Search

Short neuropeptide F (sNPF) is a neuropeptide that widely distributed among arthropods. This neuropeptide has been proposed to play pleiotropic roles in insects, but its physiological functions in crustaceans are poorly understood. Here, we cloned the cDNA sequences of sNPF and its putative receptor (sNPFR) from the swimming crab, Portunus trituberculatus, and determined their possible roles during ovarian development. PtsNPF encodes three sNPF mature peptides with a conserved C-terminal "RLRFG" motif. All three PtsNPF peptides concentration-dependently activated PtsNPFR expressed in HEK293T cells, with EC50 values in the nanomolar range. PtsNPF and PtsNPFR transcripts showed a broad distribution among neural and non-neural tissues. During the ovarian development, expression of PtsNPF and PtsNPFR in hepatopancreas and ovary both increased to the highest levels at the late-vitellogenic stage, a period for rapid vitellogenesis. The in vitro experiments further showed that, among the three sNPF peptides, sNPF3 treatments can induce the vitellogenin (Vg) gene and protein levels in the hepatopancreas, as well as the Vg receptor (VgR) gene and protein levels and vitellogenin (Vn) deposition in the ovary. Opposing effects were observed for the dsPtsNPFR treatments, suggesting that PtsNPFR plays a role in the PtsNPF-mediated vitellogenesis. Additionally, it was found that the PtsNPF/PtsNPFR system can activate different second messengers species in hepatopancreas and ovary, suggesting it may act via different G proteins. [ABSTRACT FROM AUTHOR]

Simple Summary: Functional studies of neuropeptides are of great significance in revealing the neuroendocrine regulation mechanism in crustaceans, and in guiding and developing artificial regulation techniques in economic species. In this paper, we investigated the effect of a crustacean neuropeptide corazonin (Crz) on ecdysteroid synthesis based on the high expression of Crz receptor in the Y-organ, the main site of ecdysteroid synthesis. By using Crz treatment and CrzR silencing, we found that Crz/CrzR signaling could cause up-regulation of ecdysteroid synthesis genes and an increase in ecdysteroid levels both in vitro and in vivo. In addition, it was also observed that Crz/CrzR signaling affects the expression level of ecdysis-triggering hormones. Our results provide new insights into the understanding of Crz function in crustaceans. The neuropeptide corazonin (Crz) exerts diverse physiological effects in insects, yet its role in crustaceans remains elusive. The abundant expression of Crz receptor (CrzR) in the Y-organs of several crustaceans suggests a potential involvement of Crz in regulating ecdysteroid synthesis. In this study, we examined the effects of PtCrz on ecdysteroid synthesis during the molting period of Portunus trituberculatus through PtCrz treatments and PtCrzR silencing. Our results showed that PtCrz peptide stimulates ecdysteroid levels and the gene expression involved in ecdysteroidogenesis both in vitro and in vivo, whereas dsPtCrzR treatments had opposite effects on ecdysteroid levels and associated gene expression. Thus, our study suggests that PtCrz may modulate ecdysteroid synthesis via Y-organ-expressed PtCrzR. Furthermore, we also discovered the involvement of PtCrz/PtCrzR signaling in regulating PtETH expression. Notably, the inhibitory effect of dsPtCrzR on ecdysteroid synthesis or PtETH expression can be reversed by PtCrz treatment, suggesting the potential existence of multiple receptors for PtCrz. This study provides new insights into the function of crustacean Crz and, for the first time, elucidates the presence of a neuropeptide that can stimulate ecdysteroid synthesis in crustaceans. [ABSTRACT FROM AUTHOR]

This study aimed to assess the influence of varying dietary levels of astaxanthin (AST) on the growth, antioxidant capacity and lipid metabolism of juvenile swimming crabs. Six diets were formulated to contain different AST levels, and the analyzed concentration of AST in experimental diets were 0, 24.2, 45.8, 72.4, 94.2 and 195.0 mg kg−1, respectively. Juvenile swimming crabs (initial weight 8.20 ± 0.01 g) were fed these experimental diets for 56 days. The findings indicated that the color of the live crab shells and the cooked crab shells gradually became red with the increase of dietary AST levels. Dietary 24.2 mg kg−1 astaxanthin significantly improved the growth performance of swimming crab. the lowest activities of glutathione (GSH), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and peroxidase (POD) were found in crabs fed without AST supplementation diet. Crabs fed diet without AST supplementation showed lower lipid content and the activity of fatty acid synthetase (FAS) in hepatopancreas than those fed diets with AST supplementation, however, lipid content in muscle and the activity of carnitine palmitoyl transferase (CPT) in hepatopancreas were not significantly affected by dietary AST levels. And it can be found in oil red O staining that dietary 24.2 and 45.8 mg kg−1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas. Crabs fed diet with 195.0 mg kg−1 AST exhibited lower expression of ampk, foxo, pi3k, akt and nadph in hepatopancreas than those fed the other diets, however, the expression of genes related to antioxidant such as cMn-sod, gsh-px, cat, trx and gst in hepatopancreas significantly down-regulated with the increase of dietary AST levels. In conclusion, dietary 24.2 and 45.8 mg kg−1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas and im-proved the antioxidant and immune capacity of hemolymph. [ABSTRACT FROM AUTHOR]

The present research assessed the impact of dietary valine on nutritional and energy metabolism, as well as muscle development in swimming crabs (Portunus trituberculatus) over a period of six weeks. Swimming crabs, initially weighing around 23.34 ± 0.03 g, were given six diets identical in nitrogen and lipid levels (45 % and 8 % respectively). These diets contained valine contents of 0.99 %, 1.24 %, 1.56 %, 1.69 %, 1.90 %, and 2.20 % respectively. One hundred and eighty crabs were randomized into six treatments, each treatment including three replicates. The results suggested that significant increases were discovered in FW, PWG, as well as SGR of crabs when dietary valine increasing from 0.99 % to 1.69 %, but these measurements decreased when dietary valine increased to 2.20 %. Compare to the control treatment, crabs that were given diets with 1.90 % and 2.20 % valine showed increased level of muscle protein. Crabs that were given the diets containing 1.56 % and 1.69 % valine showed significantly increased concentration of GLU in hemolymph compared to the control group. Additionally, crabs that were given the diets containing 1.69 % valine and 1.90 % valine respectively showed significantly increased concentrations of T-CHO and TG in hepatopancreas. Hepatic glycogen concentration significantly decreased as the level of valine in diets increased from 0.99 % to 1.56 %, but significantly increased as valine level further increased to 2.20 %. Compared with the control group, crabs that were given diets with 1.90 % valine showed increased expression levels of genes associated to amino acid metabolism (pi3k, akt, alt, ast, 4ebp1 and eif4e3) and energy metabolism (pk, cs1, idh, nd1, cytb and cox2). Crabs given diets containing 2.20 % valine showed significantly increased expression level of pepck in hepatopancreas, while crabs given diets containing 1.24 %, 1.56 %, and 1.69 % valine exhibited significantly increased expression level of cpt1 in hepatopancreas. Crabs given the diet with 1.69 % valine had the highest expression levels of tor and pax7 in muscle. Increased dietary valine significantly reduced myofiber density but promoted higher frequency of myofibers in larger diameters. In conclusion, the optimal valine requirement for P. trituberculatus was 1.56 % of diet based on PWG by a quadratic modeling. 1.69–1.90 % valine promoted amino acid metabolism and muscle growth, moreover, enhanced energy metabolism by driving the consumption of glycogen rather than lipids.

Ovarian development is a complex and dynamical process regulated by the coordinated actions of the hepatopancreas and ovary. In mammals, lipids provide necessary energy for oocytes to mature, whereas their regulatory role in crustaceans is not fully understood. This study compares lipid mobilization and deposition in hepatopancreas and ovary of the swimming crab at different stages of ovarian maturation. The results revealed that cholesterol (CHO) and triglyceride (TG) content in hepatopancreas increased with ovary development increased from stage I to Ⅲ, and then decreased at stage V, while those content in ovary significantly increased from stage I to V. Additionally, apolipoprotein (ApoA and ApoB) contents in hepatopancreas and ovary increased significantly during ovary development. Moreover, the highest expression levels of cholesterol transport related genes (srb, ldlr, lrp2 and abcg1) were observed in the hepatopancreas at stage Ⅲ and in the ovary at stage Ⅳ. Furthermore, as ovary development form stage I to Ⅳ, the hepatopancreas up-regulated the expression levels of genes related to lipid anabolism (fas, acc, g6pd, and 6pgd) and fatty acid transport (fabp9 and fatp4). Concurrently, genes related to lipid catabolism (il) and fatty acid β-oxidation (acox2 and acox3) in the hepatopancreas were down-regulated. Differently, with the ovary development increased from stage I to Ⅳ, the ovary up-regulated gene expression levels involved in lipid anabolism (acc, 6pgd, g6pd, dgat1, and gpat3), fatty acid synthesis (elovl and elovl4) and fatty acid β-oxidation (cpt1, cpt2, acox1, and acox3). The mRNA expression levels of lipolysis (tgl) and fatty acid transport (fabp1, fbap9, and fatp4) in ovary were down-regulated. Overall, these findings demonstrate that the hepatopancreas and ovary exhibit different responses to lipid metabolism during ovarian development.

The purpose of present study was to evaluate the effects of vitamin D3 supplementation in high-fat diet on growth performance, calcium and phosphorus in tissue, immunity and lipid metabolism, and to explore whether adding vitamin D3 to high-fat diet can alleviate the adverse effects of high-fat diet on swimming crab (Portunus trituberculatus). The three experimental diets were normal fat diet (NFD, 9.35 % fat, 45.53 % protein), high fat diet (HFD, 14.69 % fat, 44.93 % protein) and high fat diet supplemented with 0.47 mg/kg VD3 (HFD+VD), respectively. A total of 108 healthy swimming crabs with an initial body weight of 9.42±0.13 g were selected for an 8-week feeding trial. The results showed that crabs fed with HFD+VD diet exhibited significantly higher percent weight gain (PWG), specific growth rate (SGR), feed efficiency (FE) and molting rate (MR) compared to those fed with HFD diet (P < 0.05). It was observed from hepatopancreas crude lipid content, TG content and hepatopancreas sections that HFD caused hepatopancreatic cell damage and abnormal lipid accumulation (P < 0.05), however, there were no significant differences in hepatopancreas crude fat content, TG content and hepatopancreas section observation between HFD+VD group and NFD group (P > 0.05). Crabs fed HFD diets with or without VD3 significantly down-regulated the expression of genes related to fatty acid transport, such as fabp9 and lpr1 in hepatopancreas (P < 0.05), moreover, the expression of genes related to fatty acid β-oxidation (cpt2 and acox1) were significantly up-regulated and genes related to lipid synthesis (fas and 6pgd) were significantly down-regulated in the hepatopancreas of the crabs fed with HFD+VD diet compared to those fed with HFD diet (P < 0.05). In conclusion, the results of present study indicated that a high-fat diet can cause deformation and rupture of hepatopancreas cells through abnormal lipid accumulation, thereby causing associated inflammation, leading to large calcium and phosphorus deposits in hemolymph and muscle, however, high fat diet supplemented with vitamin VD3 mainly enhanced the β-oxidation of fatty acids, inhibited lipid synthesis, alleviated abnormal lipid accumulation, and thus maintained the balance of lipid metabolism in hepatopancreas cells and promoted growth performance and feed utilization for swimming crab.

To clarify the influence of different water temperatures on the development of Portunus trituberculatus (swimming crab) larvae during off-season (early autumn) breeding, a gradient of four rearing temperatures of 27, 29, 31 and 33°C was set up, and the effects of water temperature on larval development were systematically compared. The results showed that the moulting cycle (MC) from the zoea 1 (Z1)-zoea 2 (Z2) stage was not significantly affected by water temperature (P > 0.05), remaining at approximately 3 days. However, in the Z2-megalopa (M) stage, the MC in the 31°C group was consistently the shortest. The total developmental duration and total effective cumulative temperature during Z1-M in the 31°C group were the lowest at 9.97 days and 250 days · °C, respectively. According to the equation of water temperature and larval development rate, the development rate was the fastest when the water temperature was 31°C. As the water temperature increased, the survival rate (SR) of larvae at various stages gradually decreased. The SR of the 27°C group was consistently significantly higher than that of the 33°C group (P < 0.05), especially in the M stage, where the SR of the 33°C group was only 2%, which was significantly lower than that of the 27°C and 29°C groups (P < 0.05). Among the antioxidant indexes, both superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) were the lowest in the 29°C group at 315.75 U/mg protein and 0.36 mmol/g protein, respectively, and both were significantly lower than those in the 33°C group (P < 0.05). Catalase (CAT) and glutathione peroxidase (GSH-PX) were both the lowest in the 31°C group, and in this group the CAT was significantly lower than in the 33°C group, and GSH-PX was significantly lower than in the 27°C group (P < 0.05). For malondialdehyde (MDA) content, the four groups were basically maintained at about 2.5 nmol/mg protein, and there was no significant difference (P > 0.05). In terms of digestive enzyme activity, the activity of lipase (LPS) was basically maintained at 1.93 U/g protein. The other four digestive enzyme activity differences were mainly reflected in that the 31 and 33°C groups maintained relatively higher levels than the 27 and 29°C groups, especially the activities of α -amylase (AMS), and cellulase (CL) in the 33°C group, which were significantly higher than those in the 27 and 29°C groups (P < 0.05). Comprehensive indicators indicate that a water temperature between 29 and 31°C is the appropriate temperature for the development of the larvae of off-season breeding swimming crabs. [ABSTRACT FROM AUTHOR]

The objective of the present study was to evaluate the effects of replacing fish meal (FM) with spray-dried blood meal (SDBM) on growth performance, antioxidant capacity, digestive enzyme activity, tissue Fe content, gene expression related to inflammation, and the TOR pathway in juvenile swimming crab (Portunus trituberculatus). Four isonitrogenous (47.0% protein) and isolipidic (9.0% lipid) diets were formulated to contain different levels of SDBM, with FM replaced by SDBM at 0, 10%, 20%, and 30%, respectively. The results showed that crabs fed diet SDBM30 exhibited the lowest survival among all treatments, and crabs fed the SDBM20 diet had the highest final weight, percent weight gain, specific growth rate and feed efficiency among all treatments. In addition, the protein content of the crab hepatopancreas decreased significantly and the lipid content increased significantly as SDBM replaced FM in the diets. Compared to other diets, crabs fed the SDBM30 diet had the lowest activities of antioxidant enzymes and the highest concentration of malondialdehyde in the hepatopancreas and hemolymph. The Fe contents in hepatopancreas and gill increased significantly, and the color of the hepatopancreas got darker as replacement of FM with SDBM increased from 0% to 30%. The expression of genes related to TOR (tor, akt, s6, and s6k1) and antioxidant (gpx) pathways in the hepatopancreas were down-regulated significantly with increased replacement of dietary FM with SDBM. In contrast, expression levels of genes related to protein translation (4ebp1, eif4e1a, eif4e2, and eif4e3) and inflammation pathways (myd88, traf6, relish, and irak4) were up-regulated significantly in crabs fed diets with SDBM supplementation. In summary, replacing FM with less than 20% of SDBM can promote the growth, but can darken the hepatopancreas, negatively affect antioxidant capacity, and induce an inflammatory response.

Objective: To investigate the changes in the quality characteristics of abdomen and cheliped muscle of swimming crab (Portunus trituberculatus) during chilled storage. Methods: The swimming crab was taken as the object. During chilled storage at 4 ℃, the abdomen and cheliped muscle of swimming crab was conducted quantitative descriptive analysis. At the same time, the physicochemical indicators of muscle such as water holding capacity, water content, water activity, pH, total volatile base nitrogen, trimethylamine, TCA-soluble peptide, myofibrillar protein content, and fragmentation index were measured. Results: With the extension of chilled storage time, the characteristics of the abdomen and cheliped muscle of swimming crab showed a similar trend of change, in which the quality sensory characteristics, water holding capacity, water content, and water activity of muscle showed a downward trend. The pH of muscle showed a trend of decreasing first and then increasing. The pH of the abdomen muscle was 7.7 on the 5th day of chilled storage, while the pH of the cheliped muscle reached 7.99 on the 4th day of chilled storage. Total volatile base nitrogen, trimethylamine, TCA-soluble peptide, and myofibril fragmentation index showed an upward trend. The myofibrillar protein content showed a significant downward trend (P

Abstract Background Temperature is an important environment factor that is critical to the survival and growth of crustaceans. However, the mechanisms by which crustaceans detect changes in temperature are still unclear. The transient receptor potential (TRP) channels are non-selective cation channels well known for properties in temperature sensation. However, comprehensive understandings on TRP channels as well as their temperature sensing functions are still lacking in crustaceans. Results In this study, a total of 26 TRP genes were identified in the swimming crab, Portunus trituberculatus, which can be classified into TRPA, TRPC, TRPP, TRPM, TRPML, TRPN and TRPV. Tissue expression analysis revealed a wide distribution of these TRP genes in P. trituberculatus, and antennules, neural tissues, and ovaries were the most commonly expressed tissues. To investigate the responsiveness of TRP genes to the temperature change, 18 TRPs were selected to detect their expression after high and low temperature stress. The results showed that 12 TRPs showed induced gene expression in both high and low temperature groups, while 3 were down-regulated in the low temperature group, and 3 showed no change in expression in either group. Conclusions This study characterized the TRP family genes in P. trituberculatus, and explored their involvement in response to temperature stress. Our results will enhance overall understanding of crustacean TRP channels and their possible functions.

Background: Anxiety refers to the pathological persistence and intensification of emotional responses to danger, affecting health from psychological and physical aspects. Serotonin is an important neurotransmitter involved in the onset of anxiety. Methods and Results: To explore the biological changes in the formation of anxiety in crustaceans under the regulation of serotonin, we applied the open field-like test method for assessing anxiety states of larval Portunus trituberculatus, a highly aggressive crustacean species with a more simple neural structure compared with rodents and mammals. Compared with the control group, serotonin treatment resulted in a significant decrease in the time spent by the larvae in the central zone, suggesting anxiety-like behavior. Clonazepam treatment reversed this result and provided further evidence that the behavior of larval P. trituberculatus displayed anxiety. Moreover, a non-targeted metabolomic analysis found a significant alteration in the metabolites involved in tryptophan metabolism pathways associated with anxiety, including L-kynurenine, N-acetyl serotonin, and serotonin. These metabolites are involved in the serotonin pathway, the kynurenine pathway, and other pathways that affect anxiety through tryptophan metabolism. There were no significant differences in tryptophan metabolism levels between the control and clonazepam treatment groups. Conclusions: Our results demonstrate the possible existence of anxiety-like behavior in the larvae of P. trituberculatus from two perspectives. Being a species with a simpler neural structure than that of mammals, the larvae of P. trituberculatus offer a convenient model for studying the mechanisms of anxiety in crustaceans.

The toxic effect and differences of Cr(VI) on superoxide dismutase (SOD) activity, MDA, and metallothionein (MT) content in the hepatopancreas and gill of Portunus trituberculatus were investigated during Cr(VI) enrichment (15 days) and release experiments (15 days). Results showed that the 1.50 and 0.30 mg/L test groups significantly exhibited higher SOD, MDA, and MT content in the hepatopancreas and gill compared with the control group after 15 days of enrichment (p < 0.05). After 15 days of Cr release, the SOD, MDA, and MT content in the hepatopancreas and gill of both test groups recovered to the normal level of the control group (p > 0.05). The gill of P. trituberculatus achieved the highest SOD activity, MDA, and MT content earlier than the hepatopancreas, but the highest values were lower. The gill showed a shorter recovery time than the hepatopancreas. We concluded that the gill of P. trituberculatus exhibited a more rapid response to, and recovery from, Cr(VI) exposure compared to the hepatopancreas, making it a more sensitive tissue for assessing Cr(VI) toxicity, though both tissues showed a capacity for recovery after the removal of the contaminant.

The neuropeptide corazonin (Crz) exerts diverse physiological effects in insects, yet its role in crustaceans remains elusive. The abundant expression of Crz receptor (CrzR) in the Y-organs of several crustaceans suggests a potential involvement of Crz in regulating ecdysteroid synthesis. In this study, we examined the effects of PtCrz on ecdysteroid synthesis during the molting period of Portunus trituberculatus through PtCrz treatments and PtCrzR silencing. Our results showed that PtCrz peptide stimulates ecdysteroid levels and the gene expression involved in ecdysteroidogenesis both in vitro and in vivo, whereas dsPtCrzR treatments had opposite effects on ecdysteroid levels and associated gene expression. Thus, our study suggests that PtCrz may modulate ecdysteroid synthesis via Y-organ-expressed PtCrzR. Furthermore, we also discovered the involvement of PtCrz/PtCrzR signaling in regulating PtETH expression. Notably, the inhibitory effect of dsPtCrzR on ecdysteroid synthesis or PtETH expression can be reversed by PtCrz treatment, suggesting the potential existence of multiple receptors for PtCrz. This study provides new insights into the function of crustacean Crz and, for the first time, elucidates the presence of a neuropeptide that can stimulate ecdysteroid synthesis in crustaceans.

Background: Temperature is an important environment factor that is critical to the survival and growth of crustaceans. However, the mechanisms by which crustaceans detect changes in temperature are still unclear. The transient receptor potential (TRP) channels are non-selective cation channels well known for properties in temperature sensation. However, comprehensive understandings on TRP channels as well as their temperature sensing functions are still lacking in crustaceans. Results: In this study, a total of 26 TRP genes were identified in the swimming crab, Portunus trituberculatus, which can be classified into TRPA, TRPC, TRPP, TRPM, TRPML, TRPN and TRPV. Tissue expression analysis revealed a wide distribution of these TRP genes in P. trituberculatus, and antennules, neural tissues, and ovaries were the most commonly expressed tissues. To investigate the responsiveness of TRP genes to the temperature change, 18 TRPs were selected to detect their expression after high and low temperature stress. The results showed that 12 TRPs showed induced gene expression in both high and low temperature groups, while 3 were down-regulated in the low temperature group, and 3 showed no change in expression in either group. Conclusions: This study characterized the TRP family genes in P. trituberculatus, and explored their involvement in response to temperature stress. Our results will enhance overall understanding of crustacean TRP channels and their possible functions. [ABSTRACT FROM AUTHOR]

Copyright of Science & Technology of Food Industry is the property of Science & Technology of Food Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mesanophrys sp. is a parasitic ciliate that invades and destroys the hemocytes of the swimming crab (Portunus trituberculatus). In the present study, we employed an in vitro model to elucidate how Mesanophrys sp. destroys crab hemocytes. We also evaluated the relationship between the parasite’s density, the destruction rate of the hemocytes, and the rapid proliferation pattern of parasites in host crabs. We found that the survival rate and cell integrity of crab hemocytes decreased with an increase in Mesanophrys sp. density, depicting a negative correlation between hemocyte viability and parasite density. Further analyses revealed that crab hemocytes could resist destruction by a low density (10 ind/mL) of Mesanophrys sp. for a long time (60 h). Mesanophrys sp. and its culture medium (containing the ciliate secretions) destroy the host hemocytes. The natural population growth rate of Mesanophrys sp. decreased with an increase in the parasite density, but the Mesanophrys sp. density did not affect the generation time of the parasites. In summary, Mesanophrys sp. can destroy crab hemocytes, and the degree of destruction is directly proportional to the parasite density. The resistance of crab hemocytes to Mesanophrys sp. decreased gradually with an increase in the parasite density. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, we investigated the effects of pathogen infection and low-salinity stress on organismal immunity during Portunus trituberculatus culture by utilizing transcriptome technology. We depicted the dynamic expression process of the transcriptome under pathogenic infection and low-salinity stress. In addition, several immune genes were screened that were jointly affected by immune infection and low-salinity stress. These results contribute to our understanding of the impact of environmental factors on the immunoregulatory mechanisms of P. trituberculatus. Vibrio parahaemolyticus is one of the main pathogenic bacteria of Portunus trituberculatus and causes mass mortality of P. trituberculatus in aquaculture. In addition, low-salinity stimulation makes P. trituberculatus more susceptible to V. parahaemolyticus infections. In order to elucidate the molecular mechanism of resistance to V. parahaemolyticus in P. trituberculatus, comparative transcriptomic analysis of blood cells stimulated by low salinity and V. parahaemolyticus was carried out in this study. Transcriptome sequencing of low-salinity stress and pathogen infection at different time points was completed using Illumina sequencing technology. A total of 5827, 6432, 5362 and 1784 differentially expressed genes (DEGs) involved in pathways related to ion transport and immunoregulation were found under low-salinity stress at 12, 24, 48 and 72 h compared with the control at 0 h. In contrast, 4854, 4814, 5535 and 6051 DEGs, which were significantly enriched in Toll and IMD signaling pathways, were found at 12, 24, 48 and 72 h compared with the control at 0 h under V. parahaemolyticus infection. Among them, 952 DEGs were shared in the two treatment groups, which were mainly involved in apoptosis and Hippo signaling pathway. Cluster analysis screened 103 genes that were differentially expressed in two factors that were negatively correlated, including immunoglobulin, leukocyte receptor cluster family, scavenger receptor, macroglobulin and other innate-immune-related genes. These results provide data support for the analysis of the mechanisms of immunity to V. parahaemolyticus under low-salinity stress in P. trituberculatus and help to elucidate the molecular mechanisms by which environmental factors affect immunity. [ABSTRACT FROM AUTHOR]

To investigate the effect of pre-cooking treatment on the quality of swimming crab (Portunus trituberculatus) meat during frozen storage, the differences in the quality of group C (control without any treatment), group H-F (heating followed by frozen storage) and group F-H (frozen storage followed by heating) during 180 d storage at −20 ℃ were evaluated in terms of their color difference, water-holding capacity (WHC), pH, total volatile base nitrogen (TVB-N) content, total viable count (TVC), and protein composition and microstructure. The results showed that the whiteness and WHC of the three groups decreased with storage time. The pH of group C decreased first and then increased, while the pH of the other two groups showed the opposite trend and then remained steady. The TVB-N content and TVC of all groups showed an overall upward trend. The TVB-N content and TVC of group H-F were (21.12 ± 0.58) mg/100 g and (4.03 ± 0.17) (lg(CFU/g)) after 180 d, respectively, which were significantly lower than those of group F-H. The microstructure of crab muscle in group C changed from clear and ordered to fuzzy and disordered during the frozen storage process, while pre-cooked crab meat maintained a better morphology. Besides, the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) suggested that crab meat proteins in the three groups were degraded to different degrees during storage, which was more pronounced in group F-H than in group H-F. Therefore, pre-cooking treatment could efficiently reduce the quality deterioration of crab meat during frozen storage, which could provide a reference for subsequent research to improve the frozen storage quality of P. trituberculatus.

To stop the decline of swimming crab (Portunus trituberculatus) stocks in the East China Sea, escape vents on crab pots are urgently required to improve pot selectivity and enable release of sublegal-sized crabs. This study presents field comparative fishing experiments, which examined the effectiveness of different shapes and sizes of escape vents in crab pots for the release of swimming crabs. Two sizes each of rectangular, elliptic, and circular escape vents were tested. The results of comparative fishing experiments indicated that experimental pots with escape vents, regardless of their configuration, caught significantly fewer sublegal-sized crabs (

An eight-week feeding trial was conducted to determine the optimal dietary histidine requirement of juvenile swimming crab (Portunus trituberculatus). Six isonitrogenous and isolipidic diets (45.0% crude protein and 8.0% crude lipid) were formulated to contain 0.43%, 0.68%, 0.97%, 1.24%, 1.45% and 1.79% histidine, respectively. Each diet was randomly assigned to triplicate groups of 30 juvenile crabs (approximately initial weight 17.63 ± 0.08 g). The results indicated that the highest percent weight gain (PWG) and specific growth rate (SGR) was presented in crabs fed the diet with 1.24% histidine (P

Hemocyanin is a critical oxygen-transporting protein exhibiting multiple physiological functions, including protein storage and transportation, osmolarity regulation, molting, and immunomodulation in arthropods and mollusks. However, the immune function of hemocyanin in Portunus trituberculatus is rarely reported. Here, we identified ten subunit genes within the hemocyanin family from the P. trituberculatus genome. These genes exhibited conserved functional domains and copper ion binding sites. Building upon prior research, we specifically focused on investigating the immune functions of PtHc1 and PtHc2. Tissue expression analysis revealed that PtHc1 and PtHc2 were prominently expressed in the hepatopancreas and hemocytes. Upon infection with Vibrio parahaemolyticus, both PtHc1 and PtHc2 demonstrated a similar expression pattern, characterized by a gradual upregulation of expression levels in the hepatopancreas. While within the hemocytes, they exhibited a trend of initial downregulation followed by subsequent upregulation in expression. In addition, Recombinant hemocyanin was able to inhibit bacterial proliferation in a dose-dependent manner, with inhibition rates of 40 % and 39 % when the recombinant proteins of PtHc1 and PtHc2 reached 0.03 mg/mL, respectively. Besides, V. parahaemolyticus challenge resulted in a significant 20–23 % increase in mortality in P. trituberculatus following knockdown of PtHc1 and PtHc2. Overall, our study sheds light on the immune-related functions of PtHc1 and PtHc2 in P. trituberculatus, revealing their potential as key players in defending against pathogenic threats like V. parahaemolyticus. These results enriched the field of innate immunity in crustacean and providing a theoretical basis for disease resistance breeding.

The swimming crab (Portunus trituberculatus) is an economically important aquaculture species in China. Mining candidate single nucleotide polymorphisms (SNPs) and genes associated with growth traits of P. trituberculatus is of great importance for the genetic breeding of this species. Among the genes associated with growth traits, “protein still life, isoforms C/SIF type 2 (SIF)” is thought to be an important gene affecting animal growth and development. In the current study, we investigated the SIF gene from P. trituberculatus to better understand its biological function. The full-length cDNA of SIF was 6185 bp, with a 5208 bp open reading frame encoding 1735 amino acids. Homology analysis showed that SIF shared 90.07% identity with Procambarus clarkii and 40.25–86.95% with other species. Expression pattern analysis of SIF in fast- and slow-growing groups revealed a significantly higher expression level in the former than in the latter (P

Stock enhancement can effectively increase population sustainablility and improve fishery resources, making it crucial to discern the suitable habitats for stock enhancement based on efficiency considerations. In this paper, a comprehensive model was established to simulate environmental characteristics in the Liaodong Bay. A habitat suitability model was developed by considering the optimal growth conditions of the Portunus trituberculatus larvae (PTL). The coupled model showed that the optimal area for stock-enhancement with PTL occurs in late June, and the initial suitable habitat area identified represents 17.12% of the whole Liaodong Bay. Based on the larval migration model of PTL, the deviation between the larvae and the suitable habitat, as well as the actual available area for stock enhancement, were further determined after larval release in the initial suitable habitat. Only 33.67% of the larvae fulfilled the criteria of remaining within the suitable habitat for 95% of the time, and these larvae represented 6.19% of the whole area of Liaodong Bay. These findings means that the truly area available for stock enhancement is likely to be a very small portion of the entire bay, and more precise release of larvae will be necessary to ensure survival rates after release. Our study actually provides a methodological framework for the identification of suitable environment of stock enhancement. This methodology can provide technical guidance for the stock enhancement of marine larvae with same applicability for other bays, which in turn contributes to the sustainable use of marine ecosystem services and fisheries resources.

Simple Summary: To clarify the specific nutritional needs for ovary maturation of the commercially important crab Portunus trituberculatus, we compared the biochemical composition of the ovary, hepatopancreas, and muscle at five ovarian developmental stages, and also analyzed their relation to the ovarian developmental stage of P. trituberculatus. We found that the branched-chain amino acids, long-chain polyunsaturated fatty acids, and monounsaturated fatty acids accumulated in the ovary and hepatopancreas, and positively correlated with the ovary maturation stage. Also, we found an increasing tendency of carotenoid and phosphatidylcholine in phospholipid from the pre-developmental stage to the proliferative stage in the ovary, but not in the hepatopancreas and muscle, indicating their crucial role for oocyte development. Our study suggests the involvement of these compositions in the broodstock diet, which will promote the ovarian maturation of adult P. trituberculatus and ensure high-quality larval production. The swimming crab Portunus trituberculatus is one of the most important economic species in China and its mature ovary often determines its commercial value and production. Although the ovary maturation of crustaceans is generally affected by exogenous nutrition, the specific nutritional needs of ovary maturation of P. trituberculatus are poorly understood. To this end, we collected the P. trituberculatus samples with five ovarian maturation stages and measured their biochemical composition of the ovary, hepatopancreas, and muscle at each ovarian developmental stage. We further analyzed their relation to the ovarian developmental stage of P. trituberculatus by principal components analysis (PCA). We found the levels of branched-chain amino acids, long-chain polyunsaturated fatty acids (LC-PUFA), and monounsaturated fatty acids (MUFAs) in the ovary and hepatopancreas increased during the ovary maturation process, and also passively correlated with ovarian developmental stage, which highlights the necessity of these specific nutrients for oogenesis and for improving the nutrient quality of crabs. In addition, we found an increasing tendency of carotenoid content and phosphatidylcholine in phospholipid in the ovary from the pre-developmental stage to the proliferative stage, but not in the hepatopancreas and muscle, which highlights the possible involvement of carotenoids during the rapid oocyte development process. Our study may provide valuable information for developing a suitable broodstock diet that promotes the ovarian maturation of adult P. trituberculatus and ensures high-quality larval production. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian Ocean University is the property of Journal of Dalian Ocean University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Crab cell line, especially continuous crab cell line, can provide us a useful tool for studies on the virology, immunology, and molecular biology of crabs. However, no continuous crab cell line has been available due to the lacking of suitable medium and the occurrence of mitosis-arrest. In this study, long-term in vitro culture conditions for both two- (2D) and three-dimensions (3D) were successfully developed for the circulating hemocytes of swimming crab Portunus trituberculatus, designated as PTH cells. In 2D culture, a novel crab basic medium in osmolarity of 990–1 100 mOsm/kg was optimized for the first time, which is different from Leibovitz's L-15 medium in mainly the components of amino acids, containing double strengths of the contents of free amino acid mixture in the crab serum. Then an optimal crab growth medium was developed by supplementing 5% fetal bovine serum, 50-g/L yeast extract powder, 20-µg/L basic fibroblast growth factor and epidermal growth factor into the optimal crab basic medium, and found that it could support a long-term survival of PTH cells in a healthy monolayer up to 347 days and partially break through the mitosis-arrest of crab cells evidenced by the obvious increase of proliferating potential detected in the 10-d primarily cultured PTH cells. These 2D cultured PTH cells could be successfully sub-cultured for 11 times by physical flushing method and well cryopreserved in liquid nitrogen. In 3D culture, using the same crab growth medium, the PTH cell aggregates could be easily formed and healthily maintained on the surface of solidified Matrigel or in the ultra-low-attachment plate with a survival rate of 50%–60% on Day 103. This work largely improved the primary culture and subculture of crab cells and will facilitate the establishment of continuous crab cell line. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aimed to assess the influence of varying dietary levels of astaxanthin (AST) on the growth, antioxidant capacity and lipid metabolism of juvenile swimming crabs. Six diets were formulated to contain different AST levels, and the analyzed concentration of AST in experimental diets were 0, 24.2, 45.8, 72.4, 94.2 and 195.0 mg kg−1, respectively. Juvenile swimming crabs (initial weight 8.20 ± 0.01 g) were fed these experimental diets for 56 days. The findings indicated that the color of the live crab shells and the cooked crab shells gradually became red with the increase of dietary AST levels. Dietary 24.2 mg kg−1 astaxanthin significantly improved the growth performance of swimming crab. the lowest activities of glutathione (GSH), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and peroxidase (POD) were found in crabs fed without AST supplementation diet. Crabs fed diet without AST supplementation showed lower lipid content and the activity of fatty acid synthetase (FAS) in hepatopancreas than those fed diets with AST supplementation, however, lipid content in muscle and the activity of carnitine palmitoyl transferase (CPT) in hepatopancreas were not significantly affected by dietary AST levels. And it can be found in oil red O staining that dietary 24.2 and 45.8 mg kg−1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas. Crabs fed diet with 195.0 mg kg−1 AST exhibited lower expression of ampk, foxo, pi3k, akt and nadph in hepatopancreas than those fed the other diets, however, the expression of genes related to antioxidant such as cMn-sod, gsh-px, cat, trx and gst in hepatopancreas significantly down-regulated with the increase of dietary AST levels. In conclusion, dietary 24.2 and 45.8 mg kg−1 astaxanthin significantly promoted the lipid accumulation of hepatopancreas and im-proved the antioxidant and immune capacity of hemolymph.

An 8-week feeding trial was conducted to evaluate the effects of replacing fish meal with spray-dried egg meal (SEM) on growth performance, anti-oxidative capacity, mTOR pathway, and cholesterol metabolism in juvenile Portunus trituberculatus. The results showed that the highest percent weight gain was observed in crabs fed diet with 10% replacement of fish meal with SEM. Essential amino acids in the muscle and hepatopancreas significantly decreased with the increase of dietary replacement levels of fish meal with SEM. The lowest content of MDA in hepatopancreas was occurred at those fed diet with 40% replacement of fish meal with SEM, the activities of T-AOC, GSH-PX and content of GSH in hepatopancreas significantly increased with dietary SEM replacement fish meal increasing from 10% to 50%. The expression of akt, eif4e1a, eif4e2, eif4e3, and 4ebp1 significantly up-regulated, however, the expression of tor was showed significantly linear down-regulated, and the highest expression of akt, eif4e2 and 4ebp1 were found in crabs fed diet with 20% replacement of fish meal with SEM, the highest expression of eif4e1a was observed in those fed diet with 10% replacement of fish meal with SEM, the highest expression of eif4e3 was occurred in crabs fed diet with 30% replacement of fish meal with SEM. In cholesterol metabolism, the expression of abcg1 and lrp2 significantly down-regulated and the expression of npc1 significantly up-regulated with increase of replacement level of fish meal with SEM. The content of T-CHO in hemolymph and hepatopancreas significantly linear increased. In conclusion, based on quadratic broken-line regression analysis of PWG against the dietary replacement of fish meal with SEM, the optimal replacement level of fish meal with SEM was estimated to be 15.94% for juvenile swimming crab.

The swimming crab (Portunus trituberculatus) is a valuable crustacean species extensively cultivated in China, owing to its fast development, palatability, and rich nutrition. However, the genetic factors regulating its growth remain elusive, impeding the progress of breeding initiatives for this economically important species. In this study, we combined bulk segregation analysis sequencing (BSA-seq) and transcriptome sequencing (RNA-seq) to identify potential candidate genes related to the body weight of P. trituberculatus using a full-sib family. BSA-seq successfully identified five candidate intervals on chromosomes 31, 38, and 47, spanning a total length of 9.76 Mb, which encompassed 137 annotated genes. By conducting RNA-seq analysis on swimming crab individuals in two extreme weight groups, 1581 genes were mined as differentially expressed genes (DEGs), involving 357 up-regulated and 1224 down-regulated genes. GO enrichment analysis demonstrated that DEGs were significantly enriched in proteolysis, obsolete oxidation-reduction process, nucleus, cytoplasm, molecular function, and metal ion binding. KEGG enrichment analysis showed that the proteasome signaling pathway could play a prominent role in the growth difference of P. trituberculatus. The conjunctive analyses of BSA-seq and RNA-seq led to the identification of eight critical DEGs, including peripheral plasma membrane protein CASK (CASK), cytoplasmic dynein 2 heavy chain 1 (Dyh1b), RNA-binding protein 5 (Rbm5), structural maintenance of chromosomes protein 3 (Smc3), hemicentin-2 (Hmcn1), A-kinase anchor protein 13 (Akap13), zinc finger MYM-type protein 2 (Zmym3), and extracellular matrix protein FRAS1 (Fras1), which exert influence over the growth of P. trituberculatus. This study not only enhances our understanding of the molecular mechanism governing the growth of P. trituberculatus but also provides valuable insights for future aquaculture programs aimed at selective breeding of this species.

The Sry-related HMG-box (Sox) family is a group of transcriptional regulators that play a critical role in many important developmental processes in both vertebrates and invertebrates. In aquatic animals, the function of Sox genes on sexual development has attracted particular attention. The present study reported on the molecular characterization of a Sox member (PtSoxE) in the swimming crab, Portunus trituberculatus, and tissue distribution analysis showed it was male-specific. Since the highest expression of PtSoxE was found in the androgenic gland (AG), its relation to the insulin-like androgenic gland hormone (IAG) was further investigated. The PtSoxE siRNA caused a significant decrease in IAG expression in both AG and testis, whereas PtSoxE expression could be induced by treating with AG homogenate and rIAG. The result suggested a transcriptional interaction between PtSoxE and IAG. In addition, PtSoxE expression showed a closely positive correlation with several reported spermatogenesis-related genes, suggesting its involvement in the testicular development of P. trituberculatus. [ABSTRACT FROM AUTHOR]

Simple Summary: Animal behavior management is an important function of marine ranches, including the personality and the territoriality of animals, with relevant studies having important applications in marine ranch construction. To explore the relationship between the personality and territoriality of swimming crabs, we quantified their boldness and exploration using a behavior observation system. The behavior of crabs with different personalities was measured in a series of environments. The results showed that there was no boldness-exploratory behavioral syndrome in swimming crabs. Territorial behavior was positively correlated with boldness but not with exploration. The difference in boldness determines the behavior response of crabs in a dangerous environment, while exploration difference affects the behavior in habitat selection. Boldness and exploratory behavior explain the difference in the space utilization ability of swimming crabs with different personalities. The boldness and exploration of animals are closely related to their territoriality, with relevant studies having important applications in wildlife conservation. The present study establishes a behavior observation system measuring the boldness and exploration of swimming crabs (Portunus trituberculatus) to clarify the relationship between boldness, exploration, and territoriality, as well as to provide a behavioral basis for the construction of marine ranching. The behavioral tests of crabs in a safe environment (predator absence), a dangerous environment (predator presence), and habitat selection (complex and simple habitat) are analyzed. A territorial behavior score is calculated as an evaluation index of territoriality. The correlation between the swimming crabs' boldness, exploration, and territoriality is analyzed. The results show that there is no boldness-exploratory behavioral syndrome. In predator absence or presence environments, boldness is dominant in territorial behavior and positively correlates with territoriality. Exploration plays a vital role in habitat selection tests but has no significant correlation with territoriality. The experimental results preliminarily show that boldness and exploration jointly develop the difference in the space utilization ability of crabs with different personalities, improving the adaptability of swimming crabs in different conditions. The results of this study supplement the behavior rules of the dominant species of typical fishery resources in marine ranches, providing a basis for achieving animal behavior management function in marine ranches. [ABSTRACT FROM AUTHOR]

Salinity is a significant environmental factor that can affect the survival, metamorphosis, growth and feeding of Portunus trituberculatus. In order to analyze the key physiological characteristics of P. trituberculatus in response to short-term low salinity stress, the experiments of gradually decline and recovery as well as abrupt decline in salinity were carried out. The results showed that P. trituberculatus could survive in a certain low salinity range in the short term, and salinity 12 was the lowest tolerable salinity under the present experimental conditions. The change of the hemolymph osmotic pressure displayed significant positive correlations with water salinity, and the pressure was always higher than seawater osmotic pressure. Short-term low salinity stress changed the structure and morphology of gill tissue. The expansion of gill filament ends and epithelial cell shedding were conducive to osmotic adjustment. The activities of key ion transport enzymes such as Na+-K+-ATPase, carbonic anhydrase and V-ATPase also changed with the osmotic regulation, while Na+-K+-ATPase played a dominant role. In summary, as an osmotic adjustment species, P. trituberculatus rapidly adapt to the short-term low-salinity environment by osmotic adjustment in vivo, but salinity below salinity 12 is not conducive to its survival. Our result enriched the theoretical mechanism of osmotic regulation of P. trituberculatus, providing reference for the development of aquaculture technology of P. trituberculatus. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Hydrobiology is the property of Editorial Department of Journal of Hydrobiology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cholesterol, as an indispensable nutrient, regulates molting and growth in crustacean. As crustaceans are unable to biosynthesize cholesterol de novo, it is central to understand how dietary cholesterol affects molting in crustaceans. An 8-week feeding trial was conducted to evaluate the effects of dietary cholesterol level (0.12%, 0.43%, 0.79%, 1.00%, 1.30% and 2.50%) on growth, cholesterol metabolism and expression of genes related to lipid and ecdysone metabolism in female swimming crabs (Portunus trituberculatus). A total of 192 crabs (1.41 ± 0.05 g) were randomly distributed into 192 aquaria. Each treatment had 4 replicates with each replicate containing 8 crabs. Crabs fed the 1.00% cholesterol diet showed best growth performance, and thus based on percent weight gain, the optimal dietary cholesterol requirement was calculated at 1.01%. Tissue cholesterol concentrations were positively correlated with dietary cholesterol level. The contents of functional fatty acids in hepatopancreas significantly increased as dietary cholesterol increased from 0.12% to 2.50% (P

Nitrite is a common pollutant encountered in aquaculture systems. During intensive hatchery, accumulation of nitrite can cause massive mortality of juvenile crustaceans. However, the nitrite toxicity and cellular stress responses in juvenile crustaceans is not clearly understood. Here, we investigate the survival, energy metabolism, and cellular stress responses in juvenile P. trituberculatus, an important aquaculture species in China, under acute nitrite stress. The results revealed nitrite resulted in a significant decrease in survival rate of juvenile swimming crab. After nitrite exposure, the activity of catabolic enzymes, such as HK, PK, CS, and CPT-1, were initially enhanced, and then they showed significant decrease at the late stage of exposure, accompanied by reduction in ATP and adenylate energy charge (AEC). The impaired energy homeostasis was possibly associated with disturbed AMPK signaling and enhanced anaerobic metabolism, which was indicated by the high levels of LDH activity and HIF-1α expression. Furthermore, we found that nitrite stress can depress antioxidant systems and unfold protein responses, causing oxidative damage and endoplasmic reticulum (ER) stress, and this, in turn, can trigger autophagy and apoptosis through both caspase-dependent and caspase-independent pathways. The results of the present study improve our understanding regarding adverse effects of nitrite on P. trituberculatus and provide valuable information for hatchery management. [ABSTRACT FROM AUTHOR]

Portunus trituberculatus is a very important marine economic species, and its aquaculture industry has been developing rapidly. However, the phenomenon of marine wild capture of P. trituberculatus and germplasm degradation has become increasingly serious. It is necessary to develop the artificial farming industry and carry out germplasm resource protection, for which sperm cryopreservation technology is an effective method. This research compared three methods (mesh-rubbing, trypsin digestion, and mechanical grinding) for acquiring free sperm, and the best method was mesh-rubbing. Then, the optimal cryopreservation conditions were selected, and the optimal formulation was sterile calcium-free artificial seawater, the optimal cryoprotectant was 20% glycerol, and the best equilibrium time was 15 min at 4 °C. The optimal cooling program was suspending the straws at 3.5 cm on the liquid nitrogen surface for 5 min and then storing them in liquid nitrogen. Finally, the sperm were thawed at 42 °C. However, the expression of sperm-related genes and the total enzymatic activities of frozen sperm were significantly decreased (p < 0.05), which showed that sperm cryopreservation damaged the sperm. Our study improves the sperm cryopreservation technology and the yield of aquaculture in P. trituberculatus. Additionally, the study provides a certain technical basis for the establishment of a sperm cryopreservation library of crustaceans. [ABSTRACT FROM AUTHOR]

Simple Summary: The crustacean female sex hormone (CFSH) plays a crucial role in the development of secondary sexual characteristics in female Decapoda crustaceans, but its physiological function in males is less reported. In the present study, the CFSH of P. trituberculatus (PtCFSH) was identified, cloned and expressed in the recombinant form. The physiological functions of PtCFSH on the AG and testis were investigated using the RNAi and recombinant protein injection in a series of in vivo and in vitro experiments. It was confirmed that PtCFSH can negatively regulate the spermatogenesis and testicular development via a CFSH-IAG-testis endocrine axis. PtCFSH may also act directly on the testis, dependent or independent of IAG. The signaling system of PtCFSH involves the participation of cAMP, cGMP, and NO, which resembles the MIH signaling pathway. In summary, our results demonstrated the mode of CFSH action in P. trituberculatus. It has been shown in recent studies that the crustacean female sex hormone (CFSH) plays a crucial role in the development of secondary sexual characteristics in Decapoda crustaceans. However, research on the function of CFSH in the eyestalk-AG-testicular endocrine axis has been inadequate. We cloned and identified a homolog of CFSH, PtCFSH, in this study. RT-PCR showed that PtCFSH was mainly expressed in the eyestalk. A long-term injection of dsPtCFSH and recombinant PtCFSH (rPtCFSH) in vivo showed opposite effects on spermatogenesis-related gene expression and histological features in the testis of P. trituberculatus, and was accompanied by changes in AG morphological characteristics and PtIAG expression. In addition, the phosphorylated-MAPK levels and the expression of several IIS pathway genes in the testis was changed accordingly in two treatments, suggesting that PtCFSH may regulate the testicular development via IAG. The hypothesis was further validated by a mixed injection of both dsPtCFSH and dsPtIAG in vivo. The following in vitro studies confirmed the negatively effects of PtCFSH on AG, and revealed that the PtCFSH can also act directly on the testis. Treatment with rPtCFSH reduced the cAMP and cGMP levels as well as the nitric oxide synthetase activity. These findings provide vital clues to the mechanisms of CFSH action in both the eyestalk-AG-testis endocrinal axis and its direct effects on the testis. [ABSTRACT FROM AUTHOR]

Portunus trituberculatus, an economically important marine crab that was widely distributed along the coast of China, has been in short supply of high-quality crab seedlings in recent years. The larval development of P. trituberculatus is regulated by numerous biological processes at different biological levels, particularly regarding gene expression during the larval development process. Understanding the changes in these critical genes can help further regulate these biological processes to increase crab seedlings’ survival and improve crab quality. In this study, the molecular mechanisms of morphological and physiological changes in larval stages of P. trituberculatus were investigated using DNA microarrays. A total of 109,533 unigenes were obtained, of which 16 genes were differentially expressed during the whole development stages with evident timeliness. The enrichment analysis and comparison of differentially expressed genes (DEGs) showed three types of physiological activities, chitin development, energy metabolism, and neuroendocrine development. The physiological activities were evident in the early development of P. trituberculatus, especially at the Z4-M stage, which is crucial for the growth and development of crab larvae. These DEGs, cuticle proteins, retinol dehydrogenase (RDHs), Juvenile Hormone Epoxide Hydrolase (JHEH), and other vital genes were differentially expressed at the Z4-M stage. Moreover, the insulin-like androgenic gland (IAG), which was reported to be associated with sex differentiation, was highly expressed in the megalopa stage, indicating that the gender differentiation divide may occur at the beginning of this stage. Overall, this research provides a theoretical basis for the development of the swimming crab larvae, which could contribute to the artificial growing seedlings technology of P. trituberculatus.

Vibrio parahaemolyticus is one of the main pathogenic bacteria of Portunus trituberculatus and causes mass mortality of P. trituberculatus in aquaculture. In addition, low-salinity stimulation makes P. trituberculatus more susceptible to V. parahaemolyticus infections. In order to elucidate the molecular mechanism of resistance to V. parahaemolyticus in P. trituberculatus, comparative transcriptomic analysis of blood cells stimulated by low salinity and V. parahaemolyticus was carried out in this study. Transcriptome sequencing of low-salinity stress and pathogen infection at different time points was completed using Illumina sequencing technology. A total of 5827, 6432, 5362 and 1784 differentially expressed genes (DEGs) involved in pathways related to ion transport and immunoregulation were found under low-salinity stress at 12, 24, 48 and 72 h compared with the control at 0 h. In contrast, 4854, 4814, 5535 and 6051 DEGs, which were significantly enriched in Toll and IMD signaling pathways, were found at 12, 24, 48 and 72 h compared with the control at 0 h under V. parahaemolyticus infection. Among them, 952 DEGs were shared in the two treatment groups, which were mainly involved in apoptosis and Hippo signaling pathway. Cluster analysis screened 103 genes that were differentially expressed in two factors that were negatively correlated, including immunoglobulin, leukocyte receptor cluster family, scavenger receptor, macroglobulin and other innate-immune-related genes. These results provide data support for the analysis of the mechanisms of immunity to V. parahaemolyticus under low-salinity stress in P. trituberculatus and help to elucidate the molecular mechanisms by which environmental factors affect immunity.

Vegetable oil (VO) is increasingly replacing fish oil (FO) in the commercial diet of crustaceans, partly due to a global shortage of FO. But little is known about how different amounts of substitution affect the health and metabolism of crustaceans. A six-week feeding trial was conducted to evaluated the effects of different replacement levels of FO with linseed oil (LO) on growth performance, antioxidant and digestive capacity and fatty acid metabolism in swimming crab, Portunus trituberculatus. Five isonitrogenous and isolipidic diets (480 g kg−1 protein and 120 g kg−1 lipid) were formulated to contain graded levels of LO, and FO was replaced with LO at 0%, 25%, 50%, 75% and 100%, respectively. The results showed that 50% of FO could be replaced by LO without affecting the growth performance and feed utilization for juvenile swimming crab. In hemolymph, 100% dietary replacement of FO with LO, the activities of alanine aminotransferase (ALT) and aspartate transaminase (AST) exhibited significantly higher than those fed the other diets, the concentrations of triacylglycerol (TAG), total cholesterol (T-CHO) and high-density lipoprotein cholesterol (HDL-C) significantly increased with increase of dietary replacement of FO with LO, which may lead to hyperlipidemia in swimming crabs. The number of R cells and their lipid droplets in hepatopancreas gradually increased with increase of replacement of FO with LO, the results confirmed the occurrence of lipid accumulation in the hepatopancreas. The activities of glutathione (GSH), and glutathione peroxidase (GPX) in hepatopancreas significantly decreased with increase of replacement of FO with LO, and crabs fed diet with 50% replacement of FO with LO had higher activities of trypsin and lipase (LPS) than those fed the other diets. Long-chain polyunsaturated fatty acids (LC-PUFA), n-3/n-6 PUFA in hepatopancreas and muscle significantly decreased with the increase of substitution level of FO with LO. Moreover, the expression of genes related to LC-PUFA synthesis as well as fatty acid β-oxidation, such as elongase 4 (elovl4), hepatocyte nuclear factor 4-α (hnf4α), retinoid X receptor (rxr), carnitine palmitoyltransferase 2 (cpt2) and acyl-CoA oxidase (acox2), were down-regulated with increase of dietary replacement of FO with LO. In conclusion, it is suggested that the optimal substitution ratio of LO for FO should be less than 50% in the diet of Portunus trituberculatus.

Florfenicol (FLR), a broad-spectrum antibacterial agent, is commonly used in the breeding and cultivation of aquatic animals. microRNAs (miRNAs) control gene expression by mediating post-transcriptional mRNA repression. However, not much has been reported regarding their functions when crustaceans encounter FLR stress. Herein we observed histological alterations and performed small RNA sequencing to characterize differentially expressed miRNAs in the hepatopancreas of Portunus trituberculatus exposed to FLR (80 mg/kg) stress for 3 h and 12 h. Our results indicated irregularities in the tubular structure of hepatopancreas, separation between epithelium and myoepithelial layer, ruptured epithelial cells, and tubule degeneration. Thirty-five (19 up- and 16 downregulated) and 31 (17 up- and 14 downregulated) differentially expressed miRNAs were detected between Group-C and Group-FLR-3 h and between Group-C and Group-FLR-12 h, respectively. Dual luciferase reporter assay was performed for predicting target genes of miR-34 and miR-263b. We found that mir-263b directly inhibited cytochrome C expression at the cell level in vitro. Functional analyses of predicted target genes of differentially expressed miRNAs revealed that FLR stress induced xenobiotic metabolism, immune toxicity, and cell apoptosis, as well as influenced diverse metabolic processes. To our knowledge, this is the first report on the response of P. trituberculatus to FLR stress. Our findings provide evidence that miRNAs participate in cell apoptosis and immune regulation in crabs.

Insulin-like peptides (ILPs) are essential to the animal kingdom for regulating growth and development, reproduction, behavior, metabolism, and lifespan. In crustaceans, the most well-known ILP is insulin-like androgenic gland hormone, a key hormone in regulating sex differentiation and reproduction. Identification of other ILPs and their functions are still limited. In this study, an insulin-like peptide gene of the swimming crab Portunus trituberculatus was cloned and characterized. Its transcripts were mainly found in nerve tissues and expression could be induced by glucose, implying a putative role in glucoregulation. After depletion of endogenous ILP, injection of ILP dsRNA (dsILP) significantly elevated blood glucose levels and recombinant ILP (rILP) decreased hemolymph glucose levels, further clarifying the involvement of acquired ILP in hemolymph glucose regulation. Injection of dsILP decreased PtAkt, PtGS, PtPFK and increased PtGSK and PtPEPCK gene expression. The opposite profile was observed after glucose and rILP injection, indicating that PtILP might negatively regulate hemolymph glucose levels via the IIS (insulin/IGF-1 signaling) pathway by inhibiting gluconeogenesis and promoting glycogen synthesis and glycolysis. This study has refined the mechanism of glucose regulation in crustaceans and laid the foundation for further studies on ILP function.

Spätzle is a crucial ligand for Toll-like receptor (TLR) that triggers the activation of TLR signal pathway in insects. In this study, open reading frames (ORFs) of two spätzles were cloned from Portunus trituberculatus (PtSpz1 and PtSpz2). Both of PtSpzs contained the typical cystine-knot domain of spätzle. Tissue distribution analysis showed that both of PtSpzs were predominantly expressed in the gills. Transcriptional levels of the two PtSpzs in hemocytes and gill rapidly increased at 3 h and 6 h post Vibrio alginolyticus challenge, respectively. The two PtSpzs could bind to several pathogen-associated molecules including lipopolysaccharide (LPS), peptidoglycan (PGN) and envelope proteins of white spot syndrome virus (WSSV). Moreover, the two PtSpzs could directly interact with the extracellular leucine-rich repeats (LRR) domain of TLR. This study revealed that spätzle could interact with pathogen-associated molecules and TLR of host, which may be two important steps for spätzle to deliver signals into host cells. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Hydrobiology is the property of Editorial Department of Journal of Hydrobiology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ficolins, belonging to the fibrinogen-related protein superfamily, are important pattern recognition receptors in innate immunity. Here, a ficolin gene Ptficolin was characterized from the swimming crab Portunus trituberculatus. The completed cDNA sequence of Ptficolin encoded a signal peptide, a coiled-coil region and a fibrinogen-like domain but without the typical collagen region of vertebrate ficolins. Ptficolin showed higher expression in stomach and hepatopancreas, and presented a time-dependent response after pathogen challenge and injury stimulation. The recombinant Ptficolin (rPtficolin) could bind to various PAMPs and microorganisms, and agglutinate microorganisms and rabbit erythrocytes in a Ca2+-dependent manner, with strong binding ability to N -acetyl sugars. Meanwhile, rPtficolin promoted the hemocyte phagocytosis and clearance activity of Vibrio , while Ptficolin knockdown impaired the bacterial phagocytosis and clearance ability, suggesting the opsonin activity of Ptficolin. Knockdown of Ptficolin could downregulate the transcription of most complement-like genes and AMPs, but enhance the expression of most proPO system-related genes and key genes of Toll, IMD and JNK pathways. Moreover, knockdown of Ptficolin led to the increased hemolymph clotting time and the decreased expression of clotting-related genes. Our results indicate that Ptficolin could recognize and eliminate invading pathogens, and might be a prominent component in hemolymph coagulation of crab. • Ptficolin was a novel ficolin isolated from Portunus trituberculatus. • Ptficolin exhibited strong binding, agglutinating and antibacterial activity. • Ptficolin showed opsonic activity that promote phagocytosis and bacterial clearance. • Knockdown of Ptficolin downregulated the expression of complement-like genes, AMPs and clotting-related genes. • Ptficolin might be a prominent component in hemolymph coagulation of crab. [ABSTRACT FROM AUTHOR]

To investigate the effect of steaming time (0, 5, 10, 15, 20, and 25 min) on the protein degradation and non-volatile flavor substances of swimming crab (Portunus trituberculatus), the moisture content, total nitrogen (TN), non-protein nitrogen (NPN), free amino acids (FAAs), flavor nucleotides, electronic tongue analysis, and sensory evaluation were determined. The results showed that the contents of NPN and total FAAs were the highest after crabs steamed for 10 min. Meanwhile, the AMP (adenosine monophosphate) content reached the maximum value (332.83 mg/100 g) and the taste active value (TAV) reached 6.67, which indicated that AMP contributes the most to the taste of steamed crab at 10 min. The electronic tongue distinguished the taste difference well, and the sensory score was the highest at 15 min. Combined with equivalent umami concentration (EUC) and TAV value, swimming crab (weight = 200 ± 20 g) steamed for 10–15 min tasted best. [ABSTRACT FROM AUTHOR]

Lauric acid (LA), a saturated fatty acid with 12 carbon atoms, is widely regarded as a healthy fatty acid that plays an important role in disease resistance and improving immune physiological function. The objective of this study was to determine the effects of dietary lauric acid on the growth performance, antioxidant capacity, non-specific immunity and intestinal microbiology, and evaluate the potential of lauric acids an environmentally friendly additive in swimming crab (Portunus trituberculatus) culture. A total of 192 swimming crabs with an initial body weight of 11.68 ± 0.02 g were fed six different dietary lauric acid levels, the analytical values of lauric acid were 0.09, 0.44, 0.80, 1.00, 1.53, 2.91 mg/g, respectively. There were four replicates per treatment and 8 juvenile swimming crabs per replicate. The results indicated that final weight, percent weight gain, specific growth rate, survival and feed intake were not significantly affected by dietary lauric acid levels; however, crabs fed diets with 0.80 and 1.00 mg/g lauric acid showed the lowest feed efficiency among all treatments. Proximate composition in hepatopancreas and muscle were not significantly affected by dietary lauric acid levels. The highest activities of amylase and lipase in hepatopancreas and intestine were found at crabs fed diet with 0.80 mg/g lauric acid (P < 0.05), the activity of carnitine palmityl transferase (CPT) in hepatopancreas and intestine significantly decreased with dietary lauric acid levels increasing from 0.09 to 2.91 mg/g (P < 0.05). The lowest concentration of glucose and total protein and the activity of alkaline phosphatase in hemolymph were observed at crabs fed diets with 0.80 and 1.00 mg/g lauric acid among all treatments. The activity of GSH-Px in hepatopancreas significantly increased with dietary lauric acid increasing from 0.09 to 1.53 mg/g, MDA in hepatopancreas and hemolymph was not significantly influenced by dietary lauric acid levels. The highest expression of cat and gpx in hepatopancreas were exhibited in crabs fed diet with 1.00 mg/g lauric acid, however, the expression of genes related to the inflammatory signaling pathway (relish , myd88 , traf6, nf-κB) were up-regulated in the hepatopancreas with dietary lauric acid levels increasing from 0.09 to 1.00 mg/g, moreover, the expression of genes related to intestinal inflammatory, immune and antioxidant were significantly affected by dietary lauric acid levels (P < 0.05). Crabs fed diet without lauric acid supplementation exhibited higher lipid drop area in hepatopancreas than those fed the other diets (P < 0.05). The expression of genes related to lipid catabolism was up-regulated, however, and the expression of genes related to lipid synthesis was down-regulated in the hepatopancreas of crabs fed with 0.80 mg/g lauric acid. Lauric acid improved hepatic tubular integrity, and enhanced intestinal barrier function by increasing peritrophic membrane (PM) thickness and upregulating the expression of structural factors (per44 , zo-1) and intestinal immunity-related genes. In addition, dietary 1.00 mg/g lauric acid significantly improved the microbiota composition of the intestinal, increased the abundance of Actinobacteria and Rhodobacteraceae, and decreased the abundance of Vibrio, thus maintaining the microbiota balance of the intestine. The correlation analysis showed that there was a relationship between intestinal microbiota and immune-antioxidant function. In conclusion, the dietary 1.00 mg/g lauric acid is beneficial to improve the antioxidant capacity and intestinal health of swimming crab. • Lauric acid can improve the antioxidant capacity and up-regulate the expression of anti-inflammatory factors. • Lauric acid increased the thickness of peritrophic membrane in the gut of swimming crab. • Lauric acid reduced the abundance of vibrio in the intestine. • Excessive amounts of lauric acid can lead to tissue damage and metabolic disorders. [ABSTRACT FROM AUTHOR]

The swimming crab Portunus trituberculatus is one of the most important economic species in China and its mature ovary often determines its commercial value and production. Although the ovary maturation of crustaceans is generally affected by exogenous nutrition, the specific nutritional needs of ovary maturation of P. trituberculatus are poorly understood. To this end, we collected the P. trituberculatus samples with five ovarian maturation stages and measured their biochemical composition of the ovary, hepatopancreas, and muscle at each ovarian developmental stage. We further analyzed their relation to the ovarian developmental stage of P. trituberculatus by principal components analysis (PCA). We found the levels of branched-chain amino acids, long-chain polyunsaturated fatty acids (LC-PUFA), and monounsaturated fatty acids (MUFAs) in the ovary and hepatopancreas increased during the ovary maturation process, and also passively correlated with ovarian developmental stage, which highlights the necessity of these specific nutrients for oogenesis and for improving the nutrient quality of crabs. In addition, we found an increasing tendency of carotenoid content and phosphatidylcholine in phospholipid in the ovary from the pre-developmental stage to the proliferative stage, but not in the hepatopancreas and muscle, which highlights the possible involvement of carotenoids during the rapid oocyte development process. Our study may provide valuable information for developing a suitable broodstock diet that promotes the ovarian maturation of adult P. trituberculatus and ensures high-quality larval production.