Differences in stable isotope ratios of Dall’s porpoises (Phocoenoides dalli) between coastal and oceanic areas of the North Pacific

Carbon and nitrogen stable isotope ratios in the muscle of Dall’s porpoises were measured. Samples were collected from the catches of the hand harpoon fishery, incidental catches of drift net, and scientific research on the use of drift nets. Samples were from the North Pacific, Sea of Japan, Sea of Okhotsk, and Bering Sea. Although no variation in δ¹⁵N was observed, δ¹³C was significantly different between population groups near Japan and the oceanic North Pacific and Bering Sea. The difference may be due not only to local variation in prey species, but also to an overall difference in carbon stable isotope ratios that originate from coastal benthic or oceanic pelagic‐based food webs. We differentiated Dall’s porpoise population groups from both areas using carbon stable isotope ratios with an error rate of <5%. Although further study is needed, our results suggest that carbon stable isotope ratios could possibly be an indicator of whether a Dall’s porpoise belongs to a coastal benthic or oceanic pelagic food web.     

Trophic overlap between non‐native brown bullhead (Ameiurus nebulosus) and native shortfin eel (Anguilla australis) in shallow lakes

We quantified trophic overlap between the invasive, non‐native catfish brown bullhead (Ameiurus nebulosus) and the New Zealand native shortfin eel (Anguilla australis) in four peat and riverine lakes using stable isotope (δ¹³C and δ¹⁵N) and gut content analyses. Across all lakes and fish sizes over the austral spring–summer period, shortfin eel guts were dominated numerically by fish prey (57% occurrence cf 42% in brown bullhead), while Diptera larvae were most commonly encountered in guts of brown bullhead (45% cf 14% in eels). Significant differences in % composition of animal contents in guts were detected between fish species and sampling occasions (n = 4) but not between lakes. In contrast, stable isotope signatures of brown bullhead and shortfin eel did differ significantly between lakes but not between sampling occasions, indicating enduring sources of nutrition despite apparently differing ingestion patterns over time. The R mixing model MixSIAR indicated that shortfins likely assimilated higher proportions of fish prey carbon compared to brown bullheads, which appeared to show greater assimilation of invertebrates, consistent with the results of gut content analyses. Isotopic niche regions, calculated in nicheROVER using probabilistic ellipses, indicated that shortfin eels occupied at least c.60% of brown bullhead trophic niche, which occupied less than 30% of eel trophic niche in all but one lake. These estimates suggest that brown bullhead has higher potential to influence shortfin eel nutrition than vice versa, or that a broad trophic niche occupied by eels provides resilience to the effects of overlapping consumption patterns with invasive omnivores.     

Transference of heavy metals (Hg,Cu, Pb and Zn) with the trophic structure in a polyculture pond: evidence from nitrogen stable isotope

Concentrations of heavy metals, including Hg, Cu, Pb and Zn, in sediment and different organisms as well as the transference through the food web in a polyculture pond were investigated. The δ¹⁵N values of consumers showed a gradual enrichment with increasing trophic positions from the filter‐feeding bivalves (δ¹⁵N = 10.93 on average) to the predators (δ¹⁵N ≥ 12.59 for all crustacean and fish). Concentrations of heavy metals in sediments followed the decreasing order: Cu ≈ Zn > Pb > Hg, while in organisms, the order was Zn > Cu > Pb > Hg. Concentration of Cu was negatively related to the δ¹⁵N values of the animal tissues (P < 0.05), indicating the decrease in the Cu concentration with increasing trophic positions. Concentrations of Hg, Pb or Zn did not show significant relationship to the trophic positions. Food sources and feeding guilds of organisms might be more important factors determining the heavy metal concentrations in the body tissues of aquatic animals than their trophic positions.     

Stable isotope variations in otoliths of Pacific halibut (Hippoglossus stenolepis) and indications of the possible 1990 regime shift

Stable oxygen and carbon isotope ratios (δ¹⁸O and δ¹³C) from archived otoliths of Pacific halibut, Hippoglossus stenolepis, were measured to examine the most recent regime shifts in British Columbia and the Gulf of Alaska. δ¹⁸O values of these otoliths ranged from −1.5 to +2.8‰ VPDB, and were consistent with the life stages and migration behavior of halibut. δ¹³C varied from −3.3 to +0.9‰ VPDB, but did not show a transition from the juvenile to the adult stage as does δ¹⁸O. Evaluation of δ¹⁸O and δ¹³C values of mature halibut (ages 8–12) indicated that the 1977 regime shift might have a warming impact on the northeast Pacific fish stocks. In contrast, a possible regime shift around 1990 with a bottom seawater temperature decrease of about 2 °C might have occurred in both the areas. The connection between stable isotope variations in otoliths and the climate regime shifts is thus potentially useful in studying the population dynamics of Pacific halibut, and decadal scale (e.g., the last 20–30 years) ocean environmental changes.     

Intra‐annual changes in reproductive indices of male and female Himalayan snow trout,Schizothorax richardsonii (Gray, 1832)

Periodic changes in reproductive hormone levels, gonadal histology and gonadosomatic index (GSI) of snow trout, Schizothorax richardsonii, were examined to ascertain annual cycle of gonadal development and reproductive status in their natural habitat. In females, there were coherent changes in plasma 17β‐oestradiol and vitellogenin along with GSI, oocyte maturation and vitellogenic progression, collectively indicating two distinct maturation peaks during the months of September and February. Coinciding with this, in males, plasma 11‐keto testosterone was also noticeably higher during September and February, with highest GSI values in September. However, plasma 17α, 20β‐dihydroxyprogesterone levels in males were found to be persistently high from September to February. This observation suggests the potential presence of matured oozing males over a longer period, unlike in females. Overall, the close association between reproductive hormone levels, GSI and gonadal maturation stages in males and females (particularly, the presence of postovulatory follicle complexes) with apparent natural synchronization clearly indicates that S. richardsonii breeds twice in a year, possibly during late September to early November and late February to early April in the coldwater riverine habitats of the Indian Himalayan region.     

Influence of different dietary lipid sources on the growth,tissue fatty acid composition,histological changes and peroxisome proliferator‐activated receptor γ gene expression in large yellow croaker (Pseudosciaena crocea R.)

A 9‐week feeding trial was conducted to investigate the impact of dietary lipid sources on the lipid mechanisms of large yellow croaker by feeding three isonitrogenous and isoenergetic diets containing fish oil (FO), soybean oil (SO) and beef tallow (BT) respectively. The effects of the diets on the growth performance, somatic indices, tissue fatty acid composition, histological changes and peroxisome proliferator‐activated receptor (PPAR)γ expression were evaluated. Experimental diets were all well accepted by fish and no significant (P>0.05) differences were found in the weight gain, growth rate and feed conversion rate. The fatty acid profile of the fish fillet and liver reflected the fatty acid composition of the diets. Specific‐fatty acids were selectively retained, however, in the flesh of the fish; in particular, docosahexaenoic acid and arachidonic acid concentrations were higher than the dietary concentrations. When FO was replaced by SO or BT diets, the reduction in eicosapontaenoic acid in fish tissue was more pronounced, suggesting a preferred utilization of this fatty acid. The consumption of SO displayed intense lipid accumulation in the liver of the fish. The expression of PPARγ increased significantly in the SO group compared with the FO and BT groups (P<0.05).     

Comparative analysis of the predominant carotenoids and chemical components in the common and orange‐muscle mutant of Haliotis gigantea

The Xishi abalone (Haliotis gigantea) is an economically significant aquaculture species in southern China. We identified a novel orange‐muscle mutation present in less than 2% of the cultured population. High‐performance liquid chromatography and electrospray ionization mass spectrometry identified zeaxanthin and β‐carotene as the two main pigments present in the orange‐muscle abalone. The concentrations of zeaxanthin and β‐carotene detected in the orange‐muscle abalones were significantly higher than those detected in the common abalones (p < 0.01). Notably, the concentration of zeaxanthin was approximately 16.5 times higher in orange‐muscle abalones than in common abalones, which was also the species with highest carotenoid content reported in shellfish to date. Furthermore, the contents of total amino acids and essential amino acids in the orange‐muscle abalone were higher than that in the common abalone, though not significantly, while the content of non‐essential amino acids was significantly higher in the orange‐muscle abalone than that in the common abalone (p < 0.05). The saturated fatty acid content in the orange‐muscle abalones was slightly lower than that in the common abalones, and the unsaturated fatty acid content was higher in the orange‐muscle abalones than that in the common abalones. These results could provide a basis for characterizing the mechanism by which carotenoids accumulate in abalones and further guide the breeding of abalone with orange‐muscle mutants in the future.     

Population differentiation and temporal changes of carotenoid pigments and stable isotope ratios in the offspring of anadromous and non‐anadromous trout Salmo trutta

Trout (Salmo trutta) exhibit anadromous and non‐anadromous forms which are commonly sympatric. Offspring of the two forms can be separated by differences in characteristics such as stable isotope ratios and carotenoid pigments, which differ due to the influence of maternal resources. The rate of change in different characteristics due to freshwater feeding and the extent of differences between populations however remain unclear. Stable isotope (N and C) ratios and carotenoid pigment profiles were examined in the offspring of anadromous and non‐anadromous fish sampled at different times from six sites within the catchment of the River Tweed, UK. Both techniques were able to separate newly emerged fry successfully, with carbon isotopes distinguishing the forms better than nitrogen isotopes and zeaxanthin being the primary carotenoid pigment used to distinguish the offspring of different migratory forms. By 4 months, stable isotope ratios of the two forms were still distinct although both carbon and nitrogen ratios needed to be considered to distinguish the forms. Zeaxanthin levels were more variable and overlapped between the offspring of the two forms. There was significant variation between populations and over time in both isotope ratios and carotenoid composition. Comparison between the two techniques would suggest that stable isotopes are more effective for distinguishing between offspring of different forms as the distinctions are evident for longer. Population differences in isotope ratios could influence the extent to which the forms can be distinguished and need to be quantified more thoroughly to fully evaluate the technique.     

Dietary α‐linolenic acid affects lipid metabolism and tissue fatty acid profile and induces apoptosis in intraperitoneal adipose tissue of juvenile grass carp (Ctenopharyngodon idella)

A 56‐day feeding trial was conducted to elucidate the effects and mechanism action of dietary α‐linolenic acid (ALA, 18:3n‐3) on lipid accumulation and fatty acid profile of muscle, hepatopancreas and intraperitoneal fat (IPF) in juvenile grass carp using three isonitrogenous and isoenergetic semi‐purified diets containing 0.0% (control group), 1.0% and 2.0% ALA, respectively. The lowest intraperitoneal fat (IPF) ratio was found in 2.0% group. In the muscle, hepatopancreas and IPF, docosahexaenoic acid (DHA, 22:6n‐3) and eicosapentaenoic acid (EPA, 20:5n‐3) contents increased with the increase in dietary ALA. In the IPF, caspase 3, caspase 8 and caspase 9 showed the highest activities in 2.0% group, while the value of Bcl‐2/Bax (B‐cell leukaemia 2/Bcl‐2‐associated X protein) reached the lowest. Meanwhile, swelling of the IPF mitochondria was observed in 2.0% group. The gene expressions of fatty acid desaturase (FAD) and fatty acid elongase (ELO) in the hepatopancreas and muscle showed significantly higher levels in the treatment groups, whereas an opposite trend was existed in the IPF. Fatty acid synthase (FAS), sterol regulatory element binding protein‐1c (SREBP‐1c) in the IPF and hepatopancreas reached the lowest in 2.0% group. Overall, dietary ALA could promote n‐3 highly unsaturated fatty acids (HUFAs) synthesis and suppress the accumulation of lipid by decreasing the expression of related genes and promoting the apoptosis in IPF.     

Effect of dietary essential fatty acids on level of oestradiol‐17β and vitellogenin,reproductive performance and larval quality of striped catfish (Pangasianodon hypophthalmus) in out‐of‐spawning season

A study was conducted to determine the effect of essential fatty acid in striped catfish (Pangasianodon hypophthalmus) broodstock diets on a level of oestradiol‐17β and vitellogenin, reproductive performance and larval quality in out‐of‐spawning season. Five female and five male broodstock were stocked into a net cage (3 × 5 × 1.5 m³) and fed with pelleted diets containing 1.5% fish oil and different amounts of corn oil (CO) in diet formulation, that is 0%, 1%, 2% and 3% respectively. Gonadal development, oestradiol‐17ß and vitellogenin concentrations were examined every 2 weeks. Oestradiol‐17ß and vitellogenin concentrations showed an increase during the maturation process. The significantly highest percentage of female mature, fecundity, hatching rate, larval production and larval survival rate were obtained from fish fed with 2% corn oil in the diet. This result revealed that the administration of 2% corn oil in the diet as a source of n‐6 (linoleic acid) and 1.5% fish oil as a source of n‐3 (linolenic acid) can improve the reproductive performance of striped catfish broodstock in out‐of‐spawning season.     

Comparative effect of Freund's adjuvant and Aloe vera L. gel on the expression of TNF‐α and IL‐1β in vaccinated Cyprinus carpio L. with Aeromonas hydrophila C. bacterin

The comparative effects of Freund's and Aloe vera gel as adjuvants on the expression of IL‐1β and TNF‐α genes were studied in vaccinated common carp (Cyprinus carpio) with Aeromonas hydrophila bacterin. Fishes were intraperitoneally immunized with A. hydrophila bacterin in combination with Aloe vera gel or Freund's and also without any adjuvant. At day 28 after immunization, all groups were challenged by lethal dose of A. hydrophila (10⁷ cells/fish). Changes in the expression of IL‐1β and TNF‐α genes were evaluated in anterior kidney before challenge and 12, 24, 72 and 7 days postchallenge using quantitative real‐time PCR. Higher expression levels of both genes were observed in all vaccinated groups compared with non‐immunized group. Fishes which received Aloe vera gel showed higher expression of IL‐1β and TNF‐α in relation to animals which vaccinated with or without Freund's adjuvant. We concluded that Aloe vera gel in compared with Freund's adjuvant had a more stimulatory effect on the expression of immune‐related genes in vaccinated common carp and it can use as a novel adjuvant in aquaculture.     

Enhancement of the innate immune system and disease‐resistant activity in Cyprinus carpio by oral administration of β‐glucan and whole cell yeast

The effects of dietary β‐ (1,3) glucan and whole cell yeast (Sacharomyces uvarum) on the immune response and disease resistance to Aeromonas hydrophila were investigated in Cyprinus carpio. β‐(1,3) glucan was extracted from the yeast. Both β‐(1,3) glucan and whole yeast were incorporated into the diet at 1% level and fed to common carp C. carpio for a period of 60 days. Control and treated fish were exposed to A. hydrophila on the 30th and the 60th day of the experimental period. Dietary supplementation of glucan significantly increased the white blood cell count in fish on the 60th day (2.91±0.04 × 10⁴), and the highest nuetrophil nitro blue tetrazolium (NBT) activity was also observed in glucan‐fed fish (30th day). A consistent increase in neutrophil (NBT) activity was also observed in whole cell fed fish until the end of the experiment. Similarly, β‐(1,3) glucan and whole cell yeast enhanced the serum lysozyme activity from the 15th day onwards but higher activity was reported on the 30th day in glucan and the 60th day in whole cell yeast‐fed fish. Suplementation of β‐(1,3) glucan protected the fish from A. hydrophila infection. Nearly 75–80% of the fish survived pathogen exposure (relative percentage survival). However, only 54–60% survival was observed in the whole cell‐fed fish. β‐(1,3) glucan and whole cell yeast protect the fish from pathogens by enhancing the cellular and humoral immune response in C. carpio.     

Effects of dietary β‐carotene levels on growth and liver vitamin A concentrations of the soft‐shelled turtle,Pelodiscus sinensis (Wiegmann)

A feeding trial was conducted to evaluate the effect of dietary β‐carotene level on the growth and liver vitamin A concentrations in soft‐shelled turtles, Pelodiscus sinensis, fed a vitamin A‐free diet. Soft‐shelled turtles were fed diets containing 0, 14.5, 26.5, 47.5, 87.3, 112.8 and 163.8 mg β‐carotene kg^?1 for 10 weeks. Although it was not statistically significant due to high deviation within each group, mean weight gain of soft‐shelled turtles fed the diet without β‐carotene supplementation was the lowest among all test groups. Vitamin A concentrations in liver of turtles significantly (P<0.05) increased when dietary β‐carotene level reached 47.5 mg kg^?1 indicating that soft‐shelled turtles were capable of converting β‐carotene to vitamin A. Analysed by regression modelling, dietary β‐carotene levels for optimal growth and maximal liver vitamin A contents of juvenile soft‐shelled turtles fed the vitamin A‐free diets were 49.1 and 88.7 mg kg^?1 respectively.     

Characterization of a γ‐aminobutyrate type A receptor‐associated protein gene,which is involved in the response of Portunus trituberculatus to CO2‐induced ocean acidification

The γ‐aminobutyrate type A receptor‐associated protein (GABARAP) is a ubiquitin‐like modifier implicated in membrane trafficking and fusion events involving the γ‐aminobutyrate type A receptor, autophagy and apoptosis. In this study, the gene encoding GABARAP was cloned from swimming crab Portunus trituberculatus (PtGABARAP) based on the expression sequence tag (EST). The full‐length cDNA of 664 bp includes a 5′ untranslated region (UTR) of 87 bp, a 3′ UTR of 223 bp with a poly(A) tail, and an open reading frame (ORF) of 354 bp encoding a polypeptide of 117 amino acids with a predicted molecular weight of 13.96 kDa. The deduced amino acid sequence shares high similarity (93%–100%) with GABARAPs from other species and includes a conserved Atg8 domain. In a phylogenetic analysis PtGABARAP clustered with GABARAPs from other species, and more widely with other GABARAP family proteins. The impact of elevated ocean acidification (OA) on P. trituberculatus behaviours was investigated, and real‐time RT‐PCR revealed that PtGABARAP expression was up‐regulated after OA exposure. Ocean acidification also caused crabs anxiety‐like behaviours, like the shoal average speed increase, preference for dark environment (scototaxis) and fast exploration. The results indicated that GABARAP might be involved in the interactions of GABA_A receptors and elevated‐CO₂ seawater.     

Effects of dietary α‐ketoglutarate supplementation on the antioxidant defense system and HSP 70 and HSP 90 gene expression of hybrid sturgeon Acipenser schrenckii ♀ × A. baerii ♂ exposed to ammonia‐N stress

This study was conducted to determine the effects of dietary α‐ketoglutarate (AKG) supplementation on the antioxidant defense system and gene expression of heat shock protein (HSP) 70 and HSP 90 in hybrid sturgeons Acipenser schrenckii ♀ × A. baerii ♂ exposed to ammonia‐N stress. A 2 × 3 factorial experiment was arranged, in which each diet (0%, 1% AKG) was randomly assigned to 0.25 (control) 5 and 10 mg L^?1 ammonia‐N groups with three replicate aquaria for each 72 h. The 10 mg L^?1 ammonia‐N significantly increased serum ammonia concentrations and intestinal Gln concentrations and GS activity compared with the 0.25 or 5 mg L^?1 ammonia‐N groups. The intestinal Gln concentration and GS activity increased, and the serum ammonia concentration decreased, in fish given dietary supplementation of 1.0% AKG compared with fish given diets without AKG. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity in serum, gills and intestines decreased when fish were exposed to 5 or 10 mg L^?1 ammonia‐N, and their activity increased in fish given diets with 1% AKG. Catalase in the serum and gills decreased when fish were exposed to 5 or 10 mg L^?1 ammonia‐N and increased in fish given diets with 1% AKG. The 10 mg L^?1 ammonia‐N or 1% AKG supplementation increased HSP 70 and HSP 90 gene expression in the liver. The increased activity of antioxidant enzymes, and increased HSP 70 and HSP 90 gene expression in fish fed diets containing 1% AKG suggested higher tolerance to ammonia‐N stress.     

Effects of dietary supplementation of A3α‐peptidoglycan on the growth,immune response and defence of sea cucumber Apostichopus japonicus

To determine the effects of A3α‐peptidoglycan (A3α‐PG) extracted from Bifidobacterium sp. on the growth, immune response and disease resistance of sea cucumber Apostichopus japonicus, a 70‐day feeding trial was conducted in this study. A total of 216 sea cucumbers were fed with four practical diets prepared from a commercial feed with different contents (0, 1.5, 2.5 and 4.0 g kg^?1) of A3α‐PG. The specific growth rate (SGR), total coelomocyte count (TCC), phagocytotic activity and activities of four immunological enzymes in both cell‐free coelomic fluid (extracellular, EC) and coelomocyte lysate supernatant (intracellular, IC), including acid phosphatase (ACP), alkaline phosphatase (ALP), peroxidase (POD) and superoxide dismutase (SOD), were measured at the end of the feeding trial. Finally, the animals were administered a 16‐day Vibrio splendidus challenge via intraperitoneal injection to test the potency of A3α‐PG on disease resistance. Compared with the control (0 g kg^?1 A3α‐PG), a significant increase (P < 0.05) in SGR was observed in the groups fed with 1.5 and 2.5 g kg^?1 A3a‐PG. The TCC, ranging from 7.25 × 10⁶ to 1.05 × 10⁷ cells mL^?1, was not significantly affected (P > 0.05) by A3α‐PG,. Coelomocyte phagocytotic activities in all of the A3α‐PG‐supplemented groups were significantly activated (P < 0.05), but no significant difference (P > 0.05) was observed. Sea cucumbers fed with 1.5 and 2.5 g kg^?1 A3α‐PG exhibited significant activation (P < 0.05) of EC/IC‐ACP, EC/IC‐ALP, and EC/IC‐POD activities. A significant increase in EC‐SOD activities (P < 0.05) was exhibited by all groups with A3α‐PG supplementation. The challenge test showed that animals fed with diets containing 2.5 and 4.0 g kg^?1 A3α‐PG had significantly lower cumulative mortalities compared with the control 16 days after exposure. All of the results presented here show that A3α‐PG can positively enhance the growth, immune response and disease resistance of sea cucumber, suggesting that dietary supplementation of A3α‐PG has potential applications in the health management of economic species of sea cucumber.     

Dietary soybean β‐conglycinin suppresses growth performance and inconsistently triggers apoptosis in the intestine of juvenile grass carp (Ctenopharyngodon idella) in association with ROS‐mediated MAPK signalling

The current study aimed to investigate the effects of dietary soybean β‐conglycinin on growth performance and intestine apoptosis in juvenile grass carp (Ctenopharyngodon idella). For fish fed with the 80 g β‐conglycinin/kg diet for 7 weeks, the specific growth rate and feed intake were decreased. In the proximal intestine, dietary β‐conglycinin did not induce DNA fragmentation, tended to decrease the reactive oxygen species (ROS) content, and decreased ROS‐generating enzyme (NADPH oxidase [NOX]) activity. Subsequently, in the mid‐intestine, dietary β‐conglycinin caused DNA fragmentation, tended to increase the ROS content, increased caspase‐3, caspase‐8 and caspase‐9 activities, upregulated the mRNA levels of proapoptotic molecules (apoptotic protease‐activating factor‐1 [Apaf1] and Bcl‐2‐associated X protein [BAX]) and mitogen‐activated protein kinase (MAPK)‐related signal molecules (Jun N‐terminal kinase (JNK) and p38 MAPK) and increased the protein levels of p38 MAPK and phospho‐p38 MAPK. Moreover, in the distal intestine, dietary β‐conglycinin induced DNA fragmentation, elevated NOX activity and the ROS content and increased caspase‐3, caspase‐8 and caspase‐9 activities, death ligand (TNF‐α) mRNA expression level, and p38 MAPK and phospho‐p38 MAPK protein levels. In summary, dietary soybean β‐conglycinin suppressed fish growth and inconsistently caused apoptosis among the different intestinal segments which was partially associated with ROS‐mediated MAPK signalling.     

Molecular characterization,inductive expression and mechanism of interleukin‐10 gene induction in the Indian major carp,catla (Catla catla)

Interleukin‐10 (IL‐10) is a multifunctional cytokine and plays an important role in diseases. In this study, IL‐10 gene was cloned and characterized from catla (Catla catla), which is a highly commercially important fish species in the Indian subcontinent. The result indicated that the full‐length catla IL‐10 (cIL‐10) gene had five exons and four introns with an open reading frame of 540 nucleotides encoding a polypeptide of 179 amino acids. A phylogenetic analysis of cIL‐10 gene sequence showed that cIL‐10 clustered with freshwater carps group as expected. Quantitative real‐time polymerase chain reaction analysis showed that cIL‐10 was expressed in gill, liver, kidney, intestine, skin and heart and its expression profile was up‐regulated in bacterial infection and LPS treatment. A close relationship of high cIL‐10 expression and low pro‐inflammatory cytokine IL‐1β expression was observed in the treated group of fish, which might reveal the role of cIL‐10 as an anti‐inflammatory cytokine. Mechanism of cIL‐10 induction was investigated by blocking nuclear factor (NF)‐κB ‐signalling with BAY 11‐7082 in catla kidney cell culture. Blocking NF‐κB suppressed IL‐10 induction by LPS, and thus it revealed that cIL‐10 was induced through NF‐κB signalling. These data could be helpful to understand the function of IL‐10 in fish in response to vaccinations, probiotics and various diseases.     

Effects of dietary proline on swim bladder collagen synthesis and its possible regulation by the TGF‐β/Smad pathway in spotted drum,Nibea diacanthus

Swim bladder is an ideal source of collagen production in fish for improved human health. Proline (Pro) is the main proteinogenic amino acid needed for collagen production. However, the effects of Pro supplementation on the swim bladder collagen synthesis have rarely been evaluated in fish. We determined the effects of dietary Pro supplementation on swim bladder collagen synthesis and its possible signalling pathway in spotted drum, Nibea diacanthus. A total of 450 N. diacanthus (100 ± 3.05 g) were randomly assigned into six treatments and fed with diets supplemented with different levels of Pro (0, 2.5, 5, 7.5, 10 and 12.5 g/kg of dry diet, hereafter P0, P1, P2, P3, P4 and P5, respectively) for 8 weeks. At the end, we evaluated collagen synthesis in swim bladder and the expression of genes related to TGF‐β/Smad pathway in the fish. Dietary Pro levels increased significantly the contents of crude protein, total collagen (TC) and the levels of some amino acids in swim bladder than the control diet (p < .05). The optimum amount of dietary Pro inclusion in diets for swim bladder collagen synthesis in N. diacanthus was 7.6 and 7.5 g/kg based on crude protein and TC in swim bladder, respectively. Dietary Pro levels increased significantly the proline 4‐hydroxylase (P4H) content in fish serum, swim bladder, muscle and liver tissues than control (p < .05). The relative expression of collagen type I alpha 1 (COL1A1), alpha 2 (COL1A2) and mothers against decapentaplegic homolog 2 (Smad2) genes in liver and swim bladder initially increased significantly as the concentration of Pro and later decreased (p < .05). Similarly, the relative expression of transforming growth factor beta (TGF‐β), P4Ha2 and P4Ha3 genes in the swim bladder increased significantly as dietary Pro levels increased (p < .05). Using K‐means clustering analysis, dietary proline partly promoted collagen accumulation in swim bladder through upregulation of Smad2 and TGF‐βRT genes. Taken together, Pro affected the collagen metabolism in swim bladder, probably by regulating the TGF‐β/Smad pathway, most likely via transient overexpression of Smad2 gene.