Responses Of Aquatic Animals Research Articles

Effects of hypo-osmotic stress on osmoregulation, antioxidant response, and energy metabolism in sea cucumber Holothuria moebii under desalination environment

With global climate changing, hypo-salinity events are increasing in frequency and duration because of continuous rainfall and freshwater inflow, which causes reduced cytosolic osmolarity and cellular stress responses in aquatic animals. Sea cucumbers are considered stenohaline because they lack osmoregulatory organs and are vulnerable to salinity fluctuations. In this study, we performed multiple biochemical assays, de novo transcriptomics, and widely targeted metabolomics to comprehensively explore the osmoregulatory mechanisms and physiological responses of sea cucumber Holothuria moebii to hypo-osmotic stress, which is a representative specie that is frequently exposed to hypo-saline intertidal zones. Our results found that H. moebii contracted their ambulacral feet and oral tentacles, and the coelomic fluid ion concentrations were reduced to be consistent with the environment. The microvilli of intestines and respiratory trees underwent degeneration, and the cytoplasm exhibited swelling and vacuolation. Moreover, the Na+, K+, and Cl− concentrations and Na+/K+-ATPase activity were significantly reduced under hypo-osmotic stress. The decrease in protein kinase A activity and increase in 5′-AMP level indicated a significant inhibition of the cAMP signaling pathway to regulate ion concentrations. And small intracellular organic molecules (amino acids, nucleotides and their derivatives) also play crucial roles in osmoregulation through oxidative deamination of glutamate, nucleotide catabolism, and nucleic acid synthesis. Moreover, lysosomes and peroxisomes removed oxidative damage, whereas antioxidant metabolites, such as N-acetyl amino acids and glutathione, were increased to resist oxidative stress. With prolonged hypo-osmotic stress, glycerophospholipid metabolism was enhanced to maintain membrane stability. Furthermore, acyl-CoA-binding protein activity was significantly inhibited, and only a small amount of acylcarnitine was significantly accumulated, which indicated a disruption in energy metabolism. PPAR signaling pathway and choline content were up-regulated to promote fatty acid metabolism under hypo-osmotic stress. Overall, our results provide new insights into the osmoregulatory mechanisms and physiological responses of sea cucumbers to hypo-osmotic stress.

Identification of key overlapping DEGs and molecular pathways under multiple stressors in the liver of Nile tilapia (Oreochromis niloticus)

The identification of key genes and molecular pathways that are involved in the response to stressors is crucial for controlling stress in fish and sustainable aquaculture. Environmental stressors can induce stress responses in aquatic animals, resulting in compromised immune function, inhibited growth, and increased mortality rates. mRNA-seq analysis provides a powerful tool to identify key genes and pathways associated with stress response. In the present study, mRNA-seq analysis was employed to identify key overlapping differentially expressed genes (DEGs) and molecular pathways under salinity, nitrite, copper, and pH stress in the liver of Nile tilapia (Oreochromis niloticus). The pathways associated with the immune response, oxygen transport, homeostasis, and oxidative stress were enriched across all stressors. The top KEGG pathways were complement and coagulation cascades, PPAR signaling pathway, and cardiac muscle contraction. The top GO enrichment terms were oxidoreductase activity, aerobic respiration, endopeptidase inhibitor activity, endopeptidase regulator activity, heme binding, and iron ion binding. The complement genes (C3, C4, C5, factor B, and factor H), alpha-2-macroglobulin (A2M), hemoglobin subunit epsilon (HBE), hemoglobin subunit alpha (HBA), coagulation factor genes (XI and X) and the cytochrome c oxidase (COX) gene family (cox1, cox2, cox3, cytochrome P450) were identified as key shared genes across multiple stressors. The discovery of these genes and molecular pathways provided a better understanding of the molecular mechanism underlying the stress response in Nile tilapia. The results of the present study can facilitate the development of stress management strategies in Nile tilapia.

Editorial: The adaptation and response of aquatic animals in the context of global climate change

Editorial: The adaptation and response of aquatic animals in the context of global climate change

Carotenoids modulate stress tolerance and immune responses in aquatic animals

AbstractAquaculture continues to expand swiftly and remains the fastest‐growing food industry worldwide amidst ever‐present threats from chronic stressors and emerging diseases. Nutrition plays a pivotal role in the profitability and viability of the aquaculture industry that steered a paradigm shift to therapeutic nutrition. Carotenoids, also termed tetraterpenoids, have garnered considerable attention owing to their therapeutic attributes and immeasurable health benefits, which incited a surge in global demand. These biological pigments are recognized to promote immune systems and antioxidant defence mechanisms in both aquatic vertebrates and invertebrates. This review brings forth existing scientific evidence and underscores the notable roles of carotenoids as biologically active constituents with anti‐stress and immunostimulatory potentials in farmed aquatic animals whilst explicating possible mechanisms of action. Empirical data unequivocally established the modulatory functions of carotenoids on endogenous antioxidant enzymes, innate and adaptive arms of the immune response, as well as the expression of multiple antioxidant and immune‐related genes. The comprehensive information presented is beneficial to deepen our understanding of the utilization of carotenoids as potent stress alleviators and immunostimulants in cultured aquatic animals, which is translated into improved health. Advancements in aquatic animal health and welfare could principally contribute to reconstructing a more sustainable aquaculture industry. This article may be useful for subsequent investigations towards further advances in research and innovation to a greener blue revolution in solving the challenge of global food security.

Schizochytrium limacinum altered antioxidant capacity and transcriptome profiles in Pacific white shrimp fed a low-fishmeal diet

Dietary low-fishmeal (FM) have negative impacts on growth performance and metabolic responses in aquatic animals, while Schizochytrium limacinum have multiple benefits due to its rich contents of docosahexaenoic acid (DHA). However, little information is available on the effects of S. limacinum on Pacific white shrimp (Litopenaeus vannamei) in a low-FM diet (LF). An 8-week feeding trial were used to investigate the impacts of S. limacinum on growth performance, as well as morphological changes, biochemical indicators, antioxidant capacity, and transcriptomic profiles of hepatopancreas in shrimp fed a low-FM diet. Compared to LF diet, 0.3% S. limacinum (LFLD) diet significantly decreased the specific growth rate (SGR), and did not affect the feed conversion rate (FCR) and weight gain rate (WGR); whereas 0.6% S. limacinum (LFHD) diet did not affect the SGR, FCR and WGR. Histological structures of hepatopancreas showed that LFLD and LFHD treatments reduced the number and size of secretory cells and increased the number of storage cells, compared to LF group. LFLD and LFHD diets significantly decreased the concentrations of triglyceride and total cholesterol, significantly increased the levels of glutathione peroxidase and total antioxidative capacity, while did not affect the levels of malondialdehyde and superoxide dismutase. A total of 135 differential expression genes (DEGs) were identified in LFLD group and 108 DEGs were identified in LFHD group (both compared to LF group). Administration of S. limacinum altered the transcriptomic profiles, while LFHD induced a pattern similar to that of LF. LFLD and LFHD treatments mainly affected the 9 KEGG metabolic pathways, including “Arachidonic acid metabolism” and “Glutathione metabolism”. In conclusion, LFLD treatment impaired the growth performance of shrimp, while LFHD treatment did not affect it; and both treatments improved the morphological structure, lipid accumulation and antioxidant capacity of hepatopancreas.

H3K4me3 CUT&Tag and Transcriptome Analysis Reveal the Epigenetic Regulatory Landscape in Gill Tissue of Large Yellow Croaker (Larimichthys crocea) Under Low Salinity Stress

H3K4me3 is an important histone modification that could influence DNA replication and RNA translation in response to abiotic stress. Here, RNA-seq analyses were conducted in gill tissues of large yellow croaker to identify the function of H3K4me3 under low salinity stress. Additionally, CUT&Tag analyses were performed to identify the genome-wide dynamic changes in H3K4me3 and explore the mechanisms by which H3K4me3 regulates gene expression. A total of 201 differentially expressed genes (DEGs) were identified between the 5‰ low salinity group (S-group) and 25‰ normal salinity group (C-group), among which 23 DEGs (11 up-regulated H3K4me3 targets and 12 down-regulated targets) were directly regulated by H3K4me3. Our findings thus describe the epigenetic regulatory landscape of H3K4me3 in gill of large yellow croaker during low salinity stress, and provide novel insights into the regulation mechanisms of H3K4me3 mediating the responses of aquatic animals to abiotic stress.

What evidence exists for the impact of climate change on the physiology and behaviour of important aquaculture marine crustacean species in Asia? A systematic map protocol

BackgroundClimate is one of the most important driving factors of future changes in terrestrial, coastal, and marine ecosystems. Any changes in these environments can significantly influence physiological and behavioural responses in aquatic animals, such as crustacea. Crustacea play an integral role as subsistence predators, prey, or debris feeders in complex food chains, and are often referred to as good indicators of polluted or stressed conditions. They also frequently have high production, consumption, and commercial significance. However, crustacean’s responses to climate change are likely to vary by species, life-history stage, reproduction status and geographical distribution. This map is undertaken as part of the Long-Term Research Grant project which aims to identify any interactive effect on physiological compensation and behavioural strategy of how marine organisms, especially crustaceans, deal with stress from environmental change. Our proposed map will aim to outline the evidence currently existing for the impacts of climate change on the physiology and behaviour of important aquaculture crustacean species within Asia.MethodsWe will document peer-reviewed articles in English using published journal articles and grey literature. Two bibliographic databases (Scopus and Web of Science) and multiple organizational websites with Google scholars will be searched. The systematic map protocol will follow in accordance with the Collaboration for Environmental Evidence Guidelines and Standards. Literature will be screened at the title, abstract, and full-text level using pre-defined inclusion criteria. The map will highlight marine crustacea physiological compensation and behavioural strategies to cope with climate change. It will also improve our knowledge of the available evidence and current gaps for future research recommendations.

Effects of dietary arachidonic acid on growth, immunity and intestinal microbiota of Litopenaeus vannamei under microcystin-LR stress

The harmful effects of microcystin-LR (MC-LR) stress are unavoidable in shrimp culture. Arachidonic acid (AA) is a fatty acid that regulates immune responses in aquatic animals. In this study, we investigated the effects of dietary AA on growth, immunity and intestinal microbiota of Litopenaeus vannamei under MC-LR stress. The shrimp were fed a control diet (non-supplemented with AA) or a AA diet (supplemented with 8.0 g/kg AA) for 56 days, followed by an acute MC-LR stress for 72 h. The results showed that dietary AA improved the growth and feed utilization of the shrimp. Microcystin-LR exposure increased the mRNA expressions of reactive oxygen species modulator 1 (ROMO1), glutathione peroxidase (GPx), caspase-3 (Casp-3), NADPH-cytochrome P450 reductase (NCPR) and sulfotransferase (SULT), but decreased that of catalase (CAT) and cytochrome C (Cytc). Dietary AA supplementation reversed the expressions of ROMO1, CAT, GPx and NCPR to the control level, but still maintained the higher levels of Cytc, Casp-3 and SULT than the control and MC-LR stress groups. Dietary AA could not effectively reverse the changes of intestinal microbial diversity, but it could improve intestinal microbial composition variation induced by MC-LR stress. Specially, dietary AA increased the relative abundances of beneficial bacteria Bacteroides and Lactobacillus, and reversed the changes of pathogenic bacteria Vibrio and Photobacterium induced by MC-LR stress to the control level. The changes of intestinal bacteria were correlated with immune gene expression. These results revealed that dietary AA had a positive effect on L. vannamei resistance to MC-LR stress by modulating immune response and intestinal microbial composition.

Invisible or fearless: tadpole response to predator cues depends on color

Behavioral changes constitute a common response of aquatic animals to predator chemical and/or visual cues. Tadpoles frequently use such signals to evaluate predator presence/activity and, consequently, alter their own behavior to reduce detectability and susceptibility to predation. The present study aimed to test how tadpoles of Bokermannohyla martinsi and Ololygon machadoi respond to the presence of a predator (Belostoma testaceopallidum), regarding background choice and activity levels. Results showed that O. machadoi tadpoles increased the use of yellow backgrounds in the presence of the predator perceived through either chemical or visual cues. Bokermannohyla martinsi, on the other hand, did not show preference for any specific background color or changed activity levels in the presence of any predator cue. Our results corroborate the hypothesis of disruptive coloration as a defense strategy in O. machadoi and indicate that the visible and active tadpoles of B. martinsi may employ a different defensive strategy, possibly relying on a more efficient post detection escape mechanism. This hypothesis is corroborated by the higher activity levels of B. martinsi and lack of response to predator presence regarding either modulation of activity levels or background choice.

Effects of Chlorpyrifos on Cholinesterase and Serine Lipase Activities and Lipid Metabolism in Brains of Rainbow Trout (Oncorhynchus mykiss).

Chlorpyrifos is an organophosphorus insecticide that elicits acute toxicity through inhibition of acetylcholinesterase (AChE), leading to acetylcholine accumulation and prolonged stimulation of cholinergic receptors throughout the central and peripheral nervous systems. Previous studies have indicated that neurodevelopment may also be impaired through alternative pathways, including reduction of cyclic adenosine monophosphate (cAMP)-catalyzed downstream events. The upstream initiating events that underlie noncholinergic neurological actions of chlorpyrifos and other organophosphorus compounds remain unclear. To investigate the potential role of fatty acid signaling disruption as a mechanism of toxicity, lipid metabolism and fatty acid profiles were examined to identify alterations that may play a critical role in upstream signaling in the central nervous system (CNS). Juvenile rainbow trout were treated for 7 days with nominal chlorpyrifos concentrations previously reported to diminish olfactory responses (10, 20, and 40 μg/l). Although lethality was noted higher in doses, measured chlorpyrifos concentrations of 1.38 μg/l (nominal concentration 10 μg/l) significantly reduced the activity of AChE and two serine lipases, monoacylglycerol lipase, and fatty acid amide hydrolase in the brain. Reductions in lysophosphatidylethanolamines (16:0, 18:0, 18:1, and 22:6) derived from the phosphatidylethanolamines and free fatty acids (palmitic acid 16:0, linolenic acid 18:3, eicosadienoic acid 20:2, arachidonic acid 20:4, and docosahexaenoic acid 22:6) were also noted, suggesting that chlorpyrifos inhibited the metabolism of select phospholipid signaling precursors at sublethal concentrations. These results indicate that in addition to AChE inhibition, environmentally relevant chlorpyrifos exposure alters serine lipase activity and lipid metabolites in the trout brain, which may compromise neuronal signaling and impact neurobehavioral responses in aquatic animals.

Differential Transcriptomic and Metabolomic Responses in the Liver of Nile Tilapia (Oreochromis niloticus) Exposed to Acute Ammonia.

Ammonia is toxic to aquatic animal. Currently, only limited works were reported on the responses of aquatic animals after ammonia exposure using "omics" technologies. Tilapia suffers from the stress of ammonia-nitrogen during intensive recirculating aquaculture. Optimizing ammonia stress tolerance has become an important issue in tilapia breeding. The molecular and biochemical mechanisms of ammonia-nitrogen toxicity have not been understood comprehensively in tilapia yet. In this study, using RNA-seq and gas chromatograph system coupled with a Pegasus HT time-of-flight mass spectrometer (GC-TOF-MS) techniques, we investigated differential expressed genes (DEGs) and metabolomes in the liver at 6h post-challenges (6hpc) and 24h post-challenges (24hpc) under high concentration of ammonia-nitrogen treatment. We detected 2258 DEGs at 6hpc and 315 DEGs at 24hpc. Functional enrichment analysis indicated that DEGs were significantly associated with cholesterol biosynthesis, steroid and lipid metabolism, energy conservation, and mitochondrial tissue organization. Metabolomic analysis detected 31 and 36 metabolites showing significant responses to ammonia-nitrogen stress at 6 and 24hpc, respectively. D-(Glycerol 1-phosphate), fumaric acid, and L-malic acid were found significantly down-regulated at both 6 and 24hpc. The integrative analysis of transcriptomics and metabolomics suggested considerable alterations and precise control of gene expression at both physiological and molecular levels in response to the stress of ammonia-nitrogen in tilapia.

Genotoxic and cytotoxic effects of 50 Hz 1 mT electromagnetic field on larval rainbow trout (Oncorhynchus mykiss), Baltic clam (Limecola balthica) and common ragworm (Hediste diversicolor)

The aim of this research was to assess genotoxicity and cytotoxicity responses in aquatic animals exposed to 50 Hz 1 m T electromagnetic field (EMF). Rainbow trout (Oncorhynchus mykiss) at early stages of development were exposed to EMF for 40 days, whereas marine benthic invertebrates – the common ragworm Hediste diversicolor and the Baltic clam Limecola balthica – for 12 days. To define genotoxicity and cytotoxicity responses in selected animals, assays of nuclear abnormalities in peripheral blood erythrocytes of O. mykiss, coelomocytes of H. diversicolor and gill cells of L. balthica were performed. Induction of formation of micronuclei (MN), nuclear buds (NB), nuclear buds on filament cells (NBf) and cells with blebbed nuclei (BL) were assessed as genotoxicity endpoints, and 8-shaped nuclei, fragmented (Fr), apoptotic (Ap) and binucleated (BN) cells as cytotoxicity endpoints. Exposure to EMF affected all studied species but with varying degrees. The strongest responses to EMF treatment were elicited in L. balthica, in which six out of the total eight analyzed geno- and cytotoxicity endpoints were significantly elevated. Significantly induced frequencies of MN were detected in O. mykiss and H. diversicolor cells, NBf and BL only in gill cells of L. balthica, and NB in analyzed tissues of all the test species. As cytotoxicity endpoints, a significant elevation in frequencies of cells with 8-shaped nuclei was found in O. mykiss and L. balthica, while Ap and BN was observed only in L. balthica. EMF exposure did not induce any significant cytotoxic activity in H. diversicolor coelomocytes. The present study is the first to reveal the genotoxic and cytotoxic activity of 1 m T EMF in aquatic animals, and, consequently, the first one to report the adverse effect of this factor on common marine invertebrates and early life stages of fish.

Mechanistic research in aquatic toxicology: Perspectives and future directions

On the 30th anniversary of the journal, I provide a perspective on some of the questions and opportunities for new understanding that will interest aquatic toxicologists during the next 30 years. I focus on mechanisms of toxicity involving transcription factors, signalling pathways, and gene networks involved in toxic and adaptive responses in aquatic animals. Prominent questions address the value of a toxicity pathways approach in aquatic systems, issues involving extrapolation among species, identification of susceptibility genes and useful biomarkers of adverse effect, new emerging contaminants, the importance of epigenetic mechanisms, effects of multiple stressors, evolutionary toxicology, and the relative roles of technical and conceptual limitations to our understanding of chemical effects on aquatic systems.

Effects of the synthetic estrogen, 17α-ethinylestradiol, on aggression and courtship behavior in male zebrafish ( Danio rerio)

The synthetic estrogen, 17α-ethinylestradiol (EE 2), is the active component in oral contraceptive pills. It is excreted from the human body in high amounts and released via sewage treatment plant effluent into aquatic environments. In fish, estrogen receptors have strong binding affinities for EE 2, and exposure raises the possibility of adverse neuroendocrine responses in aquatic animals. In the present study we explored the effects of dissolved-phase EE 2 on the dynamics of male–male aggression and courtship behaviors in adult zebrafish. Further, we assessed whether the behavioral effects of EE 2 result in changes in male offspring paternity. We scored the aggressive behaviors of individual unexposed males and categorized these fish as either dominant or subordinate. We then exposed dominant males to EE 2 at doses of 0, 0.5, 5.0, and 50.0 ng/L for 48 h. Subsequent trials examined the agonistic behaviors of males in two testing scenarios: (1) a dyadic encounter with another male alone, and (2) a competitive spawning interaction with another male and three adult females. Competitive spawning tests were also used to assess the impacts of EE 2 exposure on courtship behavior and paternity using males that were homozygous for green fluorescent protein (GFP) expression under the control of the islet-1 promoter. We found that EE 2 at all exposure concentrations reduced male aggression during male–male dyadic encounters and caused a social dominance reversal in 50% of the fish at the highest exposure dose (50 ng/L EE 2). The frequency of courtship-specific behavior decreased in dominant males exposed to the steroid, though this effect was only significant for the lowest dose group (0.5 ng/L EE 2). In the highest exposure group (50 ng/L EE 2), 50% of dominant males relinquished paternal dominance. Our results show that short-term exposure to EE 2 at environmentally relevant levels can alter aggression, and shift individual social status and reproductive success in male zebrafish.

Biochemical responses in aquatic animals: A review of determinants of oxidative stress

AbstractThe study of biochemical responses in aquatic animals comprises a vigorous area of inquiry within ecotoxicology for a number of reasons, including the perceived need for basic research in the field, the desire for highly sensitive biomarkers useful for biomonitoring and the particular concern for elevated rates of neoplasia observed in some aquatic systems. In this paper, an approach only recently investigated by aquatic toxicologists will be described and reviewed in detail. This approach is based on theories of oxyradical generation and subsequent oxidative stress in biological systems. Of particular concern to environmental toxicologists with respect to these phenomena are the abilities of a number of common and diverse compounds to undergo enzymatically facilitated redox cycling in cells and thereby generate oxyradicals under aerobic conditions. Mechanisms of oxyradical generation, toxicological consequences of these processes and endogenous antioxidant defense systems are described. In addition, methodologies for studying these phenomena are discussed and recent studies demonstrating their applicability to aquatic toxicology are reviewed.

BIOCHEMICAL RESPONSES IN AQUATIC ANIMALS: A REVIEW OF DETERMINANTS OF OXIDATIVE STRESS

The study of biochemical responses in aquatic animals comprises a vigorous area of inquiry within ecotoxicology for a number of reasons, including the perceived need for basic research in the field, the desire for highly sensitive biomarkers useful for biomonitoring and the particular concern for elevated rates of neoplasia observed in some aquatic systems. In this paper, an approach only recently investigated by aquatic toxicologists will be described and reviewed in detail. This approach is based on theories of oxyradical generation and subsequent oxidative stress in biological systems. Of particular concern to environmental toxicologists with respect to these phenomena are the abilities of a number of common and diverse compounds to undergo enzymatically facilitated redox cycling in cells and thereby generate oxyradicals under aerobic conditions. Mechanisms of oxyradical generation, toxicological consequences of these processes and endogenous antioxidant defense systems are described. In addition, methodologies for studying these phenomena are discussed and recent studies demonstrating their applicability to aquatic toxicology are reviewed.

Myofibrillar atpase activities in red and white myotomal muscles of the American eel, Anguilla rostrata (Lesueur)

1. 1. Redandwhite myofibrillar ATPase (m-ATPase) activities have been estimatedin 9-month-fed and food-deprived and newly captured American eels. 2. 2. No differences existed in m-ATPase activities between fed and food-deprived eels, although with the decreased protein content under this situation total muscle activities are expected to decline significantly. 3. 3. Newly captured eel m-ATPase activities were significantly above those of the laboratory-held groups. 4. 4. These results support the reported exercise- and fasting-induced changes in muscle fiber diameter and fiber volume occupied by myofibrils of some teleosts. In addition, care must be taken in interpreting physiological responses in aquatic animals held in the laboratory.

A technique for the investigation of chemical responses in aquatic animals

A technique for the investigation of chemical responses in aquatic animals