Interactive effects of salinity on oxygen consumption,ammonium excretion,osmoregulation and Na+/K+‐ATPase expression in the bullseye puffer (Sphoeroides annulatus,Jenyns 1842)

A physiological study was performed to explore the effects in Sphoeroides annulatus (Jenyns 1842) juveniles of exposure to different salinities 10, 17, 23, 29, 35 and 41‰ on oxygen consumption rate (OCR), ammonium excretion rate (AER), the oxygen‐nitrogen atomic ratio (O:N), osmoregulation and Na⁺/K⁺‐ATPase expression. The OCR values ranged from 27.9 to 30.9 mg O₂ h^?1 kg^?1, displaying a Type 1 response pattern Kinne (1977). AER ranged from 0.60 to 0.69 mg h^?1 kg^?1, and O:N values were from 53.12 to 59.26, indicating that the puffers use proteins and lipids as an energy‐substrate. Osmoregulation in S. annulatus was hyposmotic in salinities of 23, 29, 35 and 41‰ and hyperosmotic in a salinity of 10‰. The isosmotic point of the bullseye puffer was 356 mmol kg^?1 (10.5‰). The enzyme expression analysis indicates that the fish acclimated to 41‰ had the highest Na⁺/K⁺‐ATPase expression level, whereas, the lowest expression level was found close to the isosmotic point. Na⁺/K⁺‐ATPase expression in the gills was found to have a U‐shaped relationship with environmental salinity. We conclude that the bullseye puffer is strongly euryhaline and can be cultivated in a wide range of environments that has important economic implications.     

Effects of salinity on osmoregulation during the embryonic development of the bullseye puffer (Sphoeroides annulatus Jenyns 1842)

To evaluate the effect of salinity on the hatching rate, hatching time, survival percentage, osmoregulation pattern and the incidence of abnormalities in newly hatched larvae, embryos of Sphoeroides annulatus (Jenyns 1842) were exposed to 5, 12, 19, 26, 33, 35 and 40 psu. The hatching percentage (HP), survival percentage (PS), normal larvae (PN), deformed larvae (PD) and hatching time (HT) were significantly affected by salinity (P < 0.05). The embryos exposure to 5 psu caused that HP, PS, and PN had lower values (2.6 ± 0.32, 7.78 ± 0.88 and 70.37 ± 7.75% respectively), PD and HT had the highest values 26.67 ± 7.54% and 55.53 ± 0.59 h respectively. However, the survival of newly hatched larvae was not possible in 5 ups, though it was in 40 ups. Osmotic pressure (OP) remained constant in each salinity, whereas isosmotic points changed from 435.5 mOsm kg^?1 in 21 h post fertilization to 342.8 mOsm kg^?1 at 47 h post fertilization, obtaining a pattern of hyper‐osmoregulation at lower salinities and hypo‐osmoregulation in higher salinities. This study is the first carried out on embryos of this species; therefore, the obtained information is essential to improve strategies and growing conditions in their initial development.     

Effect of low salinity on the expression profile of Na+/K+‐ATPase and the growth of juvenile chub mackerel (Scomber japonicus Houttuyn)

Chub mackerel (Scomber japonicus Houttuyn) is one of the most commercially important scombroid fish used as a food resource. Recently, there has been a demand for efficient rearing methods of this fish for a full‐life cycle aquaculture. In the present study, we evaluated the physiological responses in the juvenile S. japonicus to different ambient salinities. A significantly higher gain of the body mass was observed in the juveniles reared in 24 g/L and 13 g/L seawater than in those reared in natural seawater (34 g/L) within 40 days of the experimental period without affecting mortality. A principal enzyme for osmoregulation, Na⁺/K⁺‐ATPase, was expressed in the ionocytes located in the gill filaments of the juveniles. The number and the cell size of ionocytes and the enzymatic activity of Na⁺/K⁺‐ATPase in the gills decreased within 10 days after the low‐salinity challenge, which implies the reduction of the energy‐consuming active ion secretion under the low‐salinity environment. The physiological capacity for adaptation to low‐salinity seawater in chub mackerel could be basic knowledge to carry out culturing of these fish in coastal sea pens where ambient salinity fluctuates. The improvement of the growth performance by rearing in low‐salinity seawater will contribute to the efficient production of the seed juveniles for aquaculture.     

盐度胁迫对魁蚶稚贝血淋巴渗透压及鳃Na+/K+-ATP酶活力的影响

文章研究了盐度胁迫下魁蚶（Anadara broughtonii）稚贝（壳长25~35 mm）血淋巴渗透压和鳃Na+/K+-ATP酶活力的变化。结果显示,突变胁迫下,盐度20、25、35、40组的稚贝血淋巴渗透压均在48 h内显著降低或波动升高后趋于稳定,盐度15组则需96 h完成波动调整。以日变幅5渐变至高盐40过程中,稚贝血淋巴渗透压在48 h内趋于稳定;低盐15组仅需72 h完成渗透压调节,调整时间显著小于突变组。盐度突降胁迫下,各处理组稚贝鳃Na+/K+-ATP酶活力12 h后显著升高,24 h分别达到最大值,随后快速回落并稳定在高于对照组水平;盐度骤升胁迫下,鳃ATP酶活力波动降低,在12~24 h达到最小值后稳定在低于对照组水平。低盐（15）和高盐（40）渐变组的鳃ATP酶活力变幅均小于突变组。盐度胁迫下鳃Na+/K+-ATP酶活力的响应方式不同,即低盐胁迫时活力增强,高盐胁迫时活力降低。采用盐度渐变的驯化处理更有利于魁蚶稚贝应对盐度胁迫。     

Effects of dietary phospholipids levels on growth performance,lipid metabolism,and antioxidant capacity of the early juvenile green mud crab,Scylla paramamosain (Estampador)

Four iso‐nitrogenous and iso‐lipidic diets were designed to investigate the effects of dietary phospholipids (PL) levels (with 0%, 1%, 2%, and 4% PL supplementation) on growth performance, lipid metabolism, and antioxidant capacity in early juvenile green mud crab (Scylla paramamosain). There were three replicates of 28 crabs (initial body weight from 42.02 to 42.44 mg) for each diet treatment, and growth trial lasted for 8 weeks. At the end of the growth trial, there was no significant difference in survival among all treatments. Crabs fed diet with 2% PL obtained highest weight gain (WG) and specific growth rate than other crabs. The molting frequency was not affected by different dietary PL addition. Besides, the contents of whole body lipid and long chain highly unsaturated fatty acids significantly increased with elevating dietary PL levels. In the hepatopancreas, crabs fed diet with 0% PL had significantly higher malondialdehyde concentration than other crabs. And crabs fed diet with 2% PL obtained significantly higher superoxide dismutase activity than crabs fed diets with 0% and 4% PL. Moreover, the mRNA expression of Na⁺/K⁺‐ATPase was significantly down‐regulated with dietary PL supplementation over 2%. Based on the second order polynomial regression analysis of WG, 2.37% dietary PL level was the optimal demand for early juvenile S. paramamosain. Moreover, we found crabs fed diet with 2% PL obtained better antioxidant capacity than other crabs.     

高盐胁迫对黄边糙鸟蛤(Trachycardium flavum)呼吸排泄和免疫酶活性的影响

为了探讨急性高盐胁迫对黄边糙鸟蛤(Trachycardium flavum)生理代谢和免疫酶活性的影响,分析了盐度自31骤升至37后2、12、24、48和72 h黄边糙乌蛤耗氧率、排氨率和不同组织Na+/K+-ATP酶、超氧化物歧化酶(SOD)、酸性磷酸酶(ACP)和碱性磷酸酶(ALP)的活性.结果显示,处理后2h耗氧率先降低,然后逐渐升高,在24和72 h显著高于对照组(P＜0.05);排氨率在2h极显著降低(P＜0.01),且在各时间点均低于对照组.外套膜、肝胰腺中Na+/K+-ATP酶活力在12 h显著降低(P＜0.05),肌肉和鳃中活力与对照组无显著差异.外套膜、肝胰腺和鳃中SOD活力在24 h达到最高值,显著高于对照组(P＜0.05),其后逐渐降低;肌肉中SOD活力在48 h达到最高值后降低.外套膜和鳃中ACP活力先升高后降低,肝胰腺中ACP活力显著降低(P＜0.05)后逐渐升高,肌肉中ACP活力与对照组无显著差异.肝胰腺和鳃中ALP活力先降低后显著升高(P＜0.05),与对照组相比,外套膜和肌肉中ALP活力无显著差异.结果表明,急性高盐胁迫对黄边糙鸟蛤的代谢水平和免疫酶活性均有显著影响且表现出时间效应性,高盐胁迫对免疫酶活性的影响具有组织特异性.