Cyprinid Fish Species Research Articles

Trophological studies for calculating the receiving capacity in the interests of artificial reproduction of sterlet in the Volga-Caspian Fisheries Subdistrict

The article presents the results of trophological studies of pass-through and riverine fish species in the root channel and delta of the Volga River. The aim of the work was to establish food competitors of juvenile sterlet from artificial reproduction in the places of its release and feeding. As a result, the nutrition spectra and the degree of filling of the digestive tracts of a number of cyprinid, catfish and goby fish species were studied. Based on the conducted studies, the daily rations and the frequency of occurrence of forage organisms in the food of each fish species were determined. The obtained materials are included in the calculation of the receiving capacity and serve as the basis for determining the optimal volume of release of factory sterlet juveniles into the watercourses of the Volga River in the Astrakhan region.

OCCURRENCE OF LAMPROGLENA PULCHELLA (NORDMANN, 1832) (COPEPODA: LERNAEIDAE) IN SOME CYPRINID FISH FROM OHRID LAKE (MACEDONIA)

The representatives of the class Copepoda are of great importance in fish pathology. Lamproglena pulchella (Nordmann, 1832) (Copepoda: Lernaeidae) is an ectoparasite of many cyprinid fish, widespread in Europe up to the Aral Sea. During the long-term investigations of 12 species of cyprinid fish from the Lake Ohrid, a total of 7 specimens of Lamproglena pulchella was found in 5 fish from 4 fish species: Rutilus ohridanus, Squalius squalus, Scardinius knezevici and Chondrostoma ohridanus. Only fresh fish were subjected to routine parasitological examinations, dissection, and observation methods. Parasite identification was performed morphologically, based on the character of their maxilla, maxilliped, antennae, legs and uropods, using a referent key for determination. The 3 parasite specimens were found in two samples of Rutilus ohridanus, followed by 2 parasite specimens in Squalius squalus and one specimen in Scardinius knezevici and Chondrostoma ohridanus, each. These parasites attach to gills and general body surfaces by their maxilla and maxilliped, causing wounds that become the spots of secondary infection by microbes. The damage caused by this parasite is more pronounced in aquaculture systems. We did not find many parasites, but considering the potential danger that Lamproglena pulchella poses to the fish health, we point out the need to monitor infestations with this parasite and take preventive measures so that the parasite does not spread massively among fish in Lake Ohrid and to prevent its introduction into other waters in Macedonia. The record of Lamproglena pulchella in all four cyprinid fish in the present study is considered as the first from the Ohrid Lake. At the same time, Rutilus ohridanus, Scardinius knezevici and Chondrostoma ohridanus represent new hosts for this parasite, worldwide.

Unveiling the Transmission Potential of Opisthorchis viverrini and Intestinal Helminths Along the Thailand-Laos Border in Thailand.

In pursuit of enhancing prevention efforts for the notably high endemic Opisthorchis viverrini infection in lower Mekong sub-region countries, particularly Thailand and Laos, this cross-sectional study investigated the transmission potential of O. viverrini and other intestinal helminths along the Thailand-Laos border in seven Thai villages. Human and pet faecal samples, Bithynia snails and cyprinid fish were analysed for helminth infections. Additionally, a questionnaire survey assessed relevant risk factors among the human population. Two groups of helminth infections were detected in humans: foodborne infections (FBIs) including O. viverrini, minute intestinal flukes (MIFs), and Taenia spp., and soil-transmitted infections (STIs) including hookworm and Strongyloides stercoralis, with prevalence rates of 7.4%, 0.5%, 2.5%, 0.5%, 2.5% and 3%, respectively. Smoking was identified as a risk factor for O. viverrini infection [adjusted odds ratios (ORa) = 3.12, 95% confidence intervals (CI): 1.33-7.30, p = 0.009] and FBIs (ORa = 2.47, 95% CI: 1.14-5.33, p = 0.022), while male was a risk factor for FBIs (ORa = 2.62, 95% CI: 1.16-5.94, p = 0.021). In dogs, hookworm, Toxocara spp., Spirometra mansoni, Trichuris vulpis and Hymenolepis diminuta were identified with prevalence rates of 35.6%, 8.1%, 8.1%, 1.2% and 1.2%, respectively. In cats, hookworm, Toxocara spp., S. mansoni, Strongyloides spp., Platynosomum fastosum, MIFs and H. diminuta were identified with prevalence rates of 50%, 17.9%, 10.7%, 7.1%, 3.6%, 3.6% and 3.6%, respectively. Bithynia snails showed 2% virgulate and 0.7% unknown cercariae infections, while among 19 cyprinid fish species, only unknown metacercariae were found. Our findings underscore the necessity of an integrated approach following the One Health concept to effectively combat these parasitic diseases while addressing human, animal and environmental health.

О расчете приемной емкости северо-западной части Каспийского моря в интересах искусственного воспроизводства водных биоресурсов в Волжско-Каспийском рыбохозяйственном бассейне

After release into the natural habitat, juveniles of semi-passable and passable fish, raised in sturgeon hatcheries and spawning farms of the Astrakhan region, do not stay in the river and roll into the sea. The main food objects for it are organisms of the “soft” benthos – crustaceans, worms and insect larvae. According to the results of research in 2020-2023, data from the analysis of the feed base during the period of the most intense food competition showed that the biomass of benthic invertebrates in the western part of the Caspian Sea is 121.1 thousand tons, production is 484.5 thousand tons. Taking into account the diets, age composition and abundance of each species of fish living in the water area of the settlement of factory juveniles, the volume of withdrawal of forage organisms is determined. livestock. The main consumers of “soft” benthos are representatives of cyprinid, atherine and goby fish species, which makes them the main food competitors of the produced juveniles. The reserve of “soft” benthos products is distributed among the factory juveniles according to the weight and daily diet of each species during the feeding period at sea. When calculating the permissible volume of release of each of the artificially reproducible water bodies, the coefficients of the maximum possible use of the feed base by juvenile fish and an increase in its number, taking into account death during adaptation to the natural environment, are used. Based on the calculations carried out, it is shown that the potential of the forage base of the western part of the Northern Caspian Sea is not a limiting factor in the stocking of the marine area with objects of artificial reproduction. The above method of calculating the receiving capacity is used in the preparation of an annual plan of measures for the artificial reproduction of aquatic biological resources.

Changes in the liver proteome of zebrafish (Danio rerio) exposed to glyphosate and aminomethylphosphonic acid in the presence of a humic substance

Herbicide exposure can pose a considerable threat to non-target aquatic animals. We aimed to study changes in the liver proteome of a model cyprinid fish species, zebrafish Danio rerio, to provide a molecular basis for the adverse effects of environmentally relevant concentrations of glyphosate (100 μg/L), its breakdown product aminomethylphosphonic acid (AMPA; 100 μg/L), and a mixture of both (50 + 50 μg/L) in the presence of humic acid (20 mg/L), which simulated a component of natural organic matter in the aquatic environment. Proteomic analysis was performed by means of high-performance liquid chromatography–tandem mass spectrometry employing a label-free quantification approach. The results present molecular evidence of the stress responses and disturbance of primary metabolic processes such as immune response, dysregulation in DNA repair, necroptosis and apoptosis signaling pathways, oxidative phosphorylation, cholesterol, lipoprotein, and carbohydrate metabolism. We registered the synergistic effect of the glyphosate and AMPA co-exposure, which was expressed in a substantial increase in the number of dysregulated proteins compared to the solo treatments. Humic acid alleviated the effects of glyphosate and its mixture with AMPA and aggravated the impact of AMPA exposure. RuvB-like 2, a protein taking part in DNA repair, and EIF2S1, involved in the regulation of stress-induced gene expression, were downregulated in the liver of zebrafish from all treatments.

Predicting climate change impacts on the distribution of endemic fish Cyprinion muscatense in the Arabian Peninsula.

Freshwater fishes are facing considerable threats in the Arabian Peninsula which is considered as a highly stressed region in the Middle East. It is predicted that northern Oman is likely to face decreasing rainfall and increasing temperature in coming decades. In this study, we focused on an endemic cyprinid fish Cyprinion muscatense, as a model to investigate impacts of climate change on the mountain fishes inhibiting in this arid region. This species is expected to be strongly affected by climate change because of its limited distribution range in a montane area surrounded by lowlands and sea, limiting the species in shift to other areas. We used an ensemble approach by considering two regressions-based species distribution modeling (SDM) algorithms: generalized linear models (GLM), and generalized additive models (GAM) to model the species habitat suitability and predict the impacts of climate change on the species habitat suitability. Based on the distribution models, the montane area located in northeastern Oman was identified as the most suitable habitat for this species. Our results indicate that, even under the minimum greenhouse gas emissions scenario (RCP 2.6), climate change will produce a high reduction in its potential future habitats. According to the results of percent contribution, elevation and annual minimum temperature were the most important variables in predicting the species suitable habitats. Results also showed that only a small percentage of suitable habitats for the species within boundaries of protected areas. Therefore, the impact of climate change on the species appears particularly alarming. Although our study was restricted to a single cyprinid freshwater species, decreases in potential habitats are likely predicted for other cyprinid fish species restricted to the mountains of this region, suggesting severe consideration is needed for aquatic systems in future conservation planning, especially for endemic freshwater fishes.

First record of Garra kempi Hora, 1921 (Cypriniformes: Cyprinidae) from Lohandra River of Nepal

Nepal holds a high ichthyofaunal diversity, nevertheless, the molecular study of Nepalese fish is still in its early stages. The first record of a cyprinid fish species the Garra kempi Hora, 1921 for Nepal was reported from eastern Nepal’s Lohandra River. Both morphology and molecular data affirmed the existence of G. kempi in Nepal’s aquatic system. This species was previously reported from China (Tibet) and northern India. The maximum likelihood phylogenetic analysis and pairwise genetic distance based on Kimura 2 parameters using cytochrome oxidase subunit 1 (COI) segment sequences (665 bp) also confirmed the identity of the species as G. kempi. The COI sequences of specimens from Nepal formed a monophyletic clade with the sequence of G. kempi from northeastern India and the two contained a pairwise genetic distance of 1.8% only. The new record of G. kempi from Nepal warrants a detailed ichthyofaunal survey for documenting the fish diversity in Nepal.

Genomic analysis and phylogenetic characterization of Himalayan snow trout, Schizothorax esocinus based on mitochondrial protein-coding genes.

Mitochondrial DNA (mtDNA) has become a significant tool for exploring genetic diversity and delineating evolutionary links across diverse taxa. Within the group of cold-water fish species that are native to the Indian Himalayan region, Schizothorax esocinus holds particular importance due to its ecological significance and is potentially vulnerable to environmental changes. This research aims to clarify the phylogenetic relationships within the Schizothorax genus by utilizing mitochondrial protein-coding genes. Standard protocols were followed for the isolation of DNA from S. esocinus. For the amplification of mtDNA, overlapping primers were used, and then subsequent sequencing was performed. The genetic features were investigated by the application of bioinformatic approaches. These approaches covered the evaluation of nucleotide composition, codon usage, selective pressure using nonsynonymous substitution /synonymous substitution (Ka/Ks) ratios, and phylogenetic analysis. The study specifically examined the 13 protein-coding genes of Schizothorax species which belongs to the Schizothoracinae subfamily. Nucleotide composition analysis showed a bias towards A + T content, consistent with other cyprinid fish species, suggesting evolutionary conservation. Relative Synonymous Codon Usage highlighted leucine as the most frequent (5.18%) and cysteine as the least frequent (0.78%) codon. The positive AT-skew and the predominantly negative GC-skew indicated the abundance of A and C. Comparative analysis revealed significant conservation of amino acids in multiple genes. The majority of amino acids were hydrophobic rather than polar. The purifying selection was revealed by the genetic distance and Ka/Ks ratios. Phylogenetic study revealed a significant genetic divergence between S. esocinus and other Schizothorax species with interspecific K2P distances ranging from 0.00 to 8.87%, with an average of 5.76%. The present study provides significant contributions to the understanding of mitochondrial genome diversity and genetic evolution mechanisms in Schizothoracinae, hence offering vital insights for the development of conservation initiatives aimed at protecting freshwater fish species.

Label-free, whole-brain in vivo mapping in an adult vertebrate with third harmonic generation microscopy.

Comprehensive understanding of interconnected networks within the brain requires access to high resolution information within large field of views and over time. Currently, methods that enable mapping structural changes of the entire brain in vivo are extremely limited. Third harmonic generation (THG) can resolve myelinated structures, blood vessels, and cell bodies throughout the brain without the need for any exogenous labeling. Together with deep penetration of long wavelengths, this enables in vivo brain-mapping of large fractions of the brain in small animals and over time. Here, we demonstrate that THG microscopy allows non-invasive label-free mapping of the entire brain of an adult vertebrate, Danionella dracula, which is a miniature species of cyprinid fish. We show this capability in multiple brain regions and in particular the identification of major commissural fiber bundles in the midbrain and the hindbrain. These features provide readily discernable landmarks for navigation and identification of regional-specific neuronal groups and even single neurons during in vivo experiments. We further show how this label-free technique can easily be coupled with fluorescence microscopy and used as a comparative tool for studies of other species with similar body features to Danionella, such as zebrafish (Danio rerio) and tetras (Trochilocharax ornatus). This new evidence, building on previous studies, demonstrates how small size and relative transparency, combined with the unique capabilities of THG microscopy, can enable label-free access to the entire adult vertebrate brain.

Трематоды рода Apophallus (Trematoda: Heterophyidae) в фауне многоклеточных паразитов Perca fluviatilis (Perciformes, Actinopterygii) в дельте Волги

The living conditions of aquatic organisms in the Volga-Caspian Sea Shipping Canal are determined by a high level of complex multifactor anthropogenic load. As a link in a unified international transport system, the canal serves as an invasive corridor for the settlement of alien organisms, including parasites. The fauna of multicellular parasites Perca fluviatilis (Perciformes) in the canal area was studied. 6 taxa of parasitic organisms have been registered. The nematode Eustrongylides excisus occupies a dominant position in the fauna of macroparasites P. fluviatilis. An alien trematode, Apophallus muehlingi, was discovered associated with the invasive mollusk Lithoglyphus naticoides; the parasite has the status of a codominant species. A specific parasite widely distributed in perch fish populations in the Volga delta, Apophallus donicus, has not been registered. The high degree of invasion of perch by A. muehlingi during the three-year study period indicates the stability of the parasitic subsystem “A. muehlingi – P. fluviatilis”, previously uncharacteristic for this host species in the lower reaches of the Volga. Currently, more favorable conditions have developed for the invasion of perch A. muehlingi than A. donicus in certain areas of the Volga delta. Thus, structural changes were found in the host-parasite relationships systems of the trematodes of the genus Apophallus, which appear in the form of a partial restructuring of the species and host structure of the fauna of macroparasites P. fluviatils in the investigated area of the river. This situation is determined by factors that are largely anthropogenic in nature – changes in the living conditions of hosts and parasites, caused by a combination of fluctuations in the level of the Caspian Sea and the discharge of the Volgograd hydroelectric station, intensive shipping (large volume of cargo transportation) and high fishing pressure. The most likely significant additional factor of changes in the nature of infection of P. fluviatils by trematodes of the genus Apophallus is currently a decrease in the stocks of populations of some massive species of cyprinid fish – the second intermediate hosts of A. muehlingi, for which the parasite is defined as specific.

Cryptosporidium spp. and Eimeria spp. (Apicomplexa: Eimeriorina) of freshwater Cyprinid fish species in the Kura River basin in Azerbaijan territory.

This study aims to determine the prevalence of Cryptosporidium and Eimeria spp. oocysts in fish specimens in the river Kura. It was conducted during the 2021-2022 at two sites: Mingachevir reservoir in central Azerbaijan and in Neftchala district where the river finally enters the Caspian Sea through a delta of the Kura River estuary. The diagnosis of oocysts was performed microscopically. Fine smears from the intestine epithelial layers stained by Ziehl-Neelsen for Cryptosporidium oocysts. To identify Eimeria oocysts, each fish's faecal material and intestinal scrapings were examined directly under a light microscope in wet samples on glass slides with a coverslip. Results revealed a prevalence of Cryptosporidium and Eimeria species infections in fish hosts from both territories Rutilus caspicus, Alburnus filippi, Abramis brama orientalis and Carassius gibelio. Of 170 investigated fish specimens, 8.8% (15/170) were infected with Cryptosporidium species oocysts. Eimeria species oocysts were identified in 20.6% (35/170). The presence of Cryptosporidium and Eimeria infections in fish specimens are natural infections. However, their presence in fish species may be attributed to the age of the fish species and water pollution. This is the first report regarding the prevalence of Cryptosporidium oocysts in fish species in Azerbaijan.

Inter - and intraspecific phenotypic variation in co-occurring invasive and introduced cyprinid fish species

A species introduced outside of its native range will likely encounter unusual abiotic and biotic conditions,and may exhibit phenotypic traits that may facilitate survival and persistance. Phenotypic plasticity drives non-native species' development of adaptive traits in the new environment, increases their fitness, and as a result, contributes to invasion success. In this study, we examined inter and intraspecific phenotypic variation (body size and shape) for an invasive (Carassius gibelio) and introduced (Cyprinus carpio) cyprinid fish species (Teleostei: Cyprinidae) in the Düden Stream, Turkey, which is a small-scale river system. We hypothesized that interspecific phenotypic variation correlates with fish-specific variables and river site. We further hypothesized that these two species may exhibit similar phenotypic variation patterns between populations. The MANCOVA revealed that species-specific traits, river site, had significant effects on body shape variation and size along the stream. The differences in the shape of the head, the central portion of the body, and fins in both species most probably reflected differences in the swimming and feeding of the fish, possibly to avoid interspecies competition. The intraspecific phenotypic variation observed in both species may indicate rapid local adaptation, triggered by multiple founding event, or/and phenotypic plasticity.

TREMATODA AND CESTODA SPECIES IN CYPRINID FISH FROM SMALL LAKES OF THE KOSTANAY REGION

This study presents data on the epizootiological monitoring of parasitic diseases in fish from Kostanay region. It confirms the presence of previously identified permanent natural foci of opisthorchiasis in the southern districts, specifically in the Uly-Zhilanchik and Torgay rivers. Additionally, the research conducted in Zhangeldy and Amangeldy districts revealed the existence of biohelminths with both epizootiological and epidemiological significance. This study aimed to investigate the presence of parasites dangerous to humans and carnivores in cyprinid fish species. Specifically, it focused on identifying the second intermediate hosts for opisthorchiasis, metorchiasis, and ligulosis: ide (Leuciscus idus) and bream (Abramis brama). From 2021 to 2023 seven reservoirs of the Kostanay region were the monitoring objects of the parasitological situation: Verkhnetobolskoe reservoir, rivers: Torgay, Uly-Zhilanchik, Zhaldama, Tobol, Zhelkuar, Akkol Lake, where shellfish bitiniids, waterfowl and crustaceans live in large numbers, as the first intermediate host of pathogens Opisthorchis felineus (Metorchis bilis), Ligula imestinalis. Examination of eight ide (Leuciscus idus) specimens caught in the Uly Zhilanchik River revealed the presence of metacercariae of two parasitic trematodes: O.felineus and M.bilis, while the prevalence was 18.5% and 8.3%, and the infestation intensity was 1-3 and 2, respectively. In the Amangeldy region, metacercariae O. Felineus and plerocercoids Ligula imestinalis were found in two fish species: one individual of the ide species and two individuals of the bream species caught from the Torgai River. At the same time, the prevalence was 6.6% and 16.6%, and the infestation intensity was 2 and 1, respectively. Parasitic diseases of fish were not detected in the waters of Denisovsky and Zhitikarinsky districts. Based on Polymerase Chain Reaction (PCR) analyses conducted using specific primers at the National Center of Biotechnology LLP laboratory in Astana, Kazakhstan, two distinct types of opisthorchid parasites were identified in two ide (Leuciscus idus) specimens collected from Kostanay region. The species were confirmed to be Opisthorchis felineus and Methorchis bilis (PCR protocol dated April 24, 2023).

Health Risks Associated with the Concentration of Heavy Metals in Sediment, Water, and Carp Reared in Treated Wastewater from a Slaughterhouse

The use of purified slaughterhouse wastewater in carp ponds, and the use of wastewater from the pond for the irrigation of agricultural fields, was the basis for the construction of an integrated system of agricultural production as a sustainable solution for the food and fish production industries. The negative side of such integrated production systems is the concern related to the safety of fish meat produced in such a system. The aim of this research was to determine the concentration of heavy metals and metalloids in the wastewater from the slaughterhouse, in the pond water and sediment, in the carp tissue and in the water leaving the pond, and to evaluate the effectiveness of the integrated system and the safety of the produced fish. Sampling was carried out in spring and autumn. The mean concentrations in all water samples (µg/L) were: As (12–125), Cd (0.12–4.2), Hg (1.14–14.21), Pb (<0.1–17.2), Cu (<0.1–44.6), Fe (17.02–425.2) and Zn (2.91–186.2), with the highest numbers in the wastewater, where it was above the prescribed limit values for the wastewater discharged from the slaughterhouses into natural recipients in both samplings. The efficiency of the wastewater treatment plant for heavy metals and metalloids was very high, in the range of 87% to 98%. The water from the pond corresponded to class 3 in terms of the concentration of heavy metals and metalloids both in spring and autumn, and can be used freely for breeding cyprinid fish species. The water from the irrigation canal corresponded to class 2/3 and can be used for irrigation. The mean concentrations of heavy metals and metalloids in the sediments (mg/kg) were: As (3.00–4.88), Cd (0.16–0.96), Hg (0.21–1.47), Pb (0.77–2.29), Cu (49.60–60.90), Fe (3.94–5.32) and Zn (92.8–115.20). The content of heavy metals in different organs of carp differed significantly depending on the season. The trend of heavy metal accumulation in common carp muscles in spring was: Zn > Fe > Cu > Pb > Hg > Cd > As, and in autumn: Zn > Fe > Cu > Pb > As > Cd > Hg. Metal concentrations in the examined fish samples were far below the WHO guidelines. It can be concluded that carp produced in a pond supplied with purified wastewater from the slaughterhouse industry, in terms of the concentration of residues of the tested heavy metals and metalloids, is safe for human consumption.

Generation of Recombinant Snakehead Rhabdovirus (SHRV) Expressing Artificial MicroRNA Targeting Spring Viremia of Carp Virus (SVCV) P Gene and In Vivo Therapeutic Use Against SVCV Infection.

Spring viremia of carp virus (SVCV) is a highly lethal virus in common carp (Cyprinus carpio) and other cyprinid fish species. The aim of the present study was to develop an in vivo therapeutic measure against SVCV using artificial microRNA (AmiRNA) targeting the SVCV P gene transcript. Three candidates of AmiRNAs (AmiR-P1, -P2, and -P3) were selected, and their ability to downregulate SVCV P gene transcript was analyzed by both synthesized AmiRNA mimics and AmiRNA-expressing vector system, in which AmiR-P3 showed the strongest inhibitory activity among the three candidates. To overcome in vivo limitation of miRNA mimics or plasmid-based miRNA expression systems, we rescued recombinant snakehead rhabdoviruses (SHRVs) expressing SVCV P gene-targeting AmiRNA (rSHRV-AmiR-P3) or control AmiRNA (rSHRV-AmiR-C) using reverse genetic technology. The successful expression of AmiR-P3 and AmiR-C in cells infected with the rescued viruses was verified by quantitative PCR. To evaluate the availability of rSHRV-AmiR-P3 for in vivo control of SVCV, zebrafish (Danio rerio) were (i) infected with either rSHRV-AmiR-C or rSHRV-AmiR-P3 followed by SVCV infection or (ii) infected with SVCV followed by either rSHRV-AmiR-C or rSHRV-AmiR-P3 infection. Fish infected with rSHRVs before and after SVCV infection showed significantly higher survival rates than fish infected with SVCV alone. There was no significant difference in survival rates between groups of fish infected with rSHRV-AmiR-C and rSHRV-AmiR-P3 before SVCV infection; however, fish infected with SVCV followed by infection with rSHRV-AmiR-P3 showed significantly higher survival rates than fish infected with rSHRV-AmiR-C. These results suggest that rSHRV-AmiR-P3 has therapeutic potential against SVCV in fish when administered after SVCV infection, and rSHRVs expressing artificial microRNAs targeting SVCV transcripts could be used as a tool to control SVCV infection in fish for a therapeutic purpose.

Unveiling the molecular identity of the diminutive cyprinid, Horadandia brittani (Teleostei: Cyprinidae), a species endemic to Southern India.

Horadandia brittani is a small cyprinid fish species initially discovered in the coastal floodplains of southern India. For almost 50 years, the genus Horadandia was monotypic with a single species confined to Sri Lanka. In 1992, a new species H. brittani was described from south-western India. Despite being described as a separate species, H. brittani was later considered a synonym of H. atukorali, but in 2013, researchers recognized it as a distinct species based on morphological differences. Despite this clarification, there was still a need to validate the identity of H. brittani and determine its evolutionary relationship with its closely related species using DNA sequences. To address the uncertainties surrounding the identity of H. brittani, the present study utilized molecular techniques to generate DNA sequences. Sample collection involved obtaining specimens of H. brittani from their natural habitats. Subsequently, DNA was extracted from the collected samples, and the mitochondrial cytochrome C oxidase (COI) gene was amplified using appropriate methods. The analysis of DNA sequences obtained from the COI gene revealed significant genetic distinctions between H. brittani and H. atukorali. The genetic distance values between these two species ranged from 3.21 to 3.63%, clearly indicating that these two species are genetically separate entities. The study successfully established the phylogenetic relationships between H. brittani and H. atukorali based on the COI gene sequences, further confirming the validity of H. brittani as a distinct and separate species. The findings of this study conclusively demonstrate that H. brittani is a valid and separate species, distinct from H. atukorali. The genetic analysis based on mitochondrial COI gene sequences provided strong evidence for the differentiation between these two species. The molecular data generated in this research can be used to identify H. brittani quickly and accurately in the future.

Impacts of Some Trace Metals in Cyprinus carpio (Linnaeus,1758) and Tor soro (Valenciennes, 1842) on Human Health.

Although fish are rich sources of various trace metals in their bodies, when these metals exceed health safety limits, it becomes a global concern. Fish exposed to trace metal pollution in their aquatic ecosystems can lead to bioaccumulation and transfer to consumers. Monitoring trace metal contamination of fish food is crucial because they can reach humans through the aquatic food chain, resulting in health problems. Therefore, a first attempt was made for the analysis of trace metals in two cyprinid fish species, namely Cyprinus carpio (Common carp) and Tor soro (Mahseer), which were abundantly found in Khanozai Dam and assessing their potential health impacts when consumed by humans. A total of 200 fish specimens were collected from this area. These specimens were divided equally between the two carp species, with 100 individuals from each species. The fish specimens were collected over 12months, from June 2020 to May 2021 to determine the concentration of some trace metals, i.e. Manganese (Mn), Calcium (Ca), Iron (Fe), Potassium (K), and Zinc (Zn), Sodium (Na), Phosphorus (P), Magnesium (Mg), and Chlorine (Cl) using a Flame Atomic Absorption Spectrophotometer with a multi-element hollow cathode lamp. The obtained results from the trace metal analysis of Cyprinus carpio and Tor soro in this study revealed that both calcium and phosphorus were present in higher concentrations. However, iron, manganese, and zinc were not detected in both species. Additionally, magnesium was also not detected in C. carpio. For Cyprinus carpio, the arrangement was Ca > P > K > Na > Cl, while for Tor soro, it was Ca > P > Na > K > Cl > Mg in decreasing order. The health risks associated with fish consumption were assessed using factors like estimated daily intake (EDI), Target Hazard Quotient (THQ), and Total Target Hazard Quotient (TTHQ). The THQ values for all analyzed trace metals in both carp species exceeded the maximum value of 1.0, except for Cl in Tor soro. This suggests the potential for various health-related diseases in regular consumers due to their elevated levels. In both species, the TTHQ factor also surpassed the standard value of 1.0, indicating an acute health risk for humans. Although EDI values did not surpass the recommended daily allowance (RDA), continuous consumption of these contaminated fish from this area could lead to severe health complications. Therefore, these results strongly indicated that the elevated levels of trace metals found in the highly abundant cyprinid species of Khanozai Dam could pose serious health-related issues for the local inhabitants.

Intermittent hypoxia differentially affects metabolic and oxidative stress responses in two species of cyprinid fish.

Oxygen fluctuations are common in freshwater habitats and aquaculture and can impact ecologically and economically important species of fish like cyprinids. To gain insight into the physiological responses to oxygen fluctuations in two common cyprinid species, we evaluated the impact of short-term intermittent hypoxia on oxidative stress and metabolic parameters (including levels of prooxidants and oxidative lesions, antioxidants, mitochondrial enzyme activities, mitochondrial swelling, markers of apoptosis, autophagy and cytotoxicity) in silver carp Hypophthalmichthys molitrix and gibel carp Carassius gibelio. During hypoxia, gibel carp showed higher baseline levels of antioxidants and less pronounced changes in oxidative and metabolic biomarkers in the tissues than silver carp. Reoxygenation led to a strong shift in metabolic and redox-related parameters and tissue damage, indicating high cost of post-hypoxic recovery in both species. Species-specific differences were more strongly associated with oxidative stress status, whereas metabolic indices and nitrosative stress parameters were more relevant to the response to hypoxia-reoxygenation. Overall, regulation of energy metabolism appears more critical than the regulation of antioxidants in the response to oxygen deprivation in the studied species. Further research is needed to establish whether prioritizing metabolic over redox regulation during hypoxia-reoxygenation stress is common in freshwater cyprinids.

Single-cell transcriptome, phagocytic activity and immunohistochemical analysis of crucian carp (Carassius auratus) in response to Rahnella aquatilis infection.

In teleost fish, kidney is an important immune and hematopoietic organ with multiple physiological functions. However, the immune cells and cellular markers of kidney require further elucidation in crucian carp (C. auratus). Here we report on the single-cell transcriptional landscape in posterior kidney, immunohistochemical and phagocytic features of C. auratus with R. aquatilis infection. The results showed that a total of 18 cell populations were identified for the main immune cells such as monocytes/macrophages (Mo/Mϕ), dendritic cells (DCs), B cells, T cells, granulocytes and hematopoietic progenitor cells (HPCs). Pseudo-time trajectory analysis was reconstructed for the immune cells using Monocle2 to obtain additional insights into their developmental lineage relationships. In the detected tissues (liver, spleen, kidney, intestine, skin, and gills) of infected fish exhibited positive immunohistochemical staining with prepared for antibody to R. aquatilis. Apoptotic cells were fluorescently demonstrated by TUNEL assay, and bacterial phagocytic activity were observed for neutrophils and Mo/Mϕ cells, respectively. Moreover, a similar up-ward/down-ward expression trend of the selected immune and inflammatory genes was found in the kidney against R. aquatilis infection, which were significantly involved in TLR/NLR, ECM adhesion, phago-lysosome, apoptosis, complement and coagulation pathways. To our knowledge, this is the first report on the detailed characterization of immune cells and host-R. aquatilis interaction, which will contribute to understanding on the biology of renal immune cells and repertoire of potential markers in cyprinid fish species.

A trait-based approach to determine the risks of Zn to the overall health status of native fish species Barbus meridionalis

Fish adapt to changing environments by maintaining homeostasis or making energy trade-offs that impact fitness. We investigated the effect of Zn on the fitness and physiology of Barbus meridionalis, a native cyprinid fish species, under two exposure scenarios. The Osor stream's mine-effluent reach represented long-term (chronic) exposure, while the upstream reach served as a control/acute exposure. Acute exposure involved exposing B. meridionalis to 1mg/L Zn for 96 h in the laboratory. We examined physiological traits (Standard metabolic rate SMR, Maximum metabolic rate MMR, Absolute Aerobic scope AAS, Critical swimming capacity Ucrit) and antioxidant system, AS (Superoxide dismutase, SOD; Catalase, CAT; Glutathione peroxidase, GPX; Glutathione-S-transferase, GST; Glutathione, GSH; Thiobarbaturic acid reactive substances, TBARS) biomarkers. The results indicated that Zn had no significant effect on osmoregulatory cost (SMR) in either exposure scenario but impaired energetically costly exercise (low MMR). AAS reduction in both exposure groups suggested compromised energy allocation for life-history traits, evidenced by decreased locomotor performance (Ucrit) after acute exposure. Tissue-specific and time-dependent responses were observed for AS biomarkers. The fish exhibited ineffective control of oxidative damage, as evidenced by high TBARS levels in the liver and gills, despite increased CAT and GSH in the liver under acute conditions. Our findings demonstrate differential responses at the subcellular level between the two exposure scenarios, while trait-based endpoints followed a similar pattern. This highlights the utility of a trait-based approach as a supplementary endpoint in biomonitoring studies, which provides insights into impacts on individual fitness and population demography.