Effects of long-term exposure to high temperature on growth performance, chemical composition, hematological and histological changes, and physiological responses in hybrid catfish [♂Clarias gariepinus (Burchell, 1822) ×♀C. macrocephalus (Günther, 1864)]

Heat stress induces oxidative stress and weakens the immune system in catfish Clarias magur: Evidence from physiological, histological, and transcriptomic analyses

Climate change is unequivocal, causing a rise in the Earth's temperature, which ultimately impacts all ecosystems. However, aquatic ecosystems are most severely affected by rising temperatures resulting in huge losses to aquaculture industry. The present study investigated the oxidative stress, histopathological changes, and transcriptomic responses in a freshwater catfish Clarias magur subjected to acute heat stress. Fish were exposed to four different temperatures, i.e., 28, 30, 32, and 34 °C, for 96 h to assess their heat tolerance and adaptation behavior. Fish kept at 26 °C were considered the control group. Elevated levels of key antioxidative enzymes such as catalase, glutathione reductase, and superoxide dismutase, were recorded in vital organs (gills, kidney, liver, and rosette). High rates of lipid peroxidation were also observed in the gills, kidney, liver, and rosette. An analysis of the top 25 differentially expressed genes of the gill transcriptome revealed that 72 percent of the transcripts were represented by innate and adaptive immune response genes. Downregulation of BOLA class I and MHC class I molecules indicated impaired immunity whereas, upregulation of MHC class II beta chain and GTPase IMAP8 suggested a compensatory immune response. These findings were also supported by the observed histoarchitectural alterations, such as disintegration of the skin barrier, hepatic and nephrotic apoptosis, tissue hyperplasia, macrophage infiltration, and development of splenic granulomas. This study provides important insights into physiological and molecular mechanisms underlying acute heat stress responses. Understanding these mechanisms is important for developing mitigation strategies to improve the sustainability and resilience of commercially important catfish under continuously changing climatic conditions.

Long-term thermal stress reshapes the tolerance of head kidney of Hong Kong catfish (Clarias fuscus) to acute heat shock by regulating energy metabolism and immune response

Elevated water temperatures caused by climate warming can affect fish survival. However, fish can maintain normal physiological functions through physiological plasticity. When temperature fluctuations exceed their tolerance range, even stress-resistant species like Siluriformes are affected. It is known that fish have adaptive regulation mechanisms to reshape their tolerance to temperature stress, but the ability to respond to acute thermal shock and recover after adaptive remodeling remains unclear. This study investigated the effects of different culture temperatures on the ability of Hong Kong catfish (Clarias fuscus) to respond to acute heat stress and stress recovery. C. fuscus were cultured at normal temperature (NT, 26 °C) or high temperature (HT, 34 °C) for 90 days, and then their head kidney transcriptome was analyzed after acute heat stress (34 °C) and subsequent recovery (26 °C). The results revealed 8165 differentially expressed genes (DEGs) in the NT group and 8537 DEGs in the HT group during the entire temperature treatment process, with each group responding differently to various stages of temperature treatment. Enrichment analysis showed that both NT and HT groups had enriched pathways related to energy metabolism and immune response during acute heat stress. However, acute heat stress disrupted the energy supply and oxidative metabolism in the NT group, while enhancing the HT group's ability to respond to repeated heat stress. This experiment demonstrated that high-temperature culture reshaped the energy metabolism balance in the head kidney tissue, improving anti-stress and stress recovery abilities. These findings lay a foundation for further research on the plasticity of fish in coping with acute temperature changes.

Dietary Pelargonium Sidoides extract mitigates thermal stress in Oreochromis niloticus: physiological and immunological insights

Extreme water temperatures caused by climate change constitute a serious threat to aquaculture producers. Aquatic ectotherms, which are unable to regulate their body temperature, are highly affected by temperature changes and serve as excellent models for studying the effects of these factors. This study aimed to examine the impact of extreme temperature variation on the growth, biological indices, antioxidant capacity, histology, and disease resistance of Oreochromis niloticus. The fish were exposed to 17 °C, 25 °C (control), or 33 °C for 30 days, imitating extreme temperature events. Additionally, a mitigation trial was conducted via dietary Pelargonium sidoides root extract (PS). Compared with that at 25 °C, growth performance was significantly impaired by thermal stress. The exposure of O. niloticus to thermal stress, especially cold stress, elicited significant increases in stress biomarkers (cortisol and glucose), hepatorenal functions (AST, ALT, LDH, and creatinine), and lipid profiles (triglyceride, cholesterol, HDL, and LDL). Cold stress induced immunosuppression in terms of reduced total protein, phagocytosis, serum bacterial activity, total immunoglobulin, and white blood cells, all of which increased the susceptibility of the fish to Aeromonas hydrophila infection and increased mortality. In addition to severe pathological lesions in the gills, liver, and intestine, thermal stress causes an imbalance in antioxidant/oxidative stress. Nevertheless, the PS extract counteracted these detrimental impacts of thermal stress. In conclusion, PS may be recommended for enhancing immunity and antioxidative resistance to mitigate the effects of thermal stress on O. niloticus. These findings may be useful in developing hypotheses about the physiology and immunology of fish in extreme-temperature environments.

Influences of thermal stress on the growth biometrics, stress indicators, oxidative stress biomarkers, and histopathological alterations in European seabass, Dicentrarchus labrax, juveniles

This study examined how European seabass, Dicentrarchus labrax, juveniles are affected by heat stress in several ways, including growth biometrics, stress indicators, oxidative stress biomarkers, and histopathological changes. Our research aims to gain a better understanding of the impact of thermal stress on these parameters. Hence, European seabass juveniles (30-32 g) were exposed to temperatures of 20 °C, 23 °C, 26 °C, 29 °C, and 31 °C using a 28-day bioassay. It was noted that the fish showed better performance indices at 23 °C and 26 °C. However, fish reared at 20 °C showed intermediate growth, while the fish reared at 31 °C displayed poor performance with low survival rates. As the water temperature increased from 20 to 31 °C, the levels of glucose, cortisol, aspartate aminotransferase, and alanine aminotransferase in the fish blood also increased, suggesting that the fish were under stress. Furthermore, activities of superoxide dismutase (SOD) and catalase (CAT), as well as levels of malondialdehyde, increased significantly (P < 0.05) with the rise in the rearing temperature, particularly at 31 °C. This suggested that European seabass juveniles experienced oxidative stress. Additionally, the mRNA expression of SOD and CAT genes was upregulated at 31 °C compared to those reared at 23-26 °C. This high upregulation of both genes led to an increase in the secretion of SOD and CAT. Juveniles of European seabass raised in 31 °C for 28 days showed significant damage in the histological structure of their kidney, liver, and gills. In addition to fusion and blood congestion of secondary lamellae, the fish in this treatment (31 °C) displayed edema, epithelial lifting, and blood congestion of the gill epithelium. After 28 days, fish cultivated at 31 °C had sinusoid dilatation, hyperemia, and nuclear hypertrophy in their liver tissues. Furthermore, hyperemia, tubular necrosis, and severe glomerular congestion were observed in fish raised in water temperatures as high as 31 °C for 28 days. This study recommends farming European seabass at 23 °C and 26 °C, which were the optimum temperatures. By global warming due to climatic changes, water temperature may reach up to 31 °C or more, which will cause adverse effects on fish performance and increase the oxidative stress.

Impacts of dietary α-tocopherol acetate on physiological response, antioxidant activity, innate immunity, and histopathological status of Nile tilapia, Oreochromis niloticus under heat and salinity stress

Aquaculture fish face stresses include temperature, ammonia levels, water salinity, and dissolved oxygen. In order to sustain finfish output, it is necessary to assess the impact of unexpected weather on their performance. Thus, this study examined whether Nile tilapia's vitamin E intake reduces heat and salinity stress. After 56 days of feeding a diet enriched with vitamin E at 0, 150, 300, 600, and 1200 mg/kg, Nile tilapia were split into two groups: one was given a 28 g/L salinity increase, and the other to a temperature increase of 36 °C. Heat and salinity stress increased cortisol, glycose AST, ALT, triglycerides, and total cholesterol while decreasing albumin, globulin, and protein. Fish diets with vitamin E significantly improved the parameters above before and after heat and salinity stress. However, heat and salinity stress inhibited superoxide dismutase, catalase, glutathione peroxidase, nitrous oxide, lysozyme, phagocytosis, and immunoglobulin, reducing antioxidant activity and immunological responses. The Nile tilapia diet's vitamin E content increased antioxidant activity and immunological response before and after stress. Heat and salinity stress increased lipid peroxidation (malondialdehyde), but vitamin E-fed fish had lower values than controls. In addition to mild hepatocyte degeneration, pyknosis, and hepatic central vein congestion, heat and salinity stress cause severe vascular congestion with gill lamellar epithelium degeneration, sloughing, and primary filament congestion. In Vit E-treated groups, histomorphology returned to normal. Results showed that vitamin E at 1200 mg/kg in the Nile tilapia diet may be an effective antioxidant immunostimulant against environmental stressors like heat and salinity.

Long-term thermal acclimation enhances heat resistance of Hong Kong catfish (Clarias fuscus) by modulating gill tissue structure, antioxidant capacity and immune metabolic pathways

The rapid temperature changes caused by global warming significantly challenge fish survival by affecting various biological processes. Fish generally mitigate stress through physiological plasticity, but when temperature changes exceed their tolerance limits, even adaptable species like Siluriformes can experience internal disruptions. This study investigates the effects of extreme thermal climate on Hong Kong catfish (Clarias fuscus), native to tropical and subtropical regions. C. fuscus were exposed to normal temperature (NT, 26 ℃) or high temperature (HT, 34 ℃) condition for 90 days. Subsequently, histological, biochemical, and transcriptomic changes in gill tissue were observed after exposure to acute high temperatures (34 ℃) and subsequent temperature recovery (26 ℃). Histological analysis revealed that C. fuscus in the HT group exhibited less impact from sudden temperature shifts compared to the NT group, as they adapted by reducing the interlamellar cell mass (ILCM) and lamellae thickness (LT) of gill tissue, thereby mitigating the aftermath of acute heat shock. Biochemical analysis showed that catalase (CAT) activity in the high temperature group continued to increase, while malondialdehyde (MDA) levels decreased, suggesting establishment of a new oxidative balance and enhanced environmental adaptability. Transcriptome analysis identified 520 and 463 differentially expressed genes in the NT and HT groups, respectively, in response to acute temperature changes. Enrichment analysis highlighted that in response to acute temperature changes, the NT group inhibited apoptosis and ferroptosis by regulating the activity of alox12, gclc, and hmox1a, thereby attenuating the adverse effects of heat stress. Conversely, the HT group increased the activity of pfkma and pkma to provide sufficient energy for tissue repair. The higher degree of heat shock protein (Hsp) response in NT group also indicated more severe heat stress injury. These findings demonstrate alterations in gill tissue structure, regulation of oxidative balance, and the response of immune metabolic pathways to acute temperature fluctuations in C. fuscus following thermal exposure, suggesting potential avenues for further exploration into the thermal tolerance plasticity of fish adapting to global warming.

Black sand nanoparticles and heat stress impacts the neurological and oxidative stress indices and splenic-renal histology of Clarias gariepinus

In Egypt, while many studies have focused on the radiometry and mineralogy of black sands, research on their effects on nearby aquatic organisms is rare. This study aimed to assess the combined effects of heat stress (HS) and black sand nanoparticles (BS-NPs) on renal function, antioxidant responses (TAC, SOD, CAT), neuro-stress indicators (AchE, cortisol), and to conduct histopathological investigations in the kidney and spleen tissues of African catfish Clarias gariepinus over a 15-day period to exposure to control, HS (32 °C), BS (6.4 g/kg diet) and HS + BS groups. The outcomes revealed that thermal stress alone showed no significant difference from the control. However, creatinine and uric acid levels were significantly higher in the BS-NPs and HS + BS-NPs groups (p < 0.001). Antioxidant markers (TAC, SOD, and CAT) were substantially reduced across all treated groups (0.05 ≥ p < 0.0001). AchE levels were significantly elevated in BS-NPs and HS + BS-NPs (p < 0.001), while cortisol levels were higher in these groups but not significantly different in HS. Degeneration and necrosis in the white and red pulps, scattered lymphocytes, and increased collagen fiber surrounding blood vessels and the lining of the ellipsoid structure were all evident in the spleen, along with the enlargement of the melanomacrophage centers with big granular, irregular, and brown pigments (hemosiderin). Our study, therefore, provides new insights into how heat stress, an abiotic environmental factor, influences the toxicity of black sand nanoparticles in catfish.

Effect of temperature fluctuation on the physiological stress response of hybrid pearl gentian grouper during waterless keeping alive

Temperature fluctuations are inevitable and have an important impact on the survival of fish during transportation. Therefore, the effect of temperature fluctuation (15 ± 1 °C, 15 ± 2 °C, 15 ± 3 °C) on the muscle quality, physiological, and immune function of hybrid pearl gentian grouper before waterless keeping alive, during keeping alive (0 h, 3 h, 6 h, 9 h, 12 h), and after revival for 12 h was investigated. The plasma glucose concentration of grouper gradually decreased to 0.645 ± 0.007 mg/mL, 0.657 ± 0.006 mg/mL, and 0.677 ± 0.004 mg/mL after keeping alive for 12 h under different temperature fluctuations of 15 ± 1 °C, 15 ± 2 °C, and 15 ± 3 °C, respectively. The cortisol concentration and lysozyme activity of pearl gentian grouper significantly increased (P < 0.05) during the keeping alive period. The results suggested that fish bodies would produce acute stress response, strengthen immune defense ability, and quickly consume a lot of energy to adapt to the low-temperature anhydrous environment. In all treatment groups, the activities of plasma alanine transaminase (ALT) and aspartate aminotransferase (AST) and the content of creatinine gradually increased with the prolongation of the survival time. The hardness and springiness of muscle decreased from 5965.99 ± 20.15 and 0.90 ± 0.00 to 3490.69 ± 27.59 and 0.42 ± 0.01, respectively. In the meanwhile, the change of glycogen and lactic acid content was opposite, indicating that temperature fluctuation harmed the liver, kidney function, and muscle quality. In the later stage of keeping alive, the superoxide dismutase (SOD) and catalase (CAT) activities decreased, especially in the temperature fluctuation group of ±3 °C (125.99 ± 5.48 U/mgprot, 44.21 ± 0.63 U/mgprot), leading to an imbalance of fish immunity. In summary, higher temperature fluctuation would influence the physiological function and immune defense ability and decrease the quality of pearl gentian grouper.

Effects of climate change and mixtures of pesticides on the Amazonian fish Colossoma macropomum

Several studies highlighted the complexity of mixing pesticides present in Amazonian aquatic environments today. There is evidence that indicates that ongoing climate change can alter the pattern of pesticide use, increasing the concentration and frequency of pesticide applications. It is known that the combination of thermal and chemical stress can induce interactive effects in aquatic biota, which accentuates cell and molecular damage. However, considering that the effects of climate change go beyond the increase in temperature the objective of this study was to evaluate the effect of climate change scenarios proposed by 6 th IPCC report and a mixture of pesticides on the tambaqui (Colossoma macropomum). The hypothesis of this study is that the negative effects will be accentuated by the combination of an extreme climate changes scenario and a mixture of pesticides. To test the hypothesis, juvenile tambaqui were exposed to a combination of four pesticides (chlorpyrifos, malathion, carbendazim and atrazine) in two scenarios, one that simulates current environmental conditions and another that predicted the environmental scenario for the year 2100. Fish were subjected to the experimental conditions for 96 h. At the end of the experiment, samples of blood, gills, liver, brain, and muscle were obtained for hematological, genotoxic, biochemical, and histopathological analyses. The results demonstrate that environmentally realistic concentrations of pesticides, when mixed, can alter the biochemical responses of tambaqui. The extreme scenario promotes hematological adjustments, but impairs branchial antioxidant enzymes. There is an interaction between the mixture of pesticides and the extreme scenario, accentuating liver tissue damage, which demonstrates that even increased activity of antioxidant and biotransformation enzymes were not sufficient to prevent liver damage.

Effect of different temperature variations on the physiological state of catfish species: a systematic review

Catfish are a highly diverse group of fish that are found in various regions across the globe. The significance of catfish culture extends to various aspects, including food security, economic advancement, preservation of cultural legacy, and ecological stewardship. The catfish industry is presently encountering unprecedented challenges as a consequence of the variability in water temperature caused by climate change. Temperature is a significant abiotic component that regulates and restricts fish physiology throughout their life cycle. The impact of severe temperatures on various species of catfish is dependent upon the magnitude of the stressor and additional influencing factors. This paper presents an analysis of the effects of temperature fluctuations on various aspects of catfish species, including growth and survival, blood parameters, enzymatic and hormone response, oxygen consumption rates, sound generation and hearing skills, nutritional requirements, and other phenotypic attributes. While this review is certainly not exhaustive, it offers a broad synopsis of the ideal temperature ranges that are most favorable for several catfish species. In-depth research to investigate the interacting impacts of severe temperature occurrences in conjunction with other associated environmental stresses on a wider variety of catfish species is crucial in order to further our understanding of how catfish species will respond to the anticipated climate change in the future.

Effects of Chronic Heat Stress on Growth, Apoptosis, Antioxidant Enzymes, Transcriptomic Profiles, and Immune-Related Genes of Hong Kong Catfish (Clarias fuscus)

Chronic heat stress can have detrimental effects on the survival of fish. This study aimed to investigate the impact of prolonged high temperatures on the growth, antioxidant capacity, apoptosis, and transcriptome analysis of Hong Kong catfish (Clarias fuscus). By analyzing the morphological statistics of C. fuscus subjected to chronic high-temperature stress for 30, 60, and 90 days, it was observed that the growth of C. fuscus was inhibited compared to the control group. The experimental group showed a significant decrease in body weight and body length compared to the control group after 60 and 90 days of high-temperature stress (p < 0.05, p < 0.01). A biochemical analysis revealed significant alterations in the activities of three antioxidant enzymes superoxide dismutase activity (SOD); catalase activity (CAT); glutathione peroxidase activity (GPx), the malondialdehyde content (MDA), and the concentrations of serum alkaline phosphatase (ALP); Aspartate aminotransferase (AST); and alanine transaminase (ALT) in the liver. TUNEL staining indicated stronger apoptotic signals in the high-temperature-stress group compared to the control group, suggesting that chronic high-temperature-induced oxidative stress, leading to liver tissue injury and apoptosis. Transcriptome analysis identified a total of 1330 DEGs, with 835 genes being upregulated and 495 genes being downregulated compared to the control group. These genes may be associated with oxidative stress, apoptosis, and immune response. The findings elucidate the growth changes in C. fuscus under chronic high temperature and provide insights into the underlying response mechanisms to a high-temperature environment.

Recent advances in the color of aquatic products: Evaluation methods, discoloration mechanism, and protection technologies

Color plays a pivotal role in guiding and assessing the industrial production of aquatic products due to the swift sensory perception of information through vision. This review provides a comprehensive overview of the following four aspects: (a) mechanisms governing natural color formation in aquatic products, (b) factors and mechanisms contributing to the discoloration of aquatic products, (c) cutting-edge methods for color analysis and detection, and (d) current valuable techniques for preserving color quality. The natural color of aquatic products is derived from skin chromatophores, endogenous pigment proteins, and astaxanthin. Discoloration of aquatic products can occur due to lipid oxidation, as well as enzymatic and non-enzymatic browning. Furthermore, this review examines frontier color protective technologies, encompassing physical methods like ultra-high pressure, irradiation, and low-temperature plasma, as well as chemical methods involving natural preservatives. The findings of this study offer significant insights into the development of high-quality aquatic products.

Effects of thermal stress responses in goldfish (Carassius auratus): growth performance, total carotenoids and coloration, hematology, liver histology, and critical thermal maximum

The present study aimed to investigate the effect of thermal stress on growth, feed utilization, coloration, hematology, liver histology, and critical thermal maximum (CTmax) in goldfish (Carassius auratus) cultured at three different acclimation temperatures including 27 °C, 30 °C, and 34 °C for 10 weeks. Goldfish were assigned randomly to tanks with a quadruplicate setup, accommodating 20 fish per tank. The result showed that fish acclimated to different temperatures did not significantly differ in weight gain (WG) and specific growth rate (SGR). However, increasing temperature significantly decreased feed efficiency ratio (FER), protein efficiency ratio (PER), and protein productive value (PPV), but significantly increased feed conversion ratio (FCR) (P < 0.05). The coloration parameters significantly decreased by high temperature in the trunk region with increasing temperature (L* and a* at week 5; L*, a*, and b* at week 10; P < 0.05). Total carotenoid contents in serum, fin, muscle, and skin also significantly decreased with increasing temperature (P < 0.05). Total protein, albumin, and globulin levels exhibited a notable decrease, while the albumin: globulin ratio showed a slight insignificant increase, with increasing temperature. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total cholesterol, and triglycerides significantly increased with increasing temperature (P < 0.05). While, high-density lipoprotein cholesterol (HDL-c) decreased linearly (P < 0.05). Glucose and cortisol levels linearly increased with increasing temperature, the highest levels being observed in the 34 °C group. Liver histology showed swollen hepatocytes, nuclei displacement, and infiltration of inflammation in fish cultured at 34 °C. Goldfish acclimated to 34 °C displayed a higher CTmax of 43.83 °C compared to other groups. The present study showed that temperature should be kept below 34 °C for goldfish culture to prevent high FCR, fading coloration, and liver damages.

A simple dataset of water quality on aquaponic fish ponds based on an internet of things measurement device

This dataset contains pH, TDS, and water temperature measurements using internet of things devices and sensors. The dataset is collected using an IoT sensor with ESP8266 as the microcontroller. Urban farmers can use this dataset with limited land in aquaponic cultivation as initial reference values or novice researchers to implement basic machine learning algorithms. Measurements were made on aquaculture consisting of 1m3 pond media with a water volume of 1 m x 1 m × 70 cm and hydroponic media with the Nutrient Film Technique (NFT) system. Measurements were carried out for three months from January 2023 to March 2023. The available datasets are raw data and filtered data.

Transcriptomic and Phenotypic Analysis of CRISPR/Cas9-Mediated gluk2 Knockout in Zebrafish

As a subtype of kainite receptors (KARs), GluK2 plays a role in the perception of cold in the periphery sensory neuron. However, the molecular mechanism for gluk2 on the cold stress in fish has not been reported. In this article, real-time PCR assays showed that gluk2 was highly expressed in the brain and eyes of adult zebrafish. To study the functions of gluk2, gene knockout was carried out using the CRISPR/Cas9 system. According to RNA-seq analysis, we selected the differentially expressed genes (DEGs) that had significant differences in at least three tissues of the liver, gill, intestine, skin, brain, and eyes. Gene Ontology (GO) enrichment analysis revealed that cry1ba, cry2, per1b, per2, hsp70.1, hsp70.2, hsp70l, hsp90aa1.1, hsp90aa1.2, hspb1, trpv1, slc27a1b, park2, ucp3, and METRNL were significantly enriched in the ‘Response to temperature stimulus’ pathway. Through behavioral phenotyping assay, the gluk2^−/− larval mutant displayed obvious deficiency in cold stress. Furthermore, TUNEL (TdT-mediated dUTP Nick-End Labeling) staining proved that the gill apoptosis of gluk2^−/− mutant was increased approximately 60 times compared with the wild-type after gradient cooling to 8 °C for 15 h. Overall, our data suggested that gluk2 was necessary for cold tolerance in zebrafish.