A checklist of parasites of non-native populations of the fish rotan Perccottus glenii (Odontobutidae): Communication II

The fish rotan, Perccottus glenii Dybowski, 1877 (Odontobutidae) is one of the most successful fish invaders during 20th and beginning of 21st century in European and Asian fresh waters. The diversity of its parasites within its invaded range was first reviewed by Sokolov, Reshetnikov, et al. (2014). The current paper analyzes new data from 2013 to 2019 on protistan and metazoan parasites of the non-native populations of this fish. We used information from peer-reviewed journals, difficult to access grey literature and our own recently obtained original data. 45 literature sources were included in the analysis. The newly-available data originate from 95 water bodies of 13 river basins, isolated lakes in West Siberia, and Gulf of Finland, spanning a total of eight countries. A total of 132 recently detected parasite species/taxa are listed in this paper. Each species is presented with its location in/on the host, geographical localities, countries, and according literature sources. When available, number of examined fish as well as prevalence and range of intensity of infection are cited from the original source. This review enlarges contemporary knowledge on parasites of non-native populations of the studied fish species up to 167 species/taxa. We highlight perspectives for further parasitological investigations of this invasive fish.     

The host‐specific parasite Nippotaenia mogurndae confirms introduction vectors of the fish Perccottus glenii in the Volga river basin

Two alternative hypotheses about aquarium vs fish‐farm vectors of non‐native distribution of the fish rotan, Perccottus glenii (Odontobutidae), within the Volga River Basin were assessed using a parasitological approach. Three separate locations were studied where rotan populations were assumed to have different introduction histories: (i) vicinities of Tarakanovo pond, Moscow province (aquarium release in 1950), (ii) Ilev fish farm, Nizhniy Novgorod province (unintentional transportation together with stocking of commercial fish in 1970), (iii) the lower Volga River, Saratov province (unknown origin; first record in 1983). The odontobutid‐specific tapeworm Nippotaenia mogurndae was the most informative species because it has a complex life cycle and therefore does not persist in aquarium conditions. Absence of this tapeworm in the rotan populations in the first locality and presence in the second location are in agreement with the available information about appropriate vectors of introduction. Populations of rotan in the lower Volga (third locality) where N. mogurndae occurs could originate from individuals unintentionally transported to fish farms together with commercial fish species or have mixed origins. Thus, the presented parasitological data are in agreement with information concerning introduction vectors of P. glenii and confirm that the specific parasite N. mogurndae is a valuable biological tag for analysing vectors and pathways of geographical dispersal of rotan, P. glenii.     

A checklist of the protozoan and metazoan parasites of European eel (Anguilla anguilla): checklist of Anguilla anguilla parasites

A comprehensive literature review on prevalence and distribution of parasites of the European eel (Anguilla anguilla) in European waters was conducted to set a baseline for future trend analyses and biodiversity considerations. The resulting checklist compiled from peer reviewed journals as well as grey literature including scientific reports, conference contributions, PhD theses and own survey data includes all protozoan and metazoan parasites of the European eel from freshwater, brackish and marine habitats. Parasites are arranged according to phylum and family. Species within families are listed alphabetically. Infected host organs, recorded habitats, localities, countries and literature citations are provided for each species. A total of 161 parasite species ? taxa from 30 countries are listed. With the trypanorhynch cestode Tentacularia coryphaenae a new host record could be documented. Furthermore, three new locality records of parasitic nematodes could be added based on own survey data: Anisakis simplex from an eel caught in the Baltic Sea, Eustrongylides mergorum for German freshwaters, and Goezia anguillae from the Tagus estuary in Portugal. Special consideration was given to the distribution of the swimbladder nematode Anguillicola crassus. A map and table of first reported records of this neozoan parasite species for 25 countries as well as a survey map indicating all published localities documented in the checklist are provided.     

Range expansion of rotan <Emphasis Type="Italic">Perccottus glenii</Emphasis>, sunbleak <Emphasis Type="Italic">Leucaspius delineatus</Emphasis>, and bleak <Emphasis Type="Italic">Alburnus alburnus</Emphasis> in the Ob River basin

The ranges of three alien fish species (rotan Perccottus glenii, sunbleak Leucaspius delineatus, and bleak Alburnus alburnus) in the Ob River basin, West Siberia, have expanded. Our data prove the expansion of rotan and sunbleak ranges to the north. In particular, for the first time, populations of rotan are reported from the lower section of the Ob. We also present new data about range expansion of the studied fish species southward. All three species have probably reached the southern limits of their possible distribution in the Upper Ob system, entering the potamon/rhithron transition zone, because the species under study prefer lowland waters. The spatio-temporal dynamics of their expansion reveals the role of the Ob River as the main invasion corridor, enhancing their distribution mostly in meridional direction. In the system of the Upper Ob, rotan and sunbleak were found by us in isolated ponds and lakes, as well as in floodplain systems. This is in agreement with the concept of two invasion vectors: the translocation of fish by humans between water bodies and self-distribution along the river courses.     

Contrasting the seasonal and elevational prevalence of generalist avian haemosporidia in co‐occurring host species

Understanding the ecology and evolution of parasites is contingent on identifying the selection pressures they face across their infection landscape. Such a task is made challenging by the fact that these pressures will likely vary across time and space, as a result of seasonal and geographical differences in host susceptibility or transmission opportunities. Avian haemosporidian blood parasites are capable of infecting multiple co‐occurring hosts within their ranges, yet whether their distribution across time and space varies similarly in their different host species remains unclear. Here, we applied a new PCR method to detect avian haemosporidia (genera Haemoproteus, Leucocytozoon, and Plasmodium) and to determine parasite prevalence in two closely related and co‐occurring host species, blue tits (Cyanistes caeruleus, N = 529) and great tits (Parus major, N = 443). Our samples were collected between autumn and spring, along an elevational gradient in the French Pyrenees and over a three‐year period. Most parasites were found to infect both host species, and while these generalist parasites displayed similar elevational patterns of prevalence in the two host species, this was not always the case for seasonal prevalence patterns. For example, Leucocytozoon group A parasites showed inverse seasonal prevalence when comparing between the two host species, being highest in winter and spring in blue tits but higher in autumn in great tits. While Plasmodium relictum prevalence was overall lower in spring relative to winter or autumn in both species, spring prevalence was also lower in blue tits than in great tits. Together, these results reveal how generalist parasites can exhibit host‐specific epidemiology, which is likely to complicate predictions of host–parasite co‐evolution.     

Global warming will reshuffle the areas of high prevalence and richness of three genera of avian blood parasites

The importance of parasitism for host populations depends on local parasite richness and prevalence: usually host individuals face higher infection risk in areas where parasites are most diverse, and host dispersal to or from these areas may have fitness consequences. Knowing how parasites are and will be distributed in space and time (in a context of global change) is thus crucial from both an ecological and a biological conservation perspective. Nevertheless, most research articles focus just on elaborating models of parasite distribution instead of parasite diversity. We produced distribution models of the areas where haemosporidian parasites are currently highly diverse (both at community and at within‐host levels) and prevalent among Iberian populations of a model passerine host: the blackcap Sylvia atricapilla; and how these areas are expected to vary according to three scenarios of climate change. On the basis of these models, we analysed whether variation among populations in parasite richness or prevalence are expected to remain the same or change in the future, thereby reshuffling the geographic mosaic of host‐parasite interactions as we observe it today. Our models predict a rearrangement of areas of high prevalence and richness of parasites in the future, with Haemoproteus and Leucocytozoon parasites (today the most diverse genera in blackcaps) losing areas of high diversity and Plasmodium parasites (the most virulent ones) gaining them. Likewise, the prevalence of multiple infections and parasite infracommunity richness would be reduced. Importantly, differences among populations in the prevalence and richness of parasites are expected to decrease in the future, creating a more homogeneous parasitic landscape. This predicts an altered geographic mosaic of host‐parasite relationships, which will modify the interaction arena in which parasite virulence evolves.     

Parasite-induced parthenogenesis in a freshwater snail: stable,persistent patterns of parasitism

Summary The role of parasites in the evolution of host reproductive modes has gained renewed interest in evolutionary ecology. It was previously argued that obligate parthenogenesis (all-female reproduction) arose in a freshwater snail, Campeloma decisum, as a consequence of severe sperm limitation caused by an unencysted trematode, Leucochloridiomorpha constantiae. In the present study, certain conditions are examined for parasitic castration to account for the maintenance of parthenogenesis: the spatial patterns of the prevalence and intensity of infection on a broad geographical scale and its relationship to host genotype; the recovery from infection after isolation from sources of infection; age-related patterns of infections; and the effects of L. constantiae on snail fecundity.In contrast to the common pattern of the aggregated distribution of parasites within host populations, many snail populations with high prevalence and intensity of infection have non-aggregated parasite distributions. Clonal genotype of the host explained little of the variation in intensity and prevalence of infection by the parasite. Female snails maintained similar prevalence and intensity of infection after isolation, and individuals accumulated parasites throughout their lifespan, both of which suggest there is no effective immune response to infection by L. constantiae. Snail fecundity is not significantly influenced by the intensity of infection. These results suggest that L. constantiae may have represented a strong selective force against males during the initial introduction of this parasite into sexual snail populations because of the persistent nature of infection.     

Populations of the damselfly Coenagrion hastulatum at the edge of the species range have fewer gregarine and water mite parasites

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New records of endoparasitic helminths in alien invasive fishes from the Carpathian region

Six non-native invasive fish species from the Slovak part of the Tisa River basin, namely Carassius gibelio, Pseudorasbora parva, Ameiurus melas, A. nebulosus, Lepomis gibbosus, Perccottus glenii, and three gobiid species from the Danube River, namely Neogobius melanostomus, N. fluviatilis and N. kessleri, were investigated for endohelminth parasites. The expanding Asian cestode Nippotaenia mogurndae (syn. Amurotaenia perccotti) (Nippotaeniidea) has been introduced to Europe with its invasive host P. glenii. Pumpkinseed, Lepomis gibbosus, is a new definitive host of Proteocephalus percae and it is reported as the second intermediate host of the bothriocephalidean cestode Triaenophorus nodulosus in Slovakia.     

Phylogeny,Evidence for a Cryptic Plastid,and Distribution of Chytriodinium Parasites (Dinophyceae) Infecting Copepods

Spores of the dinoflagellate Chytriodinium are known to infest copepod eggs causing their lethality. Despite the potential to control the population of such an ecologically important host, knowledge about Chytriodinium parasites is limited: we know little about phylogeny, parasitism, abundance, or geographical distribution. We carried out genome sequence surveys on four manually isolated sporocytes from the same sporangium, which seemed to be attached to a copepod nauplius, to analyze the phylogenetic position of Chytriodinium based on SSU and concatenated SSU/LSU rRNA gene sequences, and also characterize two genes related to the plastidial heme pathway, hemL and hemY. The results suggest the presence of a cryptic plastid in Chytriodinium and a photosynthetic ancestral state of the parasitic Chytriodinium/Dissodinium clade. Finally, by mapping Tara Oceans V9 SSU amplicon data to the recovered SSU rRNA gene sequences from the sporocytes, we show that globally, Chytriodinium parasites are most abundant within the pico/nano‐ and mesoplankton of the surface ocean and almost absent within microplankton, a distribution indicating that they generally exist either as free‐living spores or host‐associated sporangia.     

The introduced fish, rotan (Perccottus glenii), depresses populations of aquatic animals (macroinvertebrates, amphibians, and a fish)

The fish rotan (Perccottus gleniiDybowski) was accidentally introduced into European Russia from the Amur River basin. Rotan is capable of colonising small waterbodies – favourable breeding sites of native amphibians. To reveal its influence on the native aquatic fauna, monitoring of small waterbodies has been carried out since 1994 in the region of Lake Glubokoe Reserve (Moscow Province, Russia). The fish's diet includes a wide range of animal species of all trophic levels. Rotan considerably decreases the species richness of aquatic macroinvertebrates and larval amphibians. As a rule, most amphibian species (Triturus cristatus, T. vulgaris, Rana temporaria, R. arvalis, R. lessonae) and the fish Carassius carassius failed to breed successfully in ponds inhabited by rotan. In contrast, the toad Bufo bufo bred successfully in such sites because its larvae are distasteful to rotan. Rotan–amphibian interactions are discussed.     

Population‐level dynamics in experimental mixed infections: evidence for competitive exclusion among bacterial parasites of Paramecium caudatum

Parasites frequently share their host populations with other parasites. However, little is known about how different parasites respond to competition with diverse competitor species in the within‐host and between‐host environments. We explored the repeatability of competition by simultaneously exposing microcosm populations of the ciliate Paramecium caudatum to pairs of parasites from the Holospora species complex (H. undulata, H. caryophila and H. obtusa). We measured how competition affected the persistence and prevalence of each compared to single infections, across three host genotypes. Three weeks post‐inoculation we identified the presence of each parasite using fluorescence in situ hybridisation (FISH). Competitive exclusion (62/72) was more common than co‐existence (10/72) in populations inoculated with two parasites. There was a clear pattern of competitive superiority, with H. caryophila persisting in all doubly inoculated populations (with either H. undulata or H. obtusa), and H. undulata tending to exclude H. obtusa. This mirrored infection success in single infections, with H. caryophila having a higher infection prevalence in single inoculations, followed by H. undulata then H. obtusa. The probability of persistence in co‐inoculations did not change across the different host genotypes, and prevalence was the same as in single infections. Our results are consistent with superinfection models, which assume the competitive exclusion of parasites upon contact within the same host. Furthermore, such non‐random competitive epidemiological dynamics, where one parasite always wins, may be of interest for public health management, especially if the winning parasite is avirulent, as is seemingly the case here.     

Host species,and not environment,predicts variation in blood parasite prevalence,distribution, and diversity along a humidity gradient in northern South America

Environmental factors strongly influence the ecology and evolution of vector‐borne infectious diseases. However, our understanding of the influence of climatic variation on host–parasite interactions in tropical systems is rudimentary. We studied five species of birds and their haemosporidian parasites (Plasmodium and Haemoproteus) at 16 sampling sites to understand how environmental heterogeneity influences patterns of parasite prevalence, distribution, and diversity across a marked gradient in water availability in northern South America. We used molecular methods to screen for parasite infections and to identify parasite lineages. To characterize spatial heterogeneity in water availability, we used weather‐station and remotely sensed climate data. We estimated parasite prevalence while accounting for spatial autocorrelation, and used a model selection approach to determine the effect of variables related to water availability and host species on prevalence. The prevalence, distribution, and lineage diversity of haemosporidian parasites varied among localities and host species, but we found no support for the hypothesis that the prevalence and diversity of parasites increase with increasing water availability. Host species and host × climate interactions had stronger effects on infection prevalence, and parasite lineages were strongly associated with particular host species. Because climatic variables had little effect on the overall prevalence and lineage diversity of haemosporidian parasites across study sites, our results suggest that independent host–parasite dynamics may influence patterns in parasitism in environmentally heterogeneous landscapes.     

Avian Plasmodium lineages found in spot surveys of mosquitoes from 2007 to 2010 at Sakata wetland,Japan: do dominant lineages persist for multiple years?

The ecology and geographical distribution of disease vectors are major determinants of spatial and temporal variations in the transmission dynamics of vector‐borne pathogens. However, there are limited studies on the ecology of vectors that contribute to the natural transmission of most vector‐borne pathogens. Avian Plasmodium parasites are multihost mosquito‐borne pathogens transmitted by multiple mosquito species, which might regulate the diversity and persistence of these parasites. From 2007 to 2010, we conducted entomological surveys at Sakata wetland in central Japan, to investigate temporal variation in mosquito occurrence and prevalence of avian Plasmodium lineages in the mosquito populations. A polymerase chain reaction (PCR)‐based method was used to detect Plasmodium parasites and identify the blood sources of mosquitoes. Culex inatomii and C. pipiens pallens represented 60.0% and 34.8% of 11 mosquito species collected, respectively. Our results showed that the two dominant mosquito species most likely serve as principal vectors of avian Plasmodium parasites during June, which coincides with the breeding season of bird species nesting in the wetland reed beds. Fourteen animal species were identified as blood sources of mosquitoes, with the oriental reed warbler (Acrocephalus orientalis) being the commonest blood source. Although there was significant temporal variation in the occurrence of mosquitoes and prevalence of Plasmodium lineages in the mosquitoes, the dominant Plasmodium lineages shared by the two dominant mosquito species were consistently found at the same time during transmission seasons. Because vector competence cannot be confirmed solely by PCR approaches, experimental demonstration is required to provide definitive evidence of transmission suggested in this study.     

Distribution of the fish rotan (Perccottus glenii Dybowski, 1877) in the Irtysh River basin and analysis of possible consequences for environment and people

Since 1916, rotan (Perccottus glenii Dybowski, 1877) has widely distributed in northwestern Eurasia. In 1973–1976, rotan populations were first detected in the basin of the Irtysh River: in Lake Peschanoe (Mertvoe) of Chelyabinsk oblast in the basin of the Tobol, a tributary of the Irtysh. In 1975, this fish was introduced to one of the ponds of the city of Chelyabinsk. Analysis of the spatiotemporal dynamics of findings shows that earlier records of the fish correlate with the network of roads, and later findings, with the river network. The results of a special inspection of isolated and floodplain water bodies (n = 77) performed within Chelyabinsk, Kurgan, Omsk, and Tyumen oblasts in 2006 indicate that at present this unwanted invader occurs in the major part of the Tobol basin. The northernmost finding of this species is from the floodplain of the Tobol in the vicinity of Tobolsk, from the Karachino oxbow (58°02′N, 68°10′E). Rotan has also been found at the Irtysh headwaters as well as in the basins of its other tributaries: Ishim and Om. The expansion of rotan threatens the floodplain water bodies of the middle Irtysh. This species carries diseases, competes with other fish species for food, and actively eats young fish of these species. Therefore, the data on rotan distribution in the tributaries of the Irtysh should be taken into account when analyzing the dynamics of the fish community of this river. Biology of rotan assumes its influence on the functioning of the natural foci of opisthorchiasis.     

Host community similarity and geography shape the diversity and distribution of haemosporidian parasites in Amazonian birds

Identifying the mechanisms driving the distribution and diversity of parasitic organisms and characterizing the structure of parasite assemblages are critical to understanding host–parasite evolution, community dynamics, and disease transmission risk. Haemosporidian parasites of the genera Plasmodium and Haemoproteus are a diverse and cosmopolitan group of bird pathogens. Despite their global distribution, the ecological and historical factors shaping the diversity and distribution of these protozoan parasites across avian communities and geographic regions remain unclear. Here we used a region of the mitochondrial cytochrome b gene to characterize the diversity, biogeographical patterns, and phylogenetic relationships of Plasmodium and Haemoproteus infecting Amazonian birds. Specifically, we asked whether, and how, host community similarity and geography (latitude and area of endemism) structure parasite assemblages across 15 avian communities in the Amazon Basin. We identified 265 lineages of haemosporidians recovered from 2661 sampled birds from 330 species. Infection prevalence varied widely among host species, avian communities, areas of endemism, and latitude. Composition analysis demonstrated that both malarial parasites and host communities differed across areas of endemism and as a function of latitude. Thus, areas with similar avian community composition were similar in their parasite communities. Our analyses, within a regional biogeographic context, imply that host switching is the main event promoting diversification in malarial parasites. Although dispersal of haemosporidian parasites was constrained across six areas of endemism, these pathogens are not dispersal‐limited among communities within the same area of endemism. Our findings indicate that the distribution of malarial parasites in Amazonian birds is largely dependent on local ecological conditions and host evolutionary relationships.     

Spread of an introduced parasite across the Hawaiian archipelago independent of its introduced host

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Does rotan <Emphasis Type="Italic">Perccottus glenii</Emphasis> (Perciformes: Odontobutidae) eat the eggs of fish and amphibians?

The introduced fish rotan Perccottus glenii negatively affects the native ecosystems. An integrated study was performed to verify the suggestion that P. glenii feeds on eggs of fish (Rutilus rutilus, Abramis brama, Perca fluviatilis) and amphibians (Rana temporaria, R. arvalis, Bufo bufo). It was found that, during the intraoral testing of fish eggs, P. glenii perceives it as an edible item and swallows; however, under experimental conditions, this predator is limited in its ability for finding this prey because of its immobility. At the last stages of development, the movements of embryos within eggs attract the attention of P. glenii. This increases the vulnerability of fish eggs. In a large water body, there may be a spatial biotopic separation of the sites of egg deposition of some fish (for instance, perch) and the sites of concentrations of P. glenii. This makes eggs inaccessible for this predator. The amphibian eggs, on the contrary, are rejected by P. glenii after intraoral testing, which is determined by the presence of a thick jelly coat. During the period of development of eggs of frogs and toad in a pond, P. glenii actively feed (diverse invertebrates and adult newts were found in their diet); however, they ignore amphibian eggs that successfully develop in water bodies inhabited by P. glenii.     

Spatial variation in population density across the geographical range in helminth parasites of yellow perch Perca flavescens

The abundance of a species is not constant across its geographical range; it has often been assumed to decrease from the centre of a species’ range toward its margins. The central assumption of this “favourable centre” model is tested for the first time with parasites, using different species of helminth parasites exploiting fish as definitive hosts. Data on prevalence (percentage of hosts that are infected) and abundance (mean no. parasites per host) were compiled for 8 helminth species occurring in 23 populations of yellow perch Perca flavescens, from continental North America. For each parasite species, correlations were computed between latitude and both local prevalence and abundance values. In addition, the relationships between the relative prevalence or abundance in one locality and the distance between that locality and the one where the maximum value was reported, were assessed separately for each species to determine whether abundance tends to decrease away from the presumed centre of the range, where it peaks. For both the cestode Proteocephalus pearsei and the acanthocephalan Leptorhynchoides thecatus, there was a positive relationship between prevalence or abundance and the latitude of the sampled population. There was also a significant negative relationship between relative prevalence and the distance from the locality showing the maximum value in P. pearsei, but no such pattern was observed for the other 7 parasite species. Since this single significant decrease in prevalence with increasing distance from the peak value may be confounded by a latitudinal gradient, it appears that the distribution of abundance in parasites of perch does not follow the favourable centre model. This means that the environmental variables affecting the density of parasites (host availability, abiotic conditions) do not show pronounced spatial autocorrelation, with nearby sites not necessarily providing more similar conditions for the growth of parasite populations than distant sites.