Seawater Fish Research Articles

Genomic and functional characterization of the Atlantic salmon gut microbiome in relation to nutrition and health.

To ensure sustainable aquaculture, it is essential to understand the path 'from feed to fish', whereby the gut microbiome plays an important role in digestion and metabolism, ultimately influencing host health and growth. Previous work has reported the taxonomic composition of the Atlantic salmon (Salmo salar) gut microbiome; however, functional insights are lacking. Here we present the Salmon Microbial Genome Atlas consisting of 211 high-quality bacterial genomes, recovered by cultivation (n = 131) and gut metagenomics (n = 80) from wild and farmed fish both in freshwater and seawater. Bacterial genomes were taxonomically assigned to 14 different orders, including 35 distinctive genera and 29 previously undescribed species. Using metatranscriptomics, we functionally characterized key bacterial populations, across five phyla, in the salmon gut. This included the ability to degrade diet-derived fibres and release vitamins and other exometabolites with known beneficial effects, which was supported by genome-scale metabolic modelling and in vitro cultivation of selected bacterial species coupled with untargeted metabolomic studies. Together, the Salmon Microbial Genome Atlas provides a genomic and functional resource to enable future studies on salmon nutrition and health.

Environmental salinity differentiates responses to acute hypothermal stress in milkfish

Global warming has led to an increase in the frequency of cold extremes, causing significant economic losses in aquaculture, particularly in subtropical regions. Milkfish (Chanos chanos) holds significant importance in aquaculture within subtropical Asian regions. Despite milkfish's ability to tolerate varying salinity levels, frequent cold snaps associated with extreme weather events have caused substantial mortality. Understanding the molecular and cellular mechanisms underlying cold stress-induced cell death is crucial for developing effective strategies to mitigate such losses. Given the pivotal role of the liver in fish physiology, we established a primary milkfish hepatocyte culture demonstrating robust proliferation and expressing a unique marker leptin A. The molecular characterization of cold-treated hepatocytes at 18 °C showed that the mRNA levels of superoxide dismutase (sod1) and catalase (cat), responsible for neutralizing reactive oxygen species (ROS), were downregulated in freshwater (FW) conditions, while cat expression was upregulated in seawater (SW) conditions. This differential modulation of ROS signaling implies distinct responses in FW and SW, leading to higher ROS levels and increased cell death in FW condition compared to those in SW. Transcriptomic analysis of liver tissues from milkfish reared in FW or SW, with or without cold stress, revealed distinct gene expression patterns. Although cold stress affected a common set of genes in both FW and SW conditions, SW-specific cold responsive genes are associated with metabolic pathways while FW-specific genes were linked to cell proliferation pathways. Notably, gene set enrichment analysis highlighted the downregulation of cytochrome-related genes, a major source of ROS production, in response to cold stress in SW. In summary, our study unveils an insightful mechanism whereby the salinity of SW counteracts cold stress-induced ROS signaling, emphasizing the feasibility and practicality of preconditioning fish in SW as a preventive measure against cold stress-induced mortality.

Anti-fouling ternary zwitterionic coating membrane with strong surface hydration and salt resistant for efficient long-term emulsion separation in high salinity marine environment

Membrane separation has been acknowledged as an advanced technology to handle the oil spills. However, most of the superhydrophilic/underwater superhydrophobic membranes currently applied for oil/water separation would lose their superwettability when exposed to salty marine environments, leading to serious membrane plugging and separation performance deterioration. Herein, inspired by seawater fish and mussels, a simple, green, and versatile one-step co-deposition strategy is proposed for fabricating a ternary zwitterionic coating with strong surface hydration on diverse membranes, showing excellent anti-fouling properties in high salinity environments, even in the saturated NaCl solution. Moreover, the modified membrane performs well in the long term when separating surfactant-stabilized oil-in-seawater emulsion and with impressive recyclability. The ternary zwitterionic coating membrane exhibits great potential in treating oily wastewater in marine.

Susceptibility and Target Organ of Lymphocystis Disease Virus Infection in Giant Gourami (Osphronemus goramy), Hybrid Tilapia (Oreochromis sp.), Siamese Fighting Fish (Betta splendens), and Hybrid Catfish (Clarias sp.)

Highlight Research 1. Lymphocystis disease is reported to infect seawater and freshwater fishes 2. The four important freshwater fish species in Indonesia are evaluated on their susceptibility to Lymphocystis Disease Virus 3. Lymphocystis infection causes behavioural changes and mortality with different onset times after infection on the four fish species 4. LCDV load is varied in quantity among different organs. Abstract Lymphocystis disease has a broad host range and has been reported to enter Indonesia. However, information regarding its susceptibility and predilection organs in fish is lacking. This study examined the susceptibility of four important fish species in Indonesia, namely, giant gourami (Osphronemus goramy), hybrid tilapia (Oreochromis sp.), Siamese fighting fish (Betta splendens), and hybrid catfish (Clarias sp.). The fish were infected with virus filtrate by intraperitoneal injection and immersion. The postinfection observation period was 60 days. Viral load was quantified by qPCR and expressed as major capsid protein (MCP) copy number/mg tissue. Mortality was observed in all fish species, with the highest recorded in hybrid catfish and the lowest in Siamese fighting fish. All the fish species showed changes in their clinical symptoms, such as anorexia and separation from schools. However, only giant gourami showed internal change seven days after injection (dpi), with white lesion detected in the liver. Viral load quantification showed that LCDV had different predilection organs in the four fish species. The highest viral load of giant gourami (1.7 x 104) was observed in the liver at 7 dpi, hybrid tilapia (7.5 x 103) was observed in the fins at 21 dpi, Siamese fighting fish (8.4 x 103) was observed in the fins at 14 dpi, and hybrid catfish (1.2 x 103) were observed in the fins and gills at 7 and 14 dpi. The findings indicated that giant gourami, hybrid tilapia, Siamese fighting fish, and hybrid catfish were susceptible to LCDV infection with different predilection organs.

Melatonin influences reproduction in the sapphire devil Chrysiptera cyanea via regulation of dopamine 2b receptor transcription

Melatonin and dopamine participate in the regulation of reproduction-related hormone/peptide synthesis and secretion at the hypothalamic–pituitary–gonadal axis in fish. Here, we report a unique reproduction-related interaction of melatonin and dopamine in the brain of the sapphire devil Chrysiptera cyanea, a tropical damselfish with a long-day preference. We examined the expression of arylalkylamine N-acetyltransferase 2 (aanat2)—a rate-limiting enzyme of melatonin, dopamine 2b receptor (d2b), gonadotropin-releasing hormone (gnrh1), and β-subunit of follicle-stimulating hormone (fshβ) and luteinizing hormone (lhβ)—in the brain of the sapphire devil. During the reproductive season, mature females were divided into the early vitellogenesis (EV), late vitellogenesis (LV), and post-spawning (PS) stages; a day-low and night-high profile of aanat2 was observed during EV and LV but not during PS. There were nocturnal increases in gnrh1 during EV and LV as well as d2b during LV, suggesting that melatonin has a positive effect on the levels of gnrh1 and d2b transcripts in mature fish. When the brains of females in the non-breeding season were sampled at 4-h intervals, nocturnal increases in the levels of fshβ and lhβ transcripts were observed at 00:00 and 04:00, respectively. The immersion of immature fish in melatonin-containing seawater for 6 h resulted in the upregulation of fshβ and lhβ, as well as downregulation of d2b, in the brain. Additionally, in situ hybridization analysis showed that melatonin treatment lowered the signals of d2b transcripts in the ventral hypothalamus, rostral pars distalis, proximal pars distalis, and pars intermedia, suggesting that melatonin has a negative impact on the levels of d2b transcripts in the hypothalamus and pituitary of immature females; the opposite effect is likely concerning the levels of fshβ and lhβ transcripts in the pituitary. In conclusion, melatonin positively and negatively acted on the hypothalamus and pituitary in the sapphire devil; these opposite effects were related to differences in gonadal development status.

Sea water acclimation of rainbow trout (Oncorhynchus mykiss) modulates the mucosal transcript immune response induced by Vibrio anguillarum and Aeromonas salmonicida vaccine, and prevents further transcription of stress-immune genes in response to acute stress

Mucosal tissues appear to be more important in fish than in mammals due to living in a microbial-rich aquatic milieu, yet the complex interaction between the immune and the neuroendocrine system in these tissues remains elusive. The aim of this work was to investigate the mucosal immune response in immunized rainbow trout vaccinated with Alpha ject vaccine (bivalent), kept in fresh water (FW) or transferred to seawater (SW), and to evaluate their response to acute stress (chasing). Acute stress resulted in higher levels of plasma cortisol (Sham + Stress and Vaccine + Stress). A similar response was observed in skin mucus, but it was lower in Vaccine + Stress compared with stressed fish. With a few exceptions, minimal alterations were detected in the transcriptomic profile of stress-immune gene in the skin of vaccinated and stressed fish in both FW and SW. In the gills, the stress elicited activation of key stress-immune components (gr1, mr, β-ar, hsp70, c3, lysozyme, α-enolase, nadph oxidase, il1β, il6, tnfα, il10 and tgfβ1) in FW, but fewer immune changes were induced by the vaccine (nadph oxidase, il6, tnfα, il10 and igt) in both SW and FW. In the intestine, an array of immune genes was activated by the vaccine particularly those related with B cells (igm, igt) and T cells (cd8α) in FW with no stimulation observed in SW. Therefore, our survey on the transcriptomic mucosal response demonstrates that the immune protection conferred by the vaccine to the intestine is modulated in SW. Overall, our results showed: i) plasma and skin mucus cortisol showed no additional stress effect induced by prolonged SW acclimation, ii) the stress and immune response were different among mucosal tissues which indicates a tissue-specific response to specific antigens/stressor. Further, the results suggest that the systemic immune organs may be more implicated in infectious events in SW (as few changes were observed in the mucosal barriers of immunized fish in SW) than in FW.

Impact of transport conditions and underlying disease on post-stocking survival of juvenile Lates calcarifer.

Diseases caused by pathogens commonly occurring in the aquatic environment or those that are non-host specific are prevalent and threaten the rapid growth of tropical aquaculture. This study investigates causes of mortality in 12 batches of newly stocked juvenile Lates calcarifer from three different hatcheries. Cytology based on Diff-Quik™-stained tissue and blood smears provides rapid diagnosis of possible causes of mortality, while histopathology and haematology provide a better understanding of how prolonged transport and fish with existing chronic disease are more likely to experience elevated mortality post-stocking. Our findings showed that accumulation of ammonia during prolonged transport causes extensive damage to epithelial barriers in gastrointestinal tracts and depressed immunity due to marked hypoglycaemia, predisposing fish to acute Streptococcosis. Lates calcarifer with chronic bacterial enteritis developed severe hypoglycaemia, had low circulating total plasma protein, and suffered high mortality within 24 hours post-stocking. Hypoglycaemia and low circulating blood proteins disrupt osmoregulation and exacerbate dehydration, which is fatal in fish in sea water. Dying L. calcarifer tested PCR positive for scale drop disease virus (SDDV) at 28 days post-stocking showed a 10-fold elevation of white blood cell counts, severe vasculitis, and obstruction of blood supply to major organs. Destruction of important immune organs such as spleen is a hallmark of SDDV infection that explains high incidences of opportunistic Vibrio harveyi infections in 61% of fish with SDDV. Overall, this study reiterates the importance of stocking disease-free fish and reducing transport stress.

An ammonia-sensitive fluorescence sensor based on polyvinyl alcohol-graphene quantum dots/halloysite nanotubes hybrid film for monitoring fish freshness

A fluorescent hybrid film composed of nitrogen-doped graphene quantum dots (N-GQDs) loaded on halloysite nanotubes (HNTs) (N-GQDs/HNTs nanocomposite) as a sensitive element and polyvinyl alcohol (PVA) as a film-forming matrix was designed for freshness detection. The PVA-N-GQDs/HNTs hybrid film exhibited significantly enhanced fluorescence attributed to the loading of N-GQDs onto the surface of HNTs through electrostatic interactions and hydrogen bonding, effectively reducing their aggregation. The fluorescence of the hybrid film could be quenched by ammonia via photoinduced electron transfer (PET), with good linearity in the range of 20 ppm to 500 ppm ammonia and a limit of detection (LOD) of 0.63 ppm. In addition, the hybrid film was applied to monitor the freshness of seawater fish and freshwater fish stored at refrigeration and room temperature to evaluate the practicality of this approach. The developed hybrid film showed promise for nondestructive and on-site monitoring of fish spoilage.

Impact of land development along the western Mediterranean coast of Egypt regarding surfactant sources, interfering elements and ecotoxicity

The effect of recent land development of the western side of the Egyptian Mediterranean coast on the fates, behaviors, interactions, and ecotoxicology of surfactant (LAS), F, Br, B, Ca, Mg, and P was studied. Samples of seawater and sediments were collected from 15 stations at different depths representing, 5 perpendicular sectors. Elevated levels of LAS were identified in seawater columns in the El-Hamam (467.3 ± 220.8 μg/L) and El-Dabaa (480.0 ± 314.1 μg/L) stations. LAS homologue in sediment was in the range of 0.013–0.024, 0.042–0.184, 0.086–0.402, and 0.025–0.058 μg/g for C10, C11, C12, and C13, respectively. Studied parameters showed mixture risk characterization ratios RCRmix > 1 for algae, invertebrates, and fish in seawater and sediments, except for P, which showed low risk (RCRmix ≤ 1) in sediment. Acute relative contribution (RC) of LAS reflected that fish were the most sensitive species (RCFish = 48.5), followed by algae (RCAlgae = 44.4) and invertebrates (RCInvert = 7.1).

Growth, productivity and nutrient removal rates of sea lettuce (Ulva lactuca) in a land-based IMTA system with white seabass (Atractoscion nobilis) in Southern California

Three consecutive 3-week trials were conducted to assess the growth, productivity, and nutrient removal rates of sea lettuce (Ulva lactuca) cultured in effluents from white seabass (Atractoscion nobilis) raceways. All U. lactuca cultivation trials were conducted in 175 L tanks with a surface area of 0.89 m2 run in triplicate, with water quality and growth measurements taken weekly. For the shading trial, U. lactuca was stocked at 0.56 kg/m2 with either 0%, 30%, or 60% shade and seawater supplied at 63 tank volumes per day (vol./day) water exchange (7.6 L/min) for each tank. The removal rate of total ammonia nitrogen (TAN) decreased with increasing shade levels, and the peak exceeded 80% removal at 0% shading. Growth rate and productivity of U. lactuca under 0% shading was 12.09 ± 3.13%/d and 13.28 ± 4.66 g DW/m2/d, which were both significantly higher than other shading levels. For the stocking density and water exchange rate trial, the stocking density of U. lactuca was 0.56 or 1.12 kg/m2, and seawater exchange rates were 4, 12, or 63 vol./day in a 2-factor design. In this trial, TAN removal rates were 100% across all treatment combinations. Growth rate of U. lactuca was highest (20.36 ± 2.36%/d) at 0.56 kg/m2 under the exchange rate of 63 vol./day, and the productivity reached up to 30.89 ± 6.53 g DW/m2/d, which was not different than that of U. lactuca stocked with 1.12 kg/m2 at the same exchange rate (p = 0.47). In a trial comparing sand-filtered seawater (RAW seawater) with seawater effluent from a raceway containing A. nobilis (FISH seawater), TAN removal rate by U. lactuca was consistently nearly 100% when supplied with FISH seawater with a TAN concentration ranging from 0.11 to 0.18 mg/L. Growth rate and productivity of U. lactuca supplied with FISH seawater were 21.36 ± 2.25%/d and 33.83 ± 7.29 g DW/m2/d, respectively, which was not different than that for U. lactuca supplied with RAW seawater. However, the protein content of U. lactuca cultured with FISH seawater was significantly higher and C/N ratio significantly lower than those cultured with RAW seawater (p < 0.01), which indicated that U. lactuca was in a nitrogen-limited situation when cultured with RAW seawater. In light of the better understanding of U. lactuca performance achieved in our study, the optimum U. lactuca and A. nobilis density combinations will be confirmed in future studies based on nitrogen balance to maximize the nutrient removal rates and diversity of seafood production.

Sediment-seawater partitioning, bioaccumulation, and biomagnification of perfluorobutane sulfonamide in marine environment

Environmental occurrence of perfluorobutane sulfonamide (PFBSA) has only been recently discovered. The current knowledge regarding the occurrence and environmental behaviors of PFBSA in the marine environment is still relatively limited. In this study, PFBSA and other 37 poly- and perfluoroalkyl substances were analyzed in seawater (n = 43), sediment (n = 43), and marine fish (n = 176) samples collected from East China Sea and Antarctic Ocean. PFBSA was detected in > 90% of seawater from East China Sea and Antarctic Ocean, with the concentrations of 1.0 − 19 ng/L and < LOD−228 pg/L, respectively. The field-based mean log-transformed sediment-seawater partitioning coefficients of PFBSA were 1.6 ± 0.19 L/kg dw and 1.1 ± 0.19 L/kg dw in East China Sea and Antarctic Ocean, respectively, which are lower than that of perfluorooctanoate and perfluorooctane sulfonate. This indicates its long-range transport potential in global oceans with ocean currents. The mean log-transformed bioaccumulation factor values of PFBSA determined in the multiple species of whole-body marine fishes from East China Sea and Antarctic Ocean were 2.3 L/kg ww and 2.4 L/kg ww, respectively, which are comparable to that of perfluoroheptanoate (2.3 L/kg ww) in marine fishes from East China Sea. We did not observe an obvious biomagnification or biodilution of PFBSA along the marine food chain in East China Sea or Antarctic Ocean. This study provides the first data on the environmental behaviors of PFBSA in the marine environment.

Freshwater history influences farmed Atlantic salmon (Salmo salar) performance in seawater

The quality of smolts is one of the key factors for successful salmon production. We compared growth performance, physiological traits, and environmental adaptation in Atlantic salmon (Salmo salar) after transfer into a sea cages farm site from recirculating aquaculture system (RAS) to a similar sized group of the same genetic linage and produced in the same husbandry facility but under flow through system (FTS) conditions. Fish vertical distribution within the sea cages and water environment were continuously recorded, while biometry data and biological samples were collected monthly. No significant difference in size and smolt development between the FTS and RAS-produced fish were observed at the end of the freshwater phase. However, after transfer into seawater, the RAS fish showed an array of physiological and molecular differences that were maintained and resulted in significantly increased mortality and lower growth over the full production cycle. The RAS smolts were characterized by lower body weight, length, K factor, HSI (indicator of energy reserve), NKA activity, plasma levels of lactate, triacylglycerol, sodium, calcium, and phosphorus than FTS fish in seawater. This implicated osmoregulatory and allostatic maladaptation for the RAS fish during the first months in seawater. Both FTS and RAS fish showed physiological and behavioral adjustments during the seawater production linked with predictable (e.g., seasonal, diurnal) and short-term unpredictable variation in water temperature and oxygen. However, the RAS fish were characterized by lower physiological response to stressful effects of unpredictable environmental variability.Based on our data, the freshwater history sets the basis for the performance success of the FTS and RAS smolts in seawater. FTS fish showed faster adaptation to the seawater environment, with higher osmoregulatory capacity, and higher physiological robustness to seasonal changes than RAS fish, which reflected in their difference in growth and harvest size. We emphasize the crucial role of the freshwater rearing conditions as the foundation for successful physiological adaptation to seawater, growth, and the success of salmon farming production.

Analysis of fish consumption patterns in the people of Bekasi Regency, West Java

Bekasi people's awareness to consume fish is still very low. Though fish is one of the foods that are cheap, easy to find, and have a high nutritional content. The purpose of this study was to analyze fish consumption patterns. The study was conducted by analyzing primary data on fish consumption patterns influenced by perceptions and preferences for fish products through direct interviews with 110 household members. The methods used in this study are descriptive analysis, logit analysis, quantitative analysis using the Chi-square test. The choice of fish as a source of animal protein consumed shows the consumption pattern of fresh fish both freshwater fish and seawater fish, based on the frequency of consumption patterns included in the large category, namely 70.9% fresh seawater fish and 24.5% fresh freshwater fish.

Analysis and modelling of profiles to understand fractionation processes for contaminations with polychlorinated biphenyls observed in fish

Polychlorinated biphenyls (PCB) both continue to spread into the environment and to bioaccumulate from primary urban and industrial sources as well as from secondary sources such as soils and the oceans. Fractions of congeners in PCB mixtures, i.e. PCB profiles, can be used as fingerprints to trace contamination pathways from sources to sinks because PCB mixtures fractionate during transport due to congener specific phase changes and degradation. Using a statistical analysis of a total of 8584 PCB profiles with seven congeners (CB28, CB52, CB101, CB118, CB138, CB153, CB180) for contaminated fish from two international datasets as well as a modelling of profiles, two major fractionation processes related to distinct contamination pathways were identified: (1) A relative enrichment of lighter congeners (CB28, CB52, CB101) in seawater fish due to a predominantly atmospheric transport, whereas freshwater and some coastal fish had higher fractions of heavier congeners (CB138, CB153) because those were mainly contaminated by particle-sorbed PCB from surface runoff. (2) A temperature driven fractionation tended to affect congeners with a medium molecular weight (CB118) as well as the heaviest congeners (CB180), a fractionation process which was conceptually associated with transport of PCB from secondary sources. Specifically, medium chlorinated PCB is sufficiently volatile and persistent for a preferred transport into cooler waters. In warmer climates, only the highest chlorinated congeners are persistent enough to ultimately accumulate in fish. Our analysis and modelling provide a starting point for the development of systems to trace – better than before - sources of PCB contaminations observed in fish.

Comparison of RT-PCR and rRT-PCR Methods in Detection of Viral Hemorrhagic Septicemia Virus (VHSV) in Marine Ornamental Fish

Reverse Transcription PCR (RT-PCR) and Real Time Reverse Transcription PCR (rRT-PCR) are methods that can be used to detect VHSV (Viral Hemorrhagic Septicemia Virus) on freshwater and seawater fish. rRT-PCR is more widely used than the RT-PCR method because of several advantages such as requiring shorter time and fewer stages. Both methods have their own advantages and disadvantages, so it is necessary to compare the two methods in detecting the presence of VHSV in marine ornamental fish. The research was carried out with 3 steps: sensitivity test, specificity test, and sample test. The sensitivity test showed that the smallest dilution concentration that could be detected by both methods was the same at 10-3 with 100 copies in the 77bp band. Specificity tests on both methods showed that VHSV primers used are specific. Sample tests in both methods showed the same results in each of the samples tested. The results of sensitivity, specificity and sample tests conducted on RT-PCR and rRT-PCR methods showed the same results (positive) thus both methods can be used to detect the VHSV in marine ornamental fish.

Produksi Ikan Nila Dengan Kolam Terpal di Desa Kramajaya, Lombok Barat Untuk Mencegah Stunting

Kramajaya Village is one of the stunting loci in Narmada District, West Lombok Regency. Stunting is a problem of chronic malnutrition caused by inadequate nutritional intake over a long period of time due to providing food that is not in accordance with nutritional needs. The way to overcome and prevent stunting from a food perspective is to provide nutritious food to pregnant women, breastfeeding mothers and toddlers. These nutritious foods can include eggs, beef, chicken, seawater fish or freshwater fish. Tilapia is a fish that has high nutritional value and is classified as a fish that is low in cholesterol so it is healthy to consume. The results of discussions with the Mandiri Jaya Youth Organization, Kramajaya Village, Narmada District, West Lombok Regency, has abundant water sources. Apart from that, in Kramajaya hamlet there are many yards of residents' houses that have not been utilized optimally. There are no residents who know that the yard can be used to produce tilapia due to lack of knowledge about the technology of cultivating tilapia using tarpaulin ponds. Therefore, there is a need for knowledge transfer and assistance so that village residents, especially the Mandiri Jaya Youth Organization, Kramajaya Village, can produce tilapia fish in tarpaulin ponds to fulfill community nutrition, especially to prevent stunting and help improve the family economy. This counseling will be carried out using the Focus Group Discussion (FGD) method. Tilapia fish production using tarpaulin ponds in Kramajaya Village, West Lombok, is an effective solution in preventing stunting and improving community nutrition

Method for obtaining reliable R-waves in fish electrocardiograms by utilizing conductivity of seawater

A simple method for measuring bioelectric signals of fish in seawater is expected for managing the health of farmed fish and clarifying the ecophysiology of natural fish. We previously proposed a simple and unique method for measuring bioelectric signals of fish by inserting only one special internal electrode (which can be isolated from seawater) into the fish’s body and by sinking an external electrode in seawater (for utilizing the conductivity of seawater). However, the proposed method could not obtain fish electrocardiograms (ECGs) with reliable R-waves in the same manner as the conventional method. In this study, we thus experimentally investigated whether the R-waves of ECGs could be observed by optimizing the insertion position of the internal electrode into the fish’s body. The results of the experiment show that for four species of fish (each slightly longer than 10 cm) with different body shapes, reliable R-waves could be observed by inserting the internal electrode near the heart. We also investigated the possibility of simultaneously measuring ECGs of multiple fish by the proposed method. The results of the investigation show that the fish ECGs with R-waves of three fish could be observed simultaneously even when one single common external electrode replaced multiple external electrodes. This result indicates the advantage of the proposed method in reducing the total number of bioelectrodes compared to the conventional method for ECG measurements of multiple fish.

Temperature modulates the osmosensitivity of tilapia prolactin cells

In euryhaline fish, prolactin (Prl) plays an essential role in freshwater (FW) acclimation. In the euryhaline and eurythermal Mozambique tilapia, Oreochromis mossambicus, Prl cells are model osmoreceptors, recently described to be thermosensitive. To investigate the effects of temperature on osmoreception, we incubated Prl cells of tilapia acclimated to either FW or seawater (SW) in different combinations of temperatures (20, 26 and 32 °C) and osmolalities (280, 330 and 420 mOsm/kg) for 6 h. Release of both Prl isoforms, Prl188 and Prl177, increased in hyposmotic media and were further augmented with a rise in temperature. Hyposmotically-induced release of Prl188, but not Prl177, was suppressed at 20 °C. In SW fish, mRNA expression of prl188 increased with rising temperatures at lower osmolalities, while and prl177 decreased at 32 °C and higher osmolalities. In Prl cells of SW-acclimated tilapia incubated in hyperosmotic media, the expressions of Prl receptors, prlr1 and prlr2, and the stretch-activated Ca2+ channel, trpv4,decreased at 32 °C, suggesting the presence of a cellular mechanism to compensate for elevated Prl release. Transcription factors, pou1f1, pou2f1b, creb3l1, cebpb, stat3, stat1a and nfat1c, known to regulate prl188 and prl177, were also downregulated at 32 °C. Our findings provide evidence that osmoreception is modulated by temperature, and that both thermal and osmotic responses vary with acclimation salinity.

Salinity induced changes in the progression of water, ion and nutrient fluxes along the gastrointestinal tract of Atlantic salmon smolt (Salmo salar)

Water ingestion in fish increases with both water salinity and feeding. However, it is unclear whether, during feeding, water ingestion is intended to aid chyme liquefaction in the stomach or to maintain the osmotic homeostasis within the body of the fish. We investigated the effects of increasing water salinity (0, 10, 20, 35 ppt) on the progression of water, ion and nutrient fluxes in the gastrointestinal tract of Atlantic salmon smolt (Salmo salar) fed a commercial-like diet. Furthermore, the effect of water salinity on blood pH, plasma osmolality and ions was investigated. The experiment lasted for 8 weeks. Chyme was collected from 4 gastrointestinal tract (GIT) segments (stomach, proximal, middle and distal intestine) and analysed for dry matter, pH, osmolality, crude protein and mineral content. Water and electrolyte fluxes, kinetic of digestion and faecal digestibility were measured using yttrium oxide (Y2O3) as an inert marker. We found that between 0 and 35 ppt chyme dry matter decreased by 1.6% and 4.8% in the stomach and proximal intestine, respectively. Chyme pH was not affected by water salinity in the stomach, but it increased linearly (p < 0.001) with salinity in all intestinal segments. Chyme osmolality increased linearly (p < 0.001) with salinity in the stomach and it decreased in all intestinal segments. Water fluxes were similar among salinities in the stomach, but they increased nearly fivefold (6.2 versus 27.3 ml g−1 ingested DM) in the proximal intestine between 0 ppt and 35 ppt. An efflux of monovalent ions (Na+ and K+) increased linearly (p < 0.001) with salinity in the proximal intestine. An efflux of divalent ions (Ca2+ and Mg2+) increased curvilinearly (p < 0.001) with salinity in the middle intestine. Plasma osmolality and ion levels increased with salinity. Crude protein digestibility and protease activity decreased significantly with water salinity in the intestine. Our study highlights that when Atlantic salmon moves from freshwater to higher water salinity environments, drinking of saltwater does not interfere with hydration of feed in the stomach, but instead bypasses to the proximal intestine to aid in osmoregulatory water uptake. Therefore, we suggest that water ingestion in seawater fish is intended for osmoregulation rather than to aid digestion by liquefying chyme in the stomach.

Analysis of diet structure of Kashin-beck disease area in Chamdo-Lhorong of Tibet in 2021

To investigate and compare the dietary structure between healthy people and patients in KBD area of Chamdo-Lhorong of Tibet. A case-control study design was used, retrospectively select patients who had completed screening and registered in the national Kashin-Beck Disease surveillance system in 2021 in Luolong County, Qamdo, Tibet as the source population of the case group, and randomly selected people who had not been screened for Kashin-Beck disease in the same county as the control group. The self-made diet questionnaire was used to record the types of food consumption, frequency of food intake, basic information of the respondents, family size and other basic information in the past year by one-on-one interview. The staple food with the highest response among the patients(97.33%) was rice(rice/rice noodle), and the highest response among the healthy people(90%) was non-wheat products, non-fried pasta(bread/steamed bun/noodles/dumplings), except instant noodles.78.7% of patients chose not to eat local wheat(Tibetan noodles), and the number of non-patients who chose to eat non-local wheat(Tibetan noodles) 3-4 times a week was significantly higher than that of patients. The meat and meat products with the highest response in both patients(93.33%) and healthy people(90%) was yak meat(local). The control group also chose to consume beef(non-local/lamb/mutton/other non-processed meat), poultry and livestock offal, fish(all seawater and freshwater fish), shrimp and crabs or other seafood, and their consumption rate and intake frequency were significantly higher than those of the case group. The consumption rate and frequency of tomato, onion and garlic(garlic shoots/leek/onion/onion) and fresh eggs(egg/duck egg/quail egg/goose egg) in control group were significantly higher than those in case group. There was no significant difference in consumption rate and frequency of fruits, milk and dairy products between the two groups. In addition to the local highland barley(zanba), most people also chose to purchase rice and flour, which changed the situation of single staple food in the past. However, compared with the healthy population in the disease area, the consumption rate and intake frequency of fish, shrimp and crabs, poultry and livestock viscera, eggs(fresh eggs) and vegetables(tomatoes, scallions, ginger and garlic) in KBD patients were significantly lower, the selection of meat varieties is single, mainly local yak meat, and the overall dietary structure still presents the risk of single type and unbalanced diet.