Sea Perch Lateolabrax Japonicus Research Articles

Spatial distribution of bacterial communities driven by environmental factors in the sediment of Lateolabrax japonicus ponds

Dynamic changes of bacterial communities in the sediment are very important for preventing diseases and water quality in aquaculture ponds. In this study, bacterial communities in the sediment of Sea perch Lateolabrax japonicus, an important farmed fish in China, ponds were studied using 16S rRNA Illumina sequencing and functional gene array. At the phylum level, Pseudomonadota, Actinomycetota and Chloroflexota were the dominant species. The bacterial community composition was different in spatial variation. Among the environmental factors, the concentration of nitrogen related factors (TN, NO3−-N NH3-N, NO2−N) and total organic carbon was the main impact on the composition of bacterial community, especially denitrifying bacterial community. Nitrifying and denitrifying bacteria accounted for 4.81 %, and bacteria related to nitrogen cycle accounted for 18.36 %. Higher diversity of bacteria in healthy fish pond than that of the diseased fish pond. In the diseased fish pond, lower abundance of Nitrosospira and higher abundance of Nitrobacter were found, and the contents of NH3-N, NO2−-N and total organic carbon were significantly higher. This study would help to reveal that microbial community structure could reflect the health of cultured animal and surroundings, and it could provide a theoretical reference for the healthy environments in the sediment of Sea perch ponds in South China.

IFNh and IRF9 influence the transcription of MHCII mediated by IFNγ to maintain immune balance in sea perch lateolabrax japonicus

The major histocompatibility complex class II (MHCII) molecules are crucial elements of the adaptive immune system, essential for orchestrating immune responses against foreign pathogens. However, excessive expression of MHCII can disrupt normal physiological functions. Therefore, the host employs various mechanisms to regulate MHCII expression and maintain immune homeostasis. Despite this importance, limited studies have explored the negative regulation of MHCII transcription in bony fish. In this study, we found that interferon h (IFNh), a subtype of type I IFN in sea perch Lateolabrax japonicus, could inhibit the activation of IFNγ induced-MHCII expression by modulating the transcription of the class II major histocompatibility complex transactivator (CIITA). Transcriptome analysis revealed 57 up-regulated and 69 down-regulated genes in cells treated with both IFNγ and IFNh compared to those treated with IFNγ alone. To maintain cellular homeostasis, interferon regulatory factor 9 (IRF9) was up-regulated following IFNγ stimulation, thereby preventing MHCII overexpression. Mechanistically, IRF9 bound to the CIITA promoter and suppressed its expression activated by IRF1. Furthermore, IRF9 inhibited the promoter activity of both MHCII-α and MHCII-β induced by CIITA. Our findings highlight the roles of IFNh and IRF9 as suppressors regulating MHCII expression at different hierarchical levels. This study provides insights into the intricate regulation of antigen presentation and the foundation for further exploration of the interaction mechanisms between aquatic virus and fish.

Interaction between Sea perch iridovirus (SPIV) infection and gut microbes in sea perch Lateolabrax japonicus

Sea perch iridovirus (SPIV) infection causes severe disease of fish and has led to economic loss of the sea perch Lateolabrax japonicus aquaculture industry. In this study, severe pathological damage of SPIV-infected sea perch was observed; the relationship of SPIV infection, gut microbial community structure, and gut transcripts of sea perch were explored. SPIV infection could inhibit normal immune function of the gut. The expression levels of immune genes such as MHC I, MHC II, TCR, BCR, and IgM were down-regulated during SPIV infection. Intestinal immunosuppression breaks the balance between mucosal immunity and gut microbes. Opportunistic pathogens such as Lawsonella, Corynebacterium, and Achromobacter expanded substantially following SPIV infection. The abundance of potential probiotics in aquatic animals such as Romboutsia declined following SPIV infection. Intestinal microbial lipopolysaccharide biosynthesis and bacterial secretion related functions increased in SPIV infection and correlated with the expression of intestinal lipopolysaccharide binding protein (LBP), TLR5, IL-1β and other genes. These results suggest that gut microbes can stimulate the innate immune system and trigger an acute inflammatory response through LPS. In conclusion, we analyzed the interaction between SPIV infection and gut microbes and provided a basis for further studies on the mechanism of SPIV pathogenesis and treatment.

The effects of acute and chronic ammonia exposure on growth, survival, and free amino acid abundance in juvenile Japanese sea perch Lateolabrax japonicus

Japanese sea perch, Lateolabrax japonicus is an economically important marine fish and is widely cultured in coastal area of China. In recent years, ammonia poisoning has seriously affected the yield and quality of perch, but data on its ammonia tolerance is sparse. This study used a sequential approach to evaluate how perch tolerate acute and chronic ammonia exposure. First, we estimated the effects of acute ammonia poisoning on perch (16.08 ± 0.12 g) and calculated 96-h LC50 that, based on linear interpolation (y = 2.64× – 99.11, R2 = 0.94 where y = % mortality and x = mg L−1 T-AN ammonia concentration), was 56.50 mg L−1 total ammonia nitrogen (T-AN). Then we measured the 42-d survival, growth and concentration of free amino acids in muscle of perch (16.12 ± 0.95) g reared in 0.00, 0.28, 0.57, 1.13 and 2.06 mg L−1 T-AN. The survival rate decreased when ammonia concentration exceeded 0.57 mg L−1 T-AN, but the weight gain, condition factor and hepatosomatic index were inhibited when ammonia concentration exceeded 0.28 mg L−1 T-AN. The changes in free amino acids concentration may be potentially related to the ammonia exposure. We recommend that Japanese sea perch not be exposed to ammonia concentrations >0.28 mg L−1 T-AN for prolonged periods of time.

Dietary Composition and Trophic Niche Partitioning of Spotty‐bellied Greenlings Hexagrammos agrammus, Fat Greenlings H. otakii, Korean Rockfish Sebastes schlegelii, and Japanese Seaperch Lateolabrax japonicus in the Yellow Sea Revealed by Stomach Content Analysis and Stable Isotope Analysis

AbstractStable nitrogen and carbon isotope ratios of fish tissues, in combination with stomach content analysis, provide insights into how energy flows through marine food webs. Using these techniques, we investigated the diets and trophic niches of four important fish species of the Yellow Sea: the Spotty‐bellied Greenling Hexagrammos agrammus, Fat Greenling H. otakii, Korean Rockfish Sebastes schlegelii, and Japanese Seaperch Lateolabrax japonicus. The stomach content analysis revealed that Spotty‐bellied Greenlings mainly fed on crabs and fish; Fat Greenlings mainly preyed on fish, crabs, and shrimps; Korean Rockfish primarily consumed fish and shrimps; and Japanese Seaperch mainly fed on fish. Korean Rockfish had the highest dietary breadth index among the four fish species. Dietary composition of the four species did not overlap significantly, as indicated by Schoener's index. Prey category composition varied across fish species and differed between species pairs (except Korean Rockfish and Japanese Seaperch), as suggested by permutational ANOVA tests. The stable isotope analysis suggested that Japanese Seaperch had significantly higher δ13C and δ15N and had a significantly different centroid position, both of which indicated a higher trophic position. The corrected standard ellipse area on the δ15N–δ13C (‰) biplot varied in size among species and significantly overlapped in the three rockfishes, with the largest overlap area observed between Fat Greenlings and Korean Rockfish. The results, in general, suggested that the three rockfish species, especially Korean Rockfish and Fat Greenlings, had similar trophic niches, but they were partitioned by prey resources according to the stomach content composition. Our study provides novel insights into the dietary niches and trophic dynamics of these four exploited species, which could help to improve ecosystem‐based fisheries management in the Yellow Sea.

Identification and characterization of the melanoma differentiation – associated gene 5 in sea perch, Lateolabrax japonicus

The RIG-I-like receptors family is a group of cytosolic RNA helicase proteins that can recognize viral RNA via binding to pathogen associated molecular pattern motifs within RNA ligands. A novel vertebrate RLR counterpart named LjMDA5 was firstly identified from the marine fish sea perch Lateolabrax japonicus in this study. The full-length cDNA of LjMDA5 is 3750 bp and encodes a polypeptide of 988 amino acids, containing two N-terminal tandem caspase activation and recruitment domains, a DExH (Asp-Glu-X-His) box domain, an HELICc domain, and a C-terminal domain RIG-I. Phylogenetic analysis showed that LjMDA5 shared the closest genetic relationship with the MDA5 of Larimichthys crocea. Quantitative RT-PCR analysis showed that LjMDA5 was ubiquitously expressed and up-regulated significantly in all selected tissues in vivo post NNV infection. Time course analysis showed that LjMDA5 transcripts significantly increased in spleen and kidney. We found LjMDA5 could be regulated in the sea perch LJB and LJF cell lines after lipopolysaccharide, polyinosinic-polycytidylic acid treatment and NNV challenge. RNA interference experiment indicated that silencing of LjMDA5 significantly increased RGNNV replication and virus production in NNV infected LJF cells. Our results revealed that MDA5 was essential for host defense against NNV, which provided new insights into the function of RLR signaling pathway during NNV infection in fish.

Methylation status and chromatin structure of the myostatin gene promoter region in the sea perch Lateolabrax japonicus (Perciformes)

Myostatin is a negative regulator of the growth and development of skeletal muscle mass. In fish, myostatin is expressed in several organs in addition to skeletal muscle. To understand the mechanisms regulating myostatin gene expression in the sea perch, Lateolabrax japonicus, we examined the methylation status of the myostatin gene promoter region in several tissues (liver, eye, kidney, brain, and heart) isolated from adult specimens. The frequency of methylated cytosines was very low in all tissues, regardless of the level of myostatin expression, suggesting that DNA methylation is not involved in the tissue-specific regulation of myostatin expression. Southern blot analysis of genomic DNA obtained from micrococcal nuclease-treated nuclei showed that chromatin digestion occurs in tissues where the myostatin gene is actively transcribed and that the myostatin gene is protected from micrococcal nuclease in tissues where myostatin is not expressed. The chromatin structure in the myostatin gene region appears to regulate its expression without DNA methylation.

Molecular cloning and mRNA expression analysis of interleukin-8 gene in Japanese sea perch (Lateolabrax japonicus)

Interleukin-8 (IL-8), the first known chemokine, is a CXC chemokine, which is cable of attracting neutrophils and inducing them to release lysozomal enzymes, triggering the respiratory burst. In the present study, the cDNA of an IL-8 was cloned from Japanese sea perch Lateolabrax japonicus (designated LjIL-8) by homology cloning and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of LjIL-8 consisted of 803 nucleotides with a canonical polyadenylation signal sequence AATAAA and a poly(A) tail, and an open reading frame (ORF) of 300 bp encoding a polypeptide of 99 amino acid residues with a predicted molecular weight of 6.6 kDa. The high identity of LjIL-8 with IL-8 in other organisms indicated that LjIL-8 should be a new member of the IL-8 family. By fluorescent quantitative real-time PCR, mRNA transcript of LjIL-8 was detectable in all the examined tissues with higher level in spleen and head-kidney. The temporal expression of LjIL-8 mRNA in the spleen was up-regulated by lipopolyssacharide (LPS) stimulation and reached the maximum level at 6 h post-stimulation, and then dropped back to the original level gradually. These results indicated that LjIL-8 was a constitutive and inducible acute-phase protein that perhaps involved in the immune defense of L. japonicus.

Density-dependence in post-recruit Japanese seaperch Lateolabrax japonicus in the Chikugo River, Japan

Density-dependence in feeding, growth, and mortality was evident in the post-recruit riverine period (15-20 mm in length) of Japanese seaperch Lateolabrax japonicus located within the estuarine turbidity maximum of the Chikugo River, Japan. Based on otolith microstructure analysis, the weight-specific growth coefficient (G, d -1 ) and abundance-at-age were estimated for post-recruit Japanese seaperch from 1990 to 2000. Abundance at recruitment (15 mm, A15) and at 20 mm (A20), and the mortality coefficient during the post-recruit period (M, d -1 ) were estimated for each year using the larval production method. The A15 varied by a factor of 24 during the 11 yr period, and its variability had a significant effect on G, M, A20, and the ratio of M to G as an index of Japanese seaperch relative recruitment potential. G was low, and M, ratio of M to G, and A20 were high when recruitment was successful. A lower coefficient of variation (%) was observed in A20 (25.0) than in A15 (33.5) for the 11 yr. A significant effect of A15 was also found on the prey ingestion of the post-recruit Japanese seaperch. Mean gut fullness (gut content weight per unit body weight) was low when recruitment was successful. Density-dependent regulation through competition for prey resources operates on Japanese seaperch in the post-recruit period corresponding with the migration from Ari- ake Bay to the Chikugo River, a spatially restricted nursery.

Growth and mortality of larval and juvenile Japanese seaperch Lateolabrax japonicus in relation to seasonal changes in temperature and prey abundance in the Chikugo estuary

Japanese seaperch Lateolabrax japonicus migrate from Ariake Bay to the estuarine turbidity maximum (ETM) zone of the Chikugo River and inhabit there through the post-migration period (15–20 mm in standard length). The feeding, growth and mortality during the post-migration period of Japanese seaperch were analyzed in relation to seasonal changes in temperature and prey concentration. Larvae and juveniles were collected from ten sampling stations at 4–7 day intervals from 24 February to 24 April 2005 in the Chikugo estuary. Based on the otolith microstructure analysis the sampled fish were divided into nine cohorts, each cohort covering a 5 day hatch date period (22 December 2004 to 4 February 2005). The growth coefficient ( G, day −1) was higher and the mortality coefficient ( M, day −1) was lower in the later cohorts. The ratio of G to M as an index of stage-specific survival during the post-migration period significantly increased as the season progressed and exceeded 1.0 in the last cohort examined. Variability in abundance of the major prey organism, Sinocalanus sinensis, had a significant effect on the Japanese seaperch ingestion rate. Increase in temperature and spring bloom of S. sinensis is concluded to provide the later cohorts with a higher survival probability through increasing ingestion and growth rates during their post-migration period in spring 2005.

Effects of river flow on larval growth and survival of Japanese seaperch Lateolabrax japonicus (Pisces) in the Chikugo River estuary, upper Ariake Bay

The abundance and growth history of larval and juvenile Japanese seaperch Lateolabrax japonicus were investigated in the Chikugo River estuary, upper Ariake Bay, from 1990 to 2000. Growth during the larval period (up to 15 mm standard length, LS, the size at recruitment into the estuary) was backcalculated using sagittal otolith microstructures by the biological intercept method. Growth rates in length declined at body sizes >14 mm LS. High freshwater discharge through the Chikugo River was associated with high temperatures of the upper Ariake Bay where the larvae spend their planktonic life. Mean larval stage duration (days) from hatch to 15 mm (D15) varied between 48·8 and 76·2 days and was inversely correlated with the estimated mean temperature history [mean daily temperature (° C) experienced by the larvae during the period from hatch to 15 mm, T15]. Mean abundance (number m−2) of larvae and juveniles was highest in years when T15, D15 and freshwater discharge were at intermediate levels. Although the abundance was not correlated with either of these variables, an exponential relationship between abundance and D15 was found when data collected during the highest river discharge years (1990, 1991 and 1998) were excluded. The increase in freshwater discharge through the Chikugo River probably had the potential to enhance or diminish Japanese seaperch recruitment in two ways: 1) it could increase recruitment probability by increasing temperature and larval growth and 2) high river flow also had the potential to decrease the probability of immigration into the river by increasing larval seaward dispersion, predation due to decreased turbidity and starvation due to decreased zooplankton prey abundance in the estuary.

Influence of spring river flow on the recruitment of Japanese seaperch <em>Lateolabrax japonicus</em> into the Chikugo estuary, Japan

The estuarine turbidity maximum (ETM) zone is considered to serve as a predation refuge for fish during the early life stages due to the high turbidity and high prey concentration. River flow can be one of the important determinants for survival of early life stages of estuarine dependent fish because it affects both the physical and biological properties of the ETM. We tested the hypothesis that fluctuation of river flow explains the variability in recruitment of Japanese seaperch Lateolabrax japonicus around the ETM region of the Chikugo River estuary, upper Ariake Bay, Japan. Japanese seaperch recruitment showed a 43.3-fold fluctuation from 1990 to 2000 and was inversely correlated with the mean daily river flow of the Chikugo River in March. The recruitment was high and variable in years of low March river flow and was poor in years of high March river flow. We conclude that high river flow potentially decreases Japanese seaperch recruitment in the Chikugo River estuary by blocking the larval migration into the river and by increasing the probability of larval dispersion to the downriver/upper bay areas, where potential predators (jellyfish and Sagitta spp.) were more abundant, and prey (Sinocalanus sinensis) availability and turbidity were lower.

Development and characterization of cell lines from heart, liver, spleen and head kidney of sea perch Lateolabrax japonicus

Five cell lines (LJHK, LJS, LJL, LJH‐1 and LJH‐2) were established from the head kidney, spleen, liver and heart of sea perch Lateolabrax japonicus. The cell lines LJHK, LJS, LJL, LJH‐1 and LJH‐2 were subcultured 46, 32, 32, 36 and 34 times in minimum essential medium (MEM) supplemented with foetal bovine serum (FBS), sea perch serum and 10 ng ml−1 basic fibroblast growth factor (bFGF). Morphology of primary cultures and subcultures of the five cell lines were observed continuously by microscopy. The suitable temperature for growth was 18 to 30° C for all of these cell lines with the optimum growth at 24° C and a reduced growth rate <18° C. The optimum concentration of FBS was found to be 10% and addition of bFGF to the medium significantly increased the growth rate of the cells. The doubling time of LJS, LJH‐1, LJL, LJH‐2 and LJHK cells was determined to be 52·7, 54·9, 57, 58·7 and 66 h at a plating density of 1 × 105 cells ml−1 at 24° C, respectively. Chromosome analysis revealed that 42, 48, 38, 43 and 45% cells maintained normal diploid chromosome number (48) in the LJH‐1, LJH‐2, LJHK, LJL and LJS cell lines, respectively. The LJHK cells were successfully transfected with green fluorescent protein (GFP) reporter plasmids and the expression of GFP gene in the cells indicated the possible utility of the cells in gene expression studies. Furthermore, treatment of the LJHK cells with lipopolysaccharide led to increased expression of IL‐1β, demonstrating that LJHK cells might be a valuable tool for studying the expression and function of immunomodulatory gene in fishes.

Three new continuous fish cell lines of SPH, SPS and RSBF derived from sea perch ( Lateolabrax japonicus) and red sea bream ( Pagrosomus major).

The continuous fish cell lines SPH and SPS were derived from heart and spleen tissues of sea perch Lateolabrax japonicus in 1993, and the cell line RSBF from fin tissue of red sea bream Pagrosomus major in 1994. They were subcultured for 106, 102 and 96 times respectively in the medium Eagle's MEM supplemented with 10% FBS. The growth temperature range was 15 to 30°C for all of the cell lines with the optimum growth at 25°C for SPH and SPS and at 30°C for RSBF. The distribution of chromosome number was 30 to 96 for SPH at passage 70, 36 to 86 for SPS at passage 65 and 10 to 62 for RSBF at passage 62. Nevertheless, the modal number of the chromosomes of all cell lines was 48. All of the cell lines were susceptible to fish birnavirus IPNV, though the titers were relatively low.