Phylogenetic analysis of bacterial communities in the shrimp and sea cucumber aquaculture environment in northern China by culturing and PCR–DGGE

In this study, we investigated the bacterial communities in the shrimp and sea cucumber culture environment, including shrimp ponds (SP), sea cucumber ponds (SCP), mixed-culture ponds (MCP) and the effluent channel (EC) in Qingdao, China. Bacteria cultivation showed that the counts of heterotrophic, nitrate-reducing and sulfate-reducing bacteria in the sediment of SP were higher than that in the sediment of SCP and MCP, varying between 8.7 × 10⁴ and 1.86 × 10⁶, 2.1 × 10⁴ and 1.1 × 10⁵, and 9.3 × 10¹ and 1.1 × 10⁴ CFU g^?1, respectively. In contrast, the counts of ammonium-oxidizing and nitrifying bacteria in the sediment of SP was lower than that in the sediment of SCP and MCP. Denaturing gradient gel electrophoresis (DGGE) of 16S rDNA gene and dendrogram analyses showed that bacterial diversity in the mixed-culture environment was higher than that in the monocultures. The similarity of bacterial community between EC and SCP or MCP was higher than that between EC and SP. These results indicated that sea cucumber culture played a significant role in influencing the environmental bacterial communities that were composed mainly of Flavobacteriaceae (64.3%), Bacteriodetes (21%) and delta proteobacteria (14.7%), including the genera of Croceimarina, Lutibacter, Psychroserpens and so on. The results explained the benefit of sea cucumber culture in shrimp ponds at the level of microbial ecology.     

Depletion of serum alternative complement pathway activity in gilthead seabream caused by α-tocopherol and n-3 HUFA dietary deficiencies

Studies on the alternative complement pathway (ACP) activity in fish have suggested the particular relevance of this pathway as a non-specific immune mechanism being its activation directly related with the availability of certain nutrients. In the present study ACP activity in gilthead seabream fed different dietary levels of a-tocopherol and n-3 HUFA deficiencies was studied under different stress conditions (overcrowding and repetitive chasing).A reduction in ACP activity was found when diets with deficiencies in -tocopherol and n-3 HUFA were assayed at any of the experimental conditions assayed. Levels of plasma cortisol were similar to those of fish after crowding stress subjected to dietary deficiencies at low stocking density, suggesting that dietary deficiencies produced a chronic elevation of cortisol. When fish were subjected to repetitive chasing, plasma cortisol from fish fed control diet showed a progressive increase whereas plasma cortisol levels from both dietary deficient groups showed a transitory peak 4 days after the beginning of the repetitive chasing. However, ACP activity levels of fish fed deficient diets remained lower than the control group and constant during chasing period. These results suggest that both a-tocopherol and n-3 HUFA nutritional deficiencies rather than stress are an important determinant of fish complement activity.     

Effects of 3,5,3′-triiodo-L-thyronine (T3) and 6-n-propyl-2-thiouracil (PTU) on growth of GH-transgenic coho salmon, Oncorhynchus kitsutch

GH-transgeniccoho salmon (Oncorhynchus kitsutch) juveniles were fed diets containing 3,5,3-triiodo-L-thyronine (T₃; 30 ng/g fish) or 6-n-propyl-2-thiouracil (PTU; 20 ug/g fish), to assess the effect of these drugs on the physiology, growthand survival in comparison with untreated transgenicand non-transgenic salmon. After 84 days, food intake, feed efficiency, survival, growth, hepato-somatic index (HSI), viscera-somatic index (VSI), plasma L-thyroxine (T₄), T₃and growth hormone (GH) levels,and cranial morphological abnormalities were determined. Growth of transgenic salmon was significantly faster than the nontransgenic salmon,and was increased by exogenous T₃and reduced by PTU. Food intake of transgenic salmon was higher than that of the nontransgenic group, but was reduced by exogenous PTU administration. Food conversion efficiency of transgenic salmon was lower than that of nontransgenic salmon,and also was increased by T₃ but reduced by PTU in the transgenic fish. The survival rate in all transgenic groups was significantly higher than that of nontransgenic,and transgenic T₃and PTU treatment groups showed higher survivals than the transgenic-control group. The HSIand VSI of the transgenic fish were higher than the nontransgenic fish;and both parameters in the transgenic salmon were increased by PTU, but reduced by T₃. The plasma T₄ level in transgenic salmon was approximately 1.5-fold higher relative to the nontransgenic fish, whereas no difference was observed among the transgenic groups. Plasma T₃ levels in transgenic salmon were also approximately 2-fold higher relative to the nontransgenic fish. However, the plasma T₃ level in transgenic animals was increased by exogenous T₃ administration, but was reduced by exogenous PTU to that observed in nontransgenic salmon. The plasma GH level of transgenic fish was higher than that of the nontransgenic salmon,and the level was increased by the exogenous T₃, whereas exogenous PTU did not reduce significantly GH levels in transgenic salmon. Transgenic fish also displayed cranium, jawand opercular abnormalities typical of the effects of this gene construct incoho salmon, indicating that some imbalance in growth processes has been induced. However, these abnormalities (especially cranial disruptions) were diminished by administration of exogenous PTU. In conclusion, exogenous T₃and PTU treatments can induce hyperthyroidismand hypothyroidism, respectively,and have inverse effects on growthand skeletal abnormalities of transgenic salmon constitutively expressing GH.     

Molecular characterization and expression analysis of hypoxia-inducible factor-1α, factor-2α, and factor-3α and physiological response to hypoxia exposure in Amur minnow (Phoxinus lagowskii)

Aquaculture International - To further enhance our understanding of hypoxia tolerance in the fish Phoxinus lagowskii, hypoxia-inducible-factor (HIF) genes were cloned to analyze their biological...     

Gonadotropins I and II do not stimulate thein vitro secretion of 17α,20β-dihydroxy-4-pregnen-3-one 20-sulphate by rainbow trout gonads during final sexual maturation

Thein vitro secretion of 17,20-dihydroxy-4-pregnen-3-one 20-sulphate (17,20-P-sulphate) and the free steroid 17,20-dihydroxy-4-pregnen-3-one (17,20-P), by rainbow trout (Oncorhynchus mykiss) gonads, in response to gonadotropin (GTH) I and GTH II, were studied during the final stages of sexual maturation. Substantial amounts of 17,20-P-sulphate were produced, by both mature ovaries and testes, indicating considerable 20-hydroxysteroid sulphotransferase (20-HST) activity within these tissues. In the post-ovulatory ovary the level of 17,20-P-sulphate (36.6 ng ml^–1) greatly exceeded that of 17,20-P (8.59 ng ml^–1). The amount of 17,20-P-sulphate produced in incubations of both mature ovary and testes was unaffected by either GTH I or GTH II treatment at physiological concentrations up to 100 ng ml^–1. Similarly, incubations of maturing ovary and testes, treated with GTH I or GTH II, in the presence of added 17,20-P at 100 ng ml^–1 of medium, produced levels of 17,20-P-sulphate that were similar to those of the controls. In incubations of mature ovarian follicles at the stages of germinal vesicle breakdown and preovulation, both GTHs significantly stimulated secretion of 17,20-P, although GTH II was always more potent than GTH I. GTH II significantly elevated the levels of 17,20-P in testicular incubations from mature males more than 4-fold relative to GTH I and controls, which did not differ from one another.In conclusion, 20-HST, the enzyme responsible for the sulphate conjugation of 17,20-P, was found to be active in the ovaries and testes of rainbow troutin vitro. However, the levels of this enzyme do not appear to be regulated by either GTH I or GTH II.     

Effects of dietary borage oil [enriched in γ-linolenic acid,18:3(n-6)] or marine fish oil [enriched in eicosapentaenoic acid,20:5(n-3)] on growth,mortalities, liver histopathology and lipid composition of juvenile turbot (Scophthalmus maximus)

A marine fish oil, Marinol K (MO) and borage oil (BO) were used to formulate diets relatively rich in eicosapentaenoic acid [EPA; 20:5(n-3)] and -linolenic acid [GLA; 18:3(n-6)], respectively. The diets were fed to duplicate groups of juvenile turbot (Scophthalmus maximus) of initial weight 1.4 g for a period of 12 weeks. No differences were observed in final weights either between duplicate tanks or between dietary treatments. Mortalities in the MO-fed group were significantly greater than in the BO-fed group. In the MO-fed group, 7 out of 12 fish sampled for histological analysis showed a pronounced liver histopathology whereas only 1 of 12 fish sampled in the BO-fed group showed slight pathology. EPA levels were increased 2.2-fold and its elongation product, 22:5(n-3), was increased 1.8-fold while arachidonic acid [AA; 20:4(n-6)] was decreased by 30% in MO-fed fish compared to the initial carcass composition. GLA was increased 53-fold and its elongation product dihomo--linolenic acid [DHGLA; 20:3(n-6)] was increased 16-fold while AA was reduced by 90% in BO-fed fish compared to the initial carcass composition. The amount of triacylglycerol in liver of BO-fed fish was significantly greater than levels in MO-fed fish. The fatty acid compositions of individual phospholipids from liver showed marked differences between dietary treatments. Fish fed MO had significantly higher levels of the (n-3) polyunsaturated fatty acids (PUFA), 20:5(n-3), 22:5(n-3) and 22:6(n-3), and also significantly more 20:4(n-6) compared to BO-fed fish which had significantly higher 18:2(n-6), 18:3(n-6), 20:2(n-6) and 20:3(n-6). The composition of liver phosphatidylinositol was particularly unusual in BO-fed fish having DHGLA as the major C₂₀ PUFA which was 2.2-fold greater than AA and 3.9-fold greater than EPA. This study demonstrates that the carcass composition of turbot can be altered, by means of dietary lipids, to contain increased levels of EPA and DHGLA which would be of potential benefit in human as well as in fish nutrition. However, caution should be exercised when using very highly unsaturated oils relatively rich in EPA which may generate histopathological lesions in the fish.Abbreviations AA arachidonic acid - ANOVA analysis of variance - BHT butylated hydroxytoluene - BO borage oil - DHA docosahexaenoic acid - DHGLA dihomo--linolenic acid - EPA eicosapentaenoic acid - GLA -linolenic acid - HPTLC high performance thin-layer chromatography - MO Marinol K - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - PUFA polyunsaturated fatty acid - TLC thin-layer chromatography     

The effects of hairtail protein hydrolysate–Fe<Superscript>2+</Superscript> complexes on growth and non-specific immune response of red swamp crayfish (<Emphasis Type="Italic">Procambarus clarkii</Emphasis>)

The experiment was conducted to investigate the effects of prepared hairtail protein hydrolysate–Fe²⁺ (PH–Fe²⁺) complexes on growth and non-specific immune responses of crayfish (Procambarus clarkii). The diets with five different levels of PH–Fe²⁺ (200, 400, 600, 800, and 1000 mg/kg) were fed to crayfish for 60 days. The results indicated that the survival rate, weight gain percentage, specific growth rate, and muscle index of crayfish with 400–1000 mg/kg of PH–Fe²⁺ feeding were significantly higher, 9.94–10.10, 8.55–8.72, 0.24–0.29 %/day, and 2.39–3.05 %, respectively, than the control values after 60 days of feeding. Additionally, after 30 days of feeding, 200–400 mg/kg of PH–Fe²⁺ showed no significant (P > 0.05) improvement effect on activities of superoxide dismutase (SOD), phenoloxidase (PO), lysozyme (LSZ), and acid phosphatase (ACP) in serum or hepatopancreas of crayfish. However, significant improvement effects were observed in 800–1000 mg/kg groups. After 60 days of feeding, 400–600 mg/kg of PH–Fe²⁺ significantly (P < 0.05) improved the activity of SOD and LSZ, but did not affect the activity of PO and ACP significantly (P > 0.05). Moreover, the activities of SOD, PO, LSZ, and ACP in serum and hepatopancreas were all significantly enhanced upon treatment with 800–1000 mg/kg of PH–Fe²⁺. For these reasons, PH–Fe²⁺ can be recommended as a supplement in crayfish feed to increase the growth and immunity.     

Cloning,expression, and induction by 17-β estradiol (E<Subscript>2</Subscript>) of a vitellogenin gene in the white cloud mountain minnow <Emphasis Type="Italic">Tanichthys albonubes</Emphasis>

Vitellogenins (Vtgs), the precursors for the yolk proteins, are very important for the embryonic development of teleosts, and have also been studied extensively as biomarkers for environmental estrogenic mimics. The cDNA for a Vtg was isolated from the liver of the female white cloud mountain minnow (Tanichthys albonubes) by 3′- and 5′-RACE methods. It is 4,171 bp in full length, and encodes a putative protein of 1,326 amino acids. This putative Vtg, designated as wcmmVtg, contains complete portions of LVI and PV, but lacks the C-terminal half of LVII and thus belongs to type I vitellogenin. In addition to the liver of the female fish, wcmmVtg was also shown to be expressed in the ovary. During ovarian development, the mRNA expression of wcmmVtg in both the liver and ovary was continuously increased from the previtellogenic to late vitellogenic stages, but then decreased significantly at post-spawning stage. In the male fish, expression of wcmmVtg mRNA was induced in the liver by treatment with E₂ (10 and 100 ng/l) for 14 days. These results suggest that the Vtg originated from the ovary of the white cloud mountain minnow may also contribute to the accumulation of yolk proteins during oocyte growth, and that the male white cloud mountain minnow is sensitive to the estrogenic treatment in terms of Vtg mRNA expression, which could also be applied to monitor the environmental estrogenic mimics.     

Echium oil increased the expression of a Δ4 Fads2 fatty acyl desaturase and the deposition of n-3 long-chain polyunsaturated fatty acid in comparison with linseed oil in striped snakehead (<Emphasis Type="Italic">Channa striata</Emphasis>) muscle

Despite the potential of vegetable oils as aquafeed ingredients, a major drawback associated with their utilization is the inferior level of beneficial n-3 long-chain polyunsaturated fatty acids (LC-PUFA). Echium oil (EO), which is rich in stearidonic acid (SDA, 18:4n-3), could potentially improve the deposition of n-3 LC-PUFA as the biosynthesis of LC-PUFA is enhanced through bypassing the rate-limiting ?6 desaturation step. We report for the first time an attempt to investigate whether the presence of a desaturase (Fads2) capable of ?4 desaturation activities and an elongase (Elovl5) will leverage the provision of dietary SDA to produce a higher rate of LC-PUFA bioconversion. Experimental diets were designed containing fish oil (FO), EO or linseed oil (LO) (100FO, 100EO, 100LO), and diets which comprised equal mixtures of the designated oils (50EOFO and 50EOLO) were evaluated in a 12-week feeding trial involving striped snakeheads (Channa striata). There was no significant difference in growth and feed conversion efficiency. The hepatic fatty acid composition and higher expression of fads2 and elovl5 genes in fish fed EO-based diets indicate the utilization of dietary SDA for LC-PUFA biosynthesis. Collectively, this resulted in a higher deposition of muscle eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) compared to LO-based diets. Dietary EO improved the ratio of n-3 LC-PUFA to n-6 LC-PUFA in fish muscle, which is desirable for human populations with excessive consumption of n-6 PUFA. This study validates the contribution of SDA in improving the content of n-3 LC-PUFA and the ratio of EPA to arachidonic acid (ARA, 20:4n-6) in a freshwater carnivorous species.