First data on parasites of the invasive brown bullhead Ameiurus nebulosus (Siluriformes: Ictaluridae) in Ukraine.

This study describes the parasite community of non-native brown bullhead, Ameiurus nebulosus (Actinopterygii: Ictaluridae), collected at three sites in the river Vistula Basin (Lake Svitiaz, Lake Pisochne, and Lake on Plastova) and one site in the river Diester Basin (Lake Stryiska), in Ukraine. Our data represent the first comprehensive study of parasite community in this fish species in Europe. Sixteen parasite taxa were found, including species co-introduced from North America and species acquired in the European range. Maximum parasite richness (13 spp.) was recorded in Lake Svitiaz situated in a Natural Protected Area, while lowest species richness (3 spp.) was observed at Lake on Plastova, an artificial pond in the city of Lviv. Three co-introduced monogenean species, Gyrodactylus nebulosus, Ligictaluridus pricei and Ligictaluridus monticellii, are recorded in Ukraine for the first time, widening the knowledge of the European distribution of these North American parasites. Metric features for hard parts of invasive and native monogeneans showed overlap in ligictalurid parasites, but slightly smaller metrics in Ukrainian G. nebulosus, possibly reflecting water temperature during fish sampling. Though prevalence and abundance of acquired parasites was relatively low, infection parameters for metacercariae of Diplostomum spp. were relatively high at Lake Svitiaz and the natural Lake Stryiska in Lviv. In two lakes in the Vistula basin, we found high prevalence and abundance of Anguillicola crassus, an Asian nematode infecting eels, possibly supporting the invasional meltdown hypothesis. Our study confirms both further spread of non-native parasites in Europe and use of non-native fish as competent hosts for local native and introduced parasites.

Onchocleidus principalis (Monogenea: Ancyrocephalidae) Co-introduced to Europe with Centrarchid Fish.

BACKGROUND: Non-native parasites are often translocated into novel areas together with their natural hosts, but the parasite diversity is frequently lower compared to the host's native range. PURPOSE: This paper provides morphological and molecular characterisation for non-native monogenean parasite Onchocleidus principalis (Ancyrocephalidae) co-introduced with its fish host to Portugal, Europe, including new details on the species' vaginal morphology and metrics. METHODS: Two host species, the largemouth bass Micropterus salmoides and pumpkinseed sunfish Lepomis gibbosus, were sampled from two reservoirs (Landeira, Coruche) in the Atlantic Sea drainage. Morphometric analysis and sequencing of 28S rDNA were performed. RESULTS: Presence of O. principalis was confirmed in all individuals of largemouth bass. Accidental findings on pumpkinseed sunfish at both sampling sites represent new host records for this parasite species. The morphometric description of O. principalis showed high similarity to the species in its native range. No intraspecific sequence variation of partial 28S rDNA was observed between specimens from the two sampling sites. Presence of another North-American ancyrocephalid parasite Onchocleidus dispar was confirmed in pumpkinseed sunfish at both sites, and in largemouth bass from the Coruche Reservoir, this representing the first record of O. dispar on largemouth bass in Europe. CONCLUSION: Onchocleidus principalis has been confirmed to parasitise both centrarchid fish species introduced to Europe. Compared to other studies, the species collected in Portugal exhibits pronounced vaginal armament.

First record of the American cestode Proteocephalus ambloplitis (Leidy, 1887) (Proteocephalidae) in Europe.

Here, we report the first record of pleroceroids of the Nearctic tapeworm Proteocephalus ambloplitis (Leidy, 1887) in European fresh waters. The plerocercoids were found encapsulated in the internal organs of the invasive pumpkinseed Lepomis gibbosus (Linnaeus, 1758) in a pond in Bègles Plage, Bordeaux, France. This parasite species was not observed in L. gibbosus collected from two nearby localities, Bordeaux Lac and a pond in the Parc de Fontaudin. Species identification was confirmed using molecular data and morphological characteristics.

Limited parasite acquisition by non-native Lepomis gibbosus (Actinopterygii: Centrarchidae) at two ponds in the Upper Rhine basin, Germany.

Metazoan parasite communities of Lepomis gibbosus (Centrarchidae), one of the most successfully introduced fish species in Europe, were studied at two isolated ponds (Knielingen, Tropfen) along the Upper Rhine in Germany. Nine parasite taxa were observed, including North American species co-introduced to Europe (ancyrocephalid monogeneans, diplostomid trematodes), circumpolar species infecting L. gibbosus in both their native and non-native ranges (bothriocephalid cestodes) and locally acquired parasitic nematodes. Both parasite communities consisted predominantly of North American species. Acquisition of local parasites was not observed at Tropfen, where the fish community comprised just two species, with L. gibbosus dominant. Low prevalence and abundance of acquired parasites was found at Knielingen, which supported a diverse fish community. At Tropfen, a high abundance of the North American parasite Posthodiplostomum centrarchi probably contributed to the lower condition index, hepatomegaly and splenomegaly observed. Due to low local parasite competency, L. gibbosus appears to have no significant impact on parasite dynamics in affected habitats.

Dactylogyrids (Platyhelminthes: Monogenea) from Sudanese Labeo Spp., with a Description of Dogielius Sennarensis n. Sp. and a Redescription of Dogielius Flosculus Guégan, Lambert & Euzet, 1989.

Dactylogyrid monogeneans of Labeo horie Heckel, 1847 and L. niloticus (Linnaeus, 1758) (Cyprinidae) were surveyed at two sites on the River Nile in Sudan. The present study reports the presence of ten species of Dactylogyrus Diesing, 1850 and three species of Dogielius Bychowsky, 1936 based on a morphometric evaluation of the sclerotised structures. The species found include: Dactylogyrus nathaliae Guégan, Lambert & Euzet, 1988; D. rastellus Guégan, Lambert & Euzet, 1988; D. retroversus Guégan, Lambert & Euzet, 1988; D. senegalensis Paperna, 1969, D. yassensis Musilová, Rehulková & Gelnar, 2009 and five other undescribed species of Dactylogyrus. The genus Dogielius was represented by Dogielius flosculus Guégan, Lambert & Euzet, 1989; the newly identified D. sennarensis n. sp., and one undescribed Dogielius species. While D. sennarensis n. sp. resembles D. intorquens, it differs from this species and other congeners by having a longer ventral bar and anchor points and nosclerotised vagina. In addition, this study redescribes D. flosculus based on the morphology of specimens collected from L. horie. All specimens studied had a single large vagina, in contrast to the original description which reported a vagina composed of two unconnected parts. All dactylogyrid species in this study represent new host and geographical records.

Parasite communities and infection levels of the invasive Chinese sleeper Perccottus glenii (Actinopterygii: Odontobutidae) from the Naab river basin, Germany.

The Chinese sleeper (Perccottus glenii), an invasive Asian fish, was first registered in Germany in 2009 (westernmost extent of its invasive range). We sampled Chinese sleepers from two localities on the Bücherlgraben creek (a tributary of the River Naab) in south-eastern Germany in November 2015 and examined them for parasite infection. Twelve taxa were registered, including ciliates (unidentified Trichodina), a monogenean, three cestode species, two digenean taxa, two acanthocephalan species, two nematode species and one mollusc glochidia. Infracommunities consisted of 1-5 species, with 10% of fish uninfected. Three parasite species (Acanthocephalus anguillae, Gyrodactylus luciopercae and Pseudocapillaria tomentosa) were recorded on Chinese sleepers for the first time. The results highlight the important role of the Chinese sleeper as a second intermediate host in the life cycle of heron and grebe parasites. The Chinese sleeper parasite community displayed low homogeneity at both localities sampled, with allogenic parasites (metacercariae and mesocercoids) mostly shared. Differences between localities were mainly caused by autogenic parasites. No invasive parasites associated with the Chinese sleeper were observed in the study area, all parasites being representatives of European fauna. This supports the hypothesis of introduction via the aquarium trade or through transport with commercial fish.

Experimental evidence for parasite-induced over-winter mortality in juvenile Rhodeus amarus.

In this study, the effects of the eye fluke Diplostomum pseudospathaceum (Trematoda) infection on over-winter survival of young-of-the-year (YOY) European bitterling Rhodeus amarus (Cyprinidae) were examined between September 2010 and April 2011. The fish were reared in semi-natural conditions to ensure that results were not confounded by other parasite infections. The cumulative mortality of R. amarus from November until April was significantly higher in D. pseudospathaceum-infected fish (57·3%) compared to controls (42·1%). Infection of the parental generation did not have any effect on the mortality of juveniles. The results indicate that D. pseudospathaceum infection increases over-winter mortality of YOY R. amarus. The possible mechanisms causing mortality are discussed.

Overwinter body condition, mortality and parasite infection in two size classes of 0+ year juvenile European bitterling Rhodeus amarus.

Body condition and parasite abundance were examined in two size classes of European bitterling Rhodeus amarus during the first overwintering period in two seasons (2007-2008 and 2009-2010). Body condition of large fish did not change during winter, and increased significantly in March. From November to February, small fish showed a decreasing trend in condition. Despite a significant increase in March condition of small fish only reached the same level as before winter. Total parasite abundance increased significantly in winter in both fish size classes, reflecting a seasonal increase in monogenean infection. Large fish were parasitized significantly more than small fish during winter, but only in small fish was a negative correlation between parasite infection and condition found and a significant decrease in parasite abundance recorded after wintering, indicating mortality of heavily infected individuals with low condition during the winter. A trend for higher overwinter mortality in small fish was found under semi-experimental conditions. The decrease in condition during the winter period in small fish may reflect faster energy depletion generally expected in smaller individuals. The results indicate that parasite infection may contribute to the overwinter mortality of 0+ year R. amarus, with a stronger effect in smaller individuals.

Parasite diversity and microsatellite variability in native and introduced populations of four Neogobius species (Gobiidae).

Species introduced into new areas often show a reduction in parasite and genetic diversity associated to the limited number of founding individuals. In this study, we compared microsatellite and parasite diversity in both native (lower Danube) and introduced populations of 4 Ponto-Caspian gobies, including those (1) introduced from within the same river system (middle Danube; Neogobius kessleri and N. melanostomus), and (2) introduced from a different river system (River Vistula; N. fluviatilis and N. gymnotrachelus). Microsatellite data confirmed the lower Danube as a source population for gobies introduced into the middle Danube. Both native and introduced (same river system) populations of N. kessleri and N. melanostomus had comparable parasite species richness and microsatellite diversity, possibly due to multiple and/or continual migration/introduction of new individuals and the acquisition of local parasites. Reduced parasite species richness and microsatellite diversity were observed in introduced (different river system) populations in the Vistula. A low number of colonists found for N. fluviatilis and N. gymnotrachelus in the Vistula potentially resulted in reduced introduction of parasite species. Insufficient adaptation of the introduced host to local parasite fauna, together with introduction into an historically different drainage system, may also have contributed to the reduced parasite fauna.

Monogenean parasites of introduced pumpkinseed Lepomis gibbosus (Centrarchidae) in the Danube River Basin.

The pumpkinseed, Lepomis gibbosus, a centrarchid fish native to eastern North America, was introduced into Europe at the end of the 19th century. Lepomis gibbosus now represents one of the most successful of introduced fish species, having spread widely throughout many European countries. In this study, we collected monogenean parasites of L. gibbosus from four sites in the Danube River Basin. We recorded four monogenean species: Gyrodactylus sp., probably acquired in the area of introduction, and Onchocleidus similis, O. dispar and Actinocleidus recurvatus, species introduced together with their host. Onchocleidus similis dominated the parasite community at all sampling sites. Actinocleidus recurvatus has only been reported from southern Europe to date and, therefore, this is the first report of A. recurvatus from Central Europe and the Danube River Basin. We observed high morphological variability in both anchor pairs of A. recurvatus. Only in O. similis was there a positive correlation observed between haptor metric traits and fish host length. Differences in metric traits between native and introduced O. similis populations may reflect a difference in fish host size, the introduced fish host achieving a smaller size than fish from native populations. A detailed analysis of microhabitat distribution indicated a preference for the second gill arch for both dominant species O. similis and A. recurvatus, with dissimilar site segregation.

Dactylogyrus species parasitizing European Barbus species: morphometric and molecular variability.

The aims of the study were (1) to describe the Dactylogyrus communities living on selected South European Barbus species, (2) to analyse morphometric variability of their attachment and reproductive organs, and (3) to perform molecular phylogenetic analyses, in order to investigate the mode of speciation in Dactylogyrus species parasitizing congeneric hosts. In Bulgaria, Dactylogyrus crivellius, D. dyki and D. petenyi were found on B. balcanicus, and D. dyki on B. cyclolepis. In Spain, Dactylogyrus carpathicus and D. dyki were detected on B. meridionalis. Morphometric analyses of D. dyki revealed significant differences in the attachment and reproductive organs when individuals from different Barbus species were compared. Two monophyletic groups were recognized from the molecular phylogenetic analyses: the first included D. carpathicus and D. crivellius which have large body size and anchors, with a weakly supported basal position of D. malleus from B. barbus; the second included D. dyki and D. petenyi which have small body and anchor sizes. The comparison of host and parasite phylogenies did not indicate the intrahost speciation. Intraspecific molecular variability was found between individuals of D. dyki and D. carpathicus from different Barbus species, suggesting the need for a taxonomic revision for these species.

The costs and benefits in an unusual symbiosis: experimental evidence that bitterling fish (Rhodeus sericeus) are parasites of unionid mussels in Europe.

Interspecific symbiotic relationships involve a complex network of interactions, and understanding their outcome requires quantification of the costs and benefits to both partners. We experimentally investigated the costs and benefits in the relationship between European bitterling fish (Rhodeus sericeus) and freshwater mussels that are used by R. sericeus for oviposition. This relationship has hitherto been thought mutualistic, on the premise that R. sericeus use mussels as foster parents of their embryos while mussels use R. sericeus as hosts for their larvae. We demonstrate that R. sericeus is a parasite of European mussels, because it (i) avoids the cost of infection by mussel larvae and (ii) imposes a direct cost on mussels. Our experiments also indicate a potential coevolutionary arms race between bitterling fishes and their mussel hosts; the outcome of this relationship may differ between Asia, the centre of distribution of bitterling fishes, and Europe where they have recently invaded.

Sexual selection for male dominance reduces opportunities for female mate choice in the European bitterling (Rhodeus sericeus).

Sexual selection involves two main mechanisms: intrasexual competition for mates and intersexual mate choice. We experimentally separated intrasexual (male-male interference competition) and intersexual (female choice) components of sexual selection in a freshwater fish, the European bitterling (Rhodeus sericeus). We compared the roles of multiple morphological and behavioural traits in male success in both components of sexual competition, and their relation to male reproductive success, measured as paternity of offspring. Body size was important for both female choice and male-male competition, though females also preferred males that courted more vigorously. However, dominant males often monopolized females regardless of female preference. Subordinate males were not excluded from reproduction and sired some offspring, possibly through sneaked ejaculations. Male dominance and a greater intensity of carotenoid-based red colouration in their iris were the best predictors of male reproductive success. The extent of red iris colouration and parasite load did not have significant effects on female choice, male dominance or male reproductive success. No effect of parasite load on the expression of red eye colouration was detected, though this may have been due to low parasite prevalence in males overall. In conclusion, we showed that even though larger body size was favoured in both intersexual and intrasexual selection, male-male interference competition reduced opportunities for female choice. Females, despite being choosy, had limited control over the paternity of their offspring. Our study highlights the need for reliable measures of male reproductive success in studies of sexual selection.

Posthodiplostomum cuticola (Digenea: Diplostomatidae) in intermediate fish hosts: factors contributing to the parasite infection and prey selection by the definitive bird host.

Infection parameters of Posthodiplostomum cuticola, a digenean parasite with a complex life-cycle, were investigated in fish (the second intermediate host) from 6 floodplain water bodies over 2 years. A broad range of factors related to abiotic characteristics of localities, density of the first intermediate (planorbid snails) and definitive (wading birds) hosts and fish community structure were tested for their effects on P. cuticola infection in juvenile and adult fish. Characters of the littoral zone and flood duration were found to be important factors for the presence of the first intermediate and definitive hosts. Visitation time of definitive bird hosts was also related to adult fish host density. Localities with P. cuticola infected fish were visited by a higher number of bird species. Infection of P. cuticola in fish and similarities in infection among fish host assemblages were correlated with fish host density and fish species composition. Parasite infection in both adult and juvenile fishes was associated with the slope of the bank and the bottom type, in particular in juvenile fish assemblages with snail host density. We conclude that habitat characteristics, snail host density and fish community structure contribute significantly to P. cuticola infection in fish hosts.

[Use of cytochalasin B in the micronucleus test in human peripheral lymphocytes]. / Aplikace cytochalasin B mikronukleus testu v lidských periferních lymfocytech.

The micronucleus test is one of the alternative procedures of cytogenetic analysis. Its modification with the use of cytochalasine B (Calbiochem AG) ensures safely the recording of changes of the genetic apparatus in the first cellular cycle after an attack of a mutagenic agent on human peripheral lymphocytes. The authors elaborated a reproducible modification of the original work of Fenech and Morley--published in this country by Kocisová and Srám--and describe in detail its individual steps. The cytochalasine MN-test which should become part of obligatory standard procedures of Czechoslovak preventive health services (formerly hygiene service) is thus open to confirmation.