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Parasites exhibiting a high degree of host specificity are expected to be intimately associated with their hosts. Therefore, the evolution of host-specific parasites is at least partially shaped by the evolutionary history and distribution of such hosts. Gill ectoparasites of Dactylogyrus (Monogenea) are specific to cyprinid fish. In the present study, we investigated the evolutionary history of 47 Dactylogyrus species from the Balkan Peninsula, the Mediteranean region exhibiting the highest cyprinid diversity in Europe, and from central European cyprinids. Phylogenetic analyses revealed four well-supported clades of endemic and non-endemic Dactylogyrus spp. with four basal taxa. Endemic cyprinids with a limited distribution range were parasitized by endemic Dactylogyrus species, but some of them shared several Dactylogyrus species with central European cyprinids. Species delimitation analyses based on molecular data suggest that Dactylogyrus diversity is higher than that defined from morphology. Some endemic cyprinid species harboured Dactylogyrus species of different origins, this probably resulting from multiple host switching. Our results support the view that the evolution of Dactylogyrus in the Balkans has been influenced not only by the historical dispersion and distribution of their cyprinid hosts, but also by recent contacts of non-native cyprinid species with endemic cyprinid fauna in this region.

Background: Host specificity in parasites represents the extent to which a parasite's distribution is limited to certain host species. Considering host-specific parasites of primarily freshwater fish (such as gill monogeneans), their biogeographical distribution is essentially influenced by both evolutionary and ecological processes. Due to the limited capacity for historical dispersion in freshwater fish, their specific coevolving parasites may, through historical host-parasite associations, at least partially reveal the historical biogeographical routes (or historical contacts) of host species. We used Dactylogyrus spp., parasites specific to cyprinid fish, to infer potential historical contacts between Northwest African and European and Asian cyprinid faunas. Using phylogenetic reconstruction, we investigated the origin(s) of host-specific Dactylogyrus spp. parasitizing Northwest African and Iberian cyprinid species., Results: In accordance with hypotheses on the historical biogeography of two cyprinid lineages in Northwest Africa, Barbini (Luciobarbus) and Torini (Carasobarbus), we demonstrated the multiple origins of Northwest African Dactylogyrus. Dactylogyrus spp. of Carasobarbus spp. originated from Asian cyprinids, while Dactylogyrus spp. of Luciobarbus spp. originated from European cyprinids. This indicates the historical Northern route of Dactylogyrus spp. dispersion to Northwest African Luciobarbus species rather than the Southern route, which is currently widely accepted for Luciobarbus. In addition, both Northwest African cyprinid lineages were also colonized by Dactylogyrus marocanus closely related to Dactylogyrus spp. parasitizing African Labeo spp., which suggests a single host switch from African Labeonini to Northwest African Luciobarbus. We also demonstrated the multiple origins of Dactylogyrus spp. parasitizing Iberian Luciobarbus species. One Iberian Dactylogyrus group was phylogenetically closely related to Dactylogyrus of Moroccan Carasobarbus, while the second was related to Dactylogyrus of Moroccan Luciobarbus., Conclusions: Our study confirms the different origins of two Northwest African cyprinid lineages. It suggests several independent historical contacts between European Iberian Luciobarbus and two lineages of Northwest African cyprinids, these contacts associated with host switches of Dactylogyrus parasites.

A new dactylogyrid monogenean Dactylogyrus bicorniculus sp. nov. is described from the gills of the kazetoge bitterling, Rhodeus atremius atremius (Jordan and Thompson, 1914), an endemic species in Japan, from Saga Prefecture, northern Kyūshū. D. bicorniculus sp. nov. resembles Dactylogyrus bicornis Malevitskaja, 1941 and Dactylogyrus lophogonus Zhang and Ji, 1980 because they have two common features, a large V-shaped ventral bar and well-developed second marginal hooks. However, the new species is distinguished from these congeners by a shorter penis and an accessory piece. A phylogenetic analysis of 28S rDNA shows that D. bicorniculus sp. nov. is a basal species with the T-shaped ventral bar in the genus. The new species has strict host-specificity to R. a. atremius, one of the endangered freshwater fishes in Japan, and may face the danger of co-extinction with its host., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

A new species of monogenean diplozoid, Paradiplozoon iraqensis n. sp., from the gills of Cyprinion macrostomum Heckel from the Tigris River in Tikrit, Iraq is described. P. iraqensis n. sp. is distinguished from other species of the genus by the size of plicae on the fore- and hind body, the number of the branches of the intestinal caecum in fore body, intestinal caecum not extending to haptor, the size of the clamps and the morphology of the clamp sclerites, and by the length of the central hooks. Details of the shape and size of eggs, and of the reproductive system and prohaptoral region are provided. The present study raises the number of species of Paradiplozoon recorded in Iraq to 15.

Background: Translocation of native species and introduction of non-native species are potentially harmful to the existing biota by introducing e.g. diseases, parasites and organisms that may negatively affect the native species. The enemy release hypothesis states that parasite species will be lost from host populations when the host is introduced into new environments., Methods: We tested the enemy release hypothesis by comparing 14 native and 29 introduced minnow (Phoxinus phoxinus) populations in Norway with regard to the ectoparasitic Gyrodactylus species community and load (on caudal fin). Here, we used a nominal logistic regression on presence/absence of Gyrodactylus spp. and a generalized linear model on the summed number of Gyrodactylus spp. on infected populations, with individual minnow heterozygosity (based on 11 microsatellites) as a covariate. In addition, a sample-based rarefaction analysis was used to test if the Gyrodactylus-species specific load differed between native and introduced minnow populations. An analysis of molecular variance was performed to test for hierarchical population structure between the two groups and to test for signals of population bottlenecks the two-phase model in the Wilcoxon signed-rank test was used. To test for demographic population expansion events in the introduced minnow population, we used the kg-test under a stepwise mutation model., Results: The native and introduced minnow populations had similar species compositions of Gyrodactylus, lending no support to the enemy release hypothesis. The two minnow groups did not differ in the likelihood of being infected with Gyrodactylus spp. Considering only infected minnow populations it was evident that native populations had a significantly higher mean abundance of Gyrodactylus spp. than introduced populations. The results showed that homozygotic minnows had a higher Gyrodactylus spp. infection than more heterozygotic hosts. Using only infected individuals, the two minnow groups did not differ in their mean number of Gyrodactylus spp. However, a similar negative association between heterozygosity and abundance was observed in the native and introduced group. There was no evidence for demographic bottlenecks in the minnow populations, implying that introduced populations retained a high degree of genetic variation, indicating that the number of introduced minnows may have been large or that introductions have been happening repeatedly. This could partly explain the similar species composition of Gyrodactylus in the native and introduced minnow populations., Conclusions: In this study it was observed that native and introduced minnow populations did not differ in their species community of Gyrodactylus spp., lending no support to the enemy release hypothesis. A negative association between individual minnow host heterozygosity and the number of Gyrodactylus spp. was detected. Our results suggest that the enemy release hypothesis does not necessarily limit fish parasite dispersal, further emphasizing the importance of invasive fish species dispersal control.

An unidentified monogenean diplozoid species was collected from the gills of moggel in the Vaal River and Vaal Dam, South Africa. Specimens were removed from gills of the hosts and observed using light and electron microscopy to compare these diplozoids with known species. The second internal transcribed spacer (ITS2) of the ribosomal gene was amplified, sequenced and compared to that of other diplozoid taxa. Morphological species delimitation was used to determine the identity of these diplozoids, but they did not match the description of any diplozoid taxa. This species is recognized by the specific size of the hooks, number of plicae in posterior and trapezoid anterior projection of the median sclerite connecting to the clamp jaws via a single sclerite, occasionally with two small additional sclerites. Genetic characteristics based on sequence data from the ITS2 region also distinguish this taxon from all other diplozoid taxa. This South African diplozoid grouped in the same clade as Paradiplozoon ichthyoxanthon Avenant-Oldewage, 2013. Data clearly indicate that diplozoids collected from moggel represent a new, distinct taxon of Paradiplozoon Akhmerov, 1974 and are described here as Paradiplozoon vaalense n. sp.

Baseline information on parasitic infections, including monogenean infections on wild fishes, may aid in implementation of proactive measures as opposed to reactive research aimed at crisis control with reference to future aquaculture applications. The aim of this project was to examine the freshwater monogenean fauna of the Vaal Dam, Vaal River system, South Africa. This short communication reports on infection statistics for monogenean species, some representing new locality records. Parasites were collected from host species other than Labeo spp. from the Vaal Dam, during a summer (January 2010) survey. Fish collected using gill nets of varying mesh sizes were weighed and measured. Mucous smears were prepared from the skin and fins with the aid of microscope slides. Fish were killed humanely by severing the spinal cord behind the head. Gills were carefully removed and divided into areas which were separately scraped to investigate potential parasite site preference. The areas examined were dorsal, median and ventral positions on both the anterior and posterior hemibranch. Both mucous smears and gill scrapings were examined with the aid of a stereo microscope. More parasites were collected from the first or second gill arches, the medial position on the gill, and the anterior hemibranch. Preference for either left or right gill set was inconclusive. Spatial distribution of parasites is thought to result from water flow over the gills during respiration. This paper reports a new locality record for the following monogenean species: Quadriacanthus aegypticus, Dactylogyrus extensus, Dactylogyrus minitus, Gyrodactylus kherulensis and Dactylogyrus lamellatus.

A new species, Paradiplozoon ichthyoxanthon (Monogenea: Diplozoidae) is described from the gills of Labeobarbus aeneus (Cyprinidae) in the Vaal Dam and Vaal River Barrage in the Vaal River, South Africa. This species is the first in this genus from southern Africa; Paradiplozoon aegtyptense and Paradiplozoon ghanense have been described from northern Africa. The new species differs from all other Paradiplozoon species on the basis of the combination of morphological characteristics, namely disk-like haptor, eggs without filaments, clamp and central hook morphology and size of specimens. The species description is accompanied by a description of the reproductive organs. The internal transcribed spacer of the ribosomal gene (ITS2) was studied and the South African individuals formed a distinct clade, supporting the establishment of a new species.

Two new Dactylogyrus spp., D. angorae and D. turcicus have been described from the gills of the endemic cyprinid fishes, Capoeta angorae and C. mauricii from the Anatolian Region of Turkey. The shape of the anchors, hooks and the copulation organ of both species differ from those of the Dactylogyrus spp. found on other Capoeta species known from the Ponto-Caspian and Tigris-Euphrates regions.

As part of the endangered humpback chub (HBC; Gila cypha ) Adaptive Management Program, a parasite survey was conducted from 28 June to 17 July 2006 in 8 tributaries and 7 adjacent sections of the main stem of the Colorado River, U.S.A. In total, 717 fish were caught, including 24 HBC. Field necropsies yielded 19 parasite species, 5 of which (Achtheres sp., Kathlaniidae gen. sp., Caryophyllaidae gen. sp., Myxidium sp., and Octomacrum sp.) are new records for Grand Canyon, Arizona, U.S.A. Spearman's correlation coefficient analyses showed no correlations between parasite burden and fork length for various combinations of fish and parasite species. Regression analyses suggest that no parasite species had a strong effect on fish length. The most diverse parasite community (n = 14) was at river kilometer (Rkm) 230, near the confluence of Kanab Creek. The most diverse parasite infracommunity (n = 12) was found in the non-native channel catfish (CCF; Ictaluris punctatus). Overall parasite prevalence was highest in CCF (85%) followed by that in HBC (58%). The parasite fauna of humpback chub was mainly composed of Bothriocephalus acheilognathi and Ornithodiplostomum sp. metacercariae.

The present study has revealed new data on chromosome complements of diplozoid parasites, namely Diplozoon paradoxum from freshwater bream Abramis brama, Paradiplozoon bliccae from white bream Blicca bjoerkna, Paradiplozoon sapae from white-eye bream Ballerus sapa, and Paradiplozoon nagibinae from zope Ballerus ballerus. Particularly, D. paradoxum is characterized by four pairs (2n=8) of long (up to 22.1 μm) chromosomes: pairs 1, 2, and 3 are metacentric and pair 4 acrocentric. Karyotypes of three Paradiplozoon species are nearly identical in number and morphological classification of chromosomes, each comprising diploid number of 14 one-armed chromosomes of very similar length ranging up to 12.5 μm in P. bliccae, 9.2 μm in P. sapae, and 9.9 μm in P. nagibinae. All four species are similar in their total complement length, ranging from 64.4 to 50.4 μm. Interspecific differences were found in location of secondary constriction: it is situated on short arm of the 1st chromosome pair in D. paradoxum, on long arm of the 7th pair in P. bliccae and on long arm of the 4th pairs in P. sapae and P. nagibinae. Phylogenetic interrelationship within the diplozoids and hypothetic karyotype evolution is here discussed.

The structure and stability of parasite communities have been mainly explained by high diversity and strong interactions among parasite species. During 16 months, 558 Barbus martorelli gill infracommunities were studied in a tropical zone to determine whether parasite infrapopulations interact. Three levels were retained: the infracommunity level, the gill filament level, and the filament fraction level. Single species infections in Barbus martorelli were very rare and only concerned the core species: Dactylogyrus bopeleti, D. insolitus, D. simplex and Myxobolus barbi. Mixed infections appeared as a general rule in this fish species. Interspecific interactions at all three levels were statistically non significant. Our results suggest that Barbus martorelli gill parasites are non interactive (isolationist).

A survey of gill parasites was conducted in 164 Cyprinion macrostomum (Cyprinidae) collected from the Tigris River at Tikreet city, Salah Al-Deen province, in central Iraq, in 2009-2010. The monogenean Paradiplozoon amurensis Akhmerov, 1974 (Diplozoidae) was observed in the gills of 26.2% of these fishes with a mean intensity of 2.3. This is the first report of P amurensis in Iraq. A description and morphometrics of P amurensis specimens are presented.

Aim of this study was to investigate the helminths and their monthly prevalence in 120 Blicca bjoerkna (white bream) in the Kocadere stream (Bursa province) from February 2005 to January 2006. As a result, 98.3% of B. bjoerkna were found to be infected with one or more helminth species and a total of 5 different helminth species were identified. The distribution of these parasites in B. bjoerkna and the average prevalence (annually) were as follows: Dactylogyrus sphyrna (24.2%), D. distinguendus (30.8%), Diplostomum spathaceum metacerceria (95.8%), Caryophyllaeus laticeps (2.5%) and Eustrongylides sp. larvae (8.3%).

The gill monogene communities of Pimephales promelas (fathead minnow) in 3 distinct sites on converging streams were investigated from 2004 to 2006 in 3 different seasons. Thirty collections of P. promelas were made in southeastern Nebraska along 3 converging tributaries: Elk Creek (40.88534°N, 96.83366°W), West Oak Creek (40.9082°N, 96.81432°W), and Oak Creek (40.91402°N, 96.770583°W), Lancaster County, Nebraska. In all, 103 P. promelas were collected from Elk Creek, 115 from West Oak Creek, and 78 from Oak Creek and examined for gill monogenes. Among the P. promelas collected, 93.5% were infected with up to 3 species of Dactylogyrus, including Dactylogyrus simplex Mizelle, 1937, Dactylogyrus bychowskyi Mizelle, 1937, and Dactylogyrus pectenatus Mayes, 1977. Mean intensities at Elk Creek, West Oak Creek, and Oak Creek were 17.6, 22.8, and 25.1, and prevalences 88, 95, and 97%, respectively. At these 3 sites: (1) P. promelas does not share Dactylogyrus species with Semotilus atromaculatus (Creek chub) or Notropis stramineus (Sand shiner); (2) fish size and sex are not predictive of Dactylogyrus infection; (3) Dactylogyrus spp. vary (not always predictably) in their seasonal occurrence; (4) populations of Dactylogyrus spp. respond to environmental differences among sites; and (5) the community structure of Dactylogyrus spp. (order of abundance) is independent of environment.

Component communities of parasites of Phoxinus phoxinus from the Chovju River near Syktyvkar City (Komi Republic) are investigated in seasonal aspect. Material for the study has been collected in May-September 2000 from 90 host specimens of ages 0+-1+. Calculations of diversity indices and other coefficients have been made by two ways -- for metazoan parasites only and for whole parasite community including protozoan species. In both these cases three states of the community have been established, 1) forming community in May-June, 2) completely formed community in the end of June-July, 3) disintegrating community in August, 4) forming community in September. Seasonal dynamics of the component communities in young minnow thus found to be different from that in adult fish hosts.

Previous studies on long term gyrodactylid infections on isolated fish have shown that for the majority of Gyrodactylus-fish interactions, infections peak at a maximum level and then decline as the host mounts an effective immune response. In the current study, juvenile chub collected from the wild still harboured Gyrodactylus lomi infections after 6 - 10 months in the laboratory despite being individually maintained at 12 C.

Gyrodactylid monogeneans are considered to be the most invasive fish parasites. They are omnipresent on teleost fishes and host change might play a crucial role in their biology. In the present study, related fish species were kept in single- or mixed-species groups to test the ability of Gyrodactylus species to change their host fish under experimental conditions. The first group included two percid fish species, perch Perca fluviatilis L. and ruffe Gymnocephalus cernuus (L.), and the second group two cyprinid species, roach Rutilus rutilus (L.) and minnow Phoxinus phoxinus (L.). A total of 4,182 specimens of 19 monogenean species belonging to five genera were observed, and eight species of Gyrodactylus were identified. There were three species of Gyrodactylus found on roach and six species on minnow. Gyrodactylus vimbi parasitized both cyprinid fish species and was the only species that increased in intensity during the experiments and also assumed to transmit from minnow to roach, while the other recorded host change case, Gyrodactylus macronychus, was represented by a single individual that transmitted from minnow to roach. Gyrodactylus rutilensis and Gyrodactylus pannonicus remained on their original hosts (roach and minnow, respectively). Gyrodactylus cernuae was the only species observed on both ruffe and perch, but ruffe appeared more susceptible to this parasite. Most of the gyrodactylids observed on roach and minnow were situated on the fins, while gyrodactylids of perch and ruffe parasitized mainly the gill chamber and head.

In this study, metazoan parasites of bream (Abramis brama Linnaeus, 1758) in the Lake Durusu (Terkos) were investigated between June 2002 and May 2003. During this study, a total of 67 bream were examined for the presence of metazoan parasites. Ten species of parasites were found on 64 of the 67 fish examined. These parasites are: Dactylogyrus sphyrna (Linstow, 1878) and D. distinguendus (Nybelin, 1936) Monogenoidea, Caryophyllaeus laticeps (Pallas, 1781) Cestoidea, Tetracotyle sp, Diplostomum sp. and Tylodelphys clavata (Nordmann, 1832) metacercaria Trematoda, Eustrongylides excisus (Jagerskiöld, 1909) Nematoda, Piscicola geometra (Linnaeus, 1758) Hirudinea, glochidia of mollusk, Bivalvia, Argulus foliaceus (L., 1758) Crustacea. Diplostomum sp., Dactylogyrus sphyrna and D. distinguendus were found to be the dominant parasites of A. brama. Both the prevalence and intensity of other parasites were not found to be high. All identified parasites are a new finding for A. brama in the Lake Durusu. This is the first time that D. distinguendus has been identified in Turkey.

The purpose of the present study was to determine the helminth fauna of the bleak (Alburnus alburnus L.). According to the results obtained, a total of 6 species of helminth parasites were encountered on the bleak. These parasites include Dactylogyrus alatus, D. fraternus and Diplozoon homoion (Monogenea) on the gills; Bothriocephalus acheilognathi (Cestoda) and Rhapdochona denudata (Nematoda) in the intestine; and Diplostomum sp. (Digenea) in the eyes, on the surface of body and on the fins.

Component communities of parasites of gudgeon from the ecologically sustainable reservoirs are studied. The general principle of their organization is established. The material had been collected in the basins of Northern Dvina (41 specimens of gudgeon were dissected) and Mezen (55 specimens of gudgeon were dissected) rivers using generally accepted methods. Errors of regression equations for all individual species groups with their subsequent summation were calculate in order to estimate the state of the component community structure. In different seasons of a year the component community of the parasites of gudgeon from the Ertom river has the same structure, which is determined by the ratio of the biomasses of its comprising species, while it is differs in its species composition, biomasses of the species, leading groups of parasites, and in the dominating species. Thus, several stable seasonal states of the communities of fish parasites can be supposed. Three groups of species distinguished by the ratio of their biomasses are the general for the component communities of the parasites of gudgeon from the basins of Northern Dvina and Mezen rivers. The generalist species is more frequently the dominating species. The group of autogenic species always leads in the community. When methods of parasites collection are violated, the decrease in the number of species groups down to two is recorded. When the materials collected in different periods of a year from an ecologically sustainable reservoir are mixed, the sum of the errors of regression equations become higher than 0.250.

The second internal transcribed spacer (ITS2) of the ribosomal RNA genes of Diplozoon paradoxum and Paradiplozoon nagibinae were amplified and sequenced. The polymerase chain reaction product of D. paradoxum was bigger (840 bp) than that of P. nagibinae (820 bp). There was no intraspecific variability recorded in sequences from either species. Sequence comparisons and ITS2 restriction fragment length polymorphism (RFLP) pattern of 8 European diplozoid species aimed to resolve their identification and amend the previous studies. RFLP was used to distinguish the 2 species from each other and from P. bliccae, P. homoion, P. megan, P. pavlovskii, P. sapae, and Eudiplozoon nipponicum, using restriction enzymes AluI, HaeIII, HinfI, RsaI, and SphI. The criteria for morphological identification of 8 European diplozoids are also included, with the main morphological characters of clamps, trapeze spur, and anterior joining sclerites of 8 diplozoid species being illustrated. Combination of the shape and comparison of length of the trapeze spur and anterior joining sclerites could lead to accurate identification of diplozoid species.

We investigated the abundance-prevalence relationships in monogeneans belonging to the genus Dactylogyrus. A total of 182 dactylogyrid populations representing nine species were collected from the gills of roach ( Rutilus rutilus). Local abundance was found to be strongly positively correlated with prevalence. Two hypotheses were tested to explain this relationship: (1) the core-satellite hypothesis, and (2) the ecological specialisation hypothesis. Abundance was log-normally distributed, and the relationship between mean abundance and variance of abundance followed Taylor's power law prediction. Prevalence showed a negative binomial distribution, which does not confirm the core-satellite hypothesis. The positive relationship between abundance and prevalence was found for both specialists and generalists. However, generalists were found to be more widely distributed among hosts and had higher abundances than specialists, which supports the ecological specialisation hypothesis.

Neodiplozoon polycotyleus Paperna, 1973 is recorded from Barbus marequensis Smith, 1841, Barbus neefi Greenwood, 1862, and Barbus trimaculatus Peters, 1852 in the Limpopo River System, Northern Province, South Africa.