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The coexistence of sexual and asexual lineages is rarely documented in vertebrates. Various ecological and evolutionary mechanisms have been proposed to explain their stable coexistence. Gibel carp (Carassius gibelio), a highly invasive freshwater fish in Europe, is one such example of a sexual and asexual vertebrate, combining gynogenesis (sperm-dependent parthenogenesis) and sexual reproduction. In this study, we focused on vigour-related traits in gynogenetic and sexual forms of gibel carp coexisting in the same habitat, to reveal whether there is a link between parasite load and vigour-related traits reflecting the potential advantage of one reproductive form over another, which may eventually facilitate the obligatory coexistence of sperm-dependent gynogenetic females with sexual males. Using physiological parameters (indexes of somatic condition, energetic condition, and reproductive performance; glucose levels; and erythrocytes-related variables), diploid sexual males, diploid sexual females, and triploid gynogenetic females were found to be differentiated from one another. However, based on immune variables representing innate immunity, specific immunity, and index of immunocompetence, mostly sexual males were found to be weakly differentiated from both groups of females. We revealed different patterns of interactions between parasite abundance and immune variables between sexual and gynogenetic forms. Using parasite assemblage composition, different relationships between parasite assemblage and immunity or physiology in sexual males and sexual females were evidenced, potentially related to male reproduction biology. In contrast, gynogenetic females exhibited the advantage that parasite assemblage composition did not affect their immunity or physiology. Our study suggests that reproduction mode-associated costs of physiology and immunity may facilitate the coexistence of the asexual-sexual complex. We highlight that multiple ecological processes and evolutionary mechanisms contribute to the coexistence of asexual and sexual gibel carp. [ABSTRACT FROM AUTHOR]

Fishes of the genus Carassius are useful experimental vertebrate models for the study of evolutionary biology and cytogenetics. Carassius demonstrates diverse biological characteristics, such as variation in ploidy levels and chromosome numbers, and presence of microchromosomes. Those Carassius polyploids with ≥ 150 chromosomes have microchromosomes, but the origin of microchromosomes, especially in European populations, is unknown. We used cytogenetics to study evolution of tandem repeats (U1 and U2 small nuclear DNAs and H3 histone) and microchromosomes in Carassius from the Czech Republic. We tested the hypotheses whether the number of tandem repeats was affected by polyploidization or divergence between species and what mechanism drives evolution of microchromosomes. Tandem repeats were found in tetraploid and hexaploid Carassius gibelio , and tetraploid Carassius auratus and Carassius carassius in conserved numbers, with the exception of U1 small nuclear DNA in C. auratus. This conservation indicates reduction and/or loss in the number of copies per locus in hexaploids and may have occurred by divergence rather than polyploidization. To study the evolution of microchromosomes, we used the whole microchromosome painting probe from hexaploid C. gibelio and hybridized it to tetraploid and hexaploid C. gibelio , and tetraploid C. auratus and C. carassius. Our results revealed variation in the number of microchromosomes in hexaploids and indicated that the evolution of the Carassius karyotype is governed by macrochromosome fissions followed by segmental duplication in pericentromeric areas. These are potential mechanisms responsible for the presence of microchromosomes in Carassius hexaploids. Differential efficacy of one or both of these mechanisms in different tetraploids could ensure variability in chromosome number in polyploids in general. [ABSTRACT FROM AUTHOR]

The hypoxia-inducible factor (HIF) is considered key in the transcriptional response to low oxygen. Yet, the role of HIF in the absence of oxygen (anoxia) and in preparation for reoxygenation remains unclear. Recent studies suggest that mounting a HIF response may be counterproductive for anoxia survival. We here studied one of the champions of anoxia survival, the crucian carp (Carassius carassius), and hypothesized that expression of prolyl hydroxylase domains (PHDs; the upstream regulators of HIF) are upregulated to circumvent an energy-costly activation of HIF in anoxia and to prepare for reoxygenation. We measured whole brain mRNA and protein levels of the three isoforms PHD1, PHD2, and PHD3, coded for by multiple paralogs of the genes egln2, egln1, and egln3, using quantitative PCR and Western blotting in the brain of crucian carps exposed to 5 days normoxia or anoxia, and 5 days anoxia followed by 3 or 24 h of reoxygenation. The mRNA levels of most egln paralogs were increased in anoxia and upon reoxygenation, with egln3 showing the largest increase in mRNA level (up to 17-fold) and highest relative mRNA abundance (up to 75% of expressed egln). The protein level of all PHDs was maintained in anoxia and increased upon reoxygenation. We then explored PHD distribution in different brain regions and found PHD immunoreactivity to be associated with axonal branches and showing region-specific changes during anoxia-reoxygenation. Our results support an overall upregulation of egln under prolonged anoxia and PHDs upon reoxygenation in crucian carp, likely aimed at suppressing HIF responses, although regional differences are apparent in such a complex organ as the brain. [ABSTRACT FROM AUTHOR]

Simple Summary: It is almost 50 years since amoeba-associated granulomatosis was first described in goldfish (Carassius auratus), but the aetiologic agent has never been identified. In this study, a new archamoeba species, Endolimax carassius, is characterised as the causative agent of systemic granulomatous disease in goldfish. Phylogenetic analyses determined the new goldfish parasite species as a genotype sister of Endolimax piscium, the causative agent of systemic granulomatous disease in Senegalese sole. The fish genotypes clustered with other available genotypes from mammals in a well-supported Endolimax clade within the Mastigamoebidae. Endolimax is a genus of intestinal amoebae which stands among the least known human protists. Previous studies on amoebic systemic granulomatosis of a marine fish (Solea senegalensis) resulted in the unexpected characterization of a new organism which was related to Endolimax and named E. piscium. The existence of multiple reports of systemic granulomatosis caused presumptively by unidentified amoebae in goldfish lead us to investigate the organism involved in goldfish disease. Analysed goldfish presented small whitish nodules in the kidney, which correspond to chronic granulomatous inflammatory reactions with a ring-layer of amoebae in the periphery. Amoebae were amitochondriate and were located in a parasitophorous vacuole within macrophages, as previous studies on this condition in goldfish and other freshwater fish pointed out. SSU rDNA characterization confirmed a new Endolimax lineage which appears closely related to E. piscium, but the molecular evidence, distinct pathological features and lack of ecological overlapping between the hosts support their assignment to a new species, E. carassius. The results support the existence of a considerable unexplored diversity of Endolimax spp. among fish, and their proper characterization can contribute to an understanding of Archamoebae evolution and pathogenic potential. [ABSTRACT FROM AUTHOR]

The contamination of freshwater environments by pharmaceuticals is a growing problem. Modern healthcare uses nearly 3000 substances, many of which are designed to work at low dosages and act on physiological systems that have been evolutionarily conserved across taxa. Because drugs affect the organisms from different trophic levels, pharmaceutical pollution is likely to disturb species interactions. However, such effects are still only poorly understood. We investigated the impacts of environmentally relevant concentrations of the common drug fluoxetine (Prozac), an increasingly common contaminant of European waters, on predation behavior of crucian carp (Carassius carassius), a common planktivorous European fish, and the somatic growth of its prey, the water flea (Daphnia magna), a widespread planktonic crustacean. We exposed these two organisms to environmentally relevant levels of fluoxetine (360 ng L−1): the fish for 4 weeks and the water fleas for two generations. We tested the growth of the daphnids and the hunting behavior (reaction distance at which fish attacked Daphnia and feeding rate) of the fish under drug contamination. We found that Daphnia exposed to fluoxetine grew larger than a nonexposed cohort. The hunting behavior of C. carassius was altered when they were exposed to the drug; the reaction distance was shorter, and the feeding rate was slower. These effects occurred regardless of Daphnia size and the treatment regime they were subjected to. Our results suggest that contamination of freshwater environments with fluoxetine can disrupt the top‐down ecological control of herbivores by reducing the hunting efficiency of fish and, as a consequence, may lead to increases in cladoceran population numbers. Environ Toxicol Chem 2023;42:385–392. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Simple Summary: Roundup is a widely used herbicide. Its active component, glyphosate, is described as an endocrine disrupter. The effect of this glyphosate-containing herbicide on the reproductive parameters of crucian carp (Carassius carassius) was investigated in this study. The entire pituitary glands and ovarian fragments of crucian carp were incubated in vitro in the medium containing two different concentrations of Roundup (1 and 10 ng/mL). We assessed the final oocyte maturation and ovulation, structural changes in follicles, levels of 17,20β-progesterone, and luteinizing hormone. The mRNA levels of zona radiata (chorion) genes, kisspeptin, and its receptor as well as luteinizing hormone and estrogen receptors were also determined. Obtained results indicate that Roundup may adversely affect oocyte maturation and the quality of crucian carp eggs, suggesting that exposure to this herbicide can lead to reproductive disorders in fish. Roundup, the most popular herbicide in global agriculture, is regarded as an endocrine disruptor causing alterations of important hormones at the hypothalamic−pituitary−gonadal axis as well as impairment of gametogenesis. The whole pituitary glands of crucian carp (Carassius carassius) were incubated for 3 h in the medium containing Roundup (0-control, 1 and 10 ng/mL). The level of luteinizing hormone (LH), and mRNA transcript abundance of kisspeptin (kiss-1) and its receptor (gpr54), were determined. The isolated ovarian fragments were incubated for 24 h in the presence of Roundup and the following effects on reproductive parameters were determined: the final oocyte maturation and ovulation, structural changes in follicles, secretion of 17,20β-progesterone (17,20β-P) as well as mRNA transcript abundance of the luteinizing hormone receptor (lhr), estrogen receptors (erα, erβ1, erβ2), and zona radiata (chorion) proteins (zp2 and zp3). Roundup inhibited final oocyte maturation and decreased the percentage of ovulated eggs, and furthermore, caused structural changes in the ovarian follicular components. There were no significant changes in the measured hormone levels and analyzed genes mRNA transcript abundance. Summing up, obtained results indicate that Roundup may adversely affect oocyte maturation and the quality of eggs, suggesting that exposure to this herbicide can lead to reproductive disorders in fish. [ABSTRACT FROM AUTHOR]

The aim of the investigation was to study the current structure of the parasitic fauna of the gibel carp (Carassius gibelio) population in the Georgian part of Jandari Lake. In total, 423 young gibel carp collected during 2014-2018 years from Jandari Lake have been subject to parasitological examination. The 20.3% (n=86) of examined fish were invaded by 11 species of parasites belonging to 5 taxonomic groups. The dominant taxonomic groups were discovered to be Protozoa and Monogenea. The eight species were registered for the first time in the gibel carp of freshwater reservoirs in Georgia. In general, young fish were more invaded by the monoxenic species of the direct life cycle. None of the revealed parasites were specific to gibel carp. The parasitic fauna of Jandari Lake is relatively poor, though it is comparatively rich and diverse in spring. Trichodina sp. from Protozoa, Ancyrocephalus sp., Dactylogyrus vastator, Gyrodactylus elegans from Monogenea, and Contracaecum sp. from Nematoda were revealed as the species most sensitive to annual changes. The main factor determining the parasite fauna of gibel carp in Lake Jandari is anthropogenic eutrophication, which changes the qualitative and quantitative composition of zooplankton, the main food source of juvenile fish and intermediate hosts of helminths. The difference in invasion indices between female and male gibel carp was insignificant. The synergetic relationship between some parasitic protozoans and monogeneans was marked. [ABSTRACT FROM AUTHOR]

Two fish species from the middle reaches of the Yangtze River, China, were sampled to investigate the occurrence, tissue distribution, age-dependent accumulation and ecological risk assessment of 24 organophosphorus flame retardants (OPFRs). Seventeen OPFRs were detected in tissue samples with a total concentration ranging from not detected (ND) to 1092 ng g−1 dw. Cl-OPFRs were predominant in all tissues (mean: 145 ng g−1 dw, median: 72.9 ng g−1 dw) and the concentrations of OPFRs in brain were the greatest (crucian carp: 525 ng g−1 dw, silver carp: 56.0 ng g−1 dw) compared with the other three organs (e.g., liver, muscle and gonad). Furthermore, the total concentrations of OPFRs in crucian carp tissues were significantly greater than those in silver carp (P < 0.01). Age-dependent accumulation of OPFRs was observed in the two fish species, but the accumulation profiles in the two fish species were different. Ecological risk assessment demonstrated that both fish species were at medium to high risk, and TDCIPP was a main contributor (>50%). [Display omitted] • OPFRs were widely detected in fish from the Yangtze River. • Brain was a main accumulation organ of OPFRs. • OPFRs caused age-dependent bioaccumulations in wild fish. [ABSTRACT FROM AUTHOR]

Piscicola geometra and Argulus foliaceus are two haematophagous parasites collected through sporadic seasonal fishing carried out in the spring of 2009 and 2012, in the study area represented by ten reservoirs from the Oltenia Plain. These parasites are the most common in these lakes and affect a wide range of host fish, both in natural and artificial pools. In the spring of 2009, we sampled 42 specimens of fish and the etiological agent was the crustacean Argulus foliaceus, which was reported only for two fish species: Perca fluviatilis and Cyprinus carpio. In 2012, 47 fish specimens were captured belonging to the species – Scardinius erythrophthalmus, Lepomis gibbosus, Abramis brama, Carassius gibelio, Perca fluviatilis. The Piscicola geometra parasite was identified only in Carassius gibelio. It has been found out that an important common factor in causing these parasites is water temperature; consequently, the invasion decreases when water temperature increases. Although these parasitosis evolved subclinically without mortality, prevention and treatment measures were proposed to prevent their spreading. Thus, wood panels were installed into the water so that the Argulus foliaceus parasite could lay its eggs and, as measures of combat, the literature recommends the treatment with Trichlorfon at a dose of 1g/6m³ of water. The destruction of the macrophyte vegetation and prevention of the penetration of fish species from one basin to another, given that they communicate via spillways, are some prophylactic measures to prevent fish infestation. [ABSTRACT FROM AUTHOR]

The invasion success of gibel carp (Carassius gibelio) depends on demographic and competitive traits. The major biological trait responsible for the invasiveness of C. gibelio is the mode of reproduction. Apart from sexual reproduction, which is typical in fish, C. gibelio is a unique cyprinid species able to reproduce through asexual gynogenesis, which is also known as sperm-dependent parthenogenesis, observed in allfemale populations. Though the sexual and asexual forms of C. gibelio co-exist widely in natural habitats, the gynogenetic form has the capacity to modulate the range of effective ecological niches, which may facilitate the process of invasion. In this paper, we reviewed current knowledge of the sexual and gynogenetic forms of gibel carp along with their physiological advantages, immunological traits, and ability to withstand different environmental conditions. As parasitic infection may directly alter the immunology of hosts, and also indirectly alter their investment in reproduction, we provide some insights into the role of parasites as one of the potential drivers facilitating the coexistence of asexual and sexual forms. We highlight evidence that gibel carp have been identified as a serious threat to native species; hence, its impact on the ecosystem is also discussed. [ABSTRACT FROM AUTHOR]

The invasion success of gibel carp (Carassius gibelio) depends on demographic and competitive traits. The major biological trait responsible for the invasiveness of C. gibelio is the mode of reproduction. Apart from sexual reproduction, which is typical in fish, C. gibelio is a unique cyprinid species able to reproduce through asexual gynogenesis, which is also known as sperm-dependent parthenogenesis, observed in allfemale populations. Though the sexual and asexual forms of C. gibelio co-exist widely in natural habitats, the gynogenetic form has the capacity to modulate the range of effective ecological niches, which may facilitate the process of invasion. In this paper, we reviewed current knowledge of the sexual and gynogenetic forms of gibel carp along with their physiological advantages, immunological traits, and ability to withstand different environmental conditions. As parasitic infection may directly alter the immunology of hosts, and also indirectly alter their investment in reproduction, we provide some insights into the role of parasites as one of the potential drivers facilitating the coexistence of asexual and sexual forms. We highlight evidence that gibel carp have been identified as a serious threat to native species; hence, its impact on the ecosystem is also discussed. [ABSTRACT FROM AUTHOR]

This is the first study on the diet of the great cormorant wintering in Algeria. It is carried out in Beni Haroun, the largest dam lake in the country, in the North-East of Algeria. The trophic menu of Phalacrocorax carbo in this lake is based on four species of fish: Abramis brama, Carassius carassius, Barbus barbus, and Cyprinus carpio. However, Barbus barbus and Carassius carassius represent the two most important species in the great cormorant's diet. The total consumed biomass is 155,364.18 g, and the average biomass contained in each pellet varies between 330.7 and 2,953 g. The biomass of consumed fish varies between 36.89 g and 2,501 g. The size of the caught fish records values between 13.7 cm and 52.49 cm. The number of consumed fish per pellet varies between 1 and 9. The results show that the great cormorant of Beni-Haroun dam lake consumes between 573 g and 2,353.3 g of fish per day and between 49.8 t and 185 t tonnes each month. However, the highest value is recorded in January (between 81.5 and 300.5 t). The great cormorant of Beni-Haroun dam lake could have a significant impact on continental and recreational fishing at this site. [ABSTRACT FROM AUTHOR]

While the fish gut microbiome composition is important to fish health, studies of the gut microbiome of fish lag behind those of terrestrial vertebrates. Whether the microbial communities in an aquatic habitat affect the gut microbiomes of resident fish is unclear. This study investigates and compares the composition of bacterial communities in the gut of crucian carp and humpback and in the water of their habitat using high-throughput sequencing of two hypervariable regions (V3 and V4) of the 16S rRNA gene. We identified 2058 operational taxonomic units (OTUs) in the humpback, 2551 OTUs in crucian carp, and 1760 OTUs in their habitat water. 218 OTUs were common to all three bacterial communities. Linear discriminant analysis revealed multiple species that differed significantly in abundance between the communities. This study aims to improve our understanding of the influence of the aquatic habitat on fish–microbe relationships. [ABSTRACT FROM AUTHOR]

Rahnella aquatilis is widely recognized as an opportunistic pathogen of fish, but molecular detection and diagnostic techniques for it remain to be developed. In a previous study, we isolated the pathogenic R. aquatilis strain KCL-5 from diseased crucian carp Carassius auratus and identified it as a new fish pathogen causing enteritis and septicemia. Here, we describe novel real-time quantitative PCR (RT-qPCR) and loop-mediated isothermal amplification (LAMP) assays for the rapid and sensitive detection of R. aquatilis. Specific RT-qPCR and LAMP primers were developed for the outer membrane protein (OmpA) gene. Their reaction systems were optimized using the recombinant plasmid pMD18-T containing the OmpA gene and their specificities were confirmed using various bacterial fish pathogens including Aeromonas hydrophila , A. veronii , A. allosaccharophila , Yersinia ruckeri , Vibrio vulnificus , V. alfacsensis, Providencia rettgeri , and R. aquatilis. The sensitivities of the RT-qPCR and LAMP assays were further evaluated using serial dilutions of the positive recombinant plasmid pMD18-T/ OmpA. Both the RT-qPCR and LAMP assays were able to reliably detect the presence of R. aquatilis with high accuracy and a specificity of 100%. The lowest detection limits of the RT-qPCR and LAMP assays were 2.3 copies/μL and 2.3 × 101 copies/μL, respectively. To the best of our knowledge, this is the first report of RT-qPCR and LAMP methods for R. aquatilis detection, and provides a means for its rapid detection and diagnosis in fish. • Development of qPCR assay for detection of R. aquatilis in fish. • Establishment of LAMP assay for detection of R. aquatilis with MDL of 2.3 × 101 copies/μL. • The qPCR and LAMP methods were firstly established for the rapid detection of R. aquatilis. • Analysis of bacterial loads was performed for R. aquatilis infection in fish. [ABSTRACT FROM AUTHOR]

Polyploid species represent a challenge for both cytogenetic and genomic studies due to their high chromosome numbers and the morphological similarity between their paralogous chromosomes. This paper describes the use of low-coverage high-throughput sequencing to identify the 14 most abundant tandemly arranged repetitive elements in the paleotetraploid genome of the crucian carp (Carassius carassius, 2n = 100). These repetitive elements were then used for molecular cytogenetic studies of a closely related functionally triploid form of the Prussian carp (Carassius gibelio, 3n = 150 + Bs) and a relatively distant diploid species, the tench (Tinca tinca, 2n = 48). According to their distribution on the chromosomes of the 3 aforementioned species, the repetitive elements here identified can be divided into 5 groups: (1) those specific to a single genomic locus in both Carassius species, despite the recent carp-specific genome duplication; (2) those located in a single genomic locus of T. tinca, but amplified in one or both Carassius species; (3) those massively amplified in the B chromosomes of C. gibelio; (4) those located in a single locus in C. gibelio, but amplified in many blocks in C. carassius; and (5) those located in multiple pericentromeric loci in both Carassius species. Our data indicate that some of the repetitive elements are highly conserved in cyprinoid species and may serve as good cytogenetic and genomic markers for discriminating paralogous chromosomes, while others are evolutionarily recent, and their amplification may be related to the last whole-genome duplication event. [ABSTRACT FROM AUTHOR]

The northern section of the Caspian Sea and lower reaches of the Zhaiyk (Ural) River is an important fishery for Kazakhstan. In the present study, a total of 1597 individuals of ten fish species were analysed. The fish were caught over three years, from 2018 to 2020. For each species studied – Abramis brama, Alosa saposchnikowii, Atherina boyeri caspia, Carassius gibelio, Chelon auratus, Cyprinus carpio, Leuciscus aspius, Rutilus caspius, Sander marinus and Sander volgensis – between 100 and 200 individuals were examined. A series of generalized linear models (GLMs) were used to examine the association between individual parasite intensity of infection and the Fulton index, age, year the fish was captured, where the fish was captured (northern Caspian or Zhaiyk River) and sex. For each GLM, the best-fitting probability distribution was used –either Poisson, zero-inflated Poisson, negative binomial or zero-inflated negative binomial. For some fish/parasite species, an increased Fulton index was associated with higher intensities of parasite infection, whilst, for others, the Fulton index decreased with the intensity of parasite infection. This was also true of age-related intensity of infection, with some parasites having an increased intensity of infection with age whilst others had a decreased intensity of infection with age. There was also some evidence of variation in intensity of parasite infection between different years when the fish were caught. For some species of fish that are endemic to both the fresh waters of the Zhaiyk River and the low-saline waters of the northern Caspian, there were variations in intensity of parasite infection between the two environments. The best-fitting probability distribution also gave some information about the dynamics of infection. No fish species had a Poisson distribution of parasites, which is consistent with an entirely random infection process, with all fish being potentially exposed. For some parasites, the distribution was a zero-inflated Poisson, which is consistent with either the fish being exposed to parasite infection or not; and, if exposed, infection was a random process. Other parasites had a negative binomial distribution, consistent with the entire fish population being exposed, but the infection process was clumped or there were variations in the susceptibility of infection between fish. Finally, some of the parasites had a zero-inflated negative binomial distribution, which can be interpreted as part of the fish population not being exposed and the remainder of the population being exposed to a clumped or aggregated infection process and/or a variation in individual susceptibility to infection. [ABSTRACT FROM AUTHOR]

Tactile reception in cyprinid fish (silver crucian carp Carassius auratus gibelio and common carp Cyprinus carpio) was investigated by noninvasive recording of action potentials from the head skin in response to rhythmic tactile stimulation. Responses shaped as electric potentials following synchronously with changes in the pressure force on the skin were recorded using chloro-silver electrodes. It was shown that fish, like all terrestrial vertebrates, have phasic and tonic tactile receptors. Three main types of tactile responses were distinguished: (1) tonic responses as potential fluctuations repeating the dynamics of the tactile stimulus, (2) phasic responses as on-, off-, and on-off potentials, and (3) slow deflections from the resting potential. Compound responses comprising simultaneously different types of responses were also recorded. The response latency averaging 6.1 ms for tonic and 4.4 ms for phasic responses was clearly independent of the stimulus direction (switch-on, switch-off). The threshold level of tactile sensitivity in the perioral and gular head areas was 0.05–0.2 g/mm2. Tactile receptors on the silver crucian carp and common carp heads exhibited zonal distribution patterns, with sensory areas differing in their tactile sensitivity. Most sensitive areas were on the upper and lower lips, in the perilabial skin and the gular area on the ventral side of the head. Less sensitive areas were situated rostrally and ventrally to the eyeball. The areas situated dorsally and caudally to the eyeball proved to be insensitive to the applied tactile stimulation. In all sensory areas on the fish head, most intense responses were evoked by sliding tactile stimuli. The distribution specificity of tactile sensory areas meets their functional significance for fish feeding behavior. [ABSTRACT FROM AUTHOR]

Contracaecum rudolphii (s. l.) is a complex of sibling species of anisakid nematodes having the fish-eating birds belonging to the Family Phalacrocoracidae as final hosts. The great cormorant Phalacrocorax carbo sinensis is parasitized by C. rudolphii A and C. rudolphii B. Adults and L4 specimens of C. rudolphii (s. l.) (N = 3282) were collected in cormorants from brackish and freshwater ecosystems of Central Italy. Third-stage larvae of Contracaecum (N = 882) were obtained from the fish species Dicentrarchus labrax, Anguilla anguilla, Aphanius fasciatus, Atherina boyeri, Leuciscus cephalus, Barbus barbus, and Carassius carassius captured in the same geographical areas of cormorants' standings. Contracaecum rudolphii A and C. rudolphii B were identified by a multilocus genetic approach: allozymes, sequences analysis of the mtDNA cox2, and ITS region of rDNA gene loci. Differential distribution of the two parasite species was observed in different aquatic environments. Contracaecum rudolphii B outnumbered C. rudolphii A in wintering cormorants from freshwater ecosystems; the opposite trend was found in cormorants from brackish water. Analogously, C. rudolphii A larvae were more prevalent in brackish water fish, while C. rudolphii B larvae were found infecting only freshwater fish. The findings seem to confirm that C. rudolphii A and C. rudolphii B would have a life-cycle adapted to brackish and freshwater environments, respectively. A differential feeding behavior of wintering cormorants, the ecology of the infected fish species, and abiotic factors related to early stages of the parasites are supposed to maintain the distinctiveness of the two parasite species' life cycles in the two different aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Distant hybridization occurs widely in fishes and is a useful strategy to produce different ploidy offsprings. In this study, we obtained androgenetic blunt snout bream (2n = 48, ADBSB), triploid hybrids (3n = 124, 3nJB) and tetraploid hybrids (4n = 148, 4nJB) from the hybridization of two species from different subfamilies: Carassius cuvieri (♀, 2n = 100, JCC) and Megalobrama amblycephala (♂, 2n = 48, BSB). The ploidy levels of ADBSB, 3nJB and 4nJB hybrids were confirmed by counting chromosomal numbers, forming chromosomal karyotype, and measuring DNA content. In the phenotypes and reproductive traits, 3nJB and 4nJB exhibited significantly divergences from JCC and BSB, but ADBSB took after BSB. Fluorescence in situ hybridization (FISH) and 5S rDNA analyses revealed that the genetic traits of the offsprings compared with those of their parents. This is the first report on the coexistence in vertebrates of viable androgenetic, triploid and tetraploid hybrids being produced by crossing JCC and BSB. The formation of the different ploidy offspring is great significance in both evolution and fish genetic breeding and it also provides a good model for studying the genomic variation in the first generation of interspecific hybrids. [ABSTRACT FROM AUTHOR]

Crucian carp (Carassius carassius) survive without oxygen for several months, but it is unknown whether they are able to protect themselves from cell death normally caused by the absence, and particularly return, of oxygen. Here, we quantified cell death in brain tissue from crucian carp exposed to anoxia and re-oxygenation using the terminal deoxy-nucleotidyl transferase dUTP nick-end labelling (TUNEL) assay, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen (PCNA) as well as PCNA mRNA expression. We also measured mRNA and protein expression of the apoptosis executer protease caspase 3, in laboratory fish exposed to anoxia and re-oxygenation and fish exposed to seasonal anoxia and reoxygenation in their natural habitat over the year. Finally, a behavioural experiment was used to assess the ability to learn and remember how to navigate in a maze to find food, before and after exposure to anoxia and re-oxygenation. The number of TUNEL-positive cells in the telencephalon increased after 1 day of re-oxygenation following 7 days of anoxia, indicating increased cell death. However, therewere no consistent changes in whole-brain expression of caspase 3 in either laboratory-exposed or naturally exposed fish, indicating that cell death might occur via caspase-independent pathways or necrosis. Re-oxygenated crucian carp appeared to have lost the memory of how to navigate in a maze (learnt prior to anoxia exposure), while the ability to learn remained intact. PCNA mRNA was elevated after re-oxygenation, indicating increased neurogenesis. We conclude that anoxia tolerance involves not only protection from damage but also repair after re-oxygenation. [ABSTRACT FROM AUTHOR]

Mobilization of glycogen stores was examined in the anoxic crucian carp ( Carassius carassius Linnaeus). Winter-acclimatized fish were exposed to anoxia for 1, 3, or 6 weeks at 2 °C, and changes in the size of glycogen deposits were followed. After 1 week of anoxia, a major part of the glycogen stores was mobilized in liver (79.5 %) and heart (75.6 %), and large decreases occurred in gill (46.7 %) and muscle (45.1 %). Brain was an exception in that its glycogen content remained unchanged. The amount of glycogen degraded during the first anoxic week was sufficient for the anaerobic ethanol production for more than 6 weeks of anoxia. After 3 and 6 weeks of anoxia, there was little further degradation of glycogen in other tissues except the brain where the stores were reduced by 30.1 and 49.9 % after 3 and 6 weeks of anoxia, respectively. One week of normoxic recovery following the 6-week anoxia was associated with a complete replenishment of the brain glycogen and partial recovery of liver, heart, and gill glycogen stores. Notably, the resynthesis of glycogen occurred at the expense of the existing energy reserves of the body in fasting fish. These findings indicate that in crucian carp, glycogen stores are quickly mobilized after the onset of anoxia, with the exception of the brain whose glycogen stores may be saved for putative emergency situations. [ABSTRACT FROM AUTHOR]

Being a nonessential element, lead (Pb2+) can be toxic in trace amounts for freshwater fish. The present study was designed to evaluate the induction of oxidative stress, tissue-specific antioxidant response, acetyl cholinesterase (AchE) activities, and biochemical content of muscle in Crucian carp (Carassius auratus gibelio) after 96 h of acute exposure and 21 days of chronic exposure to various environmental concentrations (5, 10, and 30 µg L-1) of waterborne Pb2+. The results indicated that exposure to 10 and 30 µg L-1 Pb2+ significantly altered the activities of catalase, superoxide dismutase, and glutathione peroxidase in different tissues, while malondialdehyde content increased in a time- and concentration-dependent manner. Inhibition of AchE after chronic exposure also confirmed a generalized neurotoxic stress. Fourier transform infrared spectroscopy revealed mild changes in the structure of proteins and lipids, whereas the integrated biomarker response indices signified the liver, kidneys, and gills as the responsive organs to environmental Pb2+ exposure. [ABSTRACT FROM AUTHOR]

Over the past few decades, endosulfan, one of the polychlorinated pesticides still in use, has received considerable attention of a number of international regulations and restriction action plans worldwide. This study aimed to evaluate the cytogenetic effects of endosulfan using robust genotoxicity assays, along with the oxidative stress pathways in order to understand biochemical mechanism, in Carassius carassius L. The LC 50–96 h (95% confidence limits) value of endosulfan was 0.070 (0.046–0.093) ppm; and on its basis three test concentrations (sub-lethal I: 0.052, II: 0.035 and III: 0.017 ppm) were selected for 35 d in vivo exposure. The mean concentration of endosulfan in aquaria was always constant, when analyzed by dispersive liquid–liquid micro extraction (DLLME) followed by GC–MS. Autopsy was done on days 1, 2, 3, 4, 7, 14, 21, 28 and 35 of endosulfan exposure; the micronucleus formation (MN), authenticated by scanning electron microscopy, and chromosomal aberrations (CA), were induced significantly ( p < 0.05) in all the treated groups, including positive control cyclophosphamide (4 ppm), when compared to negative control. Similarly lipid peroxidation (LPO) was induced significantly with the maximal at higher concentration (SL-I) on 4th day (722.45%; p < 0.01). Antioxidant biomarkers like glutathione reduced, superoxide dismutase and catalase also fluctuated significantly ( p < 0.01) in all treatment groups. Collective findings demonstrated that genotoxic effects were invariably accompanied and correlated with increased oxidative stress and disturbance of antioxidant enzymes; and the MN and CA assays are useful tools in determining potential genotoxicity of aquatic xenobiotics and might be appropriate as a part of monitoring program. [ABSTRACT FROM AUTHOR]

Oxidative stress and antioxidant responses of crucian carp, upon chronic exposure to endosulfan, were evaluatedin vivo. The lethal concentration (LC50–96 h) was 70 μg L−1; on its basis, the fish were exposed to endosulfan at 20, 35, and 50 μg L−1and autopsy was done on days 1, 2, 3, 4, 7, 14, 21, 28, and 35. Lipid peroxidation was induced in a concentration-dependent manner, being highest at 50 μg L−1(3/4 LC50–96 h, sub-lethal concentration-I, SL-I) on day 4 (720% versus control), followed in its extent (490%) at 30 μg L−1(1/2 LC50–96 h, sub-lethal concentration-II, SL-II) on day 7 and lowest (260%) at 10 μg L−1(1/4 LC50–96 h, sub-lethal concentration-III, SL-III) on day 14. Glutathione showed a concentration- and time-dependent elevation in the initial phase, with highest level on day 4 (180%) at SL-I, but showed significant reduction in all test concentrations from day 21 of post-exposure. Superoxide dismutase was decreased significantly throughout the study, with highest reduction (63%) on day 4 at SL-I; catalase increased in all test concentrations up to day 14 but showed a significant decrease from the day 28 of post-exposure. The potential role of these parameters as indicators of pesticide pollution in aquatic systems is discussed. [ABSTRACT FROM PUBLISHER]

Silver crucian carp Carassius auratus langsdorfii comprises a diploid-polyploid complex in wild Japanese populations. Bisexually reproducing diploids are sympatrically distributed with gynogenetically developing triploids and tetraploids. Triploid and tetraploid males are very rare among Japanese silver crucian carp due to their gynogenetic reproduction. We examined the genetic characteristics of progeny that arose in a tank by natural spawning of a tetraploid silver crucian carp pair. The ploidy status of 120 samples randomly collected from these progeny was determined to be tetraploid by DNA content flow cytometry. DNA fingerprints from a random amplified polymorphic DNA assay indicated that almost all the progeny examined had genotypes identical to the maternal tetraploid female with no paternally derived fragments. Selected specimens’ cytogenetic analyses revealed that the progeny examined had tetraploid chromosome numbers, categorized into 40 metacentric, 80 submetacentric, and 80 subtelocentric or telocentric chromosomes, which were arranged into quartets and six supernumerary microchromosomes. Fluorescence in situ hybridization signals were detected in four homologous chromosomes in all analyzed metaphases prepared from diploid goldfish specimens. Contrary, tetraploid silver crucian carp gave eight rDNA signals. These results suggest that gynogenetic development in eggs spawned by tetraploid females should be triggered by tetraploid males’ homospecific sperm. [ABSTRACT FROM AUTHOR]

Abstract: The present study investigates the effect of silver nanoparticles on olfaction in Crucian carp (Carassius carassius) and Eurasian perch (Perca fluviatilis). The electro-olfactogram (EOG) signal was recorded by stimulating the olfactory epithelium with pulses of the odorant l-alanine during the pre-exposure, silver exposure and recovery periods, respectively. The nanosilver suspension concentrations applied were 0.00, 0.45 and 45μgL−1, respectively. Secondly, to compare the toxicity of silver nanoparticles with silver ions, perch were exposed to ionic silver. During exposure to nanosilver suspension, the olfactory epithelium rapidly hyperpolarized, which was not found after exposure to silver ion solution. Exposure to 0.45μgL−1 nanosilver suspension led to enhanced EOG responses, whereas exposure to 45μgL−1 silver nanoparticle suspension and silver ion solution resulted in suppressed EOG signals. The EOG signals partly recovered in silver-free water. The silver nanoparticle olfactory toxicity is believed to be a combination of silver particles and released silver ions. [Copyright &y& Elsevier]

Abstract: In general, copper is primarily an osmoregulatory toxicant to fish and Cu toxicity is thought to be related to the rate of sodium loss. Looking at a previous research it is striking that gibel carp, Carassius auratus gibelio, do not seem so susceptible to the first ionoregulatory shock phase of Cu exposure, but rather build up physiological disturbances slowly until mortality occurs. Since it was noted that gibel carp experience severe hypoxia under Cu exposure, we hypothesised that, besides the Na loss, the slow depletion of liver glycogen stores contributed equally to the collapse of physiological integrity. It is clear from our results that glycogen stores are being depleted in Cu exposed fish and that dead fish suffered more extensive glycogen losses compared to surviving fish, with liver glycogen levels of 125±8mg g− 1 in dead fish compared to 230±13mg g− 1 in surviving fish. However, changes in liver glycogen did not contribute significantly to mortality, while changes in whole body sodium and the rate of sodium loss did. Whole body Na levels dropped from 1111±48μg g− 1 dry weight in control fish to 850±54μg g− 1 in surviving fish and to 607±24μg g−1 in fish that had died resulting in Na loss rates of 1.25±0.22μg g−1 h−1 and 3.39±0.19μg g−1 h−1 in surviving and dead fish respectively. Our results support the finding that the rate of Na loss largely determines Cu toxicity in fish, even in resistant species. [Copyright &y& Elsevier]

Abstract: The full-length mRNA of the high mobility group protein 1 coding gene (HMG1) was obtained by RACE-PCR from red crucian carp (Carassius auratus red var.), blunt snout bream (Megalobrama amblycephala), and their triploid and tetraploid progeny. The sequence contained an open reading frame of 579 nucleotides coding for 193 amino acids. The nucleotide identity of HMG1 was higher between the tetraploid hybrid and the maternal red crucian carp (99%) than between the tetraploid hybrid and the paternal blunt snout bream (97%). The nucleotide identity between the triploid hybrids and each parent (95%) was lower than that between the parents (98%). The protein identity between the tetraploid hybrid and each parent (100%) was higher than that between the triploid hybrid and each parent (97%). Our results suggest that interspecific hybridization generates a shock to the HMG1 gene in triploid hybrids, causing divergence of nucleotides. The HMG1 protein of the tetraploid hybrids was consistent with that of its parents, which reduced the barrier of cross incompatibility between alleles, providing the basis for the bisexual fertile tetraploid hybrids forming a new polyploid species in nature. The secondary and tertiary structures of the HMG1 protein contain eight helices, three switches, two DNA-binding domains in the N-terminus, and a long acidic tail in the C-terminus. Together, these data suggest that the HMG1 protein plays a role of protein–DNA interactions, facilitating various DNA-dependent activities in the nucleus. We also investigated the phylogeny of fish, amphibian, reptilian, bird, and mammalian HMG1 proteins. Our results suggest that HMG1 is an ancestral protein that has been highly conserved. These data provide clues as to how interspecific hybridization may form polyploid hybrids. [Copyright &y& Elsevier]

Abstract: Circulatory responses of crucian carp injected intraperitoneally with extracted microcystins (MCs) were studied at sublethal and lethal doses (150 and 600μg MC kg−1 body mass, respectively). Mean arterial blood pressure (MAP), heart rate, hematocrit (Hct), red blood cell (RBC) counts, and circulating blood volume (BV) were assayed at 0, 1, 3, 12, 24, and 48h post-toxin administration. MAP decreased significantly in a dose-dependent manner over time. Within the 48-h test period, the lethal dose as well as the sublethal dose resulted in a steady decline of MAP without recovery. Heart rate significantly increased within 24h post-injection as blood pressure significantly dropped, then showed a terminal decline to the control level. The dose-dependent decreases in BV and Hct were directly related to the drop in MAP. Intraperitoneal injection of a lethal dose of MCs led to hepatic and gill hemorrhage. Consequently, crucian carp given MCs suffered from hypovolemic hypotensive shock. [Copyright &y& Elsevier]

The endocrine response of crucian carp injected intraperitoneally with extracted microcystins (MC) was investigated in this study. Fish were injected intraperitoneally either with 0.75% NaCl (control) and Microcystis extract corresponding to 150 and 600μg microcystins per kg body weight. The plasma levels of triiodothyronine (T3), thyroxine (T4), free triiodothyronine (FT3), free thyroxine (FT4), and cortisol were determined at 0, 1, 3, 12, 24, and 48h post-administration of MC-containing extract. Treated fish displayed abnormal behaviors, such as a startle response and disoriented swimming, as well as changes in ventilation rates. Plasma cortisol concentrations of fish in both dose groups significantly increased after administration of extracted MC and remained high throughout the experiment, which suggested that MC elicited a stress response in treated fish. The profiles of cortisol changes in treated fish appeared to be dose dependent, indicating that fish in the high dose group experienced greater MC-induced disturbance. Mortality occurred after 12h in the high dose group. Plasma levels of T4, T3, FT4, and FT3 did not vary significantly between the control fish. In contrast to this, fish exposed to MC-containing extract showed significant declines in T3, FT4, and FT3 levels in a dose-dependent manner throughout the experiment. Plasma T4 levels, however, did not vary significantly in the low dose group, whereas they decreased significantly at 48h post injection in the high dose group. This study demonstrates that administration of microcystins-containing extract causes a stress response and reduces the plasma levels of thyroid hormones in crucian carp. These results illustrate that microcystins exerted potent effects on the endocrine system of crucian carp, through activating their hypothalamus-pituitary- interrenal axis and disturbing thyroid function. [Copyright &y& Elsevier]

Simple Summary: Rapid urbanization and industrialization has resulted in substantial contamination of various ecosystems, especially aquatic environments with heavy metals. Heavy metals are classified as either essential (iron, zinc, or copper) or non-essential (cadmium, lead, or mercury) for organisms. Cadmium is a toxic, cancerogenic, and mutagenic metal, occurring as anthropogenic contamination in aquatic environments. The level of cadmium uptake in animals depends on the rate at which they are accumulated and eliminated. Exceeding the permissible levels of cadmium in fish muscle may pose risks for human health in the case of contaminated fish consumption. The aim of the present study was to evaluate the influence of melatonin on cadmium accumulation and elimination in fish muscle. Prussian carps were exposed to two doses of cadmium in the presence or without the melatonin implants. This is the first study to report that melatonin co-administration can effectively protect fish from the accumulation of cadmium in muscle tissue, improve the accumulated cadmium depuration from muscle, and prevent disturbance of the concentration of essential metals in fish body. The aim of this study was to investigate the bioaccumulation of cadmium in the muscle tissue of Prussian carp during 7 and 13 weeks of exposure to different concentrations of this metal in water (0.4 and 4.0 mg/L), and the depuration of cadmium from muscle during the following 6-week depuration period in the presence of melatonin implants. Furthermore, the relationship between cadmium accumulation and the levels of essential bioelements (copper, zinc, iron) in muscle was evaluated, as well as the bioconcentration factor of cadmium. Heavy metal concentration was determined using atomic absorption spectrometry. Cadmium accumulation in fish muscle increased with the duration of exposure. Cd concentrations exceeded the permissible levels for human consumption in groups exposed to the higher concentration of this metal. Moreover, a significant increase of Zn and Fe levels in the muscle was observed. In the fish that received melatonin implants and were exposed to Cd, its level in the muscle was significantly lower. The depuration of accumulated cadmium depended mainly on the duration of the elimination period. This is the first study to report that melatonin co-administration can effectively protect the fish from the accumulation of cadmium in muscle tissue and changes in trace metal levels. [ABSTRACT FROM AUTHOR]

Abstract: Side population (SP) cells, characterized by a specific Hoechst dye efflux pattern by flow cytometry were isolated from kidney hematopoietic tissues of ginbuna carp (Carassius auratus langsdorfii). The hematopoietic activity of SP cells was evaluated by the repopulation and multilineage potential using an in vivo transplant system of ginbuna carp (donor) and ginbuna–goldfish hybrids (recipient). In a flow cytometric (FCM) analysis, a small and distinct population of ginbuna SP cells displayed efficient effluxes of Hoechst 33342 was virtually identical to the efflux observed in mammalian SP cells. The frequency of the ginbuna SP cells was 0.17±0.08% in the kidney hematopoietic cells. Morphologically, SP cells were composed of small lymphocyte-like cells having a thin-layered cytoplasm and a round nucleus. These characteristics of ginbuna SP cells were very similar to those of mammalian SP cells. Since cyprinid fish have two hematopoietic sites, the head (anterior) and body (posterior, trunk) kidney, the distribution of SP cells were examined in head and body kidney. The proportion of SP cells were 0.33±0.15% in the body kidney, but near 0% in the head kidney. After the ginbuna SP cells were injected into ginbuna–goldfish hybrids, the major types of donor-derived cells (erythrocytes, neutrophils, basophils, monocytes, thrombocytes, T and B lymphocytes) were detected in the recipient blood over a long period (9–16 months post-transplantation). In ginbuna carp, SP cells reside in the body kidney and contain primitive populations of hematopoietic stem cells (HSCs). [Copyright &y& Elsevier]

Abstract: Laboratory studies in domesticated goldfish (Carassius auratus) show that, during the preovulatory luteinizing hormone (LH) surge, females release a complex steroidal pheromone that induces in males a rapid increase of plasma LH, which in turn increases strippable milt (sperm and seminal fluid) prior to ovulation and spawning. The objective of this study was to determine if the same phenomenon occurs in a wild congener, the crucian carp (Carassius carassius), under field conditions where fish are held in natural waters under ambient temperature and photoperiod. During the spawning season in June 2003, crucian carp were trapped in a small pond near Uppsala, Sweden, and held separately by sex in floating net pens. Addition of untreated females to male pens did not change male LH concentrations or milt volume during the 17h sampling period. In contrast, addition of females injected with Ovaprim™ (to induce an LH surge and ovulation) increased male LH concentrations at all sample times (5, 9, 13, and 17h) following female addition and increased milt volumes at all but the first (5h) sample time. Similar increases in male LH and milt that also occurred when untreated females ovulated spontaneously after addition to male pens suggest it is female ovulatory condition, rather than injection of ovaprim per se, that induced male LH and milt responses. Males also increased LH and milt 9h after addition of females injected with the goldfish pheromonal steroid 4-pregnen-17,20β-diol-3-one (17,20βP), suggesting that similar responses to ovaprim-injected females were due, at least in part, to release of preovulatory pheromonal steroid(s). The clear and consistent effects of ovulatory females on male LH and milt, and the fact that crucian carp adapted well to confinement, ovulated spontaneously, and exhibited apparently normal spawning behavior, all suggest that this species can serve as a useful cyprinid model to study reproductive processes in natural conditions. [Copyright &y& Elsevier]

Abstract: Polychlorinated biphenyls (PCBs) levels in crucian carp were determined at 20 locations along four major river systems, several small-scale rivers and a wetland in Korea. Twenty-eight congeners, ranging from tri- to hepta-CBs were detected. A gas chromatograph with a mass selective detector was used to quantify the individual PCB congeners. The objectives of this study were to investigate the levels of contamination of PCBs in freshwater fish and to observe the pattern of their distribution. The sampling locations were chosen among 31 sampling sites that are currently used as environmental residue checkpoints by the Korean Ministry of Environment. Concentrations of individual congeners ranged from not detectable (n.d.) to 0.75ngg−1 on a wet weight basis. The total concentrations of PCBs at each site ranged from n.d. to 5.41ngg−1 of wet weight. The most heavily contaminated site was the Nakdong estuary located near the Shinpyung-Janglim factory district. The PCB 153 and 138 were the principal congeners and penta- and hexa-chlorinated biphenyls comprised the main congener groups. [Copyright &y& Elsevier]

To study the projection of a special type of sensory neuron called crypt cells in the olfactory system in crucian carp, Carassius carassius, we applied the neural tracer 1,1-dilinoleyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI) in the olfactory bulb (OB). Small crystals of DiI were applied in a small area at the synaptic region at the ventral part of the OB, where a population of secondary neurons specific for sex pheromones has been identified. In those samples (4 out of 24) where only axons in the lateral bundle of the medial olfactory tract were stained, the majority (50–66%) of olfactory sensory neurons stained were crypt cells situated in the peripheral layer of the olfactory epithelium. Because this bundle of the tract mediates reproductive behavior, it is conceivable that crypt cells express olfactory receptors for sex pheromones. [ABSTRACT FROM AUTHOR]

Simple Summary: The parasites of the Anisakidae family infest mainly marine mammals; however, they have the ability to infest paratenic hosts such as mollusks, small crustaceans and fish. The consumption of meat from animals of aquatic origin favors the acquisition of the disease known as Anisakiasis or Anisakidosis, depending on the species of the infecting parasite. Currently, the identification of the members of this family is carried out through the use of molecular tests, which brings about the generation of new information. The purpose of this review was to identify the genus and species of the Anisakidae family by reviewing scientific papers that used molecular tests to confirm the genus and species. The adaptability of the Anisakidae family to multiple hosts and environmental conditions allows it to have a worldwide distribution. As it is a zoonotic agent and causes non-specific clinical symptoms, it is important to know about the different members of the Anisakidae family, as well as the hosts where they have been collected. Nematodes of the Anisakidae family have the ability to infest a wide variety of aquatic hosts during the development of their larval stages, mainly marine mammals, aquatic birds, such as pelicans, and freshwater fish, such crucian carp, these being the hosts where the life cycle is completed. The participation of intermediate hosts such as cephalopods, shrimp, crustaceans and marine fish, is an important part of this cycle. Due to morphological changes and updates to the genetic information of the different members of the family, the purpose of this review was to carry out a bibliographic search of the genus and species of the Anisakidae family identified by molecular tests, as well as the geographical area in which they were collected. The Anisakidae family is made up of eight different parasitic genera and 46 different species. Those of clinical importance to human health are highlighted: Anisakis pegreffi, A. simplexsensu stricto, Contracaecumosculatum, Pseudoterranova azarazi, P. cattani, P. decipiens and P. krabbei. The geographical distribution of these genera and species is located mainly in the European continent, Asia and South America, as well as in North and Central America and Australia. Based on the information collected from the Anisakidae family, it was determined that the geographical distribution is affected by different environmental factors, the host and the ability of the parasite itself to adapt. Its ability to adapt to the human organism has led to it being considered as a zoonotic agent. The disease in humans manifests nonspecifically, however the consumption of raw or semi-raw seafood is crucial information to link the presentation of the parasite with the disease. The use of morphological and molecular tests is of utmost importance for the correct diagnosis of the genus and species of the Anisakidae family. [ABSTRACT FROM AUTHOR]

The production of unreduced gametes is an important resource for the formation of polyploids. Here, we obtained a second generation of diploid hybrids (2nKCF 2) derived from koi carp (KOC; 2n = 100; ♀) × colored crucian carp (CCC; 2n = 100; ♂) with the unusual reproductive trait of producing unreduced diploid sperm. Compared with KOC and CCC, 2nKCF 2 had unique morphological characteristics, including a gray and golden head, golden-brown scaly outer edge, and smooth golden-yellow back. FISH and 5S rDNA analysis revealed that 2nKCF 2 not only inherited genomic DNA from their parents but also lost some parental DNA fragments. Chromosomal spreads of germ cells provided direct cytological evidence for the production of unreduced diploid sperm by male 2nKCF 2. Electron microscopy results showed that the heads of the diploid sperm generated by 2nKCF 2 were twice as large as those of the haploid sperm generated by CCC (P < 0.05), confirming that the sperm of 2nKCF 2 were diploid. A new type of tetraploid hybrid (4n = 200) was produced by crossing 2nKCF 2 males with improved female allotetraploid hybrids of red crucian carp (♀) × common carp (♂). This study provides insights into reproductive biology and aquaculture. • Male individuals capable of producing diploid sperm and infertile female ones were obtained in the F 2 through distant hybridization of koi carp (KOC, 2n=100, ♀) and color crucian carp (CCC, 2n=100, ♂) in our laboratory. • At present, a new type of tetraploid hybrid (4nAK, 4n=200) was produced by crossing F 2 males hybrids with improved female allotetraploid hybrids. The 4nAK had very important significance in the establishment of the new type of tetraploid fish lineage with special genotypes with four sets of chromosome and the hybrid genomes, and unique phenotypes including gold head, golden-brown scaly outer edge, and smooth golden-yellow back. • Both 2nKCF 2 and 4nAK enriched the resource of diploid gametes, which was of great significance in fish genetic breeding and biological evolution. [ABSTRACT FROM AUTHOR]