Low Salinity Stress Research Articles

Transcriptome Reveals the Mechanism of Immunity in the Low Salinity Stress of the Chinese Shrimp (Fenneropenaeus chinensis)

Transcriptome Reveals the Mechanism of Immunity in the Low Salinity Stress of the Chinese Shrimp (Fenneropenaeus chinensis)

Physiological and Molecular Analyses of Low-Salinity Stress Response in the Cuttlefish (Sepia pharaonis) Juveniles

Physiological and Molecular Analyses of Low-Salinity Stress Response in the Cuttlefish (Sepia pharaonis) Juveniles

Short-term fluctuations in salinity and turbidity: effects on the embryonic stage of two abalone species, Haliotis discus discus and Haliotis gigantea

Marine gastropod eggs are often distributed in the intertidal zone, where they are potentially exposed to short-term salinity and turbidity changes due to heavy rains that may adversely affect their embryonic development. In this study, the embryos of two abalone species, disk abalone Haliotis discus discus and giant abalone Haliotis gigantea, were exposed to various salinities (34, 30, 26, 22, 18 and 14 psu) or turbidities (0, 100, 300, 500 and 700 NTU) for a single 3 h period, and subsequently maintained at normal control conditions (34 psu and 0 NTU). The short-term low salinity stress decreased the hatching and survival rates, and increased the abnormality rate for both species. As for turbidity stress, negative effects on hatching and survival rates were observed in both species when their embryos were exposed to increased turbidity. The abnormality rates of both species at turbidities of 500 and 700 NTU were significantly higher than those at turbidities of 0 and 100 NTU. Overall, exposure of embryos to low salinity or high turbidity for even a short period can clearly have substantial impacts on the embryonic development of the two abalone species, and disk abalone was more sensitive to salinity and turbidity stresses compared to giant abalone.

Metabolic Response in the Gill of Portunus trituberculatus Under Short-Term Low Salinity Stress Based on GC-MS Technique

Salinity is an important factor affecting the survival, growth, and metabolism of marine crustaceans. Low-salt stress will result in the death of swimming crabs. This paper investigates the metabolic response in the gills of Portunus trituberculatus under short-term low-salt stress by comparing the metabolic molecules in the four salinity treatment groups (24‰, 16‰, 12‰, and 8‰) by GC-MS technique. In this study, nine common differential metabolites such as pyruvate, malic acid, and phosphoethanolamine were found in the gill tissues of crabs. KEGG enrichment analysis revealed that six metabolic pathways, including the citric acid cycle, pyruvate metabolism, and the HIF-1 signaling system, were significantly impacted by low salt stimulation. According to the findings, salinity 12‰ is a critical node in crab adaptation to low salinity. In the process of adaptation to short-term low-salinity environment, amino acids participated in osmotic regulation, and organic acids such as pyruvate and malic acid were involved in energy metabolism to ensure their energy supply. This research further enriched the theory of osmotic regulation and metabolic mechanism of adaptation to low salt in crustaceans, with the goal of providing guidance for the improvement of culture technique in Portunus trituberculatus.

New Insight on Vitality Differences for the Penaeid Shrimp, Fenneropenaeus chinensis, in Low Salinity Environment Through Transcriptomics

Excessive rainfall changes salinity in shrimp farming ponds in short period and exerts low salinity stress on the outdoor breeding shrimp under global warming. Fenneropenaeus chinensis can have different performance on vitality in low salinity environments. To reveal mechanisms of vitality difference in shrimp living in low saline environments. This study based on the normal and moribund F. chinensis in 10 ppt salinity environment using high-throughput sequencing identifies 1,429 differentially expressed genes (DEGs), 586 of which are upregulated, while 843 of which are downregulated in the normal group (FCN10) as compared to the moribund group (FCM10). Meanwhile, another transcriptomic analysis is conducted on the normal and moribund shrimp from 25 ppt (FCN25 vs. FCM25) salinity environment as the control, in which 1,311 DEGs (upregulated: 327 genes, downregulated: 984 genes) are identified. In this study, intersective pathways, GO (Gene Ontology) categories and DEGs from the two groups of comparative transcriptome are investigated. The two intersective pathways (Metabolism of xenobiotics by cytochrome P450, Pentose, and glucuronate interconversions) significantly enriched by DEGs are related to detoxification. In these two pathways, there is one vitality regulation-related gene (VRRG), the Dhdh (dihydrodiol dehydrogenase), which is upregulated in both the groups of FCN10 and FCN25 as compared to the groups of FCM10 and FCM25, respectively. Similarly, in the 25 top intersective GO categories, four VRRGs are revealed. Three of them are upregulated (Itgbl, kielin/chordin-like protein, Slc2a8, solute carrier family 2, facilitated glucose transporter member 8-like protein and Cyp3a30, cytochrome P450 3A30-like protein); one of them is downregulated (Slc6a9, sodium-dependent nutrient amino acid transporter 1-like protein isoform X2). These GO categories are related to transmembrane transporter activity of substance, enzyme inhibitor activity, monooxygenase activity. RT-qPCR analysis further verifies the VRRGs. The study gives new insight into understanding the vitality differences for F. chinensis, in low salinity environment. The pathways and DEGs in response to low salinity stress in modulating the vitality of F. chinensis that could serve as tools in future genetic studies and molecular breeding.

Effects of short-term low salinity stress on non-volatile flavor substances of muscle and hepatopancreas in Portunus trituberculatus

In order to determine the effects of different short - term low salinity stress on non - volatile flavor substances of Portunus trituberculatus, four salinity levels (24‰, 16‰, 12‰ and 8‰) were selected. The contents of free amino acids (FAA), nucleotides and lactic acid in both muscle and hepatopancreas of P. trituberculatus were determined by HPLC and spectrophotometry respectively. Results showed that muscle contained a relatively higher level of sweetish free amino acids (SFA), however short - term low salinity stress greatly increased the level of bitter free amino acid (BFA); hepatopancreas contained a higher level of umami free amino acids (UFA) and a higher equivalent umami concentration (EUC) value, which increased significantly with the decrease of salinity level and the degree of umami flavor reached the highest when salinity dropped to 8‰. The lactic acid content in muscle increased at 12‰ and then decreased significantly at 8‰ while no significant differences were observed in hepatopancreas. Results above revealed the flavor change in two edible parts of P.trituberculatus under short - term low salinity stress which provided a guidance for more systematic nutritional flavor evaluation in breeding process and consumption demand.

Genome-wide analysis of the hard clam mitogen-activated protein kinase kinase gene family and their transcriptional profiles under abiotic stress

Mitogen-activated protein kinase kinase (MAPKK) was the hub component of the Mitogen-activated protein kinase (MAPK) signaling pathway and played an important role in the cellular response to environmental stress. In this study, we identified five MmMAPKK genes in hard clam Mercenaria mercenaria and found that all MmMAPKK genes contain a conserved protein kinase domain. The MmMAPKK genes derived from dispersed duplication were unevenly distributed in three chromosomes. Although the genome size was highly variable among different bivalve mollusks, the number of MAPKK genes was relatively stable. Phylogenetic analysis showed that bivalve MAPKK was divided into five clades, and amino acid sequences of MAPKK from the same clade consisted of similar conserved motifs. The syntenic analysis demonstrated that MmMAPKKs had the highest number of homologous gene pairs with Cyclina sinensis. MmMAPKKs were ubiquitously expressed in all examined tissues, and all MmMAPKK genes were highly expressed in the ovary. MmMAPKK genes showed stress-specific expression under envirionmental stress. MmMAPKK7 showed an upregulated in heat and heat plus hypoxia stress while MmMAPKK1 showed an upregulated in hypoxic stress groups. Dynamic changes of MmMAPKK7, MmMAPKK6 and MmMAPKK1 in hemocytes were observed in response to air exposure. MmMAPKK4 significantly downregulated after air exposure for five days. MmMAPKK7 and MmMAPKK6 might participate in adaptation to low salinity stress. Our results provided useful information about MAPKK and laid a foundation for further studies on MAPKK evolution in the bivalve.

Genome-wide identification and low-salinity stress analysis of the Hsp70 gene family in swimming crab (Portunus trituberculatus)

No genome-wide identification and expression analysis have been performed on the heat shock protein 70 (Hsp70) gene family, which is essential to key cellular processes and responses to environmental change, in decapods. In the present study, we identified nine members of the Hsp70 gene family within the genome of swimming crab (Portunus trituberculatus) and provided insights into their response to long-term low-salinity stress. Results demonstrated that gene structure and motifs are conserved among members of this gene family in P. trituberculatus. Under low-salinity stress, the expression of this gene family in the gill of P. trituberculatus showed that hsc70l.2 was significantly upregulated, hyou1 was significantly downregulated. The hsc70l.4 was not expressed. Furthermore, selection test on duplicated genes showed a negative selection on hsc70l.1, hsc70l.2, hsc70l.3, and hsc70l.4, suggesting functional redundancy. This may be the first study that systematically identified and analyzed the Hsp70 gene family in decapods. These results can provide fundamental data for the biological research of P. trituberculatus and enhance understanding of the biological function of Hsp70 in crustaceans adapting to salinity changes.

Physiological responses and adaptive strategies to acute low-salinity environmental stress of the euryhaline marine fish black seabream (Acanthopagrus schlegelii)

The physiological metabolism of marine animals farmed in coastal areas is influenced greatly by extreme weather and frequent aqueous layer exchange, with short or long periods of heavy rain reducing seawater salinity. Black seabream (Acanthopagrus schlegelii) is a euryhaline fish, that are farmed in China under both normal/ambient salinity in seawater cages and low salinity conditions in pond culture. To explore the effects of an acute change in salinity on physiological metabolism, juvenile black seabream (weight 19.80 ± 0.37 g) was subjected to low salinity (4–5 psu) over five time points including 1 h (H1), 6 h (H6), 12 h (H12), 24 h (H24) and one week (W), with 0 h (initial, natural salinity of 22 psu) as control group. Results indicated that acute exposure to low-salinity resulted in various responses related to oxidative stress (OS) and endoplasmic reticulum stress (ERS). The key markers of OS including reactive oxygen species and malonaldehyde were significantly increased with acute salinity stress up to 6 h, then decreased to return to normal levels. A similar pattern was recorded for total antioxidant capacity, which showed significantly higher activity in the H6 group. All parameters related to ERS increased with duration of the low-salinity stress, which stimulated expression of key genes including nuclear factor kappa B (nf-κb) and c-Jun N-terminal kinase (jnk), triggering inflammation and apoptosis. However, total apoptotic cell rate decreased markedly as the duration of salinity stress increased up to one week. Gill expression of genes of long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis was up-regulated by low salinity stress with levels of docosahexaenoic (DHA), eicosapentaenoic (EPA) and arachidonic acids (ARA) being highest in the H12 group, which positively contributed to enhanced ability of osmoregulation. In conclusion, acute low-salinity stress stimulated various stress responses but, as the duration of salinity stress increased, the fish showed signs of physiological adaptation to the environmental change. During the adaptive process to maintain hemolymph osmotic pressure regulation, LC-PUFA were rapidly enriched in gill, which might be a crucial strategy allowing A. schlegelii to adapt to low-salinity stress. These findings provided further insight and understanding of the physiological responses and underlying adaptive strategy of euryhaline fish to salinity stress, and confirmed time-dependent effects.

Dietary turmeric, curcumin and nanoencapsulated curcumin can differently fight against salinity stress in Pacific white shrimp Penaeus vannamei Boone, 1931

The influence of diet supplementation with turmeric (TUR), curcumin (CUR) and nanoencapsulated curcumin (NMC) was evaluated on haemolymph biochemical parameters and hepatopancreas antioxidant enzymes of Penaeus vannamei (2.96 ± 0.10 g) exposed to low and high salinity stress at 5 and 55 g L−1 respectively. Nine dietary groups containing different dosages (g kg−1 diet) of TUR (TUR 2.5, TUR 5 and TUR 10), CUR (CUR 0.075, CUR 0.150 and CUR 0.300) and NMC (NMC 0.075, 0.150 and 0.300) along with the control group made the ten treatments. After nine weeks of feeding, CUR additives decreased the haemolymph triglycerides, cholesterol, glucose and cortisol in shrimps under normal and stress conditions compared with the control group; the lowest and highest values were observed in NMC 0.150 and control group respectively (p < 0.05). Adding TUR, CUR and NMC supplements to the diet increased total protein, total haemocytes count and differential haemocytes count in stressed and non-stressed shrimps; the highest was observed in NMC 0.150. The lowest and highest activities of antioxidant enzymes including CAT, SOD and GSH-Px before and after the salinity stress were detected in control group and NMC 0.150 respectively (p < 0.05). After the salinity stress, the experimental treatments increased the survival rate, where NMC 0.150 caused the highest survival (p < 0.05). In conclusion, different forms of dietary CUR improved antioxidant capacity and resistance of P. vannamei to acute salinity stress. Nanomicellar carriers in shrimp nutrition can promote immunity and antioxidant responses under stressful conditions through more efficient delivery of dietary immunostimulants.

The optimal reference gene validation in Cyclocarya paliurus (Batal.) Iljinskaja under environmental stresses

AbstractCyclocarya paliurus (Batal.) Iljinskaja is a special plant species grown at high elevation in southwestern China. The bark, leaves, and roots are used for many purposes including reduction of fever and enhancement of blood insulin level. However, its growth is usually limited by the fragile environment and climate variability. Previous studies attributed the environment‐relevant yield reductions to stress induced gene expression changes. The accuracy and reliability of reverse transcription quantitative polymerase chain reaction (RT‐qPCR), a commonly accepted gene expression method, depends on the choice of appropriate reference genes, which are used for gene expression normalization. However, there are no reports at present about reference genes of C. paliurus under environmental stresses. Therefore, this study was conducted to identify reference genes for C. paliurus under environmental stresses. In this work, we selected seven common reference genes as our candidates: ACT2, ACTF, GAPDH, TUA, TUB, UBQ4, and 18SrRNA. The stability of these seven reference genes in C. paliurus was quantified by RT‐qPCR and evaluated by geNorm and NormFinder algorithms. The results suggest that although there were variations of the stability of the internal reference genes, two of them were usually good enough for the normalization purpose for low temperature (4 °C), high salinity (NaCl), and drought stress (polyethylene glycol [PEG] treatment). However, these genes should not be used for high‐temperature (42 °C) stress. This study provides insight for reference gene selection under experimental stresses in C. paliurus. It also sets the foundation of wide and accurate use of RT‐qPCR under environmental stresses.

Application of Transcriptome Analysis to Understand the Adverse Effects of Hypotonic Stress on Different Development Stages in the Giant Freshwater Prawn Macrobrachium rosenbergii Post-Larvae

Salinity is one of the important environmental factors affecting survival and growth of aquatic animals. However, the impact of low-salinity stress on M. rosenbergii post-larvae at different development stages remains elusive. Therefore, the aim of this study was to explore the underlying mechanisms of hypotonic stress at different development stages of M. rosenbergii post-larvae through transcriptome analysis and antioxidant parameters detection. The salinity of the control group was 15 psu (S15) and the hypotonic stress group was 6 psu (S6). Samples were collected at 7 days-post-hatch (dph), 14 dph and 21 dph larvae. The results showed that hypotonic stress caused oxidative damage in post-larvae evidenced by decreased glutathione peroxidase (GSH-Px); superoxide dismutase (SOD); anti-superoxide anion free radical (ASAFR); and increased malondialdehyde (MDA); nitric oxide (NO); and inducible nitric oxide synthase (iNOS) levels. Transcriptome analysis showed that there were 1428, 1187, 132 DEGs including 301, 366, 4 up-regulated genes and 1127, 821, 128 down-regulated genes at 7 dph, 14 dph and 21 dph larvae under hypotonic stress, respectively. Furthermore, GO and KEGG enrichment indicated that hypotonic stress led to dysregulation of immune signals including lysosome and autophagy in the 7 dph larvae. The autophagy-related genes including beclin 1-associated autophagy-related key regulator (Barkor); ubiquitin-like modifier-activating enzyme ATG7 (ATG7); Beclin; autophagy-related protein 13 (ATG13); nuclear receptor-binding factor 2 (Nrbf2); ubiquitin-like-conjugating enzyme ATG3 (ATG3); vacuole membrane protein 1 (VMP1); and autophagy-related protein 2 (ATG2) decreased at 7 dph, and 14 dph larvae, and then increased at 21 dph larvae under hypotonic stress. In the 14 dph and 21 dph larvae, the renin-angiotensin system was activated. In conclusion, our data indicated that hypotonic stress reduced the antioxidant capacity and impaired the immune system in post-larvae, but as development progresses, the adaptability of post-larvae to hypotonic stress gradually increased, and might reach a new homeostasis through the RAS signaling pathway.

Immune and antioxidant responses of pearl oysterPinctada maximaexposed to acute salinity stress

Salinity change is a frequently occurring abiotic stress that dramatically affects the physiological and biochemical factors of marine bivalve molluscs. In this study, a total of 140 individuals of Pinctada maxima were collected from Weizhou Island (Beihai, China) for 48-h acute salinity stress. Immune enzymes (phenoloxidase [POX], lysozyme [LZM] and alkaline phosphatase [ALP]), antioxidant enzymes and substances (superoxide dismutase [SOD] and reduced glutathione [GSH]) were measured at different times after acute low-salinity (salinity 20) and high-salinity (salinity 40) stress with a salinity of 30 as the control group to assess the effects of acute salinity stress on immune and antioxidant responses of P. maxima. The results showed that the total protein (TP), GSH, SOD, POX, LZM and ALP of silver-lipped pearl oyster P. maxima were significantly influenced by the different salinity gradients and duration of salinity stress (p < 0.05). The TP, SOD, LZM and GSH of P. maxima recovered to the same level of the control group at 48 h after acute high-salinity stress (salinity 40, p > 0.05), while only TP and LZM in the low-salinity group (salinity 20) recovered to the same level of the control group at 48 h (p > 0.05), indicating that P. maxima has a stronger tolerance to high salinity (40) than low salinity (20). The study provides references for exploring the antioxidant and immune response mechanism to salinity stress in P. maxima and its cultivation.

Effects of reduced salinity caused by reclamation on population and physiological characteristics of the sesarmid crab Chiromantes dehaani

Reduced salinity is a major factor that causes macrobenthic degradation in reclaimed wetlands. We investigated populations of the sesarmid crab Chiromantes dehaani in reclaimed and natural wetlands. Then, in the laboratory, we exposed male and female crabs to four salinity levels (0, 6, 12 and 18) for 96 h to analyse the effects of reduced salinity on osmoregulatory enzyme activities in the posterior gills and digestive and immune enzyme activities in the hepatopancreas of C. dehaani. The results revealed a significant positive correlation between the number of crabs and salinity. In the laboratory, we found that the isosmotic point of C. dehaani was close to 16 ppt. The crabs showed strong hyper-osmotic regulation when exposed to 0–6 ppt salinities. Moreover, in this salinity range, amylase activities were significantly inhibited. Under low-salinity stress, the immune enzyme activities were significantly activated. However, phenoloxidase and lysozyme activities were inhibited in the freshwater environment. The male and female crabs showed no significant differences in most of the enzyme activities. Thus, reduced salinity can adversely affect the digestive and immune functions of C. dehaani, which may cause population degradation in reclaimed wetlands. Our findings can provide new insights into the effects of reclamation on macrobenthos.

Cloning, expression and function analysis of trehalose-6-phosphate synthase gene from Marsupenaeus japonicu.

Trehalose is an important disaccharide that plays an important role in extreme environmental conditions. Trehalose-6-phosphate synthase (TPS) gene is the key gene for trehalose synthesis in Marsupenaeus japonicus. In this study, a TPS gene was isolated and characterized from M. japonicus. The full-length cDNA of TPS gene of M. japonicus (MjTPS) was 3308bp, encoding 844 amino acids. The protein of the deduced MjTPS contained a glycol_transf_20 domain and a trehalose_PPase domain. The mRNA expression level of MjTPS was the highest in hepatopancreas. The further analysis found that MjTPS gene expression was up-regulated in a short time under low-salinity and high-nitrite stress, indicating that MjTPS gene had certain resistance to low-salinity and high-nitrite stress. Compared with the control group, both the expression of MjTPS and the trehalose content significantly decreased from 3h to 24h after MjTPS gene interference,. After RNAi, the mortality of M. japonicus increased, the expression level of MjTPS and the synthesis of downstream products decreased under low-salinity and high-nitrite stress, and what's more, the expression of immune genes PMO25, ERP, CD, HSP90, HSP70, HSP60, HMC and CLEC2 were significantly changed, implying that MjTPS might be participated in the immune response of M. japonicus. In addition, MjTPS gene silencing could affect the expression of CHI1 and CHS, suggesting that MjTPS might be involved in molting behavior of M. japonicus. These results provide new information for further studying the function of trehalose-6-phosphate synthase in shrimp.

Characterization of CLCN5 and Expression Profile under Low-Salinity Stress in Takifugu rubripes

Characterization of CLCN5 and Expression Profile under Low-Salinity Stress in Takifugu rubripes

Construction of a genetic linkage map, QTLs mapping for low salinity and growth-related traits and identification of the candidate genes in Pacific white shrimp (Litopenaeus vannamei)

Low-salinity tolerance and growth are crucial economic traits of shrimp in areas with low-salinity water. In the current study, an F1 full-sib family of Pacific white shrimp (Litopenaeus vannamei) was obtained by the “semidirectional cross” method, and 2 parents and 146 progenies were genotyped using double-digest restriction site-associated DNA sequencing technology (ddRAD-Seq). A total of 3335 high-quality markers were identified and used to construct a genetic linkage map. This genetic map comprised 48 linkage groups (LGs), and the total map length spanned 3954.462 centimorgan (cM) with an average marker interval of 1.186 cM. Three quantitative trait loci (QTLs) for low-salinity tolerance and 3 QTLs for growth (body weight) were detected under the condition of restricted logarithmic odds (LOD) score ≥ 2.50. With the assistance of the genome of L. vannamei and relevant annotations, 3 potential growth-related genes (sob, TJP1 and ZBTB24) and 3 low-salinity response candidate genes (Rnf168, CNOT2 and RPB3) were identified from the genomic scaffolds. Moreover, the qPCR results showed that the expression levels of the 3 candidate genes were significantly affected by low-salinity stress, indicating that they possibly play an important role in low-salinity stress. Here, we present the first report of mapping of low-salinity tolerance QTLs in the genetic mapping of L. vannamei, which will be beneficial for the selection of shrimp breeding markers and might help promote the study of the L. vannamei genome.

Characterization of the glucocorticoid receptor of large yellow croaker (Larimichthys crocea) and its expression in response to salinity and immune stressors

Glucocorticoids are steroidal hormones critical to stress responses in vertebrates. To gain further insight into the role of the glucocorticoid receptor (GR) in acute stress responses in teleost fish, the relevant cDNA of large yellow croaker (Larimichthys crocea; LcGR) was cloned using the rapid amplification of cDNA ends (RACE) technique. Multiple alignment of the amino acids (aa) of LcGR and the GR of other teleosts indicated LcGR contained four commonly conserved domains and lacked the 9-aa insert seen in GR1. Phylogenetic analysis of the amino acid sequence revealed that LcGR grouped most closely with the GR2 of other teleosts and can therefore be considered a GR2 subtype. In healthy L. crocea, Lcgr mRNA was found to be expressed at high levels in the gill, brain, and muscle tissue, expressed at intermediate levels in heart and stomach tissue, and expressed at low levels in the kidney, intestine, head kidney, liver, and spleen tissue. The response of L. crocea to acute low-salinity stress was tested, with a significant increase in plasma cortisol concentration after 3 h, peaking after 6 h, and gradually returning to base levels. Regarding changes of Lcgr expression in different body tissues under the stress, there was up-regulation of the Lcgr transcript in the brain, liver, and gill tissues, but not in muscle tissue. Responses to pathogen mimics were also tested. Injection with lipopolysaccharide resulted in Lcgr expression, with an increase-decrease-increase trend in the head kidney. In contrast, a down-regulation of Lcgr expression in the head kidney was observed throughout the experimental period upon injection of polyinosinic:polycytidylic acid, revealing different roles of Lcgr for different types of pathogens. The results offer novel insights about the effects of different stressors on GR gene expression in L. crocea, and can facilitate further investigations into stress responses in other mariculture fish species.

Fluctuations in the heart rate of abalone in response to low salinity stress

Fluctuations in the heart rate of abalone in response to low salinity stress

The influences ofBacillus subtilisC‐3102 inclusion in the red sea bream diet containing high levels of soybean meal on growth performance, gut morphology, blood health, immune response, digestibility, digestive enzymes, and stress resistance

This study evaluated the effects of replacing fish meal with dehulled soybean meal (SBM) with and without Bacillus subtilis in red sea bream diets. Five diets with dehulled SBM as a replacer for fish meal protein at 0 (FR0), 500 g kg−1 (FR50), 750 g kg−1 (FR75), 500 g kg−1 + 1 g B. subtilis (FRB50), and 750 g kg−1 + 1 g B. subtilis (FRB75) were formulated. FRB50 showed a marked increase in the growth performance parameters, whereas FR75 showed the lowest values. Interestingly, digestibility parameters were significantly enhanced in FRB50 and FRB75. FR0 and FRB50 groups showed the highest body protein content, whereas FR50 and FRB50 groups showed the highest lipid content. The intestines exhibited increased villi, enterocyte, and microvillus height in FR0, FRB50, and FRB75. FR0, FRB50, and FR50 groups showed high antioxidant potential than control and other groups. Respiratory burst activity showed significant enhancement in FRB50 and FRB75 groups. Also, fish fed on FRB50 displayed a high level of activity in immune-related enzymes. Low salinity stress resistance increased significantly with FRB50 groups, whereas FR75 showed the lowest value. In this work, dietary B. subtilis increased the inclusion of dehulled SBM without affecting red sea bream growth, digestion capacity, immunity, or health status.