Exopalaemon Carinicauda Research Articles

Insights into the intestinal microbiota of Exopalaemon annandalei and Exopalaemon carinicauda in the Yangtze River estuary.

The gut microbiota plays a crucial role in food webs, carbon cycling, and related elements. Exopalaemon annandalei and Exopalaemon carinicauda are two important forage species in the Yangtze River estuary with extremely similar living habits and morphological characteristics. Exploring the microorganisms in the guts of these two shrimp species can help us understand the survival status of forage species and gut microbiota in the Yangtze River estuary. Therefore, this study analyzed the similarities and differences in the intestinal flora of E. annandalei and E. carinicauda through high-throughput sequencing of 16S rRNA gene amplicons. The results showed that the dominant bacteria in the intestinal flora of E. annandalei and E. carinicauda at the phylum level were Proteobacteria and Firmicutes, respectively. At the genus level, the intestinal flora had higher concentrations of Psychrobacter, Bacillus, Pseudomonas, Acinetobacter, and Macrococcus. In both shrimp species, the contents of Acinetobacter and Macrococcus were higher in spring than in winter. The most important potential functions of the intestinal microbiota were amino acid metabolism and purine metabolism. Additionally, the functions of metabolism and diseases in the intestinal microbiota of E. annandalei were greatly influenced by the season. Furthermore, the experimental results indicated that a lower ratio of Firmicutes to Bacteroidetes was associated with a larger body weight in shrimp. Overall, this study provides a theoretical reference for understanding the intestinal bacterial community of shrimp in estuaries and the healthy cultivation of E. annandalei and E. carinicauda.

Integrated analysis of transcriptome and metabolome reveals chronic low salinity stress responses in the muscle of Exopalaemon carinicauda

Low salinity environment is one of the key factors threatening the survival of aquatic organisms. Due to the strong adaptability of low salinity, Exopalaemon carinicauda is an ideal model to study the low salinity adaptation mechanism of crustaceans. In this study, E. carinicauda from the same family were divided into two groups, which were reared at salinity of 4 ‰ and 30 ‰, respectively. Integrated analysis of transcriptome and metabolome was used to uncover the mechanisms of E. carinicauda adaptation to chronic low salinity environment. Under the chronic low salinity stress, a total of 651 differentially expressed genes (DEGs) and 386 differential metabolites (DMs) were obtained, with the majority showing downregulation. These DEGs mainly involved MAPK signal transduction pathway and structural constituent of cuticle. Besides, chitin binding and chitin metabolism process were inhibited significantly. Among the DMs, lipids and lipid-like molecules, flavor amino acids and nucleotides were detected, which may be related to the adjustment of energy metabolism and flavor of muscle. In addition, ubiquinone and other terpenoid-quinone biosynthesis pathway and alanine, aspartate, and glutamate metabolic pathway were induced. These results will enrich our understanding of the molecular mechanism underlying the chronic low salinity tolerance in E. carinicauda, providing an important theoretical basis and practical guidance for the research and breeding, thereby promoting the sustainable development of aquaculture.

Effects of different feed additives on the development of ovaries and testicles in the ridgetail white shrimp Exopalaemon carinicauda (Decapoda, Caridea, Palaemonidae)

Abstract To solve the problem of unsynchronized gonadal development in Exopalaemon carinicauda, different feed additives were evaluated for their effect on gonadal development among female and male individuals. Different concentrations of Schizochytrium (0%, 3%, 6%, and 9%), Porphyridium cruentum (0, 0.5, 1 and 2%) and 5-hydroxytryptamine (5-HT) creatinine sulfate (0, 0.0025, 0.005 and 0.01%) were used. For females, the gonadal index of E. carinicauda was significantly higher with the addition of 6% Schizochytrium, 1% P. cruentum, and 0.0025% 5-HT creatinine sulfate (). The ovarian development rate reached its highest at 79.30 ± 2.64%, and the final contents of blood ovarian vitellogen and oestradiol were significantly higher, compared to the other groups (). For males, the gonadal index was higher with the addition of 9% Schizochytrium, 0% P. cruentum and 0.01% 5-HT creatinine sulfate, although the difference was not significant (). No significant difference was found in the sperm survival rate (), but the activities of sperm total ATPase and lactate dehydrogenase showed significant differences in each group (). Overall, we report the effects of the three additives on gonadal development in E. carinicauda, with females showing the more significant effects.

Denitrification characteristics and potential application of a novel aerobic denitrifying bacterium, Pseudomonas plecoglossicida, isolated from the Exopalaemon carinicauda pond

Denitrification characteristics and potential application of a novel aerobic denitrifying bacterium, Pseudomonas plecoglossicida, isolated from the Exopalaemon carinicauda pond

Genetic diversity and population structure of wild and artificially selected populations of the ridgetail white prawn (Exopalaemon carinicauda) using consolidated mitochondrial cytochrome b and microsatellite markers

The ridgetail white prawn (Exopalaemon carinicauda) belongs to the family Palaemonidae and genus Exopalaemon. Owing to its significant economic value and excellent nutritional properties, it is an important species for the development of saltwater aquaculture models in China. In this study, 160 individuals were collected from four wild populations and one artificially selected population using consolidated mitochondrial cytochrome b (mt-cyt b), and microsatellite molecular markers. The results showed that the hatcheries had lower genetic diversity than the wild samples, both at the levels of mt-cyt b (haplotype diversity: 0.123 VS 0.572; nucleotide diversity: 0.0003 VS 0.0014) and microsatellite (expected heterozygosity: 0.672 VS 0.752). Among the four wild populations, the Ningbo population sampled from the East China Sea showed higher genetic diversity in both mt-cyt b and microsatellites. A pairwise comparison of genetic differentiation coefficients revealed that the artificially selected population had not genetically diverged from the Cangzhou and Rizhao populations. However, the Ningbo population exhibited moderate to high genetic differentiation (compared to other populations), whereas the Zhanjiang population showed a high level of genetic differentiation, indicating a distinct geographical distribution pattern. Structural analysis revealed the presence of three lineage clusters in all current populations, and the artificially selected population predominantly consisted of lineage 3, accounting for 71.68 % of the population. Currently, the effective population size of hatcheries was <50, rendering them susceptible to the genetic threat of inbreeding depression. These findings provide a scientific basis for the conservation of wild germplasm resources of E. carinicauda and inform future breeding and management strategies for improved varieties.

The mannose-binding lectin (MBL) gene cloned from Exopalaemon carinicauda plays a key role in resisting infection by Vibrio parahaemolyticus

Mannose-binding lectin (MBL) is a vital member of the lectin family, crucial for mediating functions within the complement lectin pathway. In this study, following the cloning of the mannose-binding lectin (MBL) gene in the ridgetail white prawn, Exopalaemon carinicauda, we examined its expression patterns across various tissues and its role in combating challenges posed by Vibrio parahaemolyticus. The results revealed that the MBL gene spans 1342 bp, featuring an open reading frame of 972 bp. It encodes a protein comprising 323 amino acids, with a predicted relative molecular weight of 36 kDa and a theoretical isoelectric point of 6.18. The gene exhibited expression across various tissues including the eyestalk, heart, gill, hepatopancreas, stomach, intestine, ventral nerve cord, muscle, and hemolymph, with the highest expression detected in the hepatopancreas. Upon challenge with V. parahaemolyticus, RT-PCR analysis revealed a trend of MBL expression in hepatopancreatic tissues, characterized by an initial increase followed by a subsequent decrease, peaking at 24 h post-infection. Employing RNA interference to disrupt MBL gene expression resulted in a significant increase in mortality rates among individuals challenged with V. parahaemolyticus. Furthermore, we successfully generated the Pet32a-MBL recombinant protein through the construction of a prokaryotic expression vector for conducting in vitro bacterial inhibition assays, which demonstrated the inhibitory effect of the recombinant protein on V. parahaemolyticus, laying a foundation for further exploration into its immune mechanism in response to V. parahaemolyticus challenges.

Chromosome-level genome assembly of ridgetail white shrimp Exopalaemon carinicauda

Exopalaemon carinicauda, a eurythermal and euryhaline shrimp, contributes one third of the total biomass production of polyculture ponds in eastern China and is considered as a potential ideal experimental animal for research on crustaceans. We conducted a high-quality chromosome-level genome assembly of E. carinicauda combining PacBio HiFi and Hi-C sequencing data. The total assembly size was 5.86 Gb, with a contig N50 of 235.52 kb and a scaffold N50 of 138.24 Mb. Approximately 95.29% of the assembled sequences were anchored onto 45 pseudochromosomes. BUSCO analysis revealed that 92.89% of 1,013 single-copy genes were highly conserved orthologs. A total of 44, 288 protein-coding genes were predicted, of which 70.53% were functionally annotated. Given its high heterozygosity (2.62%) and large proportion of repeat sequences (71.49%), it is one of the most complex genome assemblies. This chromosome-scale genome will be a valuable resource for future molecular breeding and functional genomics research on E. carinicauda.

Immune function of a C-type lectin with long tandem repeats and abundant threonine in the ridgetail white prawn Exopalaemon carinicauda

C-type lectins (CTLs) are an important class of pattern recognition receptors (PRRs) that exhibit structural and functional diversity in invertebrates. Repetitive DNA sequences are ubiquitous in eukaryotic genomes, representing distinct modes of genome evolution and promoting new gene generation. Our study revealed a new CTL that is composed of two long tandem repeats, abundant threonine, and one carbohydrate recognition domain (CRD) in Exopalaemon carinicauda and has been designated EcTR-CTL. The full-length cDNA of EcTR-CTL was 1242 bp long and had an open reading frame (ORF) of 999 bp that encoded a protein of 332 amino acids. The genome structure of EcTR-CTL contains 4 exons and 3 introns. The length of each repeat unit in EcTR-CTL was 198 bp, which is different from the short tandem repeats reported previously in prawns and crayfish. EcTR-CTL was abundantly expressed in the intestine and hemocytes. After Vibrio parahaemolyticus and white spot syndrome virus (WSSV) challenge, the expression level of EcTR-CTL in the intestine was upregulated. Knockdown of EcTR-CTL downregulated the expression of anti-lipopolysaccharide factor, crustin, and lysozyme during Vibrio infection. The recombinant CRD of EcTR-CTL (rCRD) could bind to bacteria, lipopolysaccharides, and peptidoglycans. Additionally, rCRD can directly bind to WSSV. These findings indicate that 1) CTLs with tandem repeats may be ubiquitous in crustaceans, 2) EcTR-CTL may act as a PRR to participate in the innate immune defense against bacteria via nonself-recognition and antimicrobial peptide regulation, and 3) EcTR-CTL may play a positive or negative role in the process of WSSV infection by capturing virions.

Interactions between the gut bacterial community of Exopalaemon carinicauda and infection by Enterocytozoon hepatopenaei

To explore the relationship between the intestinal flora of Exopalaemon Carinicauda and infection by Enterocytozoo Hepatopenaei (EHP), we analyzed the species and richness of gut microbiota in infected individuals in different EHP load groups [i.e., control (C), high load (H), and low load (L)] using gene sequencing after infection. The results showed that the abundance of intestinal flora in the high-load EHP group was significantly lower than that in the healthy group. Based on the UPGMA cluster tree and PCoA analysis, with comparisons to healthy shrimp, the gut microbiota of the EHP high load and low load groups were clustered into one branch, which indicated that EHP infection changed the composition of the gut microbiota of infected shrimps. The heat map analysis of species abundance clustering revealed that the dominant bacteria in the low EHP load group and the control group were beneficial genera such as Lactococcus, Ligilactobacillius, and Bifidobacterium, but the dominant bacteria in the high EHP load group were harmful genera such as Pseudomonas, Photobacterium, and Candidatus hepatincola. The functions of the intestinal flora predicted that most genes related to metabolism were more abundant in healthy shrimp, most genes related to metabolism and the organisms’ system were more abundant in the low EHP load group, and most genes related to diseases and environmental information processing were more abundant in the high EHP load group. After separation and purification, the dominant bacteria (Bifidobacterium animalis in healthy shrimp and Lactococcus garvieae in the low EHP load group) and the non-dominant bacteria (Macrococus caseolyticus in the low EHP load group) were obtained. Each of these isolated strains were used together with EHP to infect E. carinicauda, and the results showed that Bifidobacterium animali and Lactococcus garvieae significantly reduced the EHP load in EHP-infected individuals. At the same time, the morphology and structure of the hepatopancreas and intestinal tissue of EHP-infected E. carinicauda were improved. No improvement was seen in tissue that was infected with Macrococus caseolyticus.

Anesthetic effects of eugenol on adult ridgetail white prawn (Exopalaemon carinicauda) and its protective effects under simulated transportation

Anesthesia is a common practice used to improve animal welfare and reduce the negative impacts of stress factors in aquaculture settings. However, few studies have been conducted to investigate the application of anesthetics in ridgetail white prawn (Exopalaemon carinicauda). In the present study, the anesthetic efficacy and protective effects of eugenol in adults of this species were evaluated. When the prawns (n = 5) were immersed in different concentrations of eugenol in the range of 0–240 μL/L for 30 min, the results showed that 180 and 240 μL/L could lead to quick sedative and anesthesia effects with 100% mortality after 30 min exposure, while 30 μL/L failed to induce any sedative and anesthesia effects. Further tests showed that adult individuals were quickly anesthetized by eugenol at a concentration of 60–90 μL/L with a 30 min immersion, while half of the prawns were sedated in 30 μL/L eugenol after 4 h exposure, then recovered at 2 h without any mortality. Furthermore, we checked the water quality parameters after the adult prawns were immersed in four eugenol concentrations (0, 10, 20, 30 μL/L) for 8 h of simulated transportation followed by a 96 h recovery, we found that 30 μL/L eugenol treatment could significantly decrease the ammonia nitrogen concentration, and increased the survival rate at 96 h post recovery. The oxidative responses of the prawns during the 8 h transportation at 30 μL/L eugenol followed by 96 h recovery period were analyzed. The results showed that eugenol administration significantly decreased the malonaldehyde (MDA) concentration and the activities of most antioxidant-related enzymes immediately. The present data indicated that eugenol was an efficient anesthetic, which could be used for long-distance transportation of this species. It exhibited excellent protective effects to improve the animal's welfare by improving water quality and alleviating oxidative stress.

Molecular Cloning, Characterization, and Expression of a Receptor for Activated Protein Kinase C1 (RACK1) Gene in Exopalaemon carinicauda Zoea Larvae under Aroclor 1254 Stress.

The receptor for activated protein kinase C1 (RACK1) belongs to the typical WD repeat family, which is extremely conservative and important in multiple signal transduction pathways related to growth and development that coordinate the intracellular role of various life activities. As a novel protein with versatile functions, it was found in a variety of organisms. In a previous study, we identified the RACK1 sequence of white shrimp from transcriptome data. In this study, we employed specialized bioinformatics software to conduct an in-depth analysis of EcRACK1 and compare its amino acid sequence homology with other crustaceans. Furthermore, we investigated the expression patterns of RACK1 at different developmental stages and tissues, as well as at various time points after exposure to Aroclor 1245, aiming to elucidate its function and potential response towards Aroclor 1245 exposure. The length of EcRACK1 is 957 nucleotides, which encodes 318 amino acids. Moreover, there were seven typical WD repeats in EcRACK1, which have more than a 96% sequence identity with the RACK1 proteins of Penaeus. The results of tissue expression and spatiotemporal expression showed that it was significantly increased in the II and IV stages, but had a significant tissue specificity in the hepatopancreas, spermary, and muscle tissues of E. carinicauda, adult stage. Compared to the control, EcRACK1 was significantly induced in E. carinicauda zoea larvae exposed to Aroclor 1254 for 6, 10, 20, and 30 d (p < 0.05). These results suggested that EcRACK1 may play an important role in the larval development and environmental defense of E. carinicauda.

Morphological and Molecular Changes during Limb Regeneration of the Exopalaemon carinicauda.

With the increase in breeding density of Exopalaemon carinicauda, appendage breakage may occur, which seriously affects survival and economic benefits. To study the limb regeneration process of E. carinicauda, we induced autotomy of the pereopods. After a period of time, wound swelling disappeared, the pigment gradually accumulated, and a tawny film subsequently formed in the wound. The healing period of the wound occurred 24 h after autotomy, and the blastema formation stage occurred 48 h after autotomy. After 4 days of cutting, the limb buds began to differentiate, grow, and expand rapidly, and this process lasted approximately 15 days. Microscopic observations revealed significant changes in the type and number of associated cells including outer epithelial cells, granulocytes, embryonic cells, columnar epidermal cells, elongated cells, and blastoma cells, during the process from limb fracture to regeneration. A comparative transcriptome analysis identified 1415 genes differentially expressed between the J0h (0 h post autotomy) and J18h (18 h post autotomy), and 3952 and 4366 differentially expressed genes for J0 and J14d (14 days post autotomy) and J18h and J14d, respectively. Some of these genes may be related to muscle growth or molting, as indicated by the presence of troponin C, chitinase, actin, innexin, and cathepsin L. As a functional gene involved in epidermal formation, the mRNA expression level of the innexin inx2 in the pereopod of E. carinicauda changed significantly in the experimental groups (p < 0.05). The results of this study contribute to existing knowledge of regeneration mechanisms in crustaceans.

Genome-Wide Identification of Vitellogenin Gene Family and Comparative Analysis of Their Involvement in Ovarian Maturation in Exopalaemon carinicauda.

Vitellogenin (Vtg) is a precursor of yolk proteins in egg-laying vertebrates and invertebrates and plays an important role in vitellogenesis and embryonic development. However, the Vtg family remains poorly characterized in Exopalaemon carinicauda, a major commercial mariculture species found along the coasts of the Yellow and Bohai Seas. In this study, 10 Vtg genes from the genomes of E. carinicauda were identified and characterized. Phylogenetic analyses showed that the Vtg genes in crustaceans could be classified into four groups: Astacidea, Brachyra, Penaeidae, and Palaemonidae. EcVtg genes were unevenly distributed on the chromosomes of E. carinicauda, and a molecular evolutionary analysis showed that the EcVtg genes were primarily constrained by purifying selection during evolution. All putative EcVtg proteins were characterized by the presence of three conserved functional domains: a lipoprotein N-terminal domain (LPD_N), a domain of unknown function (DUF1943), and a von Willebrand factor type D domain (vWD). All EcVtg genes exhibited higher expression in the female hepatopancreas than in other tissues, and EcVtg gene expression during ovarian development suggested that the hepatopancreas is the main synthesis site in E. carinicauda. EcVtg1a, EcVtg2, and EcVtg3 play major roles in exogenous vitellogenesis, and EcVtg3 also plays a major role in endogenous vitellogenesis. Bilateral ablation of the eyestalk significantly upregulates EcVtg mRNA expression in the female hepatopancreas, indicating that the X-organ/sinus gland complex plays an important role in ovarian development, mostly by inducing Vtg synthesis. These results could improve our understanding of the function of multiple Vtg genes in crustaceans and aid future studies on the function of EcVtg genes during ovarian development in E. carinicauda.

FOXO is involved in antimicrobial peptides expression during WSSV infection in Exopalaemon carinicauda

The forkhead box transcription factor O family protein (FOXO) acts as a transcription factor that regulates biological processes regarding DNA repair, immunity, cell cycle regulation, and other biological processes. In this study, EcFOXO was identified from the ridgetail white prawn, Exopalaemon carinicauda. EcFOXO protein contains multiple low-complexity regions and a forkhead (FH) domain. Phylogenetic tree showed that EcFOXO is clustered with crustacean FOXOs. The amino acid sequences of its FH domain are highly similar to the FH domain of FOXOs from other crustaceans. The expression of EcFOXO is altered after white spot syndrome virus (WSSV) stimulation in hepatopancreas and gills. The relationship between EcFOXO and EcRelish was explored by RNA interference (RNAi). Results showed that EcFOXO and EcRelish could positively regulate each other’s expression. The expression levels of various antimicrobial peptides (AMPs) significantly reduced after interfering with EcFOXO or EcRelish. These results suggest a positive regulatory loop between EcFOXO and EcRelish, which participates in the innate immunity of ridgetail white prawn by regulating the expression of AMPs during WSSV infection. This study enriches the knowledge about the regulatory mechanism of FOXO in the innate immunity of crustaceans.

Effects of Light and Feeding on Expressions of Clock Genes and Metabolic Genes in the Ridgetail Shrimp, Exopalaemon carinicauda

The changes of the circadian clock genes expression, growth, and muscle composition in Exopalaemon carinicauda under different photoperiods and feeding time were investigated by real-time fluorescence quantitative PCR and muscle biochemical composition analysis, respectively. Results showed that four clock genes of Clock, Cry1, Tim, and Per2 showed significant circadian rhythms in both eyestalk and hepatopancreas. Their expression rhythms were highly correlated with the photoperiod in the eyestalk, but in the hepatopancreas, it was significantly correlated with the feeding time. Moreover, the expressions of several metabolic genes were also variable; adipose triglyceride lipase (ATGL) and amyloglucosidase (AGL) changed significantly with the shift of feeding time, whereas methionine synthase (MS) and succinate dehydrogenase (SDH) changed significantly with the photoperiod. This reflected the close relationship between the metabolic and circadian clock in E. carinicauda; Alterations in photoperiod or feeding time lead to changes in the biological clock systems, which affects the daily expression of metabolic genes at the downstream metabolic pathway and closely correlates their expression rhythms with epi-environmental factors such as feeding. It can be seen from the results that the feeding was also a significant factor that affected the crude protein and crude fat contents in muscle tissue of E. carinicauda; their highest values (18.69% ± 0.13%, 1.81% ± 0.02%) were also occurred in the treatment with feeding at 19:00. Differences in muscle composition through a similar mechanism of action, i.e., the biological clock system are affected by the feeding and then regulated changes in downstream metabolic processes. As a result, the optimized conditions for the cultivation of E. carinicauda were a short light-phase photoperiod (8L : 16D) with feeding after sunset (19:00).

Metabolomic responses based on transcriptome of the hepatopancreas in Exopalaemon carinicauda under carbonate alkalinity stress

High carbonate alkalinity is one of the major stress factors for survival of aquatic animals in saline-alkaline water. Exopalaemon carinicauda is a good model for studying the saline-alkaline adaption mechanism in crustacean because of its great adaptive capacity to alkalinity stress. In this study, non-targeted liquid chromatography-mass spectrometry (LC-MS) metabolomics analyses based on high-throughput RNA sequencing (RNA-Seq) were used to study the metabolomic responses of hepatopancreas in E. carinicauda at 12 h and 36 h after acute carbonate alkalinity stress. The results revealed that most of the significantly differential metabolites were related to the lipid metabolism. In particular, the sphingolipid metabolism was observed at 12 h, the glycerophospholipid metabolism was detected at 36 h, and the linoleic acid metabolic pathway was significantly enriched at both 12 h and 36 h. The combined transcriptome and metabolome analysis showed that energy consumption increased at 12 h, resulting in significant enrichment of AMPK signaling pathways, which contributed to maintain energy homeostasis. Subsequently, the hepatopancreas provided sufficient energy supply through cAMP signaling pathway and glycerophosphate metabolism to maintain normal metabolic function at 36 h. These findings might help to understand the molecular mechanisms of the E. carinicauda under carbonate alkalinity stress, thereby promote the research and development of saline-alkaline resistant shrimp.

CRISPR/Cas9-mediated gene mutation of EcIAG leads to sex reversal in the male ridgetail white prawn Exopalaemon carinicauda.

In the culture of crustaceans, most species show sexual dimorphism. Monosex culture is an effective approach to achieve high yield and economic value, especially for decapods of high value. Previous studies have developed some sex control strategies such as manual segregation, manipulation of male androgenic gland and knockdown of the male sexual differentiation switch gene encoding insulin-like androgenic gland hormone (IAG) in decapods. However, these methods could not generate hereditable changes. Genetic manipulation to achieve sex reversal individuals is absent up to now. In the present study, the gene encoding IAG (EcIAG) was identified in the ridgetail white prawn Exopalaemon carinicauda. Sequence analysis showed that EcIAG encoded conserved amino acid structure like IAGs in other decapod species. CRISPR/Cas9-mediated genome editing technology was used to knock out EcIAG. Two sgRNAs targeting the second exon of EcIAG were designed and microinjected into the prawn zygotes or the embryos at the first cleavage with commercial Cas9 protein. EcIAG in three genetic males was knocked out in both chromosome sets, which successfully generated sex reversal and phenotypic female characters. The results suggest that CRISPR/Cas9-mediated genome editing technology is an effective way to develop sex manipulation technology and contribute to monosex aquaculture in crustaceans.

De novo transcriptional analysis of the response to starvation stress in the white ridgetail prawn, Exopalaemon carinicauda

To study the mechanism of the biomolecular response in Exopalaemon carinicauda to starvation stress, we subjected muscle tissue RNA samples from four stress points, including 0 d(control group), 10 d, 20 d, and 30 d, to starvation stress on white ridgetail prawn with a body weight of 1.41 + 0.42 g, aquaculture water temperature of 23–25 °C, salinity of 26, dissolved oxygen ≥5 mg/L, and pH 8–8.5, Then performed de novo transcriptome assembly and gene expression analysis using BGISEQ-500 with a tag-based digital gene expression (DGE) system. By de novo assembling at the four times, we obtained 28,167, 21,115, 24,497, and 27,080 reads, respectively. The results showed that the stress at 10 d led to no significant difference in the expressed genes, while the stress at 20 d and 30 d showed a significant increase (or decrease) in the expression of 97 (276) and 143 (410) genes, respectively, which were involved in 8 different metabolic pathways. In addition, we detected 2647 unigene transcription factors. Eleven upregulated and sixteen downregulated genes from the different starvation stress groups were choose to verify the reliability of the transcriptome data, and the results showed that the expression trends of these genes were consistent with the results shown by the transcriptome. The analysis of the experimental data and our discussion of the response mechanism of white ridgetail prawn under starvation stress provides a foundation for further screening of the key genes of starvation stress and may help to elucidate their functions.

Delta of Exopalaemon carinicauda: molecular characterization, expression in different tissues and developmental stages, and its SNPs association analysis with development.

The Notch signaling pathway plays a significant role in the gene regulatory network of development of vertebrate and invertebrate. However, as a ligand for the Notch signaling pathway, the mechanism of Delta in the development of Exopalaemon carinicauda is still unclear. The Delta's molecular characteristics, tissue distribution and their association with development in E. carinicauda were studied by RACE (rapid amplification of cDNA end), qRT-PCR (quantitative Real-time PCR) and SNP (single nucleotide polymorphism), respectively. The delta in E. carinicauda had a full-length cDNA of 2807bp and its Delta of 808 amino-acid residue had the highest identity with the Delta of Homarus americanus (identity = 76.63%). Delta had the highest expression in the ovary, and its expression varied with different stages of embryonic, larval, and ovarian development. After delta RNA interference (with a highest interference efficiency of 66% at 24 h), the expression of Notch signaling pathway genes and developmental related genes was significantly reduced, and the ovarian development was significantly delayed. Further study found that there were 4 SNPs (ds1-4) in delta cDNA, of which two (ds2 T1521G caused a mutation Asn422Lys and ds3 G1674A caused a mutation Tyr473Cys in the EGF-like domain) were associated with the development of E. carinicauda. The Gonadosomatic Index (GSI) of the ds2 TT genotypes was 37.28% and 134.60% higher than E. carinicauda of GT and GG genotype respectively (P < 0.05). Our research indicated that delta was involved in the development of E. carinicauda and provided new insights for molecular breeding with SNP markers in E. carinicauda.

Impact of Ocean Acidification on the Gut Histopathology and Intestinal Microflora of Exopalaemon carinicauda.

Marine crustaceans are severely threatened by environmental factors such as ocean acidification, but, despite the latter's negative impact on growth, molting, and immunity, its effects on intestinal microflora remain poorly understood. This work studied the gut morphology and intestinal microflora of Exopalaemon carinicauda, grown in seawater of different pH levels: 8.1 (control group), 7.4 (AC74 group), and 7.0 (AC70 group). Ocean acidification was found to cause intestinal damage, while significantly altering the microflora's composition. However, the α-diversity did not differ significantly between the groups. At the phylum level, the relative abundance of Proteobacteria decreased in the acidification groups, while at the genus level, the relative abundance of Sphingomonas decreased. Babeliales was a prominent discriminative biomarker in the AC74 group, with Actinobacteriota, Micrococcales, Beijerinckiaceae, Methylobacterium, and Flavobacteriales being the main ones in the AC70 group. The function prediction results also indicated an enrichment of pathways related to metabolism for the acidification groups. At the same time, those related to xenobiotics' biodegradation and metabolism were inhibited in AC74 but enhanced in AC70. This is the first study examining the impact of ocean acidification on the intestinal microflora of crustaceans. The results are expected to provide a better understanding of the interactions between shrimp and their microflora in response to environmental stressors.