (meta)barcoding is applied to study biodiversity and is available for standardized biodiversity assessments. However, it suffers from PCR bias, which can lead to the loss of specific taxa. PCR-free techniques such as shotgun metagenomics are therefore thought to be more suited for biodiversity assessments, but are currently limited by incomplete reference libraries. The technique of “mitogenome-skimming” or “mitogenomics,” in which complete mitochondrial genomes are sequenced, is ideal to bridge the techniques of (meta)barcoding and metagenomics. However, without the enrichment of mitochondria, roughly 99% of all sequencing reads are of non-mitochondrial origin and mostly useless for common applications, e.g. species identification. Here, we present a simple centrifugation protocol that leads to an average 140-fold enrichment of mitochondrial DNA. By sequencing six ‘mock’-communities—comprising the freshwater taxa Corbicula fluminea, Gammarus roeselii and Hydropsyche exocellata each—we recovered whole mitochondrial genomes of these species and the acanthocephalan endoparasite Pomphorhynchus laevis. The enrichment protocol will speed up building reference libraries for whole mitochondrial genomes, as dozens of species can be sequenced on a single MiSeq run. Subsequently, it will also allow biodiversity assessments, using mitogenomics at greatly reduced costs in comparison to mitogenomic approaches without prior enrichment for mitochondria.

We suggest helminthological investigations of cod as a supplement to traditional biological and hydrographical methods for elucidation of ecological changes in the Baltic Sea. It is under discussion if oxygen deficit or seal abundance should explain the present critical situation of Baltic cod. A comparative investigation of endoparasitic helminths in Baltic cod (Gadus morhua), captured in the same marine habitat with an interval of 35 years (1983/2018) recorded 11 species of helminths comprising trematodes (Hemiurus luehei, Podocotyle atomon, Lepidapedon elongatum), nematodes (Contracaecum osculatum, Hysterothylacium aduncum, Capillaria gracilis, Cucullanus cirratus), cestodes (Bothriocephalus sp.) and acanthocephalans (Echinorhynchus gadi, Pomphorhynchus laevis, Corynosoma semerme). Significant prevalence and intensity increases were recorded for third-stage larvae of the nematode C. osculatum (liver location) and larvae of C. semerme (encapsulated in viscera). Both parasite species use grey seal as their final host, indicating the recent expansion of the Baltic seal population. A lower E. gadi intensity and an increased prevalence of L. elongatum of small cod (31–40 cm body length) suggest a lowered intake of amphipods (intermediate host) and elevated ingestion of polychaetes, respectively, but no significant changes were seen for other helminths.

A parasitological study was carried out on 330 eelpouts from two fishing grounds of the Polish fishing zone off the Oder estuary (Pomeranian Bay and Dziwna Mouth). A total of 11 species and genera of parasites from six higher taxa were recorded: 1 monogenean, 1 digenean, 5 nematodes (eelpout was a new host for Ascarophis morhuae and Capillaria gracilis), 2 acanthocephalans, 1 mollusk and 1 protist (a fungus-related pathogen). A total of 4284 autogenic countable parasites were identified. These included parasites of eight species and two genera (six higher taxa) from Pomeranian Bay, and five species (two higher taxa) from the Dziwna Mouth. The abundance of parasites per host was higher in fish from the Dziwna Mouth, while the parasitic biodiversity index was almost two times lower than in Pomeranian Bay. Pomphorhynchus laevis dominated among the eelpout parasites in both fishing grounds, but the parasite communities from the Dziwna Mouth consisted of a larger number of dominating classes. The high intensity of infection of Hysterothylacium auctum and the relative density affect more the dimensions of the dominant parasite (P. laevis) in the Dziwna Mouth than the crowding of parasites. Infection by more abundant large parasites have an important influence on the value of Fulton’s coefficient.

Aim: We used comparative phylogeography of two intestinal parasites of freshwater fish to test whether similarity in life cycle translates into concordant phylogeographical history. The thorny-headed worms Pomphorhynchus laevis and P. tereticollis (Acanthocephala) were formerly considered as a single species with a broad geographical and host range within the Western Palaearctic. Location: Central and eastern parts of Northern Mediterranean area, Western and Central Europe, Ponto-Caspian Europe. Methods: A mitochondrial marker (COI) was sequenced for 111 P. laevis and 50 P. tereticollis individuals and nuclear ITS1 and ITS2 sequences were obtained for 37 P. laevis and 21 P. tereticollis. Genetic divergence, phylogenetic relationships and divergence time were estimated for various lineages within each species, and their phylogeographical patterns were compared to known palaeogeographical events in Western Palaearctic. Biogeographical histories of each species were inferred. Results: The two species show very different phylogeographical patterns. Five lineages were identified in P. laevis, partially matching several major biogeographical regions defined in the European riverine fish fauna. The early stages of P. laevis diversification occurred in the peri-Mediterranean area, during the Late Miocene. Subsequent expansion across Western Europe and Russia was shaped by dispersal and vicariant events, from Middle Pliocene to Middle Pleistocene. By contrast, P. tereticollis has differentiated more recently within the Western and Central parts of Europe, and shows weak geographical and genetic structuring. Conclusion: Our study highlights weak to moderate similarity in the phylogeographical pattern of these acanthocephalan parasites compared to their amphipod and fish hosts. The observed differences in the timing of dispersion and migration routes taken may reflect the use of a range of final hosts with different ecologies and dispersal capabilities. By using a group underrepresented in phylogeographical studies, our study is a valuable contribution to revealing the biogeography of host–parasite interactions in continental freshwaters. © 2017 John Wiley & Sons Ltd

SUMMARYPredicting how elevated temperatures from climate change alter host–parasite interactions requires understandings of how warming affects host susceptibility and parasite virulence. Here, the effect of elevated water temperature and parasite exposure level was tested on parasite prevalence, abundance and burden, and on fish growth, using Pomphorhynchus laevis and its fish host Squalius cephalus. At 60 days post-exposure, prevalence was higher at the elevated temperature (22 °C) than ambient temperature (18 °C), with infections achieved at considerably lower levels of exposure. Whilst parasite number was significantly higher in infected fish at 22 °C, both mean parasite weight and parasite burden was significantly higher at 18 °C. There were, however, no significant relationships between fish growth rate and temperature, parasite exposure, and the infection parameters. Thus, whilst elevated temperature significantly influenced parasite infection rates, it also impacted parasite development rates, suggesting warming could have complex implications for parasite dynamics and host resistance.

a b s t r a c t Recent findings suggest that grouping with conspecifics is part of the behavioural defences developed by amphipod crustaceans to face predation risk by fish. Amphipods commonly serve as intermediate hosts for trophically transmitted parasites. These parasites are known for their ability to alter intermediate host phenotype in a way that promotes predation by definitive hosts, where they reproduce. If aggregation in amphipods dilutes the risk to be preyed on by fish, then it may dilute the probability of transmission for the parasite using fish as definitive hosts. Using experimental infections, we tested whether infection with the fish acanthocephalan Pomphorhynchus laevis alters attraction to conspecifics in the amphipod intermediate host Gammarus pulex. We also measured G. pulex’s activity and reaction to light to detect potential links between changes in aggregation and changes in other behaviours. The attraction to conspecifics in the presence of predator cue, a behaviour found in uninfected gammarids, was cancelled by the infection, while phototaxis was reversed and activity unchanged. We found no correlation between the three behaviours in infected amphipods, while activity and aggregation were negatively correlated in uninfected individuals after the detection of predation cue. The physiological causes and the adaptive value of aggregation suppression are discussed in the context of a multidimensional manipulation.

Although trophically transmitted parasites are recognized to strongly influence food-web dynamics through their ability to manipulate host phenotype, our knowledge of their host spectrum is often imperfect. This is particularly true for the facultative paratenic hosts, which receive little interest. We investigated the occurrence and significance both in terms of ecology and evolution of paratenic hosts in the life cycle of the fish acanthocephalan Pomphorhynchus laevis. This freshwater parasite uses amphipods as intermediate hosts and cyprinids and salmonids as definitive hosts. Within a cohort of parasite larvae, usually reported in amphipod intermediate hosts, more than 90% were actually hosted by small-sized fish. We demonstrated experimentally, using one of these fish, that they get infected through the consumption of parasitized amphipods and contribute to the parasite's transmission to a definitive host, hence confirming their paratenic host status. A better knowledge of paratenic host spectrums could help us to understand the fine tuning of transmission strategies, to better estimate parasite biomass, and could improve our perception of parasite subwebs in terms of host-parasite and predator-parasite links.

Many trophically transmitted parasites with complex life cycles manipulate their intermediate host behavior in ways facilitating their transmission to final host by predation. This facilitation generally results from lowering host's antipredatory defenses when the parasite is infective to the final host. However, a recent theoretical model predicts that an optimal parasitic strategy would be to protect the intermediate host from predation when noninfective, before switching to facilitation when the infective stage is reached. We tested this hypothesis in the fish acanthocephalan parasite Pomphorhynchus laevis using the amphipod Gammarus pulex as intermediate host. Gammarids parasitized by noninfective stage of P. laevis (acanthella) hid significantly more under refuges than uninfected ones. In addition, acanthella-infected gammarids were less predated upon by trout than uninfected ones. As predicted, a switch toward decreased antipredatory behavior of G. pulex and enhanced vulnerability to predation was found when P. laevis reached the stage infective to its final host. The parasites appear to be able to exploit plasticity in host antipredatory responses, and shift the host optimal response toward their own optimal balance.

In this report, European common toads; Bufo bufo, European green toads Bufo viridis and marsh frogs Rana ridibunda were collected in Amasya, Çorum, and Tokat Provinces (Middle Black Sea Region of Turkey) 2005 and 2006 and examined for helminths. Two of 2 (100 %) Bufo bufo and 8 of 8 (100 %) Bufo viridis and 57 of 63 (90.5 %) Rana ridibunda were infected with 1 or more helminths. The helminths of B. bufo included Oswaldocruzia filiformis and Oxysomatium brevicaudatum. The helminth fauna of B. viridis comprised 5 species: 1 species of trematode (Pleurogenoides medians), 1 species of cestode (Nematotaenia dispar) and 3 species of nematodes, (Oswaldocruzia filiformis, Cosmocerca ornata, and Oxysomatium brevicaudatum), while the helminth fauna of Rana ridibunda comprised 9 species: 4 species of trematodes (Gorgodera cygnoides, Gorgoderina vitelliloba, Haematoloechus breviansa, and Opisthioglyphe ranae), 3 species of nematodes Oswaldocruzia filiformis, Cosmocerca ornata, and Oxysomatium brevicaudatum), and 2 species of acanthocephalans (Pomphorhynchus laevis and Acanthocephalus ranae). Oswaldocruzia filiformis, Cosmocerca ornata, and Oxysomatium brevicaudatum were collected from all three host species. In addition, Pleurogenoides medians represents a new host record for Bufo viridis in Turkey.

Competitive interactions between coinfecting parasites are expected to be strong when they affect transmission success. When transmission is enhanced by altering host behaviour, intraspecific conflict can lead to ‘coinfection exclusion’ by the first-in parasite or to a ‘sabotage’ of behavioural manipulation by the youngest noninfective parasite. We tested these hypotheses in the acanthocephalan parasite Pomphorhynchus laevis, reversing phototaxis in its intermediate host Gammarus pulex. No evidence was found for coinfection exclusion in gammarids sequentially exposed to infection. Behavioural manipulation was slightly weakened but not cancelled in gammarids infected with mixed larval stages. Therefore, coinfecting infective and noninfective larvae both suffered competition, potentially resulting in delayed transmission and increased risk of mortality, respectively. Consequently, noninfective larva is not just a ‘passive passenger’ in the manipulated host, which raises interesting questions about the selective pressures at play and the mechanisms underlying manipulation.

Urquhart, K., Pert, C. C., Fryer, R. J., Cook, P., Weir, S., Kilburn, R., McCarthy, U., Simons, J., McBeath, S. J., Matejusova, I., and Bricknell, I. R. 2010. A survey of pathogens and metazoan parasites on wild sea trout (Salmo trutta) in Scottish waters. – ICES Journal of Marine Science, 67: 444–453. In all, 300 wild sea trout were sampled from three east coast and two west coast sites around Scotland over a 3-year period to establish the prevalence and the abundance of bacteria, viruses, and ecto- and endoparasites. No bacterial pathogens were isolated from any fish. One fish tested positive for viral pathogens (infectious pancreatic necrosis virus). The viral agent syncytium, resulting from aquareovirus infection, was found in four fish from the east coast. The parasitic fauna consisted of three classes of ectoparasite, Monogenea, Isopoda, and Copepoda, and four classes of endoparasite, Cestoda, Digenea, Nematoda, and Acanthocephala. Sea trout from the east coast sites were larger than those from the west coast. The abundance of Lepeophtheirus salmonis, Hysterothylacium aduncum, and Anisakis sp. was significantly greater at the east coast sites. The only parasite found in significantly greater numbers at a west coast site was Pomphorhynchus laevis.

This study assessed the diets and parasites of larval and 0+ juvenile twaite shad Alosa fallax fallax in the lower reaches and estuaries of the rivers Wye, Usk and Towy, UK. There were significant differences between the diets of larvae and co-habiting 0+ juveniles, and of larvae and 0+ juveniles among sites, both within and among rivers. In the Wye and Usk, the diets of twaite shad larvae were dominated by chironomid larvae, whereas those in the Towy specialised upon cyclopoid copepods. The diets of 0+ juvenile twaite shad from freshwater (River Wye) were characterised by chironomid larvae, while estuarine (Towy Estuary) individuals specialised upon calanoid copepods. Parasites infecting 0+ twaite shad were Apiosoma sp. (Protozoa), Gyrodactylus sp. (Monogenea), Proleptinae (Nematoda) larvae, Pomphorhynchus laevis (Acanthocephala), Spinitectus sp. (Nematoda) larvae and Trichodina sp. (Protozoa). Over 60% of estuarine 0+ juvenile twaite shad were infected with Apiosoma sp., with maximal estimated loadings in excess of 3,000 parasites per fish. Other parasite taxa were generally present in only small numbers. There were no significant differences in the intensity of parasite infections among sites, or the condition of parasitised and non-parasitised 0+ twaite shad.

Three Eurasian otters (Lutra lutra) originating from Pazardzhik Region (South Bulgaria) were examined for helminth parasites. Three species of acanthocephalans were recorded: Pomphorhynchus laevis, Acanthocephalus anguillae and A. ranae. These species are not specific parasites of otters, the former two occurring in various freshwater fishes and the latter being a parasite of anurans. A review of acanthocephalan species recorded from L. lutra is presented. The possible transmission routes by which otters become infested with acanthocephalans are considered to be either paratenic transfer of encysted extra-intestinal juveniles in paratenic hosts or postcyclic transmission of mature intestinal worms in definitive hosts.

The parasitological studies were carried out on bream and perch from brackish water of Pomeranian Bay and the Szczecin Lagoon — a mouth of the Odra River. Bream and perch hosted 21 and 13 parasitic species, respectively. The species richness and diversity of parasites were much higher for bream and the abundance of parasites in bream was nearly four-fold higher than that in perch. Faunistic similarity of both parasite communities was low. The dominant group of parasites in both fish hosts was digeneans. Five species were specialists of bream, while only one species was a perch specialist. Five new host records have been reported in Poland for the following species: Myxobolus dispar, Hysterothylacium aduncum, Khawia sinensis, Echinorhynchus gadi and Pomphorhynchus laevis.

7 pages; International audience; Fish acanthocephalans can modify the antipredator behaviour of their intermediate hosts in response to cues from fish predators. However, it is still unclear whether such behavioural changes are adaptive, or are just the consequence of infection. We addressed this question through studying two acanthocephalans, Pomphorhynchus laevis and Polymorphus minutus, and their intermediate host, the amphipod Gammarus pulex. Pomphorhynchus laevis completes its cycle in a freshwater fish, whereas P. minutus exploits waterbirds as final hosts.We first assessed vulnerability of infected and uninfected gammarids to predation by bullheads, Cottus gobio. Pomphorhynchus laevis-infected gammarids were more susceptible to predation than uninfected ones when a refuge was available, whereas no selective predation on P. minutus-infected individuals was recorded, independently of refuge availability. We then quantified refuge use when a bullhead was present in an enclosure or when the enclosure was empty. Individuals of each group significantly increased refuge use in the presence of a bullhead. However, a larger proportion of P. laevis-infected gammarids remained out of the refuge in the presence of a predator, compared with uninfected controls, whereas no such effect was observed in P. minutus-infected ones. Finally, we assessed reaction to bullhead olfactory cues, using a Y-maze apparatus. Pomphorhynchus laevis-infected gammarids spent significantly more time in the predator-scented arm, whereas the reverse was observed in uninfected ones. Polymorphus minutus-infected individuals, however, did not differ from uninfected controls. We discuss our results in relation with the adaptiveness of host manipulation by parasites.

The known metazoa parasite fauna of the invasive round goby Apollonia melanostoma (formerly Neogobius melanostomus) consists of 12 species. The core of the parasite fauna comprises two species: Cryptocotyle concavum and Diplostomum spathaceum; secondary species are absent; satellite species include Cercariae gen. sp. and Ergasilus sieboldi; rare species are Acanthocephalus lucii, Anguillicola crassus, Bothriocephalus sp., Dichelyne minutus, Hysterothylacium aduncum, Pomphorhynchus laevis, Piscicola geometra, and Tylodelphys clavata. Fifty percent of metazoa parasites that occurred in the invasive round goby in the Gulf of Gdańsk (an invasion that was first detected in 1990) are also typically found in the native Gulf of Gdańsk gobiids. The round goby hosts common fish parasite species: C. concavum and D. minutus, but none that are unique to the species and no Ponto-Caspian parasites. Notably, the parasite species of the invasive round goby in the Gulf of Gdańsk includes species that are atypical for this species in its native habitat. In its new habitat, the round goby variously serves the roles of definitive, second intermediate, and paratenic host for different parasite species. The fish species is involved in a parasitic system that includes fish-eating birds, fishes of different ecological groups (predatory, planktivorous, and benthivorous), and invertebrates.

Summary During a survey of the parasite fauna Neogobius spp., which only recently invaded Hungarian reaches of the Danube River upstream from Budapest, it was found that Neogobius melanostomus and N. fluviatilis had become common species. Neogobius kessleri was less frequent and the previously widespread Proterorhinus marmoratus was drastically reduced. The parasite fauna of the newcomer fish species was characterized by ubiquitous parasites of a wide host range, such as the trematode Nicolla skrjabini, the metacercariae of Metagonimus yokogawai and Apatemon cobitidis, the larval stages of the acanthocephalan Pomphorhynchus laevis and the nematode Rhaphidascaris acus, the glochidia of an Anodonta sp. (Mollusca) and the ciliophoran Ichthyophthirius multifiliis. The specific parasites of Neogobius spp. were represented by three intestinal coccidia: Eimeria daviesae, Goussia kessleri, and a new species described here as Goussia szekelyi sp. n. This survey showed that the rapid invasion of Ponto-Caspian gobies in the northern Danube caused important changes in the fish fauna composition of the Danube River and enriched the parasite fauna of Hungarian fishes.

Manipulative parasites can alter the phenotype of intermediate hosts in various ways. However, it is unclear whether such changes are just by-products of infection or adaptive and enhance transmission to the final host. Here, we show that the alteration of serotonergic activity is functionally linked to the alteration of specific behaviour in the amphipodGammarus pulexinfected with acanthocephalan parasites.Pomphorhynchus laevisand, to a lesser extent,Pomphorhynchus tereticollisaltered phototactism, but not geotactism, inG. pulex, whereas the reverse was true forPolymorphus minutus. Serotonin (5-hydroxytryptamine, 5-HT) injected to uninfectedG. pulexmimicked the altered phototactism, but had no effect on geotactism. PhotophilicG. pulexinfected withP. laevisorP. tereticollisshowed a 40% increase in brain 5-HT immunoreactivity compared to photophobic, uninfected individuals. In contrast, brain 5-HT immunoreactivity did not differ betweenP. minutus-infected and uninfectedG. pulex. Finally, brain 5-HT immunoreactivity differed significantly amongP. tereticollis-infected individuals in accordance with their degree of manipulation. Our results demonstrate that altered 5-HT activity is not the mere consequence of infection by acanthocephalans but is specifically linked to the disruption of host photophobic behaviour, whereas the alteration of other behaviours such as geotactism may rely on distinct physiological routes.

Summary Metazoan parasites were investigated in three non-native fishes (monkey goby Neogobius fluviatilis, bighead goby Neogobius kessleri and round goby Neogobius melanostomus) collected from the former and current main channel of the River Danube and from the River Hron, Slovakia, in November 2003. Thirteen parasite species were identified: Triaenophorus crassus, Diplostomum sp., Tylodelphys clavata, Metorchis xanthosomus, Nicolla skrjabini, Gyrodactylus proterorhini, Pomphorhynchus laevis, Contracoecum sp., Raphidascaris acus, Anguillicola crassus, Unio tumidus, Anodonta anatina and Pseudoanodonta complanata. The maximum parasite diversity was found in N. fluviatilis. Total parasite abundance was significantly higher in N. kessleri, but no significant differences among sampling sites were observed. Pomphorhynchus laevis and glochidia of Anodonta anatina reached 100% prevalence in N. kessleri in the new channel of the Danube and, in general, these species were also the most prevalent parasites in all three goby species. For endoparasites, gobies served mostly as intermediate (digenean, cestodes and nematodes) or paratenic (acantocephalan and nematodes) hosts. All parasite species found are common parasites in the Middle Danube basin. No parasites specific to Neogobius, known from their native populations, were observed.

The composition and diversity of the total and intestinal component endohelminth communities were determined in the cyprinid barbel from three study areas in two large river systems in Austria. Two sample sites in the Danube and one site in the River Drau are the only free flowing stretches of these rivers in Austria. Nine helminth species were identified, with the acanthocephalan Pomphorhynchus laevis being dominant in the Danube, with up to 100% prevalence. In the Drau, where the dominant species was the cestode Bathybothrium rectangulum, species diversity was higher than in the Danube.

An analysis was undertaken of intestinal helminth communities in flounderPlatichthys flesusfrom two sites on the River Thames. A comparison was made between helminth community richness and diversity from these sites at the component and infracommunity levels. At the component community level, a richer and more diverse parasite community was found in flounder from the Tilbury location (marine influence) than that from the Lots Road location (freshwater influence). At the infracommunity level, more parasite species and parasite individuals per host were found at Lots Road and the percentage of similarity values were low at both locations. Helminth species with high prevalence values in the parasite communities of the flounder are the dominant species in any individual fish, harbouring multi-specific infections. The presence of more invertebrate species, which are intermediate hosts in the helminth life cycle in the Thames, fish vagility and the high prevalence and abundance values ofPomphorhynchus laevisin the flounder, may explain the differences between the two locations.

Concentrations of As, Al, Ag, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, Mg, Mn, Ni, Pb, Sb, Sn, Sr, Tl, V and Zn were analyzed by inductively coupled mass spectrometry (ICP-MS) in the intestinal helminth Pomphorhynchus laevis and its host Barbus barbus. The fish were caught in the Danube river downstream of the city of Budapest (Hungary). Ten out of twenty one elements analyzed were found at higher concentrations in the acanthocephalan than in different tissues (muscle, intestine, liver and kidney) of barbel. Considering the fish tissues, most of the elements were present at highest concentrations in liver, followed by kidney, intestine and muscle. Spearman correlation analyses indicate that there is competition for metals between the parasites and the host. The negative relationships between parasite number and metal levels in organs of the barbel support this hypothesis. The bioconcentration factors for Ag, As, Ba, Bi, Cu, Ga, Mn, Pb, Sr, Tl, and Zn showed that the parasites concentrated metals to a higher degree than the fish tissues. They accumulated the metals As, Cd, Cu, Fe, Ni, Pb, Sr and Zn even better than established bioindicators such as the mussel Dreissena polymorpha as revealed by data from the literature. The results presented here emphasize that acanthocephalans of fish are very useful as sentinels for metal pollution in aquatic ecosystems. Ratio of metal concentrations in the parasites and the host tissues provide additional information. Not including acanthocephalans in accumulation bioindication studies with fishes (as still customarily done) may lead to false results.

The aim of this paper was to test the hypothesis that when the 2 species of AcanthocephalanPomphorhynchus laevisandAcanthocephalus clavulaare found concurrently within the intestine of brown trout under field conditions, they have the potential to interact negatively. Evidence has shown that Acanthocephala are more likely to exhibit negative interactions with their own and other species, under both field and experimental conditions. Furthermore, the likelihood of these interactions is increased in Ireland because of the absence of certain definitive hosts and the fact that concurrent infections by two or more species of Acanthocephala are more commonly observed in fish. Data collected from wild and stocked brown trout and from 2 lakes provided an opportunity to compare the 2 potentially interacting helminth species in their fundamental and realized niche and several pieces of convincing evidence are provided here to support the hypothesis. A significant negative association between the numbers of each species found in individual fish was reported and this was consistent for both wild and stocked trout. Furthermore, an analysis of the proportions of low, moderate and high intensity infections in single and concurrent infections revealed a significant reduction in increasing intensities in concurrent infections compared to single infections. Finally, strikingly different patterns of niche inhabitation were observed, particularly forP. laevisin the presence ofA. clavulain wild trout. Results from the niche width analysis also support the observations on average position in single and concurrent infections. The niche width ofP. laeviswhen it co-occurred withA. clavuladecreased markedly in high intensity infections compared to low intensity infections.

The acanthocephalan parasite Pomphorhynchus laevis is transmitted by a suitable intermediate host such as the amphipod Gammarus pulex to its definitive fish host. Parasite-induced alterations in both appearance and behaviour concur to render infected gammarids more vulnerable to predation, thus promoting parasite transmission. Experimental infection of laboratory bred full- and half-sib groups of three-spined sticklebacks (Gasterosteus aculeatus) provided evidence that the parasite imposes a survival cost proportional to the severity of infection on its final host. Variation among sibships in the susceptibility to infection was consistent. When given a choice, fish consumed significantly more infected than uninfected prey. Overall, more resistant fish did not prey upon infected gammarids more often than did relatively susceptible fish. Only fish with a relatively high physical condition properly adjusted prey selection to the extent of their parasite susceptibility, thus exploiting the enhanced profitability of infected prey.

Barbel (Barbus barbus) is the final host of the adult worm Pomphorhynchus laevis (Acanthocephala), one of the most abundant and widespread intestinal parasites of European freshwater fish. During the course of the present study, we analyzed the activities of the glutathione-dependent enzymes glutathione peroxidase (GSH-Px), glutathione reductase (GR) and the phase II biotransformation enzyme glutathione-S-transferase (GST) as well as the concentrations of total glutathione (GSH), sulfhydryl (-SH) groups and vitamin E (Vit E) in the liver and intestine of B. barbus and in its intestinal parasite P. laevis. The,fish were caught from the Danube River (Serbia) in spring and summer. We detected that GSH-Px activity in fish liver was higher in spring. GR activity was significantly higher in spring in all investigated samples, while GST activity was significantly higher in spring in fish liver and in the parasite. At that time, GST activity was ten times higher in the parasite than in fish tissues. The concentration of GSH was increased in barbel liver in spring. In summer, the concentration of SH groups was significantly increased, while the concentration of Vit E was significantly decreased in fish tissues and in the parasite. We performed Canonical Discriminant Analysis, which revealed differentiation among the examined tissues during both seasons based on the all measured antioxidant components. We found that the seasonal patterns of antioxidant defense in the parasite are closely correlated with seasonal variation and physiological change in the host and represent the parasite's adaptation to changes in the host's antioxidant system. The present investigation contributes to general knowledge and provides a basis for future studies of glutathione-dependent enzymes and non-enzymatic low molecular mass antioxidants as potential biomarkers for monitoring the influence of the environment on fishes and their parasites. (C)2015 Elsevier Ltd. All rights reserved. Ministry of Education, Science and Technological Development of the Republic of Serbia {[}173041]

Manipulative parasites often alter the phenotype of their hosts along multiple dimensions. ‘Multidimensionality’ in host manipulation could consist in the simultaneous alteration of several physiological pathways independently of one another, or proceed from the disruption of some key physiological parameter, followed by a cascade of effects. We compared multidimensionality in ‘host manipulation’ between two closely related amphipods, Gammarus fossarum and Gammarus pulex, naturally and experimentally infected with Pomphorhynchus laevis (Acanthocephala), respectively. To that end, we calculated in each host–parasite association the effect size of the difference between infected and uninfected individuals for six different traits (activity, phototaxis, geotaxis, attraction to conspecifics, refuge use and metabolic rate). The effects sizes were highly correlated between host–parasite associations, providing evidence for a relatively constant ‘infection syndrome’. Using the same methodology, we compared the extent of phenotypic alterations induced by an experimental injection of serotonin (5-HT) in uninfected G. pulex to that induced by experimental or natural infection with P. laevis . We observed a significant correlation between effect sizes across the six traits, indicating that injection with 5-HT can faithfully mimic the ‘infection syndrome’. This is, to our knowledge, the first experimental evidence that multidimensionality in host manipulation can proceed, at least partly, from the disruption of some major physiological mechanism.

Here we report the genetic variability and presence of mtDNA-like sequences of Pomphorhynchus laevis from the chub, Squalius cephalus, caught at the sampling sites along the Sava River and its tributary the Sutla River in Croatia. Sequences of the cytochrome c oxidase subunit 1 (COI) gene of the recovered P. laevis specimens were used for haplotype network construction and phylogenetic analysis. These analyses showed that some specimens contained mitochondrial-like sequences, and they uncovered the existence of a Sava River basin strain different from known strains of P. laevis. This is the first time that P. laevis has been shown to contain mtDNA-like sequences, suggesting the need to exercise caution during COI analyses of P. laevis using universal primers. Highly conserved sequences of two nuclear markers, the ITS region and 18S rRNA, were not helpful for understanding genetic variability or differentiating strains. Furthermore, analysis of the dynamics of P. laevis infections in S. cephalus from the Sava and Sutla Rivers showed decreased prevalence and abundance at sites with inferior water quality, positive association of parasite abundance with fish size, and no clear association of parasite abundance with fish condition index or sex.

Besides conspicuous changes in behaviour, manipulative parasites may also induce subtle physiological effects in the host that may also be favourable to the parasite. In particular, parasites may be able to influence the re-allocation of resources in their own favour. We studied the association between the presence of the acanthocephalan parasite, Pomphorhynchus laevis, and inter-individual variation in the lipid and glycogen content of its crustacean host, Gammarus pulex (Amphipoda). Infected gravid females had significantly lower lipid contents than uninfected females, but there was no difference in the lipid contents of non-gravid females and males that were infected with P. laevis. In contrast, we found that all individuals that were parasitised by P. laevis had significantly increased glycogen contents, independent of their sex and reproductive status. We discuss our results in relation to sex-related reproductive strategies of hosts, and the influence they may have on the level of conflict over energy allocation between the host and the parasite.

To investigate the relationship between fish parasite communities and water quality level, metazoan parasites were examined in 157 specimens of chub (Leuciscus cephalus L.), sampled in four lowland water courses (northern Italy): Ticino river (unpolluted), Naviglio Pavese Canal (slightly polluted), Lambro river near the Merone village (polluted) and near Monza (severely polluted). Dactylogyrus vistulae, Paradiplozoon ergensi, Bucephalus polymorphus, Acanthocephalus anguillae and larval stages of Tylodelphys clavata were found in all the sampled sites. The distribution of Lamproglena pulchella and Pomphorhynchus laevis was limited to the unpolluted and slightly polluted river sectors, while Asymphylodora tincae, glochidia, along with larval stages of Diplostomum spathaceum, were absent in the severely polluted site. The variability of the calculated infection indices (prevalence, mean abundance and mean intensity), the degree of interactivity among parasites, as well as parameters of species richness and diversity suggest that the structure of parasite communities are affected by the water contamination level.

When two parasite species are manipulators and have different definitive hosts, there is a potential for conflict between them. Selection may then exist for either avoiding hosts infected with conflicting parasites, or for hijacking, i.e. competitive processes to gain control of the intermediate host. The evidence for both phenomena depends largely on the study of the relative competitive abilities of parasites within their common intermediate host. We studied the effects of simultaneous infection by a fish acanthocephalan parasite, Pomphorhynchus laevis, and a bird acanthocephalan parasite, Polymorphus minutus, on the behaviour of their common intermediate host, the amphipod Gammarus pulex. We compared the reaction to light and vertical distribution of individuals infected with both parasites to those of individuals harbouring a single parasite species and uninfected ones under controlled conditions. Compared to uninfected gammarids that were photophobic and tended to remain at the bottom of the water column, P. laevis-infected gammarids were attracted to light, whereas P. minutus-infected individuals showed a modified vertical distribution and were swimming closer to the water surface. The effects of both P. laevis and P. minutus appeared to be dependent only on their presence, not on their intensity. Depending on the behavioural trait under study, however, the outcome of the antagonism between P. laevis and P. minutus differed. The vertical distribution of gammarids harbouring both parasites was half-way between those of P. laevis- and P. minutus-infected individuals, whereas P. laevis was able to induce altered reaction to light even in the presence of P. minutus. We discuss our results in relation to the occurrence of active avoidance or hijacking between conflicting manipulative parasites and provide some recommendations for future research.

A total of 112 flounder, Platichthys flesus, was surveyed for the presence of Pomphorhynchus laevis (Acanthocephala). No acanthocephalans were found in 35 fish, 40 fish were infected with 1–5 thorny-headed worms, and in 37 fish the intensity of infection exceeded 6. The fish surveyed were also studied for the composition of the resident microflora of the terminal portion of the intestine—the characteristic site for P. laevis. It turned out the number of worms was positively correlated with the bacterial count. The bacteria cultured from the material sampled from intestines of infected- and non-infected fish exhibited similar specific composition and the differences were only in the intensity of individual species. The most frequently isolated bacteria, represented the genera: Aeromonas, Pseudomonas and Shewanella. The least frequent were species of Chromobacterium, Escherichia, Providencia and Serratia. The presently reported study results, suggest that bacteria species, constituting physiological bacterial flora, may become, under certain conditions, potentially pathogenic, through substantial increase in their abundance. The factor responsible for disturbing the natural balance in the intestine may be the thorny-headed worm, Pomphorhynchus laevis.

Sures, B., and Siddall, R. 1999. Pomphorhynchus laevis: The intestinal acanthocephalan as a lead sink for its fish host, chub (Leuciscus cephalus). Experimental Parasitology93, 66–72. Aqueous lead exposure of chub (Leuciscus cephalus) experimentally infected with the parasite Pomphorhynchus laevis resulted in a rapid accumulation of this metal in the intestinal acanthocephalans, reaching concentrations which were significantly greater than in the host muscle, liver, and intestine and approximately 1000 times higher than the exposure con centration. Parasitized chub accumulated significantly less lead in their intestinal wall than their uninfected conspecifics (Mann-Whitney U test, P ≤ 0.05). From in vitro studies it was shown that lead uptake of P. laevis cystacanths clearly increases by adding 1% eel bile to a commercial RMPI-1640 medium containing 0.1 μg ml−1 Pb2+ compared to the controls, which were maintained in RMPI-1640 medium containing lead at the same concentration but without bile. It is therefore most likely that P. laevis in chub absorb bile-bound lead from the host intestine and thus reduce its reabsorption by the intestinal wall, thereby interrupting the hepatic–intestinal cycling of the metal. This is the first example of a beneficial impact of a parasite on its host.

In connection with the BMB/ICES Sea-going Workshop “Fish Diseases and Parasites in the Baltic Sea”, 200 specimens of flounder Platichthys flesus from eight stations (25 from each) distributed from the southwestern (Mecklenburg Bight) to the northeastern Baltic Sea (Gulf of Finland) were examined for metazoan parasites. A few species (e.g. Hysterothylacium aduncum, Cucullanus heterochrous, Cucullanellus minutus, and Pomphorhynchus laevis) were found at virtually all stations. Typical “marine” species (Podocotyle atomon, Brachyphallus crenatus, Anisakis simplex, Holobomolochus confusus, and Lernaeocera branchialis) were found at the western stations only, whereas the metacercariae of Diplostomum spathaceum, and Cotylurus sp., immature Corynosoma sp., the larvae of Raphidascaris acus and Contracaecum osculatum were most common towards the east and north. Echinorhynchus gadi only occurred at the western and southern stations. The small encapsulated larvae of the bird nematodes Contracaecum sp., Paracuaria sp., and Cosmocephalus sp. were found at most stations. The effects of salinity on the patterns observed in relation to the distribution of intermediate and final hosts are discussed.

The composition of the parasite fauna of the flounder,Platichthys flesus, retrieved from two locations in the tidal Thames is described in detail for the first time. The combined parasite species list of the flounders from Lots Road in the upper tideway and West Thurrock in the middle tideway consisted of one protozoan (Glugea stephani), one monogenean (Gyrodactylussp.), four larval digeneans (Cryptocotyle concava,Timoniella imbutiforme,T. praeterita, andLabratrema minimus), five adult digeneans (Derogenes varicus,Lecithaster gibbosus,Podocotylesp.,Plagioporus varius, andZoogonoides viviparus), one larval cestode (unidentified tetraphyllidean), one or possibly more larval nematodes (unidentified) plus five adult nematodes (Capillariasp.,Cucullanus heterochrous,C. minutus,Contracaecumsp. andGoeziasp.), two acanthocephalans (Pomphorhynchus laevisandAcanthocephalus anguillae), three copepods (Lepeophtheirus pectoralis,Acanthochondriasp. andLernaeocera branchialis), and one mollusc (unidentified glochidia). The overall parasite community of flounders from Lots Road and West Thurrock were compared in terms of species richness and diversity. The parasite community in flounders from the former location in the upper tideway was found to be less diverse than that of its counterpart at West Thurrock in the middle estuary. The component community of Lots Road flounders was dominated by the acanthocephalanPomphorhynchus laevis.

Zoographical distribution of metazoan fish parasites in herring, Clupea harengus, from the Baltic Sea was analysed in order to use them as potential biological indicators. A total of 210 herring from six different sampling sites were investigated, harbouring 12 different parasite species [five digeneans (D), one cestode (C), three nematodes (N) and three acanthocephalans (A)]. The distribution of the parasite species differed according to region, with a distinct gradient of decreasing species richness towards the east of the Baltic Sea. The western localities at Kiel Bay, Rügen and Poland had the highest parasite diversity, including the marine parasite species Anisakis simplex (s.s.) (N), Brachyphallus crenatus and Hemiurus luehei (both D). The eastern localities had low parasite species richness, predominated by the freshwater digenean Diplostomum spathaceum. We could identify three different Baltic herring stocks, the spring-spawning herring of the western Baltic reaching from the Kattegat to the German and Polish coast, the stock of the central Baltic proper and the northern stock of C. harengus var. membras of the Gulf of Finland. The limited distribution of the herring parasites within the Baltic Sea enables their use as biological indicators for migration patterns and stock separation. The acanthocephalan Pomphorhynchus laevis that has already been used as an accumulation bioindicator for heavy metals was only recorded for the western herring stocks. However, the presence of mainly generalistic parasites and their uneven distribution patterns make their use as indicators for regional environmental and global change more difficult.

Summary Tuz G€€ (Salt Lake) Basin is one of the largest hypersaline lakes in the world and of extremely high biological importance owing to its high diversity and high level of endemism. It is hypothesized that the basin environment and the endemism of Pseudophoxinus crassus – a species of ray-finned fish in the Cyprinidae family and found only in Turkey – might contribute to the host-specific parasite characters. A total of 92 P. crassus specimens were collected by electrofishing between spring 2009 and autumn 2010 from the _ Stream in Konya Province, Turkey. By the end of the study period, four parasitic helminth species (Gyrodactylus latus, Asymphylodora imitans, Bothriocephalus acheilognathi and Pomphorhynchus laevis) were recorded. All had been reported previously from other hosts (non-host specific). Among these parasites G. latus and A. imitans are new records for the helminth fauna of Turkey. Prevalence and infestation intensity, length classes, and sex compositions of infested populations, as well as the seasonality of infestation were obtained and the results compared with other studies.

The acanthocephalan parasite Pomphorhynchus laevis is transmitted by crustaceans such as Gammarus pulex to its paratenic or final hosts, fish. The conspicuous orange-yellow parasite is visible through the transparent cuticle of G. pulex. Infected gammarids are significantly less photophobic than uninfected ones. When hungry three-spined sticklebacks (Gasterosteus aculeatus), one of the hosts of this parasite, were offered equal numbers of uninfected and infected prey, G. pulex infected with P. laevis were eaten significantly more often. We tested experimentally whether parasite color and parasite-induced changes in host behavior affected the predation rate of G. pulex. Color effects were tested with uninfected G. pulex by painting an orange spot on their cuticle that simulated infection. Behavioral effects were tested with infected G. pulex by covering the place through which the orange parasite was visible with inconspicuous brown paint. We showed for the first time that both parasite color and changed intermediate host behavior promote the transmission of P. laevis to its next host. The evolution of orange parasite color, and why sticklebacks do not avoid infected prey, are discussed.

6 pages; International audience; Larvae of many trophically-transmitted parasites alter the behaviour of their intermediate host in ways that increase their probability of transmission to the next host in their life cycle. Before reaching a stage that is infective to the next host, parasite larvae may develop through several larval stages in the intermediate host that are not infective to the definitive host. Early predation at these stages results in parasite death, and it has recently been shown that non-infective larvae of some helminths decrease such risk by enhancing the anti-predator defences of the host, including decreased activity and increased sheltering. However, these behavioural changes may divert infected hosts from an optimal balance between survival and foraging (either seeking food or a mate). In this study, this hypothesis was tested using the intermediate host of the acanthocephalan parasite Pomphorhynchus laevis, the freshwater amphipod Gammarus pulex. We compared activity, refuge use, food foraging and food intake of hosts experimentally infected with the non-infective stage (acanthella), with that of uninfected gammarids. Behavioural assays were conducted in four situations varying in predation risk and in food accessibility. Acanthella-infected amphipods showed an increase in refuge use and a general reduction in activity and food intake. There was no effect of parasite intensity on these traits. Uninfected individuals showed plastic responses to water-borne cues from fish by adjusting refuge use, activity and food intake. They also foraged more when the food was placed outside the refuge. At the intra-individual level, refuge use and food intake were positively correlated in infected gammarids only. Overall, our findings suggest that uninfected gammarids exhibit risk-sensitive behaviour including increased food intake under predation risk, whereas gammarids infected with the non-infective larvae of P. laevis exhibit a lower motivation to feed, irrespective of predation risk and food accessibility.

The parasites of the Asian invasive fish, Chinese sleeper Perccottus glenii , were studied in 6 localities in different parts of Ukraine. In total, 15 taxa of parasites were registered; among them were 1 species of Microsporidia, 5 species of ciliates, 2 species of cestodes, 2 species of trematodes, 2 species of nematodes, 1 species of acanthocephalan, 1 species of parasitic crustacean and 1 mollusk (glochidia). The invasive Chinese sleeper is included as a paratenic host in the life cycle of the parasites of indigenous reptiles in Europe. The non-indigenous cestode Nippotaenia mogurndae occurred in the intestine of the Chinese sleeper from the Ivachiv Reservoir (Dniester River basin). This cestode is recorded for Ukrainian fauna for the first time. In addition, 3 species of parasites were recorded in the Chinese sleeper for the first time: Nicolla skrjabini , Cosmocephalus obvelatus and Pomphorhynchus laevis . We note the low similarity among the different localities and the low parasite richness, that suggest that the parasite fauna of the Chinese sleeper in Ukraine is in transition.

In this research, a total of 298 Eurasian marsh frogs, Pelophylax ridibundus (Pallas, 1771) were collected from different localities in Denizli province (Inner-west Anatolia Region, the eastern part of Aegean Region) Turkey between 2006 and 2009 and examined for helminths. Of 262 (87.91 %) Pelophylax ridibundus samples were infected with one or more helminths. Pelophylax ridibundus harbored eight species of digeneans (Diplodiscus subclavatus, Gorgoderina vitelliloba, Gorgodera cygnoides, Pleurogenoides medians, Prosotocus confusus, Skrjabinoeces breviansa, Encyclometra colubrimurorum and Ophistoglyhe ranae), one species of cestode (Nematotaenia dispar), two species of acanthocephalans (Acanthocephalus ranae and Pomphorhynchus laevis), and six species of nematodes (Rhabdias bufonis, Oswaldocruzia filiformis, Cosmocerca ornata, Oxysomatium brevicaudatum, Eustrongylides sp. and Abbreviata sp.). P. ridibundus represents a host record for Nematotaenia dispar in Turkey.

Background Parasites often face a trade-off between exploitation of host resources and transmission probabilities to the next host. In helminths, larval growth, a major component of adult parasite fitness, is linked to exploitation of intermediate host resources and is influenced by the presence of co-infecting conspecifics. In manipulative parasites, larval growth strategy could also interact with their ability to alter intermediate host phenotype and influence parasite transmission. Methods We used experimental infections of Gammarus pulex by Pomphorhynchus laevis (Acanthocephala), to investigate larval size effects on host behavioural manipulation among different parasite sibships and various degrees of intra-host competition. Results Intra-host competition reduced mean P. laevis cystacanth size, but the largest cystacanth within a host always reached the same size. Therefore, all co-infecting parasites did not equally suffer from intraspecific competition. Under no intra-host competition (1 parasite per host), larval size was positively correlated with host phototaxis. At higher infection intensities, this relationship disappeared, possibly because of strong competition for host resources, and thus larval growth, and limited manipulative abilities of co-infecting larval acanthocephalans. Conclusions Our study indicates that behavioural manipulation is a condition-dependant phenomenon that needs the integration of parasite-related variables to be fully understood.

The parasite fauna of five goby species (Gobiidae, Teleostei) was investigated in the Baltic Sea during the period 1987 to 1990. 13 parasite species were found in samples from the Lubeck Bight:Bothriocephalus scorpii, Schistocephalus sp. (Cestoda);Cryptocotyle concavum, Cryptocotyle lingua, Podocotyle atomon, Derogenes varicus (Digenea);Hysterothylacium sp. (cf.auctum),Contracaecum sp.,Anisakis simplex (Nematoda);Corynosoma sp.,Echinorhynchus gadi, Neoechinorhynchus rutili, Pomphorhynchus laevis (Acanthocephala). The number of parasite species were: 10 in the sand gobyPomatoschistus minutus, 8 in the black gobyGobius niger, 7 in the two-spotted gobyGobiusculus flavescens, 6 in the common gobyPomatoschistus microps, and 5 in the painted gobyPomatoschistus pictus. Neoechinorhynchus rutili occurred only inP. minutus, andCorynosoma sp. only inG. niger. The extent to which the gobies were parasitized clearly depended on the respective ways of life and, moreover, on the kind of prey ingested by the hosts. Additionally, the age of the hosts might be important. The highest rate of parasitism, more than 60%, was reached byHysterothylacium sp. inG. niger and byCryptocotyle concavum inP. microps. Infestation incidence lay mostly below 40% which means a satellite species status (Holmes, 1991). The number of parasite species was highest in summer; the highest intensities of single parasites occurred in spring (Podocotyle atomon) or autumn (Crytocotyle concavum).Bothriocephalus scorpii, Hysterothylacium sp. andPodocotyle infested their juvenile hosts very early, but onlyHysterothylacium was accumulated byG. niger during its whole life span, whereasBothriocephalus persisted also in older gobies in low intensities. The cercariae ofCryptocotyle spp. penetrate actively into their hosts; all the other parasites named were transmitted in larval form by prey organisms which consisted mainly of planktonic and benthic crustaceans. The gobies were final hosts for only 5 parasites; but two species may be transmitted to larger fish, and 6 species to sea birds or mammals. The parasite community of the five gobies may possibly be taken to characterize the ecological quality of the environment of the Lubeck Bight.

8 pages; International audience; Pomphorhynchus laevis, a fish acanthocephalan parasite, manipulates the behaviour of its gammarid intermediate host to increase its trophic transmission to the definitive host. However, the intensity of behavioural manipulation is variable between individual gammarids and between parasite populations. To elucidate causes of this variability, we compared the level of phototaxis alteration induced by different parasite sibships from one population, using experimental infections of Gammarus pulex by P. laevis. We used a naive gammarid population, and we carried out our experiments in two steps, during spring and winter. Moreover, we also investigated co-variation between phototaxis (at different stages of infection, 'young' and 'old cystacanth stage') and two other fitness-related traits, infectivity and development time. Three main parameters could explain the parasite intra-population variation in behavioural manipulation. The genetic variation, suggested by the differences between parasite families, was lower than the variation owing to an (unidentified) environmental factor. Moreover, a correlation was found between development rate and the intensity of behavioural change, the fastest growing parasites being unable to induce rapid phototaxis reversal. This suggests that parasites cannot optimize at the same time these two important parameters of their fitness, and this could explain a part of the variation observed in the wild.

SUMMARYConcentrations of the elements As, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Sn, V, Zn were analysed by inductively coupled plasma mass spectrometry (ICP-MS) in the acanthocephalan Pomphorhynchus laevis and its fish host Barbus barbus. A total of 27 barbels were collected from the Danube River in autumn 2006 close to the town Kozloduy (685 river kilometer) on the Bulgarian river bank. Fish were divided into 3 groups. According to their P. laevis infrapopulation size hosts were considered as heavily infected (>100 worms per fish) and lightly infected (P. laevis. The 5 elements As, Cd, Cu, Pb and Zn were detected in significantly higher concentrations in parasites compared to host tissues (muscle, intestine, liver). According to the calculated mean bioconcentration factors, 3 more elements (Co, Mn, V) showed usually higher concentrations in P. laevis. Comparisons between heavily and lightly infected fish revealed significant differences only for V with higher concentrations for the heavily infected group. Concerning sex-specific metal accumulation V and Zn showed significant differences (V, at PP=0·05), with higher levels of both metals in females of P. laevis. Our results suggest that – for the metals analysed – the size of the parasite infrapopulation plays no role in the degree of metal accumulation. Similarly, parasite sex seems not to be a crucial factor for metal accumulation in the parasites. Thus, for metal monitoring purposes there is no need to take these aspects into account, which makes the use of parasites as bioindicators more applicable.

SUMMARYBiological invasions expose parasites to new invasive hosts in addition to their local hosts. However, local parasites are often less successful in infecting and exploiting their new hosts. This may have major consequences for the competitive ability of hosts, and finally on the fate of the parasite-host community. In Burgundy (Eastern France), the acanthocephalan parasite,Pomphorhynchus laevis, infects 2 amphipod species living in sympatry: the nativeGammarus pulexand the invasiveGammarus roeseli. WhileP. laevisaffects the behaviour and the immunity ofG. pulex,G. roeseliseems unaffected by the infection. In this study, we examined in detail the ability of the parasite to affect the immune system and resource storage of both gammarid species. We found that the infection was associated with a general decrease of the prophenoloxidase activity, haemocyte density, resistance to an artificial bacterial infection and level of sugar reserves inG. pulex, but not inG. roeseli. These results demonstrate a differential ability ofP. laevisto exploit its local and its invasive gammarid hosts. Potential mechanisms of these differential physiological alterations and their potential consequences on the coexistence of both gammarid species in sympatry are discussed.

SUMMARYInfection of barbel with 10 species of metazoan parasites including 3 trematodes, 3 acanthocephalans and 4 nematodes was observed in fish collected from 3 localities in the Bulgarian part of the river Danube between summer 2004 and summer 2007. The composition as well as the diversity characteristics of the parasite communities were analysed seasonally and showed a clear correlation with the composition of the invertebrate fauna and water quality. The most prevalent species was the acanthocephalan Pomphorhynchus laevis, which was also the dominant species of the intestinal component communities at all sampling sites. The second most frequent parasite at all Danube localities was Rhabdochona hellichi, which occurred in significantly higher numbers at the less polluted sites. Overall, the diversity of helminth communities increased with decreasing levels of nutrients and pollutants at all sampling sites. Therefore, the composition and diversity of parasite communities may be used to characterize ecosystem health and integrity.

Manipulation by parasites is a catchy concept that has been applied to a large range of phenotypic alterations brought about by parasites in their hosts. It has, for instance, been suggested that the carotenoid-based colour of acanthocephalan cystacanths is adaptive through increasing the conspicuousness of infected intermediate hosts and, hence, their vulnerability to appropriate final hosts such as fish predators. We revisited the evidence in favour of adaptive coloration of acanthocephalan parasites in relation to increased trophic transmission using the crustacean amphipodGammarus pulexand two species of acanthocephalans,Pomphorhynchus laevisandPolymorphus minutus. Both species show carotenoid-based colorations, but rely, respectively, on freshwater fish and aquatic bird species as final hosts. In addition, the two parasites differ in the type of behavioural alteration brought to their common intermediate host.Pomphorhynchus laevisreverses negative phototaxis inG. pulex, whereasP. minutusreverses positive geotaxis. In aquaria, trout showed selective predation forP. laevis-infected gammarids, whereasP. minutus-infected ones did not differ from uninfected controls in their vulnerability to predation. We tested for an effect of parasite coloration on increased trophic transmission by painting a yellow–orange spot on the cuticle of uninfected gammarids and by masking the yellow–orange spot of infected individuals with inconspicuous brown paint. To enhance realism, match of colour between painted mimics and true parasite was carefully checked using a spectrometer. We found no evidence for a role of parasite coloration in the increased vulnerability of gammarids to predation by trout. Painted mimics did not differ from control uninfected gammarids in their vulnerability to predation by trout. In addition, covering the place through which the parasite was visible did not reduce the vulnerability of infected gammarids to predation by trout. We discuss alternative evolutionary explanations for the origin and maintenance of carotenoid-based colorations in acanthocephalan parasites.

Four field experiments designed to simulate the effects of the individual components of farm waste effluent (increased ammonia, reduced dissolved oxygen concentrations) on the invertebrate fauna of receiving waters were carried out on two second order streams in South Wales. In two studies the dissolved oxygen concentration was reduced to 2 and 1 mg 1−1 by the oxidation of sodium sulphite, and in a further two studies ammonia concentrations were raised to 5 and 7 mg 1−1 by dosing with ammonium chloride and the toxicant maintained in the unionized state by the simultaneous addition of sodium hydroxide to raise pH to approx. pH 9. During each simulation (6–24 h in duration) the response of several invertebrate species placed in the downstream treatment zone(s) was compared with that of animals maintained in an upstream untreated reference zone. Significant invertebrate mortalities were recorded only under conditions of reduced dissolved oxygen. The feeding rate of Gammarus pulex was significantly reduced during dosing with ammonia but recovered post-exposure. Parasitism of G. pulex with Pomphorhynchus laevis resulted in a reduced feeding rate and an increased mortality in comparison to uninfected animals. The disruption of precopula in G. pulex was a sensitive and rapid indicator of stress under both reduced dissolved oxygen and increased ammonia concentrations.

SUMMARY 1. The drift of Gammarus pulex in a population in which approximately 20% of adults are infected with the acanthocephalan parasite Pomphorhynchus laevis was monitored at margin and mid-river sites in the River Teme, England over a 24-h period in mid-summer. 2. Drift densities showed a diurnal pattern with a large increase at night, independent of parasite burden. 3. There was no significant effect of site (margin or mid-river) on the proportion of parasitized and unparasitized G. pulex found in the drift or the benthos. 4. The drift of parasitized G. pulex was significantly greater than unparasitized animals. Gammarids harbouring only one parasite were found in significantly higher proportions in the drift than those with two or more parasites. 5. At both sites (margin and mid-river) the proportion of unparasitized adult G. pulex in the drift was significantly lower than that in the benthos. However, there was a significantly higher proportion of parasitized animals in the drift than in the benthos.

SUMMARY. 1. A soft-water stream in upland mid-Wales was dosed with sulphuric acid, aluminium sulphate and limestone slurry to produce a zone of aluminium at low pH. and one of aluminium, low pH and added lime. 2. Three episodes of 24-h duration were induced, each separated by a 12-h inter-dosing period, and the responses of the crustacean Gammarus pulex monitored throughout. 3. G. pulex parasitized by the acanthocephalan Pomphorhynchus laevis were significantly more sensitive than unparasitized individuals. 4. Liming significantly reduced mortality during dosing but postexposure deaths were greatest for animals which had been exposed in the time zone. 5. The disruption of precopulalory behaviour in G. pulex was rapid and liming did not mitigate this response.