Baojun Tang

Transcriptome and analysis on the complement and coagulation cascades pathway of large yellow croaker (Larimichthys crocea) to ciliate ectoparasite Cryptocaryon irritans infection

Large yellow croaker (Larimichthys crocea) is one of the most valuable marine fish in southern China. Given to the rapid development of aquaculture industry, the L. crocea was subjected to ciliate ectoparasite Cryptocaryon irritans. It therefore is indispensable and urgent to understand the mechanism of L. crocea host defense against C. irritans infection. In the present study, the extensively analysis at the transcriptome level for Cryptocaryoniasis in L. crocea was carried out. These results showed that 15,826,911, 16,462,921, and 15,625,433 paired-end clean reads were obtained from three cDNA libraries (A: 0 theronts/fish, B: 12,000 theronts/fish, and C: 24,000 theronts/fish) of the L. crocea immune-related tissues by Illumina paired-end sequencing technology. Totally, 30,509 unique transcript fragments (unigenes) were assembled, with an average length of 1715 bp. In B/A, C/A, and C/B pairwise comparison, 972, 900, and 1126 genes showed differential expression respectively. Differently expressed immune-related genes (DEIGs) were scrutinized, in B/A pairwise comparison, 48 genes showed differential expression, including 26 up-regulated genes and 22 down-regulated genes in B; in C/A pairwise comparison, there were 39 DEIGs, including 7 up-regulated genes and 32 down-regulated genes in C; in C/B pairwise comparison, 40 genes showed differential expression, including 11 up-regulated genes and 29 down-regulated genes in C. There were 16 DEIGs enriched KEGG pathways, in which the complement and coagulation cascades pathway was the top most DEIGs enriched pathway (B:A = 42; C:A = 28; C:B = 42). The coagulation and fibrinolytic system was in a highly active state after infected by C. irritans with non-lethal concentration; the alternative complement pathway may play an important role in the early stages of C. irritans infection. These results demonstrated that low-concentration infection can significantly induce the immunological response in fishes, however, when fishes were in fatal conditions, the immunity was suppressed.

Immunological, ionic and biochemical responses in blood serum of the marine fish Trachinotus ovatus to poly-infection by Cryptocaryon irritans

To investigate the response of pompano fish (Trachinotus ovatus) to white spot disease, we used the protozoan Cryptocaryon irritans to infect live 450-g specimens at concentrations of 40,000 theronts/fish. We assessed the relative infection intensity (RII), serum immobilizing titer, and immunity-related enzyme activities (ACP, AKP, LZM), and assessed feeding, serum ion concentrations (Na(+), Cl(-), Ca(2+) and K(+)) and blood biochemistry (ALT, AST, LDH) of pompano. The fish were then treated with a lethal dose of C.u2009irritans (70,000 theronts/fish) and the number of deaths was recorded. We found that the relative infection intensities of the control group, group I, and group II were 0, 0.630u2009±u20090.179, and 0.014u2009±u20090.006. Poly-infection induced a significant increase in the serum immobilizing titer (853.33u2009±u2009295.60) of group II. In terms of the biochemical assessment, group II had significantly higher alkaline phosphatase and acid phosphatase activities than the other groups, and the lowest lysozyme activity (Pu2009<u20090.05), compared to higher activity in the control group and the highest level in group I. Only the fishes of group I had stopped feeding after treatment. The concentrations of Na(+), Cl(-), and Ca(2+) in blood serum did not differ significantly among the three groups, but K(+) concentration increased with the increasing infection frequency. Alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase activities in fish of group II were significantly higher than those of the other groups. Survival of the fish subjected to the lethal dose of C.u2009irritans was 0, 0, and 100 in groups control, I, and II, respectively. In conclusions, based on the food intake of group II, along with the results of relative infection intensity, serum immobilizing titer, and survival, we speculate that the fish in that group acquired high protective immunity following poly-infection by C.u2009irritans, experiencing limited harm for pompano.

Transcriptome analysis and discovery of genes involved in immune pathways in large yellow croaker (Larimichthys crocea) under high stocking density stress

Abstract The large yellow croaker, Larimichthys crocea, is an economically important maricultured species in southeast China. Owing to the importance of stocking densities in commercial fish production, it is crucial to establish the physiological responses and molecular mechanisms that govern adaptation to crowding in order to optimize welfare and health. In the present study, an extensive immunity‐related analysis was performed at the transcriptome level in L. crocea in response to crowding stress. Over 145 million high‐quality reads were generated and de novo assembled into a final set of 40,123 unigenes. Gene Ontology and genome analyses revealed that molecular function, biological process, intracellular, ion binding, and cell process were the most highly enriched pathways among genes that were differentially expressed under stress. Among all of the pathways involved, 16 pathways were related to the immune system, among which the complement and coagulation cascades pathway was the most enriched for differentially expressed immunity‐related genes, followed by the chemokine signaling pathway, toll‐like receptor signaling pathway, and leukocyte transendothelial migration pathway. The consistently high expression of immune‐related genes in the complement and coagulation cascades pathway (from 24 to 96 h after being subjected to stress) suggested its importance in both response to stress and resistance against bacterial invasion at an early stage. These results also demonstrated that crowding can significantly induce immunological responses in fish. However, long‐term exposure to stress eventually impairs the defense capability in fish. HighlightsAn extensively immune‐related analysis at the transcriptome level for L. crocea in response to crowding stress was performed.The complement and coagulation cascades pathway plays important roles during response to crowding stress.Crowding could significantly induce the immunological response in fish.Long‐term exposure to stress conditions would finally impair the defense capability in fish.

Comparison of the susceptibility and resistance of four marine perciform fishes to Cryptocaryon irritans infection

ABSTRACT Cryptocaryon irritans is a type of marine ectoparasitic ciliate that infects teleost fishes. To illustrate the susceptibility and innate immune mechanism of fishes to C. irritans, four species of marine perciform fishes were selected in Fujian Province, a high‐prevalence area of cryptocaryoniasis in China. The survival, diameter/number of tomonts, and infection ratio among Larimichthys crocea, Lateolabrax japonicus, Pagrus major, and Nibea albiflora were compared after artificial infection. Meanwhile, the immobilization titers of four fish species with no C. irritans infection were detected. Results showed that survival and serum immobilization titer of N. albiflora were significantly higher than those of the other three fish species. A strong negative linear correlation was found between the survival/serum immobilization titer and the mean tomont diameter. In addition, the smallest C. irritans infection ratio was found in N. albiflora, implying that the serum of fishes especially that of N. albiflora, inhibited the development of parasitic C. irritans cells, and the smallest tomont size was directly related to the number of infective theronts corresponding to the highest survival of fish. Moreover, complement activity inhibition assays suggested that the alternative complement pathway might play a major role in C. irritans resistance. HighlightsSusceptibility and resistance of four marine perciform fishes to C. irritans infection.N. albiflora has the strongest anti‐C. irritans resistance among four fish species.Alternative complement pathway of N. albiflora might play a major role in C. irritans resistance.

Anti-parasitic effects of Leptomycin B isolated from Streptomyces sp. CJK17 on marine fish ciliate Cryptocaryon irritans

The present study was conducted aiming to evaluate the in vitro and in vivo anti-parasitic efficacy of an isolated compound against the ciliate Cryptocaryon irritans. The compound was previously isolated from fermentation products of Streptomyces sp. CJK17 and designated as SFrD. Toxicity of the compound SFrD against the fish hosts (Larimichthys crocea) was also tested and its chemical structure was elucidated. The obtained results showed that the compound has potent anti-parasitic efficacy with the 10 min-, 1 h-, 2 h-, 3 h- and 4 h-LC50 (95% Confidence Intervals) of 6.8 (6.5-7.1), 3.9 (2.8-5.0), 3.3 (2.6-4.0), 2.7 (2.3-3.1) and 2.5 (2.2-2.8) mg L(-1) against theronts of C. irritans and the 6h-LC50 (95% CI) of 3.0 (2.8-3.2) mg L(-1) against the tomonts, respectively. Exposure of the compound SFrD remarkably reduced the mortality of fish infected with C. Irritans, from 100% in the control group to 61.7% and 38.3% in groups of 3.1 mg L(-1) and 6.3 mg L(-1), respectively. In the test of exposing fish to 40 mg L(-1) compound SFrD for 24h, no visible effects were observed affecting the normal behavior or any macroscopic changes. By spectrum analysis (EI-MS, (1)H NMR and (13)C NMR), the compound SFrD was identified as Leptomycin B. This study firstly demonstrated that Leptomycin B has potent anti-parasitic efficacy against ciliates in cultured marine fish.

Population genetic structure and genetic diversity of Chinese pomfret at the coast of the East China Sea and the South China Sea

Abstract The Chinese pomfret Pampus chinensis is one of the most economic and ecological important marine fish species in China. In the present study, the population genetic structure and genetic diversity of P. chinensis were evaluated from a total sample size of 180 individuals representing six populations from the East China Sea and the South China Sea using mitochondrial cytochrome c oxidase subunit I (COI) gene. A total of 24 variable sites (including 3 singleton sites and 21 parsimony information sites) were observed, and 18 haplotypes were defined. The haplotype diversity (Hd) of the populations ranged from 0.559 to 0.775, and the nucleotide diversity (π) ranged from 0.330 to 1.090%. Analysis of molecular variance (AMOVA) reveals that the main variation (66.02%) was among individuals within populations. The average pairwise differences and ϕST values indicated significant genetic differentiation between Dongxing population and the other populations. The results of the present study are helpful for the sustainable management and utilization of this species.

Food intake, survival, and immunity of Nibea albiflora to Cryptocaryon irritans infection

Cultured Nibea albiflora rarely die from cryptocaryoniasis. To explore the resistance of N. albiflora against the invasion of Cryptocaryon irritans, in this study, 40xa0g N. albiflora was artificially infected with C. irritans at a median lethal concentration (2050 theronts/g fish). The food intake, survival, relative infection intensity, and immobilization titer variation of serum and mucus at different time points after the infection were compared. Results showed that the ingestion of N. albiflora could be resumed only 1xa0day after feed deprivation by the disease, which indicated the quick resilience of N. albiflora. N. albiflora did not die out even if it was cultured continually for up to 15xa0days at 27xa0°C in a culture tank with a large quantity of C. irritans tomonts. It was because that, without any exterior force, N. albiflora could block the C. irritans cell proliferation, and then the pathogens disappear gradually. In vitro immobilization titer test results confirmed that the serum and mucus could directly eradicate C. irritans.

Gene expression during different periods of the handling-stress response in Pampus argenteus

Common aquaculture practices subject fish to a variety of acute and chronic stressors. Such stressors are inherent in aquaculture production but can adversely affect survival, growth, immune response, reproductive capacity, and behavior. Understanding the biological mechanisms underlying stress responses helps with methods to alleviate the negative effects through better aquaculture practices, resulting in improved animal welfare and production efficiency. In the present study, transcriptome sequencing of liver and kidney was performed in silver pomfret (Pampus argenteus) subjected to handling stress versus controls. A total of 162.19 million clean reads were assembled to 30 339 unigenes. The quality of the assembly was high, with an N50 length of 2 472 bases. For function classification and pathway assignment, the unigenes were categorized into three GO (gene ontology) categories, twenty-six clusters of eggNOG (evolutionary genealogy of genes: non-supervised orthologous groups) function categories, and thirty-eight KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways. Stress affected different functional groups of genes in the tissues studied. Differentially expressed genes were mainly involved in metabolic pathways (carbohydrate metabolism, lipid metabolism, amino-acid metabolism, uptake of cofactors and vitamins, and biosynthesis of other secondary metabolites), environmental information processing (signaling molecules and their interactions), organismal systems (endocrine system, digestive system), and disease (immune, neurodegenerative, endocrine and metabolic diseases). This is the first reported analysis of genome-wide transcriptome in P. argenteus, and the findings expand our understanding of the silver pomfret genome and gene expression in association with stress. The results will be useful to future analyses of functional genes and studies of healthy artificial breeding in P. argenteus and other related fish species.

Growth and Survival of Juvenile Lined Seahorse (Hippocampus erectus) at Different Food Densities

To investigate the effect of Artemia nauplii with different densities on the survival and growth of Hippocampus erectus juveniles,newly hatched H.erectus juveniles were fed with Artemia nauplii for 50 days,which were divided into three groups [5 nauplii/mL(A),10 nauplii/mL(B) and 20 nauplii/mL(C)].The results show that the survival and growth of juveniles could not be explained by three food densities during the first 10 days.The survival of juveniles with 10 nauplii/mL and 20 nauplii/mL food densities were significantly higher than that with 5 nauplii/mL from day 20 to day 50(P0.05),but there was no significant difference found between the survival in treatments B and C.Additionally,the weight and height of juveniles in treatments B and C were significantly higher than that in treatment A on day 20(P0.05).The weight and height of juveniles in treatments A and C increased dramatically than that in treatment B from day 30(P0.05),and the difference in growth among the three food densities groups reduced on day 40,then the weight and height of juveniles in treatment A was higher than those in treatments B and C(P0.05).The weight gain(WG),condition factor(CF) and special growth rates(SGR) of the juveniles with three food densities were not significantly different on day 50.The pH and DO of water decreased with increasing of food density over 24 h,however,water quality was not deteriorated to become a major factor reducing the growth of the juveniles.Furthermore,the concentration of ammonia-N in treatment C was significantly higher than that in treatments