Carassius Auratus Gibelio Research Articles

Equilibrated evolution of the mixed auto-/allopolyploid haplotype-resolved genome of the invasive hexaploid Prussian carp

Understanding genome evolution of polyploids requires dissection of their often highly similar subgenomes and haplotypes. Polyploid animal genome assemblies so far restricted homologous chromosomes to a ‘collapsed’ representation. Here, we sequenced the genome of the asexual Prussian carp, which is a close relative of the goldfish, and present a haplotype-resolved chromosome-scale assembly of a hexaploid animal. Genome-wide comparisons of the 150 chromosomes with those of two ancestral diploid cyprinids and the allotetraploid goldfish and common carp revealed the genomic structure, phylogeny and genome duplication history of its genome. It consists of 25 syntenic, homeologous chromosome groups and evolved by a recent autoploid addition to an allotetraploid ancestor. We show that de-polyploidization of the alloploid subgenomes on the individual gene level occurred in an equilibrated fashion. Analysis of the highly conserved actinopterygian gene set uncovered a subgenome dominance in duplicate gene loss of one ancestral chromosome set.

Potential of (-)-epigallocatechin-3-gallate against bacterial and viral pathogens isolated from gibel carp (Carassius auratus gibelio)

Gibel carp (Carassius auratus gibelio) is an important fish species cultured worldwide. Bacterial septicemia and herpesviral hematopoietic necrosis disease (HVHND) were caused by Aeromonas hydrophila and cyprinid herpesvirus 2 (CyHV-2) respectively, which were the main causes of mortality and economical loss in gibel carp production. With known pharmacological activities against certain gram-negative bacteria and herpesvirus, (−)-Epigallocatechin-3-gallate (EGCG) was tested here to evaluate its inhibitory activity against A. hydrophila and CyHV-2 pathogens isolated from gibel carp. The minimum inhibitory concentration (MIC) of EGCG against four A. hydrophila strains ranged from 256 to 512 μg/mL and the minimum bactericidal concentration (MBC) was determined to be 1024 μg/mL. The growth curves of A. hydrophila A56 in the presence of various amounts of EGCG indicated that the concentration and treatment time of EGCG served as the two dominant factors for EGCG-mediated inhibitory effects in vitro. The bacterial load in liver, spleen and kidney tissues of gibel carps infected with 0.1 × LD50 A56 was significantly reduced after oral administration of EGCG (40 mg/kg body weight) 8 h in advance. The inactivation effect of CyHV-2 virus treated with 50 μg/mL EGCG for 2 h could reach 99.99%, and 70 μg/mL of EGCG could completely inactivate CyHV-2 in our infection and inhibition assays in vitro. These results collectively revealed the potential and broad-spectrum useage of EGCG in gibel carp cultivation against either bacterial or viral pathogen.

Micro-computed tomography for analysis of heavy metal accumulation in the opercula

Micro-computed tomography (micro-CT) provides numerous opportunities in biomedical research. It allows the examination of samples in a non-destructive manner and visualization of the inner structures of various biological and nonbiological objects. This study was conducted to evaluate the potential of micro-CT scanner in the assessment of heavy metal accumulation in the opercula. The samples were taken from Prussian carp (Carassius gibelio) exposed to waterborne Cd (4.0 mg/L), Zn (4.0 mg/L), and the mixture of these two metals (4.0 mg Cd/L and 4.0 mg Zn/L) for 28 days. Heavy metal concentrations were determined using atomic absorption spectrometry. The results demonstrated higher concentrations of Cd and Zn in the treatment group opercula samples compared with the control group opercula samples. A simple micro-CT scan was performed to verify whether heavy metal accumulation could be determined in the reconstructed images. The results showed that micro-CT is potentially a powerful tool for metal accumulation detection. Moreover, it allowed visualization of the examined samples, revealing regions of heavy metal accumulation and providing the opportunity to compare samples exposed to different types of heavy metals.

Proteomic and Phosphoproteomic Analyses Reveal Gibel Carp Responses to Cyprinid Herpesvirus 2 Infection.

Cyprinid herpesvirus 2 (CyHV-2) is a typical linear double-stranded DNA virus, which can induce severe herpesviral hematopoietic necrosis disease (HVHND) in gibel carp. However, the CyHV-2 infection mechanisms still remain unresolved till now. Here, we combined the isobaric tag for relative absolute quantitation (iTRAQ)-labeled quantitative proteomic and phosphoproteomic analysis enriched by Ti4+-immobilized titanium ion affinity chromatography (IMAC) to uncover the host responses to CyHV-2 infection in the kidneys of symptomatic and diseased gibel carp. We totally identified 192 differential expression proteins and 951 high-confident phosphopeptides involved in 657 proteins. After being infected with CyHV-2, the proteins involved in energy generation and ion balance were significantly downregulated in the host, and the phosphorylated proteins induced by viral infection mainly participated in the regulation for RNA processing, translation, cytoskeleton organization, immunoreaction, etc. Furthermore, 11 phosphorylated CyHV-2 viral proteins were found in the diseased group by the host proteome. The virus-host protein-protein interactions were investigated, in which the potential host kinases casein kinase II (CK-II) and cyclin-dependent kinase (CDK) that interacted with viral ORF88 or ORF89 were identified and can serve as candidate targets for disease treatment in the future. Overall, our study provides a comprehensive understanding of CyHV-2-induced perturbations at the protein and phosphorylation levels in gibel carp, forming a base for the treatment of HVHND.

Morphological variations of an invasive cyprinid fish (Carassius gibelio) in lentic and lotic environments inferred from the body, otolith, and scale shapes

AbstractThis study investigated the morphological variation of gibel carp Carassius gibelio collected from various water bodies in Türkiye. The fish samples were obtained from three dams (Karacaören‐1, Karakaya, and Keban), two natural lakes (Beyşehir and Suğla), and a river (the Tigris River). The dimorphism in body shape was examined with geometric morphometrics, while elliptic Fourier analysis and shape indices were used to describe the variation in lapilli otoliths (hereafter “otoliths”) and scale shapes. The body of C. gibelio revealed higher variations, particularly in the body depth, snout length, caudal fin, and caudal peduncle, among different stations. Geometric morphometric analysis determined a streamlined body shape of C. gibelio in the Tigris River compared to other stations, while C. gibelio from the natural lakes had a deeper body shape. The body of C. gibelio exhibited a significant homogenous shape between the Beyşehir and Suğla lakes, providing the lowest Procrustes distance. The elliptic Fourier analysis revealed that the otolith shape varied significantly between all stations. However, the scale shape was remarkably similar among nearby areas such as Karacaören dam, Suğla, and Beyşehir lakes. These results evinced high degree of intra‐population morphological variation in C. gibelio in response to prevailing environmental conditions that probably facilitate their successful establishment in a novel environment.

In situ management options to improve crucian carp (Carassius carassius, L.) and brown trout (Salmo trutta, L.) population status in Central Europe: A case study from the Czech Republic.

The crucian carp (Carassius carassius, L.) and the brown trout (Salmo trutta, L.) are vanishing from freshwater ecosystems of central Europe. To conserve both species, tailor‐made conservation management of habitats and populations of both species was implemented and tested in the Czech Republic (central Europe). This management was adjusted to reflect the ecological needs of both species. This study aimed to describe the results of a tested in situ management and to analyze the population growth of brown trout and crucian carp under ideal conditions. An experiment was performed at 14 small gravel pit lakes. Seven of them were adjusted to fit the crucian carp habitat requirements while the other seven were treated as a control group. The same experiment was done on 14 smaller streams and with brown trout. The occurrence and growth of crucian carp and brown trout were surveyed over 2 years. A significantly faster growth of both crucian carp and brown trout was observed on the adjusted lakes and streams in comparison to the control group ones. Trout and carp prospered on small streams and gravel pit lakes (respectively) that were free of angling, fish stocking, pollution, piscivorous predators, and competition with hybridizing species like Prussian carp (Carassius auratus, L.) or hatchery‐reared brown trout.

Circ-Udg Derived from Cyprinid Herpesvirus 2 Promotes Viral Replication.

ABSTRACTCyprinid herpesvirus 2 (CyHV-2) has caused great losses to the gibel carp (Carassius auratus gibelio) industry. Previous studies showed that certain DNA viruses can encode circular RNAs (circRNAs) to regulate virus infection, which provides new clues for the treatment of viral disease. Whether CyHV-2 can encode circRNAs is still unknown. Here, 10 CyHV-2-derived circRNAs were identified, and the function of circ-udg, a circRNA derived from the CyHV-2 uracil DNA glycosylase (udg) gene, was studied. Although the expression level of circ-udg was lower than that of the parental gene, udg, its expression level was elevated in tandem with the proliferation of CyHV-2 and udg. In vitro experiments confirmed that circ-udg could promote the proliferation of CyHV-2. Moreover, circ-udg could encode a truncated UDG protein consisting of 147-amino-acid residues (termed circ-udg-P147). Both UDG and circ-udg-P147 were found to promote CyHV-2 proliferation, but the promoting effect of circ-udg on CyHV-2 proliferation was attenuated after circ-udg lost the ability to encode circ-udg-P147. Also, circ-udg-P147 could not change the transcription level of the udg gene. Interestingly, the UDG protein level was increased by circ-udg-P147. These results deepen the understanding of the genetic information carried by the genome of CyHV-2 and provide a new target for the treatment of gibel carp bleeding disease caused by CyHV-2.IMPORTANCE The outbreak of C. auratus gibelio gill hemorrhagic disease caused by CyHV-2 brought great losses to the gibel carp industry. Therefore, exploring the interaction between CyHV-2 and host and the molecular mechanism of viral infection is of great significance in preventing and treating the gibel carp gill hemorrhagic disease. Although some progress has been made in the study of CyHV-2, the mechanism of interaction between CyHV-2 and crucian carp is still unclear. In this study, we found that CyHV-2 can encode circRNA to regulate virus replication. Our study provides novel information on CyHV-2 functional genomics, a reference for research into the circRNA of other viruses, and theoretical guidance for preventing and treating gibel carp bleeding disease.

Food composition and feeding strategies of an invasive species, Carassius gibelio (Bloch, 1782) inhabiting a eutrophic lake in Middle Black Sea region

Diet composition and feeding features of the Prussian carp Carassius gibelio (Bloch, 1782) were studied by analysing the stomach content of 155 fish specimens sampled from Lake Ladik during November 2009-October 2010. Five of the specimens had empty stomachs. A total of 29 prey taxa belonging to eight major groups comprising aquatic insects, Copepoda, Cladocera, Rotifera, Bacillariopyhta, Chlorophyta, Cyanobacteria and fish eggs were identified in 150 full stomachs. Diet composition showed slight seasonal variation. Cladocera was the most important prey item in all seasons, with peak abndance in spring. Feeding intensity exhibited seasonal change and was maximum in summer. Summer and autumn diets of this species showed the highest similarity. The study indicated that the Prussian carp in Lake Ladik showed both omnivorous and opportunistic feeding habits, exhibiting specialised feeding strategy on Cladocera, while they showed generalised feeding strategy on most prey items. The wide dietary plasticity of invasive Prussian carp can help their population to expand rapidly in different aquatic ecosystems. Keywords: Alien species, Diet composition, Feeding habits, Lake Ladik, Prussian carp

Eğirdir Gölü’nden 10 Balık Türünün Boy-Ağırlık İlişkisi

In this study, length-weight relationship for 10 fish species (Cyprinus carpio (common and mirror carp), Aphanius iconii, Atherina boyeri, Carassius gibelio, Pseudophoxinus egridiri, Pseudorasbora parva, Sander lucioperca, Seminemacheilus ispartensis and Vimba vimba) in Lake Eğirdir were assessed. Samples were obtained monthly from January 2010 to June 2011 of Lake Eğirdir, in Turkey. Moreover, for 3 Anatolian endemics species (A. iconii, S. ispartensis and P. egridiri) determined for the first time new maximum lengths are recorded.

Two duplicated gsdf homeologs cooperatively regulate male differentiation by inhibiting cyp19a1a transcription in a hexaploid fish.

Although evolutionary fates and expression patterns of duplicated genes have been extensively investigated, how duplicated genes co-regulate a biological process in polyploids remains largely unknown. Here, we identified two gsdf (gonadal somatic cell-derived factor) homeologous genes (gsdf-A and gsdf-B) in hexaploid gibel carp (Carassius gibelio), wherein each homeolog contained three highly conserved alleles. Interestingly, gsdf-A and gsdf-B transcription were mainly activated by dmrt1-A (dsx- and mab-3-related transcription factor 1) and dmrt1-B, respectively. Loss of either gsdf-A or gsdf-B alone resulted in partial male-to-female sex reversal and loss of both caused complete sex reversal, which could be rescued by a nonsteroidal aromatase inhibitor. Compensatory expression of gsdf-A and gsdf-B was observed in gsdf-B and gsdf-A mutants, respectively. Subsequently, we determined that in tissue culture cells, Gsdf-A and Gsdf-B both interacted with Ncoa5 (nuclear receptor coactivator 5) and blocked Ncoa5 interaction with Rora (retinoic acid-related orphan receptor-alpha) to repress Rora/Ncoa5-induced activation of cyp19a1a (cytochrome P450, family 19, subfamily A, polypeptide 1a). These findings illustrate that Gsdf-A and Gsdf-B can regulate male differentiation by inhibiting cyp19a1a transcription in hexaploid gibel carp and also reveal that Gsdf-A and Gsdf-B can interact with Ncoa5 to suppress cyp19a1a transcription in vitro. This study provides a typical case of cooperative mechanism of duplicated genes in polyploids and also sheds light on the conserved evolution of sex differentiation.

How does a reservoir affect the fish assemblage structure in a Mediterranean River (Turkey)?

Most rivers around the Mediterranean region, regardless of size, are interrupted by human induced barriers. Although various studies have been conducted to investigate the impacts of reservoirs on undisrupted freshwater biota, what kind of effects they exert on the distribution of freshwater fish assemblages with respect to the presence of invasive species remains to be answered. To attend to this research need, the Karamenderes River, which is disrupted by the Bayramiç Reservoir, was selected as the research site. Relying on the river continuum concept (RCC), we hypothesized that fish assemblages in a given river would demonstrate a gradual downstream change unless the river is interrupted by any reservoir. The ad hoc unweighted pair group method with arithmetic means (UPGMA) agglomerative hierarchical cluster analyses revealed 11 fish assemblages 100 km down the studied river, which is characterized by four environmental gradients. Besides, co-occurrence network analyses were performed to gain a better understanding of the constructs of the observed fish assemblages. The analyses yielded two distinct clusters along the river and showed that the Bayramiç Reservoir had no decisive part in the spatial clustering of these fish assemblages. The migratory species Anguilla anguilla was found only in and around the river mouth area. The co-occurrence network analyses indicated that the freshwater, estuarine and introduced species were observable in distinct groups. It is notable that the non-native Cyprinus carpio and invasive Carassius gibelio were determined in the native freshwater fish species module. The research evidenced that the reservoir had a triple effect, that is, a migration barrier to migratory fish species, a donor facilitating invasion, and a cause of homogenization of river fish assemblages along the river. The results suggest that the impact of the reservoir should be assessed in view of multiple nested model and fish passageways and controlling invasive species are two contradictory problems as far as the impacts of reservoirs are concerned. Therefore, river management should be performed in a way to allow the native migratory species to migrate freely while preventing the introduced species from moving upstream or downstream to preserve and promote rivers' heterogeneity.

Fish female-biased gene cyp19a1a leads to female antiviral response attenuation between sexes by autophagic degradation of MITA.

From insects to mammals, both innate and adaptive immune response are usually higher in females than in males, with the sex chromosome and hormonal differences considered the main reasons. Here, we report that zebrafish cyp19a1a (cytochrome P450, family 19, subfamily A, polypeptide 1a), an autosomal gene with female-biased expression, causes female fish to exhibit a lower antiviral response. First, we successfully constructed an infection model by intraperitoneal injection of spring viremia of carp virus (SVCV) into zebrafish (Danio rerio) and Carassius auratus herpesvirus (CaHV) in gibel carp (Carassius gibelio). Specifically, female fish were more vulnerable to viral infection than males, accompanied by a significantly weaker interferon (IFN) expression. After screening several candidates, cyp19a1a, which was highly expressed in female fish tissues, was selected for further analysis. The IFN expression and antiviral response were significantly higher in cyp19a1a-/- than in cyp19a1a+/+. Further investigation of the molecular mechanism revealed that Cyp19a1a targets mediator of IRF3 activation (MITA) for autophagic degradation. Interestingly, in the absence of MITA, Cyp19a1a alone could not elicit an autophagic response. Furthermore, the autophagy factor ATG14 (autophagy-related 14) was found interacted with Cyp19a1a to either promote or attenuate Cyp19a1a-mediated MITA degradation by either being overexpressed or knocked down, respectively. At the cellular level, both the normal and MITA-enhanced cellular antiviral responses were diminished by Cyp19a1a. These findings demonstrated a sex difference in the antiviral response based on a regulation mechanism controlled by a female-biased gene besides sex chromosome and hormonal differences, supplying the current understanding of sex differences in fish.

Antioxidative Defense and Gut Microbial Changes under Pollution Stress in Carassius gibelio from Bucharest Lakes.

Fish are able to accumulate by ingestion various contaminants of aquatic environment, with negative consequences on their intestine, being continuously threatened worldwide by heavy metals, pesticides and antibiotics resulted from the human activities. Consequently, the health of other species can be affected by eating the contaminated fish meat. In this context, our study aimed to perform a comparison between the changes in intestine samples of Carassius gibelio individuals collected from different artificial lakes in Bucharest (Romania), used by people for leisure and fishing. The presence of various metals, pesticides and antibiotics in the gut of fish was assessed in order to correlate their accumulation with changes of antioxidative enzymes activities and microbiome. Our results showed that fish from Bucharest lakes designed for leisure (Chitila, Floreasca and Tei lakes) have an increased level of oxidative stress in intestine tissue, revealed by affected antioxidant enzymes activities and GSH levels, as well as the high degree of lipid peroxidation, compared to the fish from protected environment (Vacaresti Lake). Some heavy metals (Fe, Ni and Pb) and pesticides (aldrin and dieldrin) were in high amount in the gut of fish with modified antioxidative status. In conclusion, our study could improve the knowledge regarding the current state of urban aquatic pollution in order to impose several environmental health measures.

Dietary poly‐β‐hydroxybutyrate supplementation can effectively improve growth, digestive enzyme activities, immune‐related gene expression, disease resistance, and intestinal mucosal barrier of gibel carp, Carassius auratus gibelio

AbstractPoly‐β‐hydroxybutyrate (PHB) can promote growth and enhance immunity of aquatic animals such as gibel carp, Carassius auratus gibelio. However, the optimal dietary supplementation level and feeding duration for gibel carp are still unclear. In this study, effects of various PHB supplementation levels on gibel carp growth performance, digestive enzyme activities, immune function, disease resistance, and intestinal mucosal barrier were evaluated. Six experimental diets differing in PHB levels were formulated, that is, 0% (P0 as control), 0.5% (P0.5), 1% (P1), 2% (P2), 4% (P4), and 8% (P8). Results indicated that PHB promoted fish growth performance significantly (p < 0.05). Compared to control group P0, the intestinal lipase, protease, and amylase activities in group P4 were significantly increased after 30 days (p < 0.05). Meanwhile, dietary PHB supplementation at 4% level for 30 days and 0.5% for 60 days upregulated the mRNA expression of immune‐related genes, including IL‐11, ITLN, MPO, KRT‐8, DUSP‐1, and PNP‐5α (p < 0.01). Furthermore, PHB at 4% for 30 days showed positive effects on disease resistance against both viral and bacterial infections and exerted beneficial effects on maintaining epithelial mucosal barrier integrity. In conclusion, 4% PHB supplementation for 30 days or 0.5% for 60 days was recommended for gibel carp culture.

Two Strains of Gibel Carp (Carassius gibelio) Exhibit Diverse Responses to Carbohydrates in a Low-Lipid Diet

An 8-week feeding trial was conducted to investigate carbohydrate use in a low-lipid diet between different strains of gibel carp (Carassius gibelio). The wild-type Dongting strain and artificially selected CASIII strain were fed three levels of carbohydrate: 15%, 30%, and 45%, in a low-lipid formulation (4%). The results showed that low-lipid supplementation with high carbohydrate seems to improve the feeding rate (FR) and specific growth rate (SGR), while it did not result in hyperglycaemia in gibel carp. Transcriptional regulation was slightly affected by carbohydrate levels; only hepatic pfk expression was more increased in the 30% and 45% carbohydrate diets than in the 15% carbohydrate diet ( p < 0.05 ). Regarding the strains, CASIII obtained higher growth performance by having higher FR and SGR than Dongting ( p < 0.05 ). Relatively higher glycaemia was found in CASIII, and it was coupled with increased plasma triglycerides and insulin ( p > 0.05 ). Enhanced gene expression of pk involved in glycolysis and decreased mRNA levels of pepck in gluconeogenesis were also observed in CASIII ( p < 0.05 ). There were strong strain ∗ diet interactions of gene expression involved in lipogenesis, and Dongting had higher mRNA levels of srebp-1, acly, and fas when fed carbohydrate at 45% ( p < 0.05 ). In conclusion, the tolerant level of carbohydrates in a low-lipid diet could be up to 45% for gibel carp by an improvement of growth and noninducement of postprandial plasma glucose. CASIII had a better ability to use dietary carbohydrates for growth with active glycolysis and restrained gluconeogenesis, and Dongting had more potential in lipid metabolism in response to carbohydrate intake.

The melanocortin-4 receptor (MC4R) gene in the gibel carp Carassius auratus gibelio: cloning, tissue distribution, and fasting effects

The melanocortin-4 receptor (MC4R) gene in the gibel carp Carassius auratus gibelio: cloning, tissue distribution, and fasting effects

Identification of 2,2′,4,5,5′-Pentachlorobiphenyl (PCB101) metabolites and their transmission characteristics in silver crucian carp (Carassius auratus gibelio)

Polychlorinated biphenyls (PCBs) have been attracting global concern due to their persistence and toxicity. However, the study on the metabolites of PCBs in freshwater fish is limited. In this study, the metabolites of 2,2′,4,5,5′-Pentachlorobiphenyl (PCB101) in silver crucian carp (Carassius auratus gibelio) were identified for the first time. After intraperitoneal injection of PCB101 (2 mg/kg), the results showed that it could be metabolized to at least three types of metabolites, including hydroxylated (OH-), methoxylated (MeO-) and methyl sulfonated (MeSO2-) PCB101. The OH- metabolites identified in most tissues were 3-OH-PCB101and 4-OH-PCB101, such as liver, gallbladder, blood and muscle. MeSO2- metabolites identified in gallbladder, blood and brain were 3-MeSO2-PCB101 and 4-MeSO2-PCB101. Meanwhile, the MeO- metabolite identified in liver, gallbladder, blood and spleen of silver crucian carp was 4-MeO-PCB101. The investigation of the types and structures of PCB101 and its metabolites, as well as the tissue distribution and accumulation characteristics in silver crucian carp are beneficial to understand the transformation and metabolic mechanisms of PCBs in aquatic organisms. It is of great significance to identify potential pollution hazards of precursor compounds and their metabolites on aquatic products and ensure the quality and safety of aquatic products.

The red blood cells cytometric characteristics of young fresh-water fish of various families

The morphometric indices of red blood cells of young fish of various species inhabiting coastal zones of the water bodies were studied. The subjects of the research were the fish of four families: Carp (Alburnus alburnus, Carassius gibelio, Rhodeus amarus, Abramis brama, Rutilus rutilus), Needles (Syngnathus abaster nigro lineatus), Centrarchidae (Lepomis gibbosus), Loaches (Cobitis taenia taenia), Gobies (Neogobius fluviatilis). The hydroecological conditions were characterized by an intense oxygen regime, high content of phosphates, and heavy metals (zinc). The fish peripheral blood was taken from the tail vein; smears were made according to the classical Romanowsky-Giemsa method. Our research showed that the red blood cells of young fish belonging to the ecological group of inactive and unpretentious species (Neogobius fluviatilis, Carassius gibelio) had the largest cross-sectional area and a high index of nuclear-cytoplasmic ratio. The indicators of erythrocyte eccentricity were the highest in the active fish with high energy costs (Alburnus alburnus, Lepomis gibbosus). The largest number of erythrocytes with pathological events (cytolysis, karyolysis, pyknosis, poikilocytosis) was observed in the young Alburnus alburnus (14%), and the smallest one in Rhodeus amarus and Lepomis gibbosus (2–4%). In the individuals of Syngnathus abaster nigro lineatus affected by parasitic nematodes of the genus Ascaris, the number of erythrocytes with pathologies increased to 81%. Under the toxic load, destabilization of the fish circulatory system begins with the appearance of the young forms of erythrocytes as compensation for depleted mature erythrocytes and ends with the mass destruction of mature erythrocytes. Given these patterns, as well as the relatively low number of young ballast forms of erythrocytes and mature erythrocytes with pathological features, we can assume that the state of the red blood cells in the studied young fishes meets the conditional norm, with the exception of the blood of Syngnathus abaster nigro lineatus infected with parasites. In our opinion, the main characteristics of the fish red blood that reflect the fishes’ adaptive capacities are as follows: eccentricity ratio of erythrocytes, the nuclear-cytoplasmic ratio, ratio of the young ballast forms of erythrocytes, and the relative number of erythrocytes with pathology.

First record of microplastic occurence at the commercial fish from Orontes River

Freshwater environments are more sensitive to anthropogenic influences and usually contain higher concentrations of pollutants than marine environments. Microplastic pollution causes additional stress on freshwater animals; yet, studies evaluating the microplastic occurrence in freshwater biota are still limited. In this study, microplastic occurrence in the gastrointestinal tracts (GIT) and gill of commercial fish species (Prussian carp Carassius gibelio (Bloch, 1782); Abu mullet Planiliza abu (Heckel, 1843); Common carp Cyprinus carpio Linnaeus, 1758; European ell Anguilla Anguilla (Linnaeus, 1758); North African catfish Clarias gariepinus (Burchell, 1822); Goldfish Carassius auratus (Linnaeus, 1758) were reported from Orontes River. MPs abundance in the GIT and gill of six species were found as 5.1 ± 2 MPs fish−1 and 4.4 ± 2 MPs fish−1 with an occurrence of 95% and 74%, respectively. The majority of extracted microplastics were fiber, black and less than 1000 μm in size. FTIR analysis determined the main polymer types as polyester (50%), high-density polyethylene (HDPE) (10%), polypropylene (PP) (8%) and polyethylene terephthalate (PET) (5%). High MPs abundance and frequency of occurence indicate the exposure of microplastic pollution in freshwater biota which could threat the health of both individuals and consumers. Results obtained in this study will increase the acknowledgement of MPs pollution in the Orontes River. Also, this study will provide data to the administrators to set up necessary legislations in freshwater ecosystems.

The Influence of Contracaecum larvae (Nematoda, Anisakidae) Parasitism on the Population of Prussian carp (Carassius gibelio) in Lake Sakadaš, Croatia.

Contracaecum larvae are geographically widely distributed, utilizing many animal species as hosts; and fish represent an important paratenic host in their life cycle. Their presence in Prussian carp (Carassius gibelio) was studied in Lake Sakadaš (Croatia) in 2017 and 2018. Two gill nets of different sizes submerged during a 12-h period were used to collect the fish. Contracaecum larvae were recorded in the stomach, slightly coiled or elongated on the intestine serosa or encapsulated in a gut wall of 20 individuals. The effect of Contracaecum sp. on the health of their host was determined by estimating the effect of the parasites’ presence, number, and biomass on fish length, weight, and the Fulton’s condition factor (CF). Infected fish showed negative (b < 3; p < 0.05) and uninfected fish positive allometric growth (b > 3; p < 0.05). Fish weight and CF in infected individuals were significantly low in comparison to the uninfected ones (Mann–Whitney U test: U = 1078.00, U = 423.50, respectively; p < 0.004). These results emphasize the importance of evaluating parasitic nematode presence in economically important fish species. Even more, if this endoparasite has a detectable negative impact on a resilient species such as the Prussian carp, it is important to monitor its occurrence in other fish species.