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The signalling of the acanthocephalan Pomphorhynchus laevis in the Oncorhynchus mykiss species (Ord. Salmoniformes, Fam. Sahnonidae), was carried out in a rainbow trout fishery arrangement within the locality of Maglavit (Dolj, Romania). Fifteen rainbow trout specimens with obvious signs of disease were examined. Acanthocephaliasis evolved clinically between July and August 2017 with obvious signs of morbidity and mortality and the parasite was identified macroscopically and stereomicroscopically al the Dolj Veterinary Sanitary Laboratory and Food Safety Laboratory, with confirmation by the Bucharest Institute of Animal Hygiene and Health. The literature mentions that the more elements of the food chain, plants or animals are present in the aquatic environment, the higher the chances that the fish will meet intermediate primary hosts or accumulation of parasites represented by gamarus crustaceans (Rivulogamarus sp., Gammarus sp.). Control measures are based on prophylactic measures aimed at disrupting the biological cycle by clearing fish ponds, clearing the substrate as a favourable environment for some aquatic crustaceans, fishing and destroying final host infected fish with other vertebrates, destroying aquatic crustaceans (Rivulogamarus, Gammarus) through treatment of basins with lime chloride, but also the administration of anthelmintics introduced in fish feed. [ABSTRACT FROM AUTHOR]

Numerous freshwater acanthocephalans are able to alter the behaviour of their intermediate hosts to increase their predation risk by final hosts, thereby enhancing trophic transmission between their two hosts. Because temperature is widely expected to impact freshwater host-parasite interactions, we investigated how it can affect movements of both uninfected and Pomphorhynchus laevis-infected Gammarus pulex in an artificial stream in 5 cm/s water flow. We found that P. laevis infection of G. pulex induced both higher frequency and higher amplitude of movements along the artificial stream. Moreover, at warmer temperature (21°C), uninfected and P. laevis-infected G. pulex moved more in the artificial stream than at 15°C. In this regard, warmer temperature could then impact gammarids distribution and increase P. laevis transmission rate toward their definitive host in freshwater ecosystems. Firstly, this study provides new insights into how the key temperature factor influences gammarids species movements in the stream. Secondly, elevated temperature did not influence the intensity of P. laevis manipulation in G. pulex intermediate host. This work highlights that warmer temperature might affect the distribution and the behaviour of infected or uninfected freshwater gammarids with no direct effect on acanthocephalan trophic transmission through manipulation. [ABSTRACT FROM AUTHOR]

During the ecological study of 31 specimens of freshwater bream (Abramis brama (Linnaeus, 1758)) from Danube River, by applying standard techniques for parasites, an infestation was found with two acanthocephalan species -- Pomphorhynchus laevis and Acanthocephalus lucii. The content of arsenic in water, sediments, parasites, tissues and organs of Abramis brama (infected and uninfected) were establishedin the present study. P. laevis showed 42-170 times higher content of arsenic than its host tissues and organs. The content of arsenic in A. lucii was 37-205 times higher than the content of arsenic in its host tissues and organs. The highest concentration of arsenic in uninfected specimens of A. brama was found in liver (1.35±1.29 mg.kg-1 ). The highest concentration of arsenic for the infected with P. laevis specimens of freshwater bream was established for muscles (0.68±0.08mg.kg-1 ), while for the infected with A. lucii specimens of fish, the highest concentration of arsenic was established for skin (1.75±1.32 mg.kg-1 ). A highly significant correlation (p<0.01) was fixed for the relationship between CAs/P. laevis--CAs/Muscles. [ABSTRACT FROM AUTHOR]

The amphipod Gammarus obnixus Karaman & Pinkster, 1977 is an intermediate host for the acanthocephalan parasite Pomphorhynchus laevis (Zoega in Müller, 1776). Specimens of G. obnixus were collected from two sampling stations: (1) Işıklı Spring (clear, cold water with a fast current and hard substratum with a gravel-covered bottom) and (2) a rainbow trout net-cage area (dense community of macrophytes on a soft substratum due to net-cages residues and high water turbidity). The aim of this study was to determine monthly changes of the larval occurrence of P. laevis and to understand the effect of the fish farming on the infection rate with cystacanths of P. laevis. A total of 14,027 specimens of G. obnixus were collected. Cystacanths of P. laevis were found in the hemocoel of the gammarids. At the Işıklı Spring, P. laevis infected 832 (16.2%) of the 5149 G. obnixus examined over the total sampling period and had a mean intensity of the cystacanths of 1.5 and mean abundance 0.2 per amphipod individual. At the netcage area, P. laevis infected 3480 (39.2%) of the 8878 G. obnixus, with a mean intensity of 2.3 and mean abundance 0.9 per amphipod host. Amphipods in all 12 length classes were infected with P. laevis. The maximum intensity of the infection was 16 cystacanths of P. laevis in a single G. obnixus in August. Sex ratio of the cystacanths was approximately 1:1. Males of G. obnixus from both stations were more heavily infected than females. The results showed that the population density and infection rates of G. obnixus were higher at the net-cage area than at the Işıklı Spring. [ABSTRACT FROM AUTHOR]

Invasive species are a major threat to ecosystems worldwide. Their effects are versatile and mostly well studied. However, not much is known about the impact of invasion on native parasite communities, although parasites are usually important response variables for ecosystem health. To improve the knowledge on how native fish parasite communities and their dynamics are affected by invasive species and how these processes change local host-parasite interactions over time, we studied different host-parasite systems in four German rivers. Three of these rivers (Rhine, Ems, and Elbe) are heavily invaded by different Ponto-Caspian species such as the amphipod Dikerogammarus villosus and various gobiids such as Neogobius melanostomus and Ponticola kessleri that serve as potential hosts for different local parasite species, while the fourth river (Schwentine) was free of any Ponto-Caspian invaders. Due to the lack of additional uninvaded river systems, literature data on parasite communities before invasion were compared with the post invasion status for the rivers Rhine and Elbe. The results showed differences among the parasite communities of different host species from the three invaded rivers when compared to the Schwentine River. Among the local internal parasite communities, especially the acanthocephalan Pomphorhynchus laevis and the nematode Raphidascaris acus have to be considered as key species associated with invasions from the Ponto-Caspian region. As the examined invasive Ponto-Caspian fish species serves as suitable host for both parasite species, the increases in their infection rates in native fish species are examples of parasite spill back (R. acus) and spill over (P. laevis, at least in the river Rhine). These results were further supported by the analysis of literature data on parasite communities of the past 20 years. Consequences for local parasite communities range from decreased prevalence of native parasites towards an extinction of entire parasite species. [ABSTRACT FROM AUTHOR]

Abstract Background Several parasites with complex life-cycles induce phenotypic alterations in their intermediate hosts. According to the host manipulation hypothesis, such phenotypic alterations are supposed to increase the fitness of the parasite at the expense of that of its intermediate hosts through increasing the probability of transmission to next hosts. Although the phenomenon has received a large attention, the proximate factors modulating the occurrence and intensity of host manipulation remain poorly known. It has however, been suggested that the amount of energy reserves in the intermediate host might be a key parameter, although its precise influence on the intensity of manipulation remains unclear. Dietary depletion in the host may also lead to compromise with other parasite traits, such as probability of establishing or growth or virulence. Methods Here, we address the question through performing experimental infections of the freshwater amphipod Gammarus pulex with two different populations of the acanthocephalan fish parasite Pomphorhynchus laevis, and manipulation of host nutritional condition. Following exposure, gammarids were given either a “standard” diet (consisting of elm leaves and chironomid larvae) or a “deprived” food treatment (deprived in proteins), and infection parameters were recorded. Once parasites reached the stage at which they become infective to their definitive host, refuge use (a behavioural trait presumably implied in trophic transmission) was assessed, and metabolic rate was measured. Results Infected gammarids exposed to the deprived food treatment showed a lower metabolic rate, indicative of a lower body condition, compared to those exposed to the standard food treatment. Parasite size was smaller, and, depending on the population of origin of the parasites, intensity of infection was lower or mortality was higher in deprived hosts. However, food treatment had no effect on either the timing or intensity of behavioural modifications. Conclusions Overall, while our results suggest that acanthocephalan parasites develop better in hosts in good condition, no evidence was found for an influence of host nutritional condition on host manipulation by parasites.

The round goby, Neogobius melanostomus , is a Ponto-Caspian fish considered as an invasive species in a wide range of aquatic ecosystems. To understand the role that parasites may play in its successful invasion across Western Europe, we investigated the parasitic diversity of the round goby along its invasion corridor, from the Danube to the Upper Rhine rivers, using data from literature and a molecular barcoding approach, respectively. Among 1666 parasites extracted from 179 gobies of the Upper Rhine, all of the 248 parasites barcoded on the c oxidase subunit I gene were identified as Pomphorhynchus laevis. This lack of macroparasite diversity was interpreted as a loss of parasites along its invasion corridor without spillback compensation. The genetic diversity of P. laevis was represented by 33 haplotypes corresponding to a haplotype diversity of 0·65 ± 0·032, but a weak nucleotide diversity of 0·0018 ± 0·00015. Eight of these haplotypes were found in 88·4% of the 248 parasites. These haplotypes belong to a single lineage so far restricted to the Danube, Vistula and Volga rivers (Eastern Europe). This result underlines the exotic status of this Ponto-Caspian lineage in the Upper Rhine, putatively disseminated by the round goby along its invasion corridor. [ABSTRACT FROM AUTHOR]

During the ecological study of 28 specimens bleak (Alburnus alburnus (Linnaeus, 1758)) by applying standard techniques for parasites was found infestation with the acantocephalan Pomphorhynchus laevis (Müller, 1776). Aim of the present study is to establish the content of nickel in water, sediments, tissues and organs of A. alburnus and its parasite Pomphorhynchus laevis, and the possibilities of accumulation and circulation in the freshwater ecosystem of Danube River. From the tissues and organs of the studied specimens Alburnus alburnus, the content of nickel in samples of liver are higher than in the skin and muscles (in both infected and uninfected specimens). Differences were observed not only in nickel content, but also in the amendment of nickel content of infected (Ni Liver> Ni Muscles > Ni Skin) and uninfected (Ni Liver> Ni Skin> Ni Muscles) specimens of bleak. The obtained values for nickel content in liver, muscles and skin of A. alburnus infected with P.laevis were found to be lower than the obtained values for nickel content in liver, muscles and skin of uninfected specimens of bleak. The acanthocephalan Pomphorhynchus laevis showed significantly higher content of nickel than its host tissues and organs. Significant correlation (p<0.05) was fixed for relationships between CP. laevis Ni- CSkin Ni. [ABSTRACT FROM AUTHOR]

Acanthocephalans of the globally distributed genus Pomphorhynchus have been intensively studied during the past decades. In Europe, Pomphorhynchus species have shown a certain degree of variability in their morphological characteristics and behavior. Nowadays two different Pomphorhynchus species, namely P. laevis and P. tereticollis, have been described for different waterbodies in Western and Central Europe. However, until now it appears that both species do not co-occur at the same time in the same habitat. We assume that due to their very similar morphology some of the individuals that were identified based on their morphological characteristics as either of the two species might have been misidentified in previous studies. To avoid this possible source of error, we used molecular marker (ITS 1, COX genes) to identify Pomphorhynchus individuals from European eels that were sampled within a time period of 12 years from the Rhine River to elucidate the distribution of the two species in Western and Central Europe. Our results together with a re-examination of former studies provide evidence that P. laevis might have been introduced together with potential host species (intermediate, paratenic, and/or definitive) from the Ponto-Caspian region, and that it outcompeted and repelled the endemic P. tereticollis from the mainstream of the river. Our results also provide first evidence on the former coexistence of both Pomphorhynchus species in the river Rhine. [ABSTRACT FROM AUTHOR]

During the ecological study of 45 specimens of bleak (Alburnus alburnus (Linnaeus, 1758)) by applying standard techniques for parasites in ten specimens of fish an infestation was found with the acantocephalan Pomphorhynchus laevis. Aim of the present study is to establish the content of arsenic in water, sediments, tissues and organs of A. alburnus and its parasite Pomphorhynchus laevis, and the impact that the acanthocephalan has on the content of arsenic in his host tissues and organs. From the tissues and organs of the studied specimens of Alburnus alburnus, the content of arsenic in samples of liver were higher than in the samples of muscles and skin, and ranged as followed: CAs/Liver>CAs/Muscles>CAs/Skin (in both infected and uninfected specimens). The obtained values for the content of arsenic in skin of uninfected specimens of A. alburnus were found to be more than 3 times higher than the obtained values for content of arsenic in skin of A. alburnus infected with P. laevis. In general the content of arsenic in tissues and organs of uninfected A. alburnus was higher than the content of arsenic in tissues and organs of infected with P. laevis specimens of bleak. The acanthocephalan Pomphorhynchus laevis showed 115-3042 times higher content of arsenic than its host tissues and organs. Significant negative correlation (p<0.05) was fixed for the relationship between С As/P. laevis- С As/Sediments. [ABSTRACT FROM AUTHOR]

Predicting 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. [ABSTRACT FROM PUBLISHER]

Background: A large number of studies demonstrated that acanthocephalans exhibit a high metal accumulation potential and thus can be used as sensitive accumulation indicators. However, similar to free-living bioindicators, a seasonal variation in metal concentrations in parasites might occur. Accordingly, the influence of seasonality has to be elucidated if parasites should be applied as sentinels. Methods: In order to assess a possible seasonal profile of element concentrations, the concentrations of As, Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V and Zn in the acanthocephalan Pomphorhynchus laevis and in its host barbel (Barbus barbus) were analysed in a seasonal manner (spring, summer and autumn) using inductively coupled plasma mass spectrometry (ICP-MS). Results: Five elements (As, Cd, Cu, Pb and Zn) were detected in significantly higher concentrations in the parasites compared to host muscle, intestine and liver. Their levels in P. laevis showed a clear seasonal pattern, while the concentrations in the fish tissues remained similar during the year. The highest concentrations in the parasites were found in autumn, followed by spring and summer. Evidence from the literature suggests that this profile coincides with the seasonality of acanthocephalan transmission, as their annual concentration profile reflected the mean individual weight pattern during the year. Parasite infrapopulations in autumn consisted mainly of young worms which are characterised by an accelerated metabolism and a higher surface to volume ratio resulting in higher element concentrations when compared to older worms which are assumed to slow down their metabolism and additionally excrete metals with their eggs. Conclusions: Based on the available data from the present study and literature, a model is suggested, which visualises the accumulation kinetic of several elements under natural conditions. According to the element accumulation data the lifespan of P. laevis in barbel was roughly estimated to range between six and eight months. [ABSTRACT FROM AUTHOR]

In a small isolated lake in Slovakia, the fish acanthocephalan Pomphorhynchus laevis using Gammarus balcanicus and the minnow Phoxinus phoxinus, respectively, as its intermediate and final hosts, represented a dominant helminth species. Its prevalence and intensity of infection in fish showed no significant variation during a year fluctuating above the mean values of 89 % and 6.6 worms per fish. The mean prevalence of P. laevis larvae in Gammarus was 41.4 % with a maximum in the late summer and autumn ; individual crustaceans were infected by 1-9 larvae. There was one generation of P. laevis per year. Following up an annual cycle, an occurrence of new infections of Gammarus culminated in October and in the next May for Phoxinus. The sex ratios of both the adults and larvae of acanthocephalans were near unity but favoured slightly males in spring and autumn. The distribution of P. laevis in minnows and crustaceans was highly aggregated and fitted with the negative binomial model. The spatial distribution analysis of parasites along the fish alimentary tract showed a clear preference of P. laevis for its proximal half, with the maximum numbers in the site of the first intestinal loop. Immature worms of both sexes predominated in the proximal region and moved slightly down the alimentary tract during their growth and maturation.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: In vertebrates, the presence of enteric worms can induce structural changes to the alimentary canal impacting on the neuroendocrine system, altering the proper functioning of the gastrointestinal tract and affecting the occurrence and relative density of endocrine cells (ECs). This account represents the first immunohistochemistry and ultrastructure-based study which documents the intimate relationship between the intestinal mucous cells and ECs in a fish-helminth system, investigating the potential effects of enteric neuromodulators on gut mucus secretion/discharge. Methods: A modified dual immunohisto- and histochemical staining technique was applied on intestinal sections from both infected and uninfected fish. Sections were incubated in antisera to a range of neuromodulators (i.e. leu-enkephalin, met-enkephalin, galanin and serotonin) and the glycoconjugate histochemistry of the mucous cells was determined using a subsequent alcian blue - periodic acid Schiff staining step. Dual fluorescent staining on sections prepared for confocal laser scanning microscopy and transmission electron microscopy were also used to document the relationship between ECs and mucous cells. Results: From a total of 26 specimens of Squalius cephalus sampled from the River Paglia, 16 (i.e. 62 %) specimens were found to harbour an infection of the acanthocephalan Pomphorhynchus laevis (average intensity of infection 9.2 ± 0.8 parasites host-1, mean ± standard error). When acanthocephalans were present, the numbers of mucous cells (most notably those containing acidic or mixed glycoconjugates) and ECs secreting leu-enkephalin, met-enkephalin, galanin, serotonin were significantly higher than those seen on sections from uninfected fish. The relationship between met-enkephalin-like or serotonin-like ECs and lectin DBA positive mucous cells was demonstrated through a dual fluorescent staining. The presence of tight connections and desmosomes between mucous and ECs in transmission electron micrographs provides further evidence of this intimate relationship. Conclusions: The presence of P. laevis induces an increase in the number of enteric ECs that are immunoreactive to leu- and met-enkephalin, galanin, and serotonin anti-sera. The mucous cells hyperplasia and enhanced mucus secretion in the helminth-infected intestines could be elicited by the increase in the number of ECs which release these regulatory substances. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Several parasites with complex life-cycles induce phenotypic alterations in their intermediate hosts. According to the host manipulation hypothesis, such phenotypic alterations are supposed to increase the fitness of the parasite at the expense of that of its intermediate hosts through increasing the probability of transmission to next hosts. Although the phenomenon has received a large attention, the proximate factors modulating the occurrence and intensity of host manipulation remain poorly known. It has however, been suggested that the amount of energy reserves in the intermediate host might be a key parameter, although its precise influence on the intensity of manipulation remains unclear. Dietary depletion in the host may also lead to compromise with other parasite traits, such as probability of establishing or growth or virulence. Methods: Here, we address the question through performing experimental infections of the freshwater amphipod Gammarus pulex with two different populations of the acanthocephalan fish parasite Pomphorhynchus laevis, and manipulation of host nutritional condition. Following exposure, gammarids were given either a "standard" diet (consisting of elm leaves and chironomid larvae) or a "deprived" food treatment (deprived in proteins), and infection parameters were recorded. Once parasites reached the stage at which they become infective to their definitive host, refuge use (a behavioural trait presumably implied in trophic transmission) was assessed, and metabolic rate was measured. Results: Infected gammarids exposed to the deprived food treatment showed a lower metabolic rate, indicative of a lower body condition, compared to those exposed to the standard food treatment. Parasite size was smaller, and, depending on the population of origin of the parasites, intensity of infection was lower or mortality was higher in deprived hosts. However, food treatment had no effect on either the timing or intensity of behavioural modifications. Conclusions: Overall, while our results suggest that acanthocephalan parasites develop better in hosts in good condition, no evidence was found for an influence of host nutritional condition on host manipulation by parasites. [ABSTRACT FROM AUTHOR]

Application of fish intestinal parasites, acanthocephalans, as bioindicators in metal exposure assessment usually involves estimation of their metal levels and bioconcentration factors. Metal levels in parasite final host, fishes, are influenced by fish physiology but there is no data for acanthocephalan metal levels. Gastrointestinal Zn, Fe, Mn, Cd, Ag levels in European chub (Squalius cephalus L.) from the Sava River were significantly higher during chub spawning (April/May) compared to the post-spawning period (September). In acanthocephalans (Pomphorhynchus laevis and Acanthocephalus anguillae) significantly higher metal levels during chub spawning were observed only for Zn in P. laevis. Bioconcentration factors were twice as high for Fe, Mn, Ag, Pb in the post-spawning period, probably as a consequence of lower gastrointestinal metal levels in fish rather than metal exposure. Therefore, bioconcentration factors should be interpreted with caution, due to their possible variability in relation to fish physiology. In addition, gastrointestinal Cu, Cd and Pb levels were lower in infected than uninfected chub, indicating that metal variability in fishes might be affected by the presence of acanthocephalans. [ABSTRACT FROM AUTHOR]

The acanthocephalan worm was identified only in the carp (Cyprinus carpio), in the intestine and visceral peritoneum of the liver. It affects a wide range of host fish in both natural and aquaculture environments, causing the illness called acanthocephalosis (MUNTEANU & BOGATU, 2008). [ABSTRACT FROM AUTHOR]

Abstract: In the present study, the importance of considering fish intestinal parasites i.e. the acanthocephalans in metal exposure assessment was estimated under low metal contamination conditions. Two acanthocephalan species, Pomphorhynchus laevis and Acanthocephalus anguillae were examined in 59 specimens of European chub (Squalius cephalus L.) sampled at 5 locations along the Sava River, Croatia. Concentrations of essential (Cu, Mn) and non-essential (Ag, Cd, Pb) metals were higher in intestinal parasites than chub gastrointestinal tissue, but levels of essential metals Fe and Zn were comparable or lower in parasites, respectively. The highest accumulation in both acanthocephalan species was found for non-essential metals and followed the order: Ag>Pb>Cd. Higher infection intensity with P. laevis allowed us to present their spatial metal distribution and evaluate the influence of P. laevis on metal levels and sub-cellular biological responses (total protein and metallothionein levels) in the host infected with P. laevis. Even in the river section with low metal contamination, parasitism affected metal levels, resulting in lower Cu, Cd and Pb concentrations in chub infected with P. laevis than in uninfected chub. Although total protein and metallothionein levels remained constant in infected and uninfected chub, acanthocephalans should be considered a potential confounding factor in metal exposure assessments. Moreover, P. laevis-chub system can be suggested as an appropriate tool in biomonitoring, since in both species increased Cu and Cd concentrations towards the downstream locations were found. Higher Cu and Cd levels in P. laevis suggest acanthocephalans to be sensitive bioindicators if low metal levels have to be detected. [Copyright &y& Elsevier]

Background: Metal uptake and accumulation in fish parasites largely depends on the parasite group with acanthocephalans showing the highest accumulation rates. Additionally, developmental stage (larvae or adult) as well as parasite location in the host are suggested to be decisive factors for metal bioconcentration in parasites. By using barbel (Barbus barbus) simultaneously infected with nematode larvae in the body cavity and adult acanthocephalans in the intestine, the relative importance of all of these factors was compared in the same host. Methods: Eleven elements Arsenic (As), Cadmium (Cd), Cobalt (Co), Copper (Cu), Iron (Fe), Manganese (Mn), Lead (Pb), Selenium (Se), Tin (Sn), Vanadium (V) and Zinc (Zn) were analyzed in barbel tissues (muscle, intestine, liver) as well as in their acanthocephalan parasites Pomphorhynchus laevis and the larval nematode Eustrongylides sp. (L4) using inductively coupled plasma mass spectrometry (ICP-MS). Results: Nine elements were detected in significantly higher levels in the parasites compared to host tissues. The element composition among parasites was found to be strongly dependent on parasite taxa/developmental stage and localization within the host. Intestinal acanthocephalans accumulated mainly toxic elements (As, Cd, Pb), whereas the intraperitoneal nematodes bioconcentrated essential elements (Co, Cu, Fe, Se, Zn). Conclusion: Our results suggest that in addition to acanthocephalans, nematodes such as Eustrongylides sp. can also be applied as bioindicators for metal pollution. Using both parasite taxa simultaneously levels of a wide variety of elements (essential and non essential) can easily be obtained. Therefore this host-parasite system can be suggested as an appropriate tool for future metal monitoring studies, if double infected fish hosts are available. [ABSTRACT FROM AUTHOR]

Many trophically transmitted parasites manipulate their intermediate host phenotype, resulting in higher transmission to the final host. However, it is not known if manipulation is a fixed adaptation of the parasite or a dynamic process upon which selection still acts. In particular, local adaptation has never been tested in manipulating parasites. In this study, using experimental infections between six populations of the acanthocephalan parasite Pomphorhynchus laevis and its amphipod host Gammarus pulex, we investigated whether a manipulative parasite may be locally adapted to its host. We compared adaptation patterns for infectivity and manipulative ability. We first found a negative effect of all parasite infections on host survival. Both parasite and host origins influenced infection success. We found a tendency for higher infectivity in sympatric versus allopatric combinations, but detailed analyses revealed significant differences for two populations only. Conversely, no pattern of local adaptation was found for behavioral manipulation, but manipulation ability varied among parasite origins. This suggests that parasites may adapt their investment in behavioral manipulation according to some of their host's characteristics. In addition, all naturally infected host populations were less sensitive to parasite manipulation compared to a naive host population, suggesting that hosts may evolve a general resistance to manipulation. [ABSTRACT FROM AUTHOR]

Concentrations 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 (<20 worms per fish). The third group was used to compare heavy metal concentrations between male and female 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 P<0.05; Zn, at P=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. [ABSTRACT FROM AUTHOR]

Biological 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 native Gammarus pulex and the invasive Gammarus roeseli. While P. laevis affects the behaviour and the immunity of G. pulex, G. roeseli seems 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 in G. pulex, but not in G. roeseli. These results demonstrate a differential ability of P. laevis to 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. [ABSTRACT FROM AUTHOR]

SUMMARY: Phenotypic alterations induced by parasites in their intermediate hosts often result in enhanced trophic transmission to appropriate final hosts. However, such alterations may also increase the vulnerability of intermediate hosts to predation by non-host species. We studied the influence of both infection with 3 different acanthocephalan parasites (Pomphorhynchus laevis , P. tereticollis , and Polymorphus minutus) and the availability of refuges on the susceptibility of the amphipod Gammarus pulex to predation by 2 non-host predators in microcosms. Only infection with P. laevis increased the vulnerability of amphipods to predation by crayfish, Orconectes limosus. In contrast, in the absence of refuges, the selectivity of water scorpions, Nepa cinerea , for infected prey was significant and did not differ according to parasite species. When a refuge was available for infected prey, however, water scorpion selectivity for infected prey differed between parasite species. Both P. tereticollis - and P. laevis -infected gammarids were more vulnerable than uninfected ones, whereas the reverse was true of P. minutus -infected gammarids. These results suggest that the true consequences of phenotypic changes associated with parasitic infection in terms of increased trophic transmission of parasites deserve further assessment. [ABSTRACT FROM AUTHOR]

Parasites relying on trophic transmission to complete their life cycles often induce modifications of their host's behavior in ways that may increase their susceptibility to predation by final hosts. These modifications have often been interpreted as parasite adaptations, but very few studies have demonstrated that host manipulation has fitness benefits for the parasite. The aim of the present study was to address the adaptive significance of parasite manipulation by coupling observations of behavioral manipulation to estimates of trophic transmission to the definitive host in the natural environment. We show that the acanthocephalan parasite Pomphorhynchus laevis manipulates the drifting behavior of one of its intermediate hosts, the amphipod Gammarus pulex, but not of a sympatric host, the introduced amphipod Gammarus roeseli. We found a 26.3-28.3 times higher proportion of infected G. pulex in the stomach content of one of the definitive hosts of P. laevis, the bullhead Cottus gobio, than in the benthos. No such trend was observed for G. roeseli. The bell-shaped curve of mean parasite abundance (MPA) relative to host size observed in G. pulex also supported an increased predation mortality of P. laevis-infected individuals compared to uninfected amphipods. Again, no such pattern was observed in G. roeseli. Furthermore, our results indicate that the modifications induced by P. laevis are specific to the definitive host and do not increase the risk of predation by inappropriate hosts, here the adult edible frog Rana esculenta. Overall, our study is original in that it establishes, under field conditions, a direct link between parasitic manipulation and increased transmission to the definitive host, and more importantly, identifies the specificity of the manipulation both in the intermediate host species and toward the definitive host. [ABSTRACT FROM AUTHOR]

Abstract: Manipulative endoparasites with complex life cycles can alter their intermediate host immunity and behaviour in ways that increase survival probability within the host body cavity and enhance successful transmission to the definitive host. These parasitic manipulations are variable among and within parasite species and may result from co-evolutionary processes, in which the parasite is constrained for adaptation to the local intermediate host. Hence, arrival of a new host species in a local host population may promote local parasite maladaptation. This study tested the occurrence of local adaptation in two distantly located populations of the acanthocephalan parasite Pomphorhynchus laevis and its effect on the immunity and behaviour of its gammarid intermediate host Gammarus roeseli. This was done in France (an area for which G. roeseli is a recent invader) and Hungary (an area from which G. roeseli was believed to be native). As expected, we found no alteration in G. roeseli’s immune defence and behaviour associated with infection by P. laevis in localities, where the gammarid is invasive. Unexpectedly, we found similar results in Hungarian populations, where the parasite was even more exposed to the host immune response. Whilst these results suggest maladaptation of the parasite to the gammarid in both countries, they also suggest that the gammarid host might be locally adapted to the parasite. Genetic analyses were performed on both the parasite and the host and the results suggest that the two subsets of populations we studied harbour rather isolated host–parasite systems, both probably deriving from a common ancestral population. We propose that G. roeseli is also of recent acquisition in Hungary, and that a recent co-evolutionary history between P. laevis and G. roeseli in association with a long generation time in the parasite has constrained parasite adaptations in Europe or even favoured host adaptation to the parasite. [Copyright &y& Elsevier]

Abstract: Many parasites with complex life cycles increase the chances of reaching a final host by adapting strategies to manipulate their intermediate host’s appearance, condition or behaviour. The acanthocephalan parasite Pomphorhynchus laevis uses freshwater amphipods as intermediate hosts before reaching sexual maturity in predatory fish. We performed a series of choice experiments with infected and uninfected Gammarus pulex in order to distinguish between the effects of visual and olfactory predator cues on parasite-induced changes in host behaviour. When both visual and olfactory cues, as well as only olfactory cues were offered, infected and uninfected G. pulex showed significantly different preferences for the predator or the non-predator side. Uninfected individuals significantly avoided predator odours while infected individuals significantly preferred the side with predator odours. When only visual contact with a predator was allowed, infected and uninfected gammarids behaved similarly and had no significant preference. Thus, we believe we show for the first time that P. laevis increases its chance to reach a final host by olfactory-triggered manipulation of the anti-predator behaviour of its intermediate host. [Copyright &y& Elsevier]

Pomphorhynchus laevis is an acanthocephala which lives in the intestines of fish. These acanthocephala are characterised by a cylindrical proboscis, and an extremely long neck with a bulbous anterior expansion. In this study, the surface structures of P. laevis were examined with a scanning electron microscope. On the proboscis of this parasite 18 hook rows, each consisting of 12 hooks, were observed. The anterior hooks were smaller than the posterior hooks of the proboscis. The recurved hooks were within pockets on the proboscis. The presoma structure was porous and there were no pores on the hooks. The metasoma structure was also porous. Numerous cuticular wrinkles were observed on the metasoma. [ABSTRACT FROM AUTHOR]

Uninfected chub as well as fish experimentally infected with the acanthocephalan parasite Pomphorhynchus laevis were exposed to 210Pb2+ for up to 38 days and the uptake and distribution of lead within different fish organs and the parasites was determined at various time points. Highest metal concentrations were detected in the acanthocephalans, followed by intestine, bile, liver, gill and muscle of the fish host. Infected chub had significantly lower 210Pb levels in the gills on day 17 (P≤0.01), in the bile on day 24 (P≤0.05) and in the gills as well as in the intestine on day 38 compared with uninfected fish. A subsequent polynomial regression revealed that lead levels for the infected fish ranged below the levels determined for uninfected fish during most of the exposure period. This is the first proof that P. laevis reduces lead levels in the bile thereby diminishing or even impeding the hepatic intestinal cycling of lead, which may reduce the amount of metals available for the fish organs. This is especially important for ecotoxicological research. For example, organisms used as accumulation indicators may erroneously indicate low levels of pollution if they are infected with parasites which alter their pollutant uptake mechanisms. Additionally, the results gave further experimental evidence for acanthocephalans as accumulation indicators for metals. [Copyright &y& Elsevier]

Abstract The presence of intestinal helminths in the alimentary canal of brown trout, Salmo trutta L., can alter the number of cells that synthesize modulatory peptides. A total of 167 brown trout were collected from tributaries of the River Brenta (northern Italy), of which 119 (71.3%) specimens were infected with enteric helminths, 28 with the acanthocephalan Pomphorhynchus laevis Müller, 1776 with intensity of infection ranging from 1 to 162 (18.57 ± 30.79) worms per host and 67 fish with the cestode Cyathocephalus truncatus Pallas, 1781. Intensity of infection with C. truncatus ranged from 1 to 85 (6.87 ± 12.59) per fish. In 24 fish there were concurrent infections of both species of helminths. The caecal and middle regions of the intestine were the most heavily parasitized. Immunohistochemical tests showed a decrease in endocrine cells (ECs) of the diffuse endocrine system (DES) positive to gastrin, cholecystokinin-8, bombesin and secretin antisera in the intestine of the infected trout. The number of ECs immunoreactive to anti-glucagon serum did not show differences in the digestive tract of uninfected brown trout and in conspecifics parasitized with P. laevis . The density of cells containing glucagon-like material was low in the fish parasitized with C. truncatus . The results suggest that endoparasitic helminths induce alterations in the DES of infected S. trutta . [ABSTRACT FROM AUTHOR]