First record of metazoan parasites of hybrids between the genera Colossoma and Piaractus in natural environments.

The practice of hybridization is carried out globally in fish farms. Here, we present the first record of the parasitic fauna of hybrids among genus Colossoma and Piaractus in natural environments. We identified a total of 48 hybrids, nine F1 hybrids (nuclear DNA from both species present in the cross) and 38 advanced hybrids (nuclear DNA from one species), both from crosses between Piaractus brachypomus and Piaractus mesopotamicus, and one F1 "tambacu" corresponding to cross between Colossoma macropomum and Piaractus mesopotamicus. This is the first record of Anacanthorus penilabiatus, Anacanthorus toledoensis, Mymarothecium viatorum, Mymarothecium ianwhittington, Haementeria sp., Dadaytrema oxycephala, Rondonia rondoni, and Echinorhynchus gomesi parasitizing hybrids collected in a natural environment. With this, we expand knowledge about the diversity of fish and parasites in the upper Paraná River and warn about the risk that fish escapes can cause in the basin.

Water availability and biological interactions shape amphibian abundance and diversity in Mediterranean temporary rivers.

Amphibians, the most threatened vertebrates globally, face risks due to climate change, habitat loss, and fragmentation. Their sensitivity to environmental changes highlights their importance as ecological indicators. Temporary rivers, influenced by geological, climatic, and anthropogenic factors, play a critical role in shaping biodiversity and community structure. Some species of amphibians may be adapted to these temporary waters, a fact reflected in their life cycles and various biological traits. However, to develop effective conservation strategies for amphibians, it is essential to address the knowledge gaps surrounding the complex interactions between biological dynamics and fluvial habitat conditions. In this study, we investigated how trophic interactions between amphibians and other aquatic organisms (diatoms, macroinvertebrates, and fish), coupled with environmental factors (water availability and riparian structure), can affect amphibian abundance and diversity in temporary rivers. The study was conducted in a Mediterranean river network located in Sant Llorenç del Munt i l'Obac Natural Park (Catalonia, Spain). Our expectations were that habitats suitable for egg deposition, lacking predators (e.g. tadpole-predators and fish), and abundant in food sources would likely support higher amphibian abundance and diversity. However, water availability was identified as a crucial factor shaping abundance and diversity in the studied amphibian communities, even if it correlated with fish presence, and especially impacting amphibian species usually linked to permanent water bodies. Concerning biotic interactions, while our results suggested that amphibian populations in temporary rivers are more dependent on top-down than bottom-up interactions, the presence of aquatic predators was not as conclusive as expected, suggesting that in temporary rivers the fish-avoiding amphibian species can survive using microhabitats or breeding opportunities linked to natural river dynamics. Overall, our findings highlight the importance of considering multi-trophic interactions, hydroperiod and habitat heterogeneity in temporary river ecosystems for effective amphibian conservation.

Parasitism with Protozoa and Monogeneans in Fish from the Natural Waters of Romania.

Parasitism by protozoa and monogenean flatworms in freshwater fish from Romania was studied by collecting and examining samples from two major river systems there: 183 fish from 17 species from the Olt River and its tributaries; and 155 fish from 16 species from the Mureș River and its tributary, Târnava Mare. The average rates of parasitism in the samples from the two rivers and their tributaries were as follows: Ichthyiophthirius multifiliis (2%), Trichodina spp. (21%), Apiosoma spp. (18%), Mixobolus spp. (8%), Dactylogyrus spp. (9%), and Gyrodactylus spp. (10%). The number of parasite species varied from one river to another. I. multifiliis was found in only 3 fish species, Trichodina spp. in 13 species, Glosatella spp. in 6 species, and Mixobollus spp., Dactylogyrus spp., and Gyrodactylus spp. in 7 different species each. The highest number of parasite species (six) were identified in the European chub (Squalius cephalus) and schneider (Alburnoides bipunctatus), which seem more susceptible to parasitic infections. The aquatic environment of these rivers may represent a source of parasites for fish from neighboring countries through which these rivers pass.

Hypermucoviscous Multidrug-Resistant Klebsiella variicola Strain LL2208 Isolated from Chinese Longsnout Catfish (Leiocassis longirostris): Highly Similar to Human K. variicola Strains.

Outbreaks of bacterial diseases occur in farmed Chinese longsnout catfish (Leiocassis longirostris). Due to limited information on aquatic Klebsiella variicola-infected animals, this study aimed to identify strain LL2208 isolated from diseased L. longirostris, determine its biological features, and evaluate its risk to public health. Strain LL2208 was tested for molecular identification, challenge, string, biofilm formation, and antimicrobial susceptibility. Furthermore, the whole genome of the strain was sequenced and analyzed. Based on molecular identification, strain LL2208 was identified as K. variicola. Artificial infection showed that this strain was moderately virulent to L. longirostris with an LD50 = 7.92 × 107 CFU/mL. Antibiotic sensitivity tests showed that this strain was resistant to penicillins, macrolides, aminoglycosides, amphenicols, glycopeptides, and lincosamide, indicating multidrug resistance. Strain LL2208 has a genome size of 5,557,050 bp, with a GC content of 57.38%, harboring 30 antimicrobial resistance genes and numerous virulence-related genes. Its molecular type was ST595-KL16-O5. Collinearity analysis showed that strain LL2208 was highly similar to the human-derived K. variicola strain. In conclusion, the multidrug-resistant and virulent K. variicola strain LL2208 was isolated from fish and may have originated from humans. These results provide a foundation for further studies on the transmission of K. variicola between humans and aquatic animals.

The effects of winter cold on acute copper bioaccumulation and toxicity in brook char (Salvelinus fontinalis).

Freshwater fish that are acutely exposed to copper (Cu) can experience disturbances of ion regulation and ammonia excretion. Temperature has been shown to affect Cu bioaccumulation and toxicity in fish, but the focus has largely been on warm temperature effects. Yet, acclimation of freshwater fish to near-freezing temperatures encountered during the winter of temperate regions can challenge fish condition and physiology, including ion regulation. Thus, temperate freshwater fish might be particularly sensitive to Cu in the winter. We investigated how winter cold affects acute Cu bioaccumulation and toxicity in juvenile brook char (Salvelinus fontinalis). Following gradual acclimation to cold temperature (-2 °C/week from 14 °C, then 4 weeks at 3 °C) vs. a warmer temperature around the species thermal optimum (14 °C for 9 weeks), and following a cold challenge (-3 °C/day from 14 °C, then 24 h at 3 °C) vs. a cold acclimation (-2 °C/week from 14 °C, then 13 weeks at 3 °C), we measured gill-Cu bioaccumulation, net fluxes of ammonia (NH3), chloride (Cl-) and net and unidirectional fluxes of sodium (Na+) over a 30-h Cu exposure. Overall, winter cold did not appear to be challenging to brook char, as cold-acclimated fish had a higher fish condition and showed no sign of ion regulation impairment or increased Cu sensitivity. Contrary to our prediction, we found that Cu bioaccumulation over a 30-h Cu exposure was not significantly affected by acclimation temperature. Effects of temperature on Cu physiological effects were relatively limited (mainly on inhibition of Na+ influx and of NH3 excretion), with slightly greater effects observed in 14 °C-acclimated fish.

[Mineral content in freshwater fish in Shaanxi Province in 2021].

OBJECTIVE: To understand the mineral content of freshwater fish produced in Shaanxi Province and evaluate its related nutritional value. METHODS: According to the 2021 Shaanxi Provincial nutrition monitoring plan, the 9 mineral contents of 13 varieties of freshwater fish, produced in Shaanxi province, were determined by inductively coupled plasma atomic emission spectrometry. The nutritional evaluation of mineral elements was carried out by using the index of nutritional quality(INQ) method. Simultaneously, the correlation between 9 minerals and energy was analyzed by SPSS software. RESULTS: Among the 13 fish species, the contents of P and K were highest, with content ranges of 169-255 and 159-373 mg/100 g, respectively, followed by sodium, calcium, magnesium, iron, zinc. The contents of copper and manganese were lowest. The nutritional evaluation showed that the INQ values of P, K and Mg were than 1, the INQ value of P was highest, which was 4.57-8.72. Some fish have INQ values greater than 1 for calcium, iron, copper and zinc. The correlation between the nine minerals was not strong, as a whole. Only some elements have a correlation coefficient greater than 0.6, indicating that there was a synergistic accumulation effect or antagonistic effect in the fish body. CONCLUSION: The dominant mineral elements in different species of fish were different. However, most fish species can be used as high-quality food sources of phosphorus, potassium, magnesium, copper and zinc.

Morphological and Molecular Characterization of Three Myxosporean Species of the Genera Myxobolus, Henneguya, and Myxidium (Cnidaria: Myxozoa) Infecting Freshwater Fish, Isolated for the First Time in Japan.

The majority of myxosporean species (Cnidaria: Myxozoa) of the genera Myxobolus (35 species), Henneguya (8 species), and Myxidium (9 species) from freshwater or brackish fish in Japan were recorded more than 30 years ago (accumulatively 81.1% [43/53]). The re-discovery and molecular-genetic characterization of these species is a current research priority. During our myxosporean survey in Japanese freshwater fish, we detected three species that had never been recorded in Japan, but in the Russian Far East (Sakhalin Island, and Maritime Province): Myxobolus tribolodonus sp. n., forming cysts in the gills of Tribolodon sachalinensis (syn. M. marinus sensu Aseeva, 2000; M. marinus sensu Sokolov et Frolova, 2015, recorded from the gills of Pseudaspius (syn. Tribolodon) spp.); Henneguya pungitii Achmerov, 1953, forming cysts in the subcutis of external skin and buccal submucosa of Pungitius sinensis; and Myxidium salvelini Konovalov et Shulman, 1966, in the urinary bladder of Oncorhynchus masou ishikawae. These new isolates were characterized by integrated taxonomic approaches, i.e., myxospore morphology and molecular-genetic characterization of the small subunit ribosomal RNA gene (SSU rDNA). These new isolates were phylogenetically differentiated from any species whose SSU rDNA sequences were deposited in the DNA databases, and concurrently compared with recorded species based on classical morphological criteria. All three species were differentiated from myxosporeans previously recorded in Japan, indicating new distribution records out of the Russian Far East. For reliable species identification, accumulation of at least SSU rDNA sequences of known species worldwide is critically important.

Multiple climate change stressors reduce the emergence success of gravel-spawning fish species and alter temporal emergence patterns.

Climate change, with its profound effects on stream sediment, hydrological, and temperature dynamics, will exacerbate impacts on habitat conditions for many species, particularly those with vulnerable early life stages relying on the hyporheic zone, such as gravel-spawning fishes. Due to the complex and interactive nature of multiple stressor effects, we employed large-scale outdoor mesocosms to systemically test how the reproductive success of three gravel-spawning fish species brown trout (Salmo trutta), nase, (Chrondrostoma nasus) and Danube salmon (Hucho hucho) was affected by individual and combined effects of warming (+3-4 °C), fine sediment (increase in <0.85 mm by 22 %) and low-flow (eightfold discharge-reduction). Fine sediment had the most detrimental effect on emergence rate and fry length in all three species, reducing the emergence rate to zero in brown trout, 9 % in nase, and 4 % in Danube salmon. The emergence mortality caused by fine sediment surpassed that of hatching distinctly, suggesting that negative effects due to hypoxia were considerably exacerbated by entombment. Warming had only minor effects as a single stressor, but low flow reduced emergence rates of the spring spawning species nase and Danube salmon by 8 and 50 %, respectively. In combined treatments including fine sediment, however, the emergence success of all three species responded strongly negatively, even in the cyprinid species nase, which showed little interactive effects between stressors regarding hatching success. Warming and fine sediment also led to the earlier emergence of fry, implying a risk of asynchrony with available food resources. This study dramatically shows that climate change can have deleterious impacts on the reproductive success of gravel-spawning fish species, irrespective of taxonomic or ecological traits.

Diet composition and plastic ingestion in Poecilia reticulata from urban streams.

Fish are excellent bioindicators and can reveal the presence of plastic in the environment. Diagnosing the composition and abundance of polymers in the fish diet makes it possible to evaluate their point sources and possible trophic transfers. We aimed to use the gastrointestinal contents of Poecilia reticulata in subtropical urban streams to detect the occurrence, shape, color, size, and chemical composition of polymers. For this, the diet of 240 individuals was analyzed using the volumetric method, and the microplastics (MPs; < 5 mm) recorded were characterized using Raman spectroscopy. Individuals predominantly consumed organic detritus and aquatic macroinvertebrates, with higher proportions of Diptera. A total of 111 plastic particles (< 0.5 to 12 mm) were recorded, and a subset of 14.4% was subjected to a micro-Raman spectrometer (830 nm excitation). The occurrence of polyethylene terephthalate (PET) and polypropylene (PP) with phthalocyanine dye was recorded. Some fragments could not be identified by Raman, but they contained indigo blue dye. Poecilia reticulata had a predominantly detritivorous diet with a record of plastic consumption, reflecting environmental pollution. Our results demonstrate that individuals of P. reticulata have ingested MPs in urban streams. This reinforces the need for future studies on the relationship between the presence of MPs in fish and the level of pollution in streams, comparisons with species of different feeding habits, and the potentially harmful effects on the entire biota.

Effect of potassium ferric hexacyanoferrate in feed on 137Cs uptake and excretion by silver Prussian carp.

The present work documents potassium ferric hexacyanoferrate (KFCF) KFe[Fe(CN)6] containing feed to be an effective and inexpensive countermeasure to reduce the 137Cs contamination of fish. Laboratory aquarium experiments were performed to investigate the effect of feed containing potassium ferric hexacyanoferrate on 137Cs uptake and excretion by silver Prussian carp (Carassius gibelio (Bloch, 1782)). After the 120-day period of 137Cs uptake with feed, reaching equilibrium 137Cs level in fish, fish in some aquariums received feeds containing either 0.1 % or 1 % KFCF for 180 days in combination with clean feed or with feed containing 137Cs. These feeds resulted in 3.6 ± 0.7 and 4.4 ± 0.9 times, respectively, lower activity of 137Cs in fish compared to control fish fed 137Cs throughout the experiment and receiving feed without KFCF. Following the first 100 days with the KFCF containing feed, the 137Cs level in fish fed contaminated feed was even lower than in fish receiving clean feed, with a half-life of 137Cs activity in fish of only T1/2 = 23-35 days. Using clean feed containing 0 %, 0.1 % and 1 % KFCF for 180 days after the 120-day 137Cs uptake period, the excretion rates for 137Cs activity in fish kb' were (6.4 ± 0.2)⋅10-3 day-1, (1.08 ± 0.08)⋅10-2 day-1, and (1.3 ± 0.1)⋅10-2 day-1, respectively (T1/2 = 108 ± 3 days, 64 ± 5 days, and 53 ± 4 days). The decrease rates for 137Cs activity concentrations in fish kb were (8.4 ± 0.3)⋅10-3 day-1, (1.3 ± 0.1)⋅10-2 day-1, and (1.5 ± 0.1)⋅10-2 day-1, respectively (T1/2 = 83 ± 3 days, 53 ± 4 days, and 46 ± 3 days). Our results demonstrate a statistically significant effect (p < 0.01) of KFCF on the excretion of 137Cs from silver Prussian carp: T1/2 decreased from 108 days with clean feeding to 53-64 days when KFCF is added.

Cortisol levels reveal species-specific stress condition in fish from PFAS polluted rivers.

In the context of increasing environmental contamination, our study employed fish as bioindicators, focusing on non-invasive cortisol measurements in scales and fins in response to severe PFAS pollution in the Veneto area of Italy. Our preliminary findings showed species-specific stress responses, as observed in Squalius cephalus and Padogobius bonelli, suggesting the need for broader biomonitoring to capture the complex impact of environmental stressors on aquatic organisms. Moreover, due to the unusual characteristics of the rivers selected for the biomonitoring activity, a possible link between PFAS exposure and cortisol levels in S. cephalus demonstrates the method's potential.

The impact of electromagnetic fields generated by high-voltage power lines on the spatial arrangement of pike (Esox Lucius Linnaeus 1758) embryos.

Urbanization and technological advancements result in the dispersion of antropogenic electromagnetic fields (EMF) that can affect on ecosystems. Therefore, it is important to understand their impact on the environment. Aquatic ecosystems are subject to EMF as part of various electricity sources, e.g., high-voltage transmission lines (HVTL). We examined the impact of EMF generated by HVTL on the spatial arrangement and survival of pike (Esox lucius) embryos. Fertilized eggs were incubated under two HVTL configurations 110 kV and 220 kV compared with a control group devoid of anthropogenic EMF. Embryo orientation and survival were monitored until blastopore closure. The control group showed dominance in the arrangement of embryos along the N-S, NNW-SSE, and NNE-SSW axes, with a slight prevalence of northern directions. EMF originating from HVTL did not exert a significant influence on the spatial arrangement of pike embryos, although some deviations from the arrangement noticed in the control group were observed. Increased embryo mortality was observed only at 110 kV site, but probably due to factors unrelated to EMF. In conclusion, EMF generated by HVTL did not significantly change pike embryo orientation or chances of survival. However, longer exposure or higher EMF levels could provoke notable reactions, requiring ongoing evaluation as power networks continue to spread more widely.

Chemical properties indices for nutritional quality evaluation of Nasser Lake fish, Aswan, Egypt.

Background: Fish is considered an important food because it includes main nutrients (proteins, fats, and ash) and micronutrients (vitamins and minerals). The assessment of fish nutritional content data may offer crucial recommendations regarding freshwater fish consumption and preserving human well-being. Aim: Evaluate the safety and quality properties of Nasser Lake fish, Aswan, Egypt. Methods: A total of 250 samples, 50 of each Nile tilapia, Nile perch, Zander, Catfish, and Elephant-snout, from Nasser Lake, Aswan, Egypt; beheaded, eviscerated, filleted, and minced for determination of proximate analysis, amino acid, fatty acids (FAs), minerals and heavy metal, histamine content, cholesterol content, and sensory assessment. Results: The proximate analysis showed that all the samples examined were of good protein sources, with mean values ranging from 15.92% to 22.89%. Nile perch exhibits the highest levels of total FAs and amino acids. Heavy metal concentrations varied considerably among the analyzed samples, with a significant variance in the detection of metals among the examined fish. The findings show low histamine and cholesterol levels in the examined species, and were in accordance with those set by the National Food Safety Authority (NFSA) and the European Union Commission (EC). Accordingly, all samples are accepted based on their sensory properties. Conclusion: Nasser Lake fish are of high nutritional value and have an excellent supply of amino and FAs.

Progress in the environmental risk assessment of plant protection products in Brazil: An overview of aquatic organism proposals.

Since 2019, the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA) has actively developed pesticide environmental risk assessment (ERA) frameworks adapted to Brazil's specific ecological contexts. This endeavor, supported by funding from the Brazilian Ministry of Justice and in partnership with academic institutions, has led to a concerted effort to establish ERA protocols for various taxa, including birds and mammals, soil organisms, aquatic organisms, and reptiles and amphibians. The outcomes of this initiative were conveyed in two workshops held in February and November 2023, during which the agency communicated its findings to the technical-regulatory community. This article represents one of three articles that provide more detailed insights into the ERA propositions for all taxa. In this article, we summarize the proposals for aquatic organisms presented and discussed during the workshops, which can be used as an informational source by the technical-regulatory community. Integr Environ Assess Manag 2024;00:1-6. © 2024 The Author(s). Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Zoonotic human liver flukes, a type 1 biocarcinogen, in freshwater fishes: genetic analysis and confirmation of molluscan vectors and reservoir hosts in Bangladesh.

BACKGROUND: Opisthorchiid flukes, particularly Opisthorchis viverrini, Opisthorchis felineus, Clonorchis sinensis, and Metorchis spp. are the most common fish-borne zoonotic human liver flukes (hLFs). Liver fluke infections are more prevalent in resource-deprived and underprivileged areas. We herein estimated the prevalence of the metacercariae (MC) of major hLFs in common large freshwater fishes (lFWF) marketed for human consumption from some selected areas of Bangladesh along with detection of their molluscan vectors and reservoirs. METHODS: The current status of fish-borne zoonotic hLF infections in lFWF was investigated along with their molluscan vectors and mammalian reservoir hosts in Mymensingh and Kishoreganj in Bangladesh from July 2018-June 2022 using conventional and multiple molecular techniques, such as PCR, PCR-restriction fragment length polymorphism (RFLP), sequencing, and bioinformatic analyses. The infection rate of fishes was analyzed using the Z-test and the loads of MC were compared using the chi-squared (χ2) test. RESULTS: The MC of C. sinensis, Opisthorchis spp., and Metorchis spp. were detected in 11 species of common and popular lFWF. In lFWF, the estimated prevalence was 18.7% and the mean load was 137.4 ± 149.8 MC per 100 g of fish. The prevalence was the highest (P < 0.05) in spotted snakehead fishes (Channa punctata, 63.6%). The highest rate of infection (P < 0.05) was observed with the MC of C. sinensis (11.8%). Metacercariae were almost equally (P > 0.05) distributed between the head and body of fishes. The infection rate was slightly higher in cultured (19.6%) fishes. The MC of C. sinensis, O. felineus, O. viverrini, and Metorchis orientalis in fishes were confirmed using PCR, PCR-RFLP and bioinformatics. The cercariae of opisthorchiid (Pleurolophocercus cercariae) flukes were only recovered from Bithynia spp. (3.9%, 42 out of 1089). The ova of hLFs from dogs (4.3%, 5 out of 116) and cats (6.0%, 6 out of 100), and adult flukes (M. orientalis) from ducks (41.1% 113 out of 275) were detected. CONCLUSIONS: The MC of hLFs are highly prevalent in fresh water fishes in Bangladesh. Reservoir hosts, such as street dogs, cats, and ducks carried the patent infection, and residents of Bangladesh are at risk.

Prioritizing the multifaceted community and species uniqueness for the conservation of lacustrine fishes in the largest subtropical floodplain, China.

Hydrological variations affect habitat characteristics and fish distribution in floodplain lakes. Assessing the contributions of the local community (i.e., LCBD, community uniqueness) and species to overall ß diversity (i.e., SCBD, species uniqueness) of fish assemblages is valuable for habitat and species conservation planning, particularly from functional and phylogenetic perspectives. We examined the changes in multifaceted LCBD and SCBD of fish across different hydrological periods in the Poyang Lake, China, and analyzed their responsive mechanisms using regression models, based on which the conservation priorities of habitats and species were evaluated. The findings revealed that taxonomic, functional, and phylogenetic LCBD and SCBD were lowest during the wet season compared to the normal and dry seasons, emphasizing the regulatory effects of hydrological regimes on fish assemblages. Taxonomic and functional LCBD were significantly impacted by the mean abundance of migratory fish, highlighting the importance of specific species combinations on community uniqueness. Taxonomic and functional SCBD exhibited positive correlations primarily with mean abundance, suggesting the potential uniqueness of certain common species. Additionally, we identified the river-lake junction (Hukou station) and natural reserve (Xingzi and Nanjishan stations) with high overall community uniqueness as critical habitats. We also emphasized the necessity for increased conservation efforts for species having high overall species uniqueness during different hydrological periods, including Coilia brachygnathus, Ctenopharyngodon idella, Coilia nasus, Saurogobio dabryi, Hypophthalmichthys molitrix, Megalobrama amblycephala, and Parabramis pekinensis. This research underscores the significance of integrating multiple ecological perspectives to manage biodiversity changes and maintain ecological conservation values effectively.

A non-microcystin-producing Microcystis wesenbergii strain alters fish food intake by disturbing neuro-endocrine appetite regulation.

Cyanobacterial harmful algal blooms (cHABs) are pervasive sources of stress resulting in neurotoxicity in fish. A member of the widely distributed Microcystis genus of bloom-forming cyanobacteria, Microcystis wesenbergii can be found in many freshwater lakes, including Dianchi Lake (China), where it has become one of the dominant contributors to the lake's recurrent blooms. However, unlike its more well-known counterpart M. aeruginosa, the effects of dense non-microcystin-containing M. wesenbergii blooms are seldom studied. The disturbance of appetite regulation and feeding behaviour can have downstream effects on the growth of teleost fish, posing a significant challenge to aquaculture and conservation efforts. Here we examined the effects of M. wesenbergii blooms on the food intake of Acrossocheilus yunnanensis, a native cyprinid in southern China. This fish species has disappeared in Dianchi Lake, and its reintroduction might be negatively affected by the presence of this newly-dominant Microcystis species. We co-cultured juvenile A. yunnanensis with a non-microcystin-producing strain of M. wesenbergii at initial densities between 5 × 104 and 1 × 106 cells/mL and monitored fish feeding behaviour and changes in neurotransmitter and hormone protein levels. High-density M. wesenbergii cultures increased the feeding rate of co-cultured fish, elevating concentrations of appetite-stimulating signalling molecules (Agouti-related protein and γ-aminobutyric acid), while decreasing inhibitory ones (POMC). These changes coincided with histopathological alterations and reduced somatic indices in brain and intestinal tissues. Given this potential for detrimental effects and dysregulation of food intake, further studies are necessary to determine the impacts of chronic exposure of M. wesenbergii in wild fish.

Microelements, Fatty Acid Profile, and Selected Biomarkers in Grass Carp (Ctenopharyngodon idella) Muscle Tissue: Seasonal Variations and Health Risk Assessment.

The study assesses associations between microelement levels, fatty acid composition, and oxidative stress markers in grass carp muscle in the summer and autumn seasons. Additionally, various factors were considered, including the estimated daily intake (EDI), target hazard quotient (THQ), total THQ (TTHQ), and metal pollution index (MPI), to evaluate potential health risks for consumers. The microelements (Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, Se, Sr, and Zn) were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and total mercury was determined using cold-vapor atomic absorption spectroscopy (CV-AAS). Fatty acid profiling was realized using gas chromatography (GC) detection with a flame ionization detector (FID). The overall tendency of microelement levels was as follows: Fe > Zn > Al > Sr > Ba > Ni > Se > Cr> Cu > Mn > Pb > As > Li > Hg;

The effects of commercial 2,4-D herbicide on game fish species: Natural lake water vs. laboratory system water.

Aquatic herbicides with active ingredient 2,4-dichlorophenoxyacteic acid (2,4-D) are commonly used to control and combat aquatic non-native species that cause detrimental impacts including habitat destruction, strained resources among biota, and biodiversity loss. While many (eco)toxicology studies are performed in the laboratory under highly controlled circumstances, these studies may disregard the nuances and disorder that come with the complexity of natural aquatic ecosystems. Therefore, we conducted a series of laboratory experiments using laboratory system water, different lake waters, and different water parameters to determine the effects of ecologically relevant concentrations of 2,4-D (0.00-4.00 ppm a.e.) on the development and survival of two freshwater game species (Sander vitreus and Esox lucius). For 2,4-D exposures using different water sources, there were significant main effects of 2,4-D concentration and water source on walleye embryo and larval survival, however, there was no significant interaction between 2,4-D exposure and water source. For 2,4-D exposures and pH (5-9 pH), there were significant main effects of 2,4-D concentration and pH on walleye and northern pike embryo survival and a significant interaction between 2,4-D exposure and pH. Our results indicate that 2,4-D exposures in controlled laboratory system water can predict similar outcomes as 2,4-D exposures in natural lake water. Moreover, individual water parameters, such as pH, play a significant role in the toxicity of 2,4-D. Taken together, these results suggest that highly controlled laboratory studies are a useful tool for predicting impacts on survival of non-target fish in natural waters, but it is crucial for management agencies to consider individual water sources and specific lake water parameters in herbicide risk assessments to minimize the impacts to non-target organism.

Oxynoemacheilus fatmae, a new species from the Güzelhisar Stream in the Aegean Sea basin, Türkiye (Teleostei: Nemacheilidae).

Oxynoemacheilus fatmae, a new species, is found in the Güzelhisar Stream in the northern Aegean Sea basin. It is differentiated from all other species of Oxynoemacheilus in the northern Aegean Sea and adjacent basins by having four to eight irregularly shaped narrow black bars on the posterior part of flank, and anterior parts of the flank with a marbled pattern. O. fatmae is differentiated from the closest species Oxynoemacheilus theophilii by having 14 fixed diagnostic nucleotide substitution sites, and the pair-wise genetic distance is 2.22%. It further differs from O. theophilii by having a slenderer body (body at dorsal-fin origin: 15%-17% standard length [SL] vs. 17%-18%), a slenderer caudal peduncle (10%-12% SL vs. 12%-13%), a more forked caudal fin (length of middle caudal-fin lope: 16%-19% SL vs. 19%-23%), and the absence the dorsal and ventral adipose crests on the caudal peduncle behind the vertical of the posterior anal-fin base (vs. present). Three species delimitation tests (assemble species by automatic partitioning (ASAP), automatic barcode gap discovery (ABGD) and generalized mixed yule-coalescent (GMYC)) and phylogenetic analyses reinforce the validity of O. fatmae as a distinct species.