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In the aquatic farming industry, understanding the factors affecting fish behavior is crucial, particularly in response to infections that compromise welfare and productivity. Swimming performance is a key life history trait critical to their ecology. This study explores the swimming behavior imbalance in Nile tilapia (Oreochromis niloticus , GIFT) post-infection with Streptococcus agalactiae (GBS), a common pathogen responsible for significant losses in aquaculture. We focused on how the microbiota-gut-brain axis influences the behavioral response of tilapia to GBS infection. Behavioral changes were quantified by measuring collision times and swimming speeds, which decreased significantly following infection. This behavioral downturn is mediated by alterations in the microbiota-gut-brain axis, evidenced by increased levels of monoamine neurotransmitters (serotonin, norepinephrine, and dopamine) in the brain and intestinal tissues. The study utilized pharmacological agents, the 5-HT 1A receptor agonist (8-OH-DPAT) and antagonist (WAY-100635), to investigate their efficacy in mitigating these behavioral and biochemical changes. Both agents partially restored normal behavior by adjusting neurotransmitter concentrations disrupted by GBS infection. Additionally, a notable increase in the relative abundance of Streptococcus within the gut microbiota of infected fish highlights the potential role of specific bacterial populations in influencing host behavior. This research provides novel insights into the complex interactions between pathogen-induced gut microbiota changes and Nile tilapia's behavioral outcomes, highlighting potential avenues for improving fish health management through microbiota-targeted interventions. [Display omitted] • Demonstrated GBS's impact on tilapia's swimming behavior. • Identified microbiota changes associated with behavioral shifts. • Utilized receptor agents to counteract infection effects. • Linked neurotransmitter changes to microbiota alterations. • Proposed microbiota-targeted interventions for fish health. [ABSTRACT FROM AUTHOR]

To synthesize PEG@TiO2 with excellent energy storage properties, polyethylene glycol (PEG) was in situ encapsulated for the first time into the pores of three-dimensional (3D) porous TiO2. PEG was surrounded by the hydrolysable precursor of TiO2 and wrapped in the pores of 3D nanoporous TiO2 skeleton after the hydrolysis and condensation of the precursor, which was utterly different from that PEG was passively absorbed into the pores through physical impregnation method adopted by the present references. The 3D TiO2 framework provided excellent shape stability and inhibited the outleakage of the melted PEG. The weight percentage of the encapsulated PEG was approximately 92 wt% of PEG@TiO2 composite. The phase transition enthalpies of the crystallization and melting processes of the composite were 147.1 J/g and 153.3 J/g, which approached those of the pure PEG. Besides, the thermal conductivity value of PEG@TiO2 was 0.39 W/(mK), about 26% enhancement compared with that of pure PEG. The enthalpies of crystallization and melting processes decreased only by 0.1% and 0.2% after 100 thermal cycles. This study revealed that PEG@TiO2 composite exhibited unique energy storage properties such as energy storage capability, thermal stability, thermal reliability and thermal conductivity. [Display omitted] • It was first reported PEG was in situ encapsulated into 3D porous TiO 2 framework. • PEG stored and released thermal energy and TiO 2 acted as the supporting matrix. • The in situ package of PEG had the merits of time saving and energy conservation. • The latent heats of the freezing and melting processes were 147.1 J/g and 153.3 J/g. • PEG@TiO 2 displayed excellent thermal reliability due to the nanoscale pores of TiO 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient nitrogen-removing strain BF6 was isolated from biofilter of RAS. • Assimilation is the main nitrogen removal pathway of strain BF6. • High nitrogen removal of BF6 were obtained under different nitrogen sources. • Nitrogen could be effectively removed in RAS biofilter with addition of BF6. Biological nitrogen removal has received increasing attention in wastewater treatment. A bacterium with excellent nitrogen removal performance was isolated from biofilters of recirculating aquaculture systems (RAS) and identified as Pseudomonas chengduensis BF6. It was indicated that inorganic nitrogen is transformed into gaseous and biological nitrogen by the metabolic pathways of denitrification, anammox, and assimilation, which is the main nitrogen removal pathway of strain BF6. The strain BF6 could effectively remove nitrogen within 24 h under the conditions of ammonia, nitrate, nitrite, and mixed nitrogen sources with maximum total nitrogen removal efficiencies reaching 97.00 %, 61.40 %, 79.10 %, and 84.98 %, respectively. The strain BF6 exhibited total nitrogen removal efficiency of 91.14 %, altered the microbial diversity and enhanced the relative abundance of Pseudomonas in the RAS biofilter. These findings demonstrate that Pseudomonas sp. BF6 is a highly efficient nitrogen-removing bacterium with great potential for application in aquaculture wastewater remediation. [ABSTRACT FROM AUTHOR]

Biocarriers play a vital role in water treatment in recirculating aquaculture systems. In this study, modified oyster shell (OS)-immobilizing denitrifying bacteria were applied as biocarriers in biofilters. The results revealed that CaCO 3 was the main component of the OS calcined at 200 °C (OS 200), 400 °C (OS 400), and 600 °C (OS 600). The surface area and microbe-immobilizing ability of OS 200 , OS 400 , and OS 600 were enhanced. After immobilizing Pseudomonas putida DS2 and Pseudomonas chengduensis BF6, the average total nitrogen (TN) removal efficiencies of OS 400 -P (Pseudomonas sp. DS2 and BF6 immobilized onto OS 400) and OS 600 -P (Pseudomonas sp. DS2 and BF6 immobilized onto OS 600) reached 50.25% and 61.50%, respectively. The microbial and functional gene richness in the biofilters filled with biocarriers made of OS-immobilizing denitrifying bacteria changed. The genus Pseudomonas became the dominant microbe, which was positively correlated with NO 3 --N + NO 2 --N (p < 0.001), and TN removal (p < 0.01). Overall, these findings indicate that applying OS immobilizing denitrifying bacteria as biocarriers can be a novel strategy to enhance nitrogen removal in biofilters. [Display omitted] • The microbe immobilizing abilities of OS 200 , OS 400 and OS 600 were enhanced. • High nitrogen removal efficiencies were obtained in OS 400 -P and OS 600 -P. • OS 200 -P, OS 400 -P and OS 600 -P dramatically changed microbial communities. • The Pseudomonas immobilized in biofilter were positively related to nitrogen removal. [ABSTRACT FROM AUTHOR]

• The cDNA sequence of DDX43 was identified from tilapia (Oreochromis niloticus). • Expressions of DDX43 mRNAs were altered after Streptococcus agalactiae , LPS, and poly I:C stimulation. • The overexpression of OnDDX43 could significantly upregulate IFN-β activity in 293 T cells. • OnDDX43 interacted with both IPS-1 and TRIF. DDX43 is one of the members of the DExD/H-box protein family, and emerging data suggest that it may play an important role in antiviral immunity across mammals. However, little is known about DDX43 in the fish immune response. In this study, we isolated the cDNA sequence of ddx43 in Nile tilapia (Oreochromis niloticus). The ddx43 gene was 2338 bp in length, contained an open reading frame (ORF) of 2064 bp and encoded a polypeptide of 687 amino acids. The predicted protein of On DDX43 has three conserved domains, including the RNA binding domain KH, DEAD-like helicase superfamily DEXDc and C-terminal HELICc domain. In healthy Nile tilapia, the Onddx43 transcript was broadly expressed in all examined tissues, with the highest expression levels in the muscle and brain and the lowest in the liver. After challenge with Streptococcus agalactiae , lipopolysaccharides (LPS) and polyinosinic polycytidylic acid (Poly I:C), the expression level of Onddx43 mRNA was upregulated or downregulated in all of the tissues tested. Overexpression of On DDX43 in 293 T cells showed that it has a positive regulatory effect on IFN-β. The subcellular localization showed that On DDX43 was expressed in the cytoplasm. We performed further pull-down assays and found that On DDX43 interacted with both interferon-β promoter stimulator1 (IPS-1) and TIR domain-containing adaptor inducing interferon-β (TRIF). [ABSTRACT FROM AUTHOR]

Tilapia ( Oreochromis mossambicus , O. urolepis hornorum , their hybrids O. mossambicus ♀ ×  O. hornorum ♂ and O. hornorum ♀ ×  O. mossambicus ♂) were exposed to a high salinity environment to evaluate their osmoregulatory responses. The plasma osmolality of all the tilapia species were elevated with the salinity challenge. The activities of Na + /K + -ATPase (NKA) in both the gill and kidney showed a similar increased change tendency compared with the control. The distribution of NKA α1 mRNA in all the examined tissues suggested that NKA α1 has a possible housekeeping role for this isoform. The amount of NKA α1 mRNA in the gill and kidney was elevated in the four fishes with similar expression patterns after transfer from freshwater to seawater. The NKAα1 mRNA expression levels in the gill reached their peak level at 24 h after transfer ( P < 0.01) compared to the freshwater group, following decreases in the pretreatment level at 48 h ( P  > 0.05). However, the NKA α1 mRNA expression levels in the kidney were not significantly affected with increasing environmental salinity ( P  > 0.05). The differences in the responses to saltwater challenge may be associated with differences in saltwater tolerance between the four tilapia. The drastic increase in the plasma osmolality, NKA activities and mRNA expression suggested that the hybrids ( O. mossambicus ♀ ×  O. hornorum ♂) possess heterosis in salinity responsiveness compared to that of both the parents, indicating a maternal effect on the salinity tolerance of the tilapia hybrids. This study provides a theoretical basis to further study the mechanism of fish osmoregulation response to salinity challenge. [ABSTRACT FROM AUTHOR]

Toll-like receptor 5 (TLR5) is responsible for bacterial flagellin recognition in vertebrates. In the present study, TLR5M was identified in the Nile tilapia Oreochromis niloticus (OnTLR5), containing a conserved LRR domain, a transmembrane region and a C-terminal TIR domain, similar to that of other fishes and mammals. OnTLR5 was broadly expressed in all the tissues examined, presenting the highest expression levels in the blood and the lowest in the kidney. OnTLR5 was detected from 2 d postfertilization (dpf) to 8 dpf during embryonic development. Moreover, expression levels of OnTLR5 were clearly altered in all five tissues examined in response to Streptococcus agalactiae infection in vivo. Overexpression of OnTLR5 in HEK293T cells revealed that OnTLR5 was distributed in the cytoplasm and significantly increased NF-κB activation. In response to cotransfection with OnMyd88, OnTLR5 significantly upregulated OnMyd88-induced NF-κB activation. Pulldown assays showed that OnTLR5 interacts with OnMyd88 and revealed an interaction between TLR5 and Aeromonas hydrophila flagellin. Taken together, these findings suggest that OnTLR5 plays important roles in TLR/IL-1R signalling pathways and the immune response to pathogen invasion. • TLR5 gene was identified in Nile tilapia and was upregulated after S. agalactiae challenge. • TLR5 interacts with MyD88. • The overexpression of TLR5 significantly induced NF-κB activity in cell line. • Pulldown assays revealed the recognition of OnTLR5 for Aeromonas hydrophila flagellin. [ABSTRACT FROM AUTHOR]

Toll-like receptor 7 (TLR7) subfamily members are important pattern recognition receptors that participate in the recognition of pathogen-associated molecular patterns. In the present study, three TLR family members, OnTLR7 , OnTLR8 and OnTLR9 , were identified in the Nile tilapia Oreochromis niloticus. TLR7-, TLR8-and TLR9-deduced proteins have typical structural characteristics of TLRs, including Toll/interleukin-1 receptor (TIR), leucine-rich repeat (LRR) and transmembrane region (TM). OnTLR7 , OnTLR8 and OnTLR9 were broadly expressed in all of the tissues tested, with the highest expression levels in the brain (TLR7) and spleen (TLR8 and TLR9). Moreover, the expression levels of OnTLR7 , OnTLR8 and OnTLR9 were significantly increased in most tested tissues after Streptococcus agalactiae infection in vivo. After LPS stimulation, OnTLR7 and OnTLR9 mRNA expression levels were downregulated in the intestine and upregulated in the liver, spleen and kidney; however, OnTLR8 mRNA expression levels were upregulated in the kidney only after LPS stimulation for 5 d. After Poly I:C stimulation, OnTLR7 and OnTLR9 mRNA expression levels were upregulated in the intestine, liver, spleen and kidney, and the highest expression was found in the liver, while OnTLR8 mRNA expression levels were upregulated in the intestine, liver and kidney and downregulated in the spleen. Subcellular localization of On TLR7, On TLR8, and On TLR9 in 293T cells showed that On TLR9 was distributed in both the cytoplasm and nucleus while On TLR8 and On TLR7 were distributed mainly in the cytoplasm. Overexpression of On TLR7, On TLR8 and On TLR9 in 293T cells had no significant effect on the activity of NF-κB, but they could significantly enhance MyD88-mediated NF-κB activity after cotransfection with MyD88. Pulldown assays showed that On TLR7, On TLR8, and On TLR9 could interact with On MyD88. Taken together, these results indicate that TLR7 subfamily genes play a role in the immune response to pathogen invasion of Nile tilapia. • TLR7, TLR8 and TLR9 cDNA sequences were characterized. •TLR7, TLR8 and TLR9 were upregulated after S. agalactiae infection. •TLR7, TLR8 and TLR9 were up-regulated after LPS, Poly I:C stimulation. •TLR7, TLR8 and TLR9 upregulated the NF-κB activity induced by My-D88. •TLR7, TLR8 and TLR9 could interact with MyD88. [ABSTRACT FROM AUTHOR]

• Reciprocal crosses between Nile tilapia and Jaguar cichlid is cross incompatibility. • The sex-determining system of the Jaguar cichlid is male heterogametic (XX-XY). • Meiotic gynogenesis can improve the homozygosity and genetic similarity of fish. To investigate the distant hybridization and gynogenesis between Nile tilapia Oreochromis niloticus and Jaguar cichlid Parachromis managuensis , reciprocal crossing was first performed between the two species. No offspring, however, were viable when there were these hybridizations. Gynogenesis was induced in O. niloticus and P. managuensis using ultraviolet (UV)-irradiated spermatozoa from P. managuensis and O. niloticus , respectively. The morphology during embryonic development indicated gynogenetic offspring of both O. niloticus and the P. managuensis were normal and deformed, and the results from flow cytometric analysis indicated normal fry were diploid and deformed fry were haploid. Gynogenetic O. niloticus and P. managuensis had the same DNA content and chromosome number as their species of origin, indicating that gynogenetic individuals were produced in both species. The presence of only females for both gynogenetic P. managuensis and O. niloticus was indicative of an XX genotype in the female P. managuensis and O. niloticus. Results from studies on genetic diversity indicated the average heterozygosity of the gynogenetic diploid population of O. niloticus were less than that of the cultured population, but the genetic homozygosity of the gynogenetic diploid population of O. niloticus was greater than that of the cultured population after one generation of gynogenesis, which achieved the goal of rapidly establishing genetic homozygosity. [ABSTRACT FROM AUTHOR]