Reproduction-associated pathways in females of gibel carp (Carassius gibelio) shed light on the molecular mechanisms of the coexistence of asexual and sexual reproduction.

Gibel carp (Carassius gibelio) is a cyprinid fish that originated in eastern Eurasia and is considered as invasive in European freshwater ecosystems. The populations of gibel carp in Europe are mostly composed of asexually reproducing triploid females (i.e., reproducing by gynogenesis) and sexually reproducing diploid females and males. Although some cases of coexisting sexual and asexual reproductive forms are known in vertebrates, the molecular mechanisms maintaining such coexistence are still in question. Both reproduction modes are supposed to exhibit evolutionary and ecological advantages and disadvantages. To better understand the coexistence of these two reproduction strategies, we performed transcriptome profile analysis of gonad tissues (ovaries) and studied the differentially expressed reproduction-associated genes in sexual and asexual females. We used high-throughput RNA sequencing to generate transcriptomic profiles of gonadal tissues of triploid asexual females and males, diploid sexual males and females of gibel carp, as well as diploid individuals from two closely-related species, C. auratus and Cyprinus carpio. Using SNP clustering, we showed the close similarity of C. gibelio and C. auratus with a basal position of C. carpio to both Carassius species. Using transcriptome profile analyses, we showed that many genes and pathways are involved in both gynogenetic and sexual reproduction in C. gibelio; however, we also found that 1500 genes, including 100 genes involved in cell cycle control, meiosis, oogenesis, embryogenesis, fertilization, steroid hormone signaling, and biosynthesis were differently expressed in the ovaries of asexual and sexual females. We suggest that the overall downregulation of reproduction-associated pathways in asexual females, and their maintenance in sexual ones, allows the populations of C. gibelio to combine the evolutionary and ecological advantages of the two reproductive strategies. However, we showed that many sexual-reproduction-related genes are maintained and expressed in asexual females, suggesting that gynogenetic gibel carp retains the genetic toolkits for meiosis and sexual reproduction. These findings shed new light on the evolution of this asexual and sexual complex.

New species of Dermoergasilus Ho & Do, 1982 (Copepoda: Cyclopoida: Ergasilidae) parasitizing endemic cichlid Paretroplus polyactis (Bleeker) in Madagascar.

Dermoergasilus madagascarensis n. sp. is described from the gills of Paretroplus polyactis, an endemic cichlid fish in Madagascar, using a combined morphological (light microscopy and SEM) and molecular approach (partial 18S rDNA, 28S rDNA, and COI sequences). The new species is characterized mainly by possessing: (i) roughly pentagonal cephalosome; (ii) antennal endopodal segments covered with slightly inflated membrane; (iii) maxillule bearing 2 equally long outer setae and a minute inner seta; (iv) interpodal sternites of swimming legs ornamented with 3­4 rows of spinules; (v) genital segment and first abdominal somite both barrel-shaped; and (vi) a caudal ramus projecting into a digitiform process with inconspicuous terminal seta and bearing 3 terminal setae. The obtained DNA sequences of Malagasy species represent the first molecular data for species of Dermoergasilus. The 28S rDNA phylogeny showed the affiliation of D. madagascarensis n. sp. to Ergasilidae and its sister relationship with cosmopolitan Ergasilus sieboldi von Nordmann, 1832. The first checklist for all species of Dermoergasilus is provided.

Monogeneans in intergeneric hybrids of leuciscid fish: Is parasite infection driven by hybrid heterosis, genetic incompatibilities, or host-parasite coevolutionary interactions?

BACKGROUND: Several hypotheses have been proposed to explain parasite infection in parental species and their hybrids. Hybrid heterosis is generally applied to explain the advantage for F1 generations of hybrids exhibiting a lower level of parasite infection when compared to parental species. Post-F1 generations often suffer from genetic incompatibilities potentially reflected in the higher level of parasite infection when compared to parental species. However, the presence of specific parasites in an associated host is also limited by close coevolutionary genetic host-parasite associations. This study focused on monogenean parasites closely associated with two leuciscid fish species-common bream and roach-with the aim of comparing the level of monogenean infection between parental species and hybrids representing two F1 generations with different mtDNA and two backcross generations with different cyto-nuclear compositions. RESULTS: Monogenean infection in F1 generations of hybrids was lower when compared to parental species, in line with the hybrid heterosis hypothesis. Monogenean infection in backcross generations exhibited similarities with the parental species whose genes contributed more to the backcross genotype. The distribution of monogeneans associated with one or the other parental species showed the same asymmetry with a higher proportion of roach-associated monogeneans in both F1 generations and backcross generation with roach in the paternal position. A higher proportion of common bream-associated monogeneans was found in backcross generation with common bream in the paternal position. CONCLUSIONS: Our study indicated that cyto-nuclear incompatibilities in hybrids do not induce higher monogenean infection in backcross generations when compared to parental species. However, as backcross hybrids with a higher proportion of the genes of one parental taxon also exhibited high level of this parental taxon-associated parasites, host-parasite coevolutionary interactions seem to play an obvious role in determining the level of infection of host-specific monogeneans in hybrids.

Diversity, phylogeny and intraspecific variability of Paradiplozoon species (Monogenea: Diplozoidae) parasitizing endemic cyprinoids in the Middle East.

Diplozoidae are common monogenean ectoparasites of cyprinoid fish, with the genus Paradiplozoon being the most diversified. Despite recent studies on Diplozoidae from Europe, Africa and Asia, the diversity, distribution and phylogeny of this parasite group appears to be still underestimated in the Middle East. The objective of this study was to investigate the diversity, endemism and host specificity of diplozoids parasitizing cyprinoid fish from the Middle East, considering this region as an important historical interchange of fish fauna, and to elucidate the phylogenetic position of Middle Eastern Paradiplozoon species within Diplozoidae. Four Paradiplozoon species were collected from 48 out of 94 investigated cyprinoid species. Three known species, Paradiplozoon homoion, Paradiplozoon bliccae and Paradiplozoon bingolensis, were recorded on new cyprinoid host species, and a new species, Paradiplozoon koubkovae n. sp., was recorded on Luciobarbus capito and Capoeta capoeta from the Caspian Sea basin in Iran and Turkey. Paradiplozoon bliccae, exhibiting a wide host range in the Middle East, expressed both morphological and genetic intraspecific variabilities. The four Paradiplozoon species collected in the Middle East were placed in divergent clades, showing the rich evolutionary history of diplozoid parasites in the Middle East. Our study also revealed that two lineages of African diplozoids have a Middle Eastern origin. We stress the importance of applying an integrative approach combining morphological, ecological and molecular methods to reveal the real diversity of diplozoids.

Helminth communities of endemic cyprinoids of the Apennine Peninsula, with remarks on ectoparasitic monogeneans, and a description of four new Dactylogyrus Diesing, 1850 species.

The fauna of the Apennine Peninsula is, in comparison to other southern European peninsulas, relatively species-poor regarding the number of endemic cyprinoid species. Nonetheless, the recent introduction of non-native species has significantly increased the total number of freshwater species in this region. Such invasive species may represent a threat to the native fauna, associated among other things with the introduction of non-native parasites with their original hosts.In the present study, we investigated endemic cyprinoid species for the presence of helminth parasites. A total of 36 ectoparasitic monogenean species and five endoparasitic helminth species were collected from ten cyprinoid species in five localities in northern Italy. Out of 20 Dactylogyrus species (gill monogeneans specific to cyprinoids), four were identified as new to science and herein described: Dactylogyrus opertus n. sp. and Dactylogyrus sagittarius n. sp. from Telestes muticellus, Dactylogyrus conchatus n. sp. from T. muticellus and Protochondrostoma genei, and Dactylogyrus globulatus n. sp. from Chondrostoma soetta. All new Dactylogyrus species appear to be endemic to the Apennine Peninsula; however, they share a common evolutionary history with the endemic Dactylogyrus parasitizing cyprinoids of the Balkans. This common origin of cyprinoid-specific parasites supports a historical connection between these two (currently separated) geographical regions.

Diversity and phylogeny of Paradiplozoon species (Monogenea: Diplozoidae) parasitising endemic cyprinoids in the peri-Mediterranean area, with a description of three new Paradiplozoon species.

The Diplozoidae are monogenean parasites of mainly cyprinoid fishes with a unique life cycle, whereby two larvae undergo anastomosis and fuse into a single cross-shaped specimen. Paradiplozoon is the most species rich and widespread genus of the family, with a distribution range covering Eurasia and Africa; however, some areas remain underexplored and their diplozoid fauna is uncertain. In the present study, the Paradiplozoon diversity was investigated in the peri-Mediterranean region, which has the highest levels of cyprinoid diversity and endemism in Europe. A total of 36 endemic cyprinoid species were sampled from sites in north-west Africa and the southern European peninsulas and investigated for the presence of diplozoid parasites. Of five Paradiplozoon species collected, three were identified as new to science: Paradiplozoon moroccoensis n. sp. from the Moroccan endemic Luciobarbus lepineyi; Paradiplozoon ibericus n. sp. from Iberian endemic cyprinids and leuciscids and Paradiplozoon helleni n. sp. from the Greek endemic Scardinius acarnicus and Tropidophoxinellus hellenicus (descriptions provided herein). In addition, new host records for P. homoion and P. megan are presented, with the former being most prevalent in the investigated region. Phylogenetic analysis supported paraphyly of the genus Paradiplozoon, and suggests the need for a careful taxonomic re-evaluation of this genus. Furthermore, the results showed that endemic Paradiplozoon of the peri-Mediterranean do not form a monophyletic group, suggesting multiple origins of this parasite groups in different peri-Mediterranean regions.

Vigour-related traits and immunity in hybrids of evolutionary divergent cyprinoid species: advantages of hybrid heterosis?

Hybrid advantage, described as the superiority of hybrids in some traits over their parents and termed the "heterosis effect," is widely documented in the case of reciprocal crosses of parental species (i.e., hybrids representing the F1 generation). In fish, high survival, fast growth and better health status have been widely documented in F1 hybrids. Nonetheless, the effects of interspecific hybridization on vigour, physiology and immunity-related traits in fish are largely unknown, especially concerning native systems of coexisting parental and hybrid genomes in the same habitat. The present study examined the potential physiological and immune aspects of hybrid heterosis by comparing condition status (measured especially by indexes), haematological profile, glucose concentration and selected parameters of non-specific and specific immunity between the evolutionarily divergent non-congeneric cyprinoid species Abramis brama and Rutilus rutilus and their hybrids representing the F1 generation, all of them caught in nature. Clear differences were documented for vigour-related, physiological and immune parameters between the two divergent species. Hybrids generally tended to express intermediate characters of the measured traits, likely generated by the evolutionary divergence of the hybridizing species; nonetheless, for some traits, hybrids exhibited a character that was more similar to one parental species than to the other. This was interpreted as the heterozygote advantage for F1 hybrids. It is suggested that a maternally inherited genetic background may potentially influence the expression of some branches of non-specific immunity or other aspects related to the fish health status.

High diversity of fish ectoparasitic monogeneans (Dactylogyrus) in the Iberian Peninsula: a case of adaptive radiation?

The epicontinental fauna of the Iberian Peninsula is strongly influenced by its geographical history. As the possibilities for dispersion of organisms into and from this region were (and still are) limited, the local fauna consists almost exclusively of endemic species. Almost all Iberian freshwater fishes of the families Leuciscidae and Cyprinidae are endemic and on-going research on these taxa continually uncovers new species. Nevertheless, information on their host-specific parasites remains scarce. In this study, we investigate the diversity and phylogenetic relationships in monogeneans of the genus Dactylogyrus (gill ectoparasites specific to cyprinoid fish) in the Iberian Peninsula. Twenty-two species were collected and identified from 19 host species belonging to Cyprinidae and Leuciscidae. A high degree of endemism was observed, with 21 Dactylogyrus species reported from Iberia only and a single species, D. borealis, also reported from other European regions. Phylogenetic analysis split the endemic Iberian Dactylogyrus into two well-supported clades, the first encompassing Dactylogyrus parasitizing endemic Luciobarbus spp. only, and the second including all Dactylogyrus species of endemic leuciscids and four species of endemic cyprinids. Species delimitation analysis suggests a remarkable diversity and existence of a multitude of cryptic Dactylogyrus species parasitizing endemic leuciscids (Squalius spp. and representatives of Chondrostoma s.l.). These results suggest a rapid adaptive radiation of Dactylogyrus in this geographically isolated region, closely associated with their cyprinoid hosts. Moreover, phylogenetic analysis supports that Dactylogyrus parasites colonized the Iberian Peninsula through multiple dispersion events.

An annotated list and molecular data on larvae of gryporhynchid tapeworms (Cestoda: Cyclophyllidea) from freshwater fishes in Africa.

An annotated list of larvae (metacestodes) of gryporhynchid tapeworms (Cestoda: Cyclophyllidea) from freshwater fishes in Africa is provided with numerous new host and geographical records. Newly collected materials from Burundi, Democratic Republic of the Congo, Kenya, Madagascar, Namibia, Senegal, South Africa, Sudan and Zimbabwe practically double the total number of species reported from African fish so far. We confirm the occurrence of 16 species (five unidentified to the species level and most likely representing new taxa) belonging to the genera Amirthalingamia Bray, 1974 (1 species), Cyclustera Fuhrmann, 1901 (2 species), Dendrouterina Fuhrmann, 1912 (1 species), Neogryporhynchus Baer & Bona, 1960 (1 species), Paradilepis Hsü, 1935 (4 species), Parvitaenia Burt, 1940 (5 species), and Valipora Linton, 1927 (2 species). Additionally, metacestodes of four unidentified species of Paradilepis and Parvitaenia are reported from fish for the first time. Rostellar hooks of all species are illustrated and their measurements are provided together with a host-parasite list. The molecular phylogenetic analysis based on partial LSU rDNA sequences offers the first insight into the internal phylogenetic relationships within the family. Together with the morphological observations, the present study provides a taxonomic baseline for future studies on this largely neglected, but widely distributed and relatively frequent, group of parasites of African fishes, including economically important cichlids like tilapias and cyprinids.

Four new species of Dactylogyrus Diesing, 1850 (Monogenea: Dactylogyridae) parasitising the gills of northern Moroccan Luciobarbus Heckel (Cyprinidae): morphological and molecular characterisation.

Four new species of Dactylogyrus Diesing, 1850 are described from the gills of three species of Luciobarbus Heckel collected from various hydrographical basins in northern Morocco: Dactylogyrus scorpius n. sp. from Luciobarbus rifensis Doadrio, Casal-Lopez & Yahyaoui; D. benhoussai n. sp. from L. moulouyensis Pellegrin; and D. varius n. sp. and D. falsiphallus n. sp. from L. maghrebensis Doadrio, Perea & Yahyaoui. The descriptions of the new species are confirmed by molecular data (partial 18S rDNA, ITS1, and partial 28S rDNA sequences). All four species belong to the group of Dactylogyrus species, possessing a cross-shaped ventral bar and a male copulatory organ composed of a loosely coiled copulatory tube and an accessory piece with a capsule-like base and recurved distal portion. Given the high shape variability of the haptoral anchors reported among specimens of D. varius n. sp., three morphological forms within this species (D. varius f. vulgaris, D. varius f. magnus, and D. varius f. dromedarius) are recognised. However, specimens belonging to D. benhoussai n. sp. and D. varius f. vulgaris were morphologically very similar and were discriminated with certainty, only when using molecular data.

Seasonal changes in immune parameters of rainbow trout (Oncorhynchus mykiss), brook trout (Salvelinus fontinalis) and brook trout × Arctic charr hybrids (Salvelinus fontinalis × Salvelinus alpinus alpinus).

Despite the high number of studies concerning seasonality of immune response in fish, information for some fish species is still scarce. Here, we assess seasonal changes in leukocyte counts and several immune parameters in three groups of farmed salmonids, i.e. brook trout (Salvelinus fontinalis), brook trout x Arctic charr hybrids (Salvelinus fontinalis x Salvelinus alpinus alpinus) and rainbow trout (Oncorhynchus mykiss) reared under the same conditions and fed with the same feed. Fish were sampled in five periods of the year (late April, early July, late August, early November and early February) and leukocyte counts, respiratory burst of blood phagocytes, lysozyme concentration in skin mucus and total complement activity were measured. Generalized linear models using fish body length as a continuous predictor and sampling period and fish species as categorical predictors, were significant for each of the parameters analysed. The highest seasonal variations in measured parameters were found in rainbow trout and lowest in hybrids. Our results confirm that measures of innate and adaptive immunity are strongly affected by season in all three groups of salmonids. The results will contribute to the improved assessment of immunocompetence in farmed fishes, essential for future sustainable development in aquaculture.

Does the parasite-mediated selection drive the MHC class IIB diversity in wild populations of European chub (Squalius cephalus)?

The genes of major histocompatibility complex (MHC) provide an excellent opportunity to study host-parasite relationships because they are expected to evolve in response to parasites and variation in parasite communities. In this study, we investigated the potential role of parasite-mediated selection acting on MHC class IIB (DAB) genes in European chub (Squalius cephalus) natural populations. We found significant differences between populations in metazoan parasites, neutral and adaptive genetic diversities. The analyses based on pairwise data revealed that populations with dissimilar MHC allelic profiles were geographically distant populations with significantly different diversity in microsatellites and a dissimilar composition of parasite communities. The results from the generalized estimating equations method (GEE) on the level of individuals revealed that metazoan parasite load in European chub was influenced by the diversity of DAB alleles as well as by the diversity of neutral genetic markers and host traits reflecting condition and immunocompetence. The multivariate co-inertia analysis showed specific associations between DAB alleles and parasite species. DAB1-like alleles were more involved in associations with ectoparasites, while DAB3-like alleles were positively associated with endoparasites which could suggest potential differences between DAB genes caused by different selection pressure. Our study revealed that parasite-mediated selection is not the only variable affecting MHC diversity in European chub; however, we strongly support the role of neutral processes as the main driver of DAB diversity across populations. In addition, our study contributes to the understanding of the evolution of MHC genes in wild living fish.

Physiological and condition-related traits in the gynogenetic-sexual Carassius auratus complex: different investments promoting the coexistence of two reproductive forms?

BACKGROUND: Carassius auratus complex is an extraordinary species complex including the diploid and polyploid forms exhibiting asexual and sexual reproduction modes. The coexistence of both forms in the same habitats is currently reported. The stable coexistence of asexual and sexual forms assumes some disadvantages for asexuals that balance the costs of sex. In our study, we hypothesized and tested the differences in physiological (including heamatological and immunological), growth-related, condition-related, and fitness-related traits between gynogenetic females and sexuals. RESULTS: Our results revealed similar growth performance in gynogenetic females and sexuals measured by body size and weight, or expressed by condition factor. The energy allocation in reproduction measured by the relative size of gonads revealed no difference between gynogenetic and sexual females; in addition, both females in spawning expressed the same estradiol levels in blood plasma. We found a gender specific trade-off between investment in reproduction and immunocompetence (measured by the spleen-somatic index). Higher aerobic performance expressed by the heart index and higher oxygen-carrying capacity were found in sexual males, with increasing values before and during spawning. Our study evidenced significantly lower aerobic performance but higher oxygen-carrying capacity per erythrocyte in gynogenetic females when compared to sexuals. IgM production differed between gynogens and sexuals of C. auratus complex. CONCLUSIONS: Our study indicates that a similar amount of energy is invested by both gynogenetic and sexual females of C. auratus complex in reproductive behaviour. We suggest that lower aerobic performance in gynogens may represent their physiological disadvantage balancing the cost of sexual reproduction. A trade-off between the number of erythrocytes and the oxygen-carrying capacity per erythrocyte in sexual males and gynogenetic females may contribute to the coexistence of gynogenetic and sexual forms. In addition, the differences in specific immunity between gynogens and sexuals may also reduce the evolutionary disadvantage of sexual reproduction. In conclusion, we propose that several mechanisms contribute to the coexistence of the gynogenetic-sexual C. auratus complex.

Intraspecific variation in Gyrodactylus mediotorus and G. crysoleucas (Gyrodactylidae) from Nearctic shiners (Leuciscidae): evidence for ongoing speciation, host-switching, and parasite translocation.

A parasitological investigation of Cyprinella venusta and Notropis cf. stramineus sampled in Texas, USA, in the Guadalupe River, revealed the presence of Gyrodactylus crysoleucas Mizelle and Kritsky, 1967 on C. venusta, and Gyrodactylus mediotorus King, Marcogliese, Forest, McLaughlin & Bentzen, 2013 on both fish species. This represents new leuscicid fish hosts and locality records for these two gyrodactylids. Gyrodactylus crysoleucas previously identified from both non-native Californian Notemigonus crysoleucas and from farmed stocks in Minnesota demonstrated intraspecific variability in terms of morphology and genetics as a local adaptation associated with isolation by distance. Results further confirmed G. crysoleucas as alien in the western USA and suggested host-switching involving C. venusta and N. crysoleucas. Conservative morphology and genetics on the part of G. mediotorus from C. venusta and N. cf. stramineus (Guadalupe River) was observed, while higher genetic divergence in the ITS sequences associated with morphological discrepancy was found between the studied G. mediotorus specimens and those of Notropis hudsonius than when considering the parasites of Notropis texanus. The separation of G. mediotorus into geographical subgroups may indicate ongoing speciation linked to the Pleistocene glaciations in North America, and to hydrographic barriers that facilitated separate evolutionary paths leading to speciation. We suggest that deep investigations of Gyrodactylus populations will help to understand the speciation of these parasites and their adaptation to Nearctic fish hosts.

Title: Variation intraspécifique chez Gyrodactylus mediotorus et G. crysoleucas (Gyrodactylidae), parasites de ménés néarctiques (Leuciscidae) : preuves d'une spéciation en cours, d'un changement d'hôte et d'une translocation de parasites. Abstract: Une enquête parasitologique sur Cyprinella venusta et Notropis cf. stramineus échantillonnés au Texas, États-Unis, dans la rivière Guadalupe, a révélé la présence de Gyrodactylus crysoleucas Mizelle et Kritsky, 1967 sur C. venusta, et de Gyrodactylus mediotorus King, Marcogliese, Forest, McLaughlin & Bentzen, 2013 sur les deux espèces de poissons. Ceci représente de nouveaux poissons Leuciscidae hôtes et des nouvelles localités pour ces deux Gyrodactylidae. Gyrodactylus crysoleucas, identifié précédemment à partir de Notemigonus crysoleucas californiens non indigènes et de stocks d'élevage du Minnesota a démontré une variabilité intraspécifique en termes de morphologie et de génétique en tant qu'adaptation locale associée à l'isolement par la distance. Les résultats ont en outre confirmé que G. crysoleucas était exotique dans l'ouest des États-Unis et ont suggéré un changement d'hôte impliquant C. venusta et N. crysoleucas. Une morphologie et une génétique conservatrices pour G. mediotorus de C. venusta et N. cf. stramineus (rivière Guadalupe) ont été observées, tandis qu'une divergence génétique plus élevée dans les séquences ITS, associée à une divergence morphologique, a été trouvée chez les spécimens étudiés de G. mediotorus et de Notropis hudsonius lorsque l'on considère les parasites de Notropis texanus. La séparation de G. mediotorus en sous-groupes géographiques peut indiquer une spéciation continue liée aux glaciations du Pléistocène en Amérique du Nord et à des barrières hydrographiques qui ont facilité des chemins évolutifs séparés menant à la spéciation. Nous suggérons que des études approfondies sur les populations de Gyrodactylus aideront à comprendre la spéciation de ces parasites et leur adaptation aux poissons hôtes néarctiques.

Trematode Diplostomum pseudospathaceum inducing differential immune gene expression in sexual and gynogenetic gibel carp (Carassius gibelio): parasites facilitating the coexistence of two reproductive forms of the invasive species.

Introduction: Parasite-mediated selection is considered one of the potential mechanisms contributing to the coexistence of asexual-sexual complexes. Gibel carp (Carassius gibelio), an invasive fish species in Europe, often forms populations composed of gynogenetic and sexual specimens. Methods: The experimental infection was induced in gynogenetic and sexual gibel carp using eye-fluke Diplostomum pseudospathaceum (Trematoda), and the transcriptome profile of the spleen as a major immune organ in fish was analyzed to reveal the differentially expressed immunity-associated genes related to D. pseudospathaceum infection differing between gynogenetic and sexual gibel carp. Results: High parasite infection was found in gynogenetic fish when compared to genetically diverse sexuals. Although metacercariae of D. pseudospathaceum are situated in an immune-privileged organ, our results show that eye trematodes may induce a host immune response. We found differential gene expression induced by eye-fluke infection, with various impacts on gynogenetic and sexual hosts, documenting for the majority of DEGs upregulation in sexuals, and downregulation in asexuals. Differences in gene regulation between gynogenetic and sexual gibel carp were evidenced in many immunity-associated genes. GO analyses revealed the importance of genes assigned to the GO terms: immune function, the Notch signaling pathway, MAP kinase tyrosine/threonine/phosphatase activity, and chemokine receptor activity. KEGG analyses revealed the importance of the genes involved in 12 immunity-associated pathways - specifically, FoxO signaling, adipocytokine signaling, TGF-beta signaling, apoptosis, Notch signaling, C-type lectin receptor signaling, efferocytosis, intestinal immune network for IgA production, insulin signaling, virion - human immunodeficiency virus, Toll-like receptor signaling, and phosphatidylinositol signaling system. Discussion: Our study indicates the limited potential of asexual fish to cope with higher parasite infection (likely a loss of capacity to induce an effective immune response) and highlights the important role of molecular mechanisms associated with immunity for the coexistence of gynogenetic and sexual gibel carp, potentially contributing to its invasiveness.

MHC genes and parasitism in Carassius gibelio, a diploid-triploid fish species with dual reproduction strategies.

BACKGROUND: The gibel carp is a fish species with dual reproduction modes, gynogenesis and sexual reproduction, coexisting in mixed diploid-polyploid populations. Following the Red Queen (RQ) assumption, asexual organisms are, due to their low genetic diversity, targets for parasite adaptation. Because MHC polymorphism is maintained by selection from parasites and sexual selection, MHC genes are considered as a suitable candidate for testing the RQ hypothesis. In this study, we investigated MHC variability and the selection pressure acting on MHC genes in sexual diploids and asexual triploids. In addition, we tested whether the asexual form of gibel carp suffers from higher parasite loads than the sexual form. RESULTS: At the population level, genotype and allelic diversity of MHC were reduced in gynogenetic triploids when compared to sexual diploids. Different patterns in positively selected sites (PSS) between gynogens and sexual gibel carp were also found. A weak difference in parasite species richness was found between sexual fish and gynogens. However, two common clones of gynogens were significantly more parasitized than sexual diploids or other gynogens with rare MHC genotypes. At the individual level, the higher number of alleles was not associated with higher parasitism in either sexual diploids or gynogens. CONCLUSIONS: The differences in MHC diversity between gynogenetic triploids and sexual diploids are in accordance with the hypothesis of sexually-mediated selection increasing MHC diversity and fulfil a prerequisite of the Red Queen hypothesis. The different patterns in PSS between gynogens and sexual gibel carp also suggest the potential role of sexual selection and supports parasite-mediated selection maintaining MHC diversity. We showed that the most common MHC genotypes of gynogenetic triploids are the target of parasite selection. Our results suggest that the MHC genotype in gibel carp is more important than allelic number for immunocompetence.

Two new species of Cichlidogyrus (Monogenea: Dactylogyridae) parasitizing the gills of African cichlid fishes (Perciformes) from Senegal: morphometric and molecular characterization.

Two new species of Cichlidogyrus are described from the gills of three species of African cichlids collected from the Gambia River basin in the Niokolo-Koba National Park, Senegal: Cichlidogyrus dracolemma n. sp. from Hemichromis letourneuxi and Cichlidogyrus nageus n. sp. from Sarotherodon galilaeus and Tilapia guineensis. The new species are recognized on the basis of morphological differences in the male copulatory organs (MCOs) and apparent differences in the SSU rDNA and ITS1 sequence data. C. dracolemma n. sp. resembles specimens of Cichlidogyrus from Hemichromis bimaculatus, probably misidentified as Cichlidogyrus bychowskii by Paperna in 1965, in having morphologically similar types of haptoral sclerites and MCO. The new species is characterized by possessing an MCO with a kite-shaped termination of the accessory piece and a vagina distally surrounded by a circular superficial sclerotization of the body surface. Molecular phylogenetic analyses showed a strongly supported clade including C. dracolemma n. sp. and two species collected from Hemichromis fasciatus, namely Cichlidogyrus longicirrus Paperna, 1965 and Cichlidogyrus falcifer Dossou and Birgi, 1984. Based on both morphology and molecular phylogeny, C. nageus n. sp. appears to be closely related to Cichlidogyrus acerbus Dossou, 1982 obtained from S. galilaeus. Morphologically, C. nageus n. sp. is readily separated from all known congeners by the characteristic pestle shaped termination of the accessory piece of the MCO. Molecular phylogenetic reconstruction showed that C. dracolemma n. sp. and C. nageus n. sp. cluster with the Cichlidogyrus species possessing the same haptoral configuration and host preferences (on subfamily and tribe level, respectively).

The effect of ploidy and temporal changes in the biochemical profile of gibel carp (Carassius gibelio): a cyprinid fish species with dual reproductive strategies.

The basic biochemical profile of gibel carp (Carassius gibelio), diploid-triploid cyprinid species complex with dual reproduction modes, was investigated. The aim of the study was to test for the effect of fish group (which combines the effects of ploidy and sex) and temporal changes on indicators of the biochemical profile of blood in gibel carp. We showed that the basic biochemical profile of blood is significantly influenced by season and fish group. Triploid gynogenetic females had a better condition measured by total protein concentration than sexual diploids. The higher concentrations of triacylglycerols and cholesterol in triploid females when compared to diploids indicate a higher metabolic rate and higher energy intake during the whole year, which may represent a disadvantage for triploids. Differences in the concentrations of blood biochemical analytes between triploid females and diploids suggest a potential difference in the regulation of a wide range of physiological and biochemical processes in which these analytes participate. The biochemical profiles of two forms of C. gibelio could at least partially explain the changes of character of its naturally occurring populations.

Revealing the hidden diversity of Gyrodactylus communities (Monogenea, Gyrodactylidae) from Nearctic Catostomidae and Leuciscidae fish hosts (Teleostei, Cypriniformes), with descriptions of ten new species.

Despite the high diversity of freshwater fishes in the Nearctic region, little is known about the composition of their parasite communities. We addressed the diversity of viviparous monogeneans of Gyrodactylus parasitizing highly diversified cypriniform fish inhabiting Nearctic watersheds. Nowadays, a thorough assessment of Gyrodactylus spp. diversity requires both morphological traits and genetic data. A combination of taxonomically important haptoral features and sequences of the ITS regions and 18S rDNA revealed 25 Gyrodactylus spp. parasitizing two catostomid and 15 leuciscid species sampled in six distinct localities in the United States and Canada. These include ten Gyrodactylus species recognized as new to science and described herein (G. ellae n. sp., G. hamdii n. sp., G. hanseni n. sp., G. huyseae n. sp., G. kuchtai n. sp., G. lummei n. sp., G. mendeli n. sp., G. prikrylovae n. sp., G. scholzi n. sp., and G. steineri n. sp.), seven already known species, and finally eight undescribed species. Overall, Nearctic Gyrodactylus spp. exhibited haptoral morphotypes known from fish hosts worldwide and those apparently restricted to Nearctic Gyrodactylus lineages like the typical ventral bar with a median knob and a plate-like membrane, or the additional filament attached to the handles of marginal hooks. The integrative approach further evidenced possible ongoing gene flow, host-switching in generalist Gyrodactylus spp., and regional translocation of monogenean fauna through fish introductions. The study highlights the hitherto underexplored morphological and genetic diversity of viviparous monogeneans throughout the Nearctic region.

Title: Révélation de la diversité cachée des communautés de Gyrodactylus (Monogenea, Gyrodactylidae) des poissons hôtes néarctiques Catostomidae et Leuciscidae (Teleostei, Cypriniformes), avec la description de dix nouvelles espèces. Abstract: Malgré la grande diversité des poissons d'eau douce dans la région néarctique, on sait peu de choses sur la composition de leurs communautés de parasites. Nous avons abordé la diversité des monogènes vivipares du genre Gyrodactylus parasitant des poissons cypriniformes très diversifiés habitant les bassins versants néarctiques. De nos jours, une évaluation approfondie de la diversité de Gyrodactylus spp. nécessite à la fois des traits morphologiques et des données génétiques. Une combinaison de caractéristiques haptorales et de séquences taxonomiquement importantes des régions ITS et de l'ADNr 18S a révélé 25 espèces de Gyrodactylus sur deux espèces de catostomidés et 15 espèces de leuciscidés échantillonnées dans six localités distinctes aux États-Unis et au Canada. Celles-ci comprennent dix espèces de Gyrodactylus reconnues comme nouvelles pour la science et décrites dans cette étude (G. ellae n. sp., G. hamdii n. sp., G. hanseni n. sp., G. huyseae n. sp., G. kuchtai n. sp., G. lummei n. sp., G. mendeli n. sp., G. prikrylovae n. sp., G. scholzi n. sp. et G. steineri n. sp.), sept espèces déjà connues et enfin huit espèces non décrites. Dans l'ensemble, les espèces de Gyrodactylus néarctiques présentaient des morphotypes haptoraux connus chez les poissons hôtes du monde entier et ceux apparemment limités aux lignées néarctiques de Gyrodactylus comme la barre ventrale typique avec un bouton médian et une membrane en forme de plaque, ou le filament supplémentaire attaché aux poignées des crochets marginaux. L'approche intégrative a en outre mis en évidence le flux de gènes en cours, le changement d'hôte chez les espèces de Gyrodactylus généralistes et la translocation régionale de la faune monogène par l'introduction de poissons. L'étude met en évidence la diversité morphologique et génétique jusqu'ici sous-explorée des monogènes vivipares dans toute la région néarctique.

Nearctic Dactylogyrus species (Platyhelminthes, Monogenea) parasitizing cypriniform fishes in the context of morphology and phylogeny, with descriptions of seven new species.

Ribosomal DNA sequences are currently available for 32 morphologically recognized species of Dactylogyrus parasitizing Nearctic cypriniforms, but only 16 of them are assigned to nominal species. Herein, morphological data on 28 of the 32 species are provided, together with comments on their phylogenetic relationships in the context of the morphology of taxonomically important structures. Seven new species of Dactylogyrus are described from five species of leuciscids and one species of catostomids, as follows: D. aduncus n. sp. from Campostoma spadiceum, D. cloutmani n. sp. from Luxilus chrysocephalus isolepis, D. cornifrons n. sp. from Cyprinella venusta, D. fimbratus n. sp. from Rhinichthys cataractae, D. mcallisteri n. sp. from Semotilus atromaculatus, and D. chieni n. sp. and D. haneki n. sp. from Hypentelium nigricans. Four previously described species of Dactylogyrus, D. atromaculatus from S. atromaculatus, D. eos from C. neogaeus, D. parvicirrus from Notemigonus crysoleucas and D. perlus from L. c. isolepis, are redescribed and/or figured. As for the remaining 17 species, only the male copulatory organs (MCOs) taken from the respective hologenophores are illustrated. On the basis of phylogenetic analyses, two main clades of Nearctic Dactylogyrus were recognized and supported by the different morphology of the MCO. The first one included 22 strictly Nearctic species sharing the same MCO type with Dactylogyrus spp. parasitizing cyprinids likely of Asian origin. The second clade encompassed Dactylogyrus spp. with diverse MCO morphology and was placed in the sister position to Dactylogyrus spp. parasitizing European leuciscids and North-West African cyprinids.

Title: Espèce néarctique de Dactylogyrus (Platyhelminthes, Monogenea) parasitant des poissons cypriniformes dans un contexte de morphologie et phylogénie, avec description de sept nouvelles espèces. Abstract: Des séquences d'ADN ribosomal sont actuellement disponibles pour 32 espèces morphologiquement reconnues de Dactylogyrus parasitant les cypriniformes néarctiques, mais seulement 16 d'entre elles sont attribuées à des espèces nominales. Ici, des données morphologiques sur 28 des 32 espèces sont fournies avec des commentaires sur leurs relations phylogénétiques dans le contexte de la morphologie des structures taxonomiquement importantes. Sept nouvelles espèces de Dactylogyrus sont décrites à partir de cinq espèces de leuciscidés et d'une espèce de catostomidés, comme suit : D. aduncus n. sp. de Campostoma spadiceum, D. cloutmani n. sp. de Luxilus chrysocephalus isolepis, D. cornifrons n. sp. de Cyprinella venusta, D. fimbratus n. sp. de Rhinichthys cataractae, D. mcallisteri n. sp. de Semotilus atromaculatus et D. chieni n. sp. et D. haneki n. sp. de Hypentelium nigricans. Quatre espèces de Dactylogyrus précédemment décrites, D. atromaculatus de S. atromaculatus, D. eos de C. neogaeus, D. parvicirrus de Notemigonus crysoleucas et D. perlus de L. c. isolepis, sont redécrites et/ou figurées. Comme pour les 17 espèces restantes, seuls les organes copulateurs mâles (OCM) prélevés sur les hologénophores respectifs sont illustrés. Sur la base d'analyses phylogénétiques, deux clades principaux de Dactylogyrus néarctiques ont été reconnus et soutenus par des morphologies différentes de l'OCM. Le premier comprenait 22 espèces strictement néarctiques partageant le même type d'OCM que les Dactylogyrus spp. parasitant des cyprinidés probablement d'origine asiatique. Le deuxième clade comprenait des Dactylogyrus spp. avec diverses morphologies d'OCM et était placé en position sœur des Dactylogyrus spp. parasitant les leuciscidés européens et les cyprinidés d'Afrique du Nord-Ouest.