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Growth and lipid metabolism of the pacific white shrimp Litopenaeus vannamei at different salinities.

ABSTRACT Juvenile white shrimp Litopenaeus vannamei (1.98 [+ or -] 0.28 g) were fed a commercial diet for 8 wk in triplicate to investigate growth and lipid metabolism at 3 salinities (3, 17, and 30). Shrimp weight gain and survival at 3 were significantly less than that at 17 and 30. No differences were found in whole-body proximate composition. Linolenic acid (18:3[n-3]) and (n-3) long-chain unsaturated fatty acid levels in the hepatopancreas, and n-3 long-chain polyunsaturated fatty acid level, especially eicosapentaenoic acid (EPA; C20:5[n-3]) and docosahexaenoic acid (DHA; C22:6[n-3]) in muscle at 3 were significantly greater than at other salinities. Fatty acid synthase, hormone sensitive lipase, lipoprotein lipase, adipose triacylglycerol lipase, acyl-CoA, diacylglycerol acyltransferase 2, elongase of very long-chain fatty acid 6, and [DELTA]5 and [DELTA]6 fatty acid desaturase activity was detected and showed a negative trend with an increase of salinity, and no significant differences were found among salinity groups (P > 0.05). The results indicate that the low salinity of 3 decreases the growth of L. vannamei. Although L. vannamei could not synthesize either DHA or EPA de novo, it possibly has the potential ability to convert linolenic acid to DHA and EPA regardless of salinity. However, the factors influencing this ability remain unknown and need further study.

KEY WORDS: shrimp, Litopenaeus vannamei, salinity, lipid metabolism, fatty acids, osmoregulation

INTRODUCTION

Salinity is one of the most important factors that influence the physiological status of aquatic animals. Previous studies have shown that aquatic euryhaline animals depend on energetic reorganization to cope with ambient salinity changes (Tseng & Hwang 2008), showing that the osmoregulation of aquatic animals is an energy cost (20%-50% of total metabolic energy) process to maintain intracellular and extracellular osmotic equilibrium (Evans et al. 2005, Tseng & Hwang 2008). Therefore, studies on the energy use of aquatic animals under salinity stress are significant in understanding the mechanism of osmoregulation for aquatic animals.

Of the major energy-yield nutrients, lipids are of the greatest energy density, and many fatty acids from lipid metabolism are essential for normal growth and development of aquatic animals. In addition, phospholipids and glycolipids are indispensable components of the cell membrane and can affect osmoregulatory capacity by changing the contents in the cell membrane (Li et al. 2006, Tseng & Hwang 2008). Therefore, lipid metabolism must function correctly when responding to ambient salinity changes in aquatic animals by altering the permeability of the cell membrane (Tseng & Hwang 2008).

The Pacific white shrimp Litopenaeus vannamei is 1 of the most important shrimp species cultured worldwide (Hu et al. 2004). During the past decade, the expansion of inland saline water farming, coupled with the wide range of salinity tolerance from 0.5-50 (Samocha et al. 2002), makes L. vannamei an attractive species in aquaculture at low salinity in many countries (Saoud et al. 2003, Cheng et al. 2006). Previous studies on the isosmotic point of L. vannamei are controversial. The white shrimp L. vannamei obtained optimal growth at salinity ranges of 15-30 (Bray et al. 1994. Ponce-Palafox et al. 1997). Huang et al. (2004) found that 20 was the best salinity for the growth performance of L. vannamei. Although greater production can be obtained from low-salinity (<5) farming of white shrimp, many problems have been found, such as reduction of growth and survival (Ponce-Palafox et al. 1997, Rosas et al. 2001, Palacios et al. 2004a, Li et al. 2007) and low stress resistance (Li et al. 2007, Li et al. 2008). Therefore, it is necessary to explore a practical way to improve the performance of white shrimp farmed at low salinities. The L. vannamei in either a hypo- or hypersaline condition has greater amylase activity and a lower number of R cells, which is for nutrient reserve in the hepatopancreas (the main site for lipogenesis) of shrimp, compared with shrimp at normal seawater salinity (Li et al. 2008, Al-Mohanna & Nott 1989), indicating that lipid nutrition may have an important role in improving osmoregulation capacity. So far, although many studies have been conducted on various aspects of lipid nutrition in L. vannamei (Gonzalez-Felix et al. 2002a, Gonzalez-Felix et al. 2002b, Zhu et al. 2010, Niu et al. 2011, Ju et al. 2012), information on lipid metabolism at different salinities is still limited, and a successful method for nutrient modulation to improve the physiological status of L. vannamei at low salinity has not yet been reported because of the poor understanding of the lipid mechanisms in L. vannamei under salinity stress.

Therefore, this study aims to understand the salinity-dependent growth and lipid metabolism of white shrimp by analyzing fatty acid composition of different tissues, enzyme activity related to fatty acid catabolism (hormone sensitive lipase [HSL], lipoprotein lipase [LPL], adipose triacylglycerol lipase [ATGL]) and synthesis (elongase of very long chain fatty acids 6 [ELOVL6], fatty acid synthase [FAS] complex, [DELTA]5 fatty acid desaturase [[DELTA]5FAD], and [DELTA]6 fatty acid desaturase [[DELTA]6FAD]), and the contents of metabolic products of Litopenaeus vannamei at 3 salinities. It is hoped that the findings from this study provide insight to understanding the mechanism of osmoregulation in L. vannamei at different salinities, which should be very instructive, especially from the perspective of lipid metabolism.

MATERIALS AND METHODS

Experimental Animals, Design, and Facilities

Juvenile white shrimp were obtained from the Shenzhen base of South China Sea Fisheries Research Institute, Shenzhen, China, and were stocked in 9 tanks at a density of 40 shrimp per tank (500 L) at a salinity of 17 for 1 wk. Then, shrimp in 2 of 3 tanks were acclimated to 3 and 30, respectively, by a daily change of 2 prior to the start of the 8-wk experiment. During the acclimation and experimental periods, shrimp were fed 3 times daily at 0800 HR, 1600 HR, and 2200 HR with a commercial diet containing 10% moisture, 40% crude protein, 8% crude lipid, 12% ash, and 30% carbohydrates, and a digestible energy of 16.7 kJ/g. The known fatty acid and main ionic compositions are shown in Table 1. Based on the amount of food remaining the following day, daily rations were adjusted to a feeding level slightly more than satiation. The uneaten food was removed daily with a siphon tube. The photoperiod was 12 h light and 12 h dark. Seawater was pumped from the Dayawan Coast in Shenzhen and filtered through an activated carbon cartridge for at least 3 days before entering the culture system. Tap water was aerated before being added to the tank to adjust the salinity level. During the experiment, water was exchanged once daily with one third of the tank volume. Water-quality parameters were monitored 2-3 times a week throughout the feeding trial, and were maintained at a pH of 7.5-7.9, a temperature of 26-28[degrees]C, a dissolved oxygen level of 4.8-6.4 mg/L, and a total ammonia nitrogen level of less than 0.02 mg/L during the trial. Some mineral ion information for all salinity treatments is shown in Table 2.

At the end of the experiment, shrimp were deprived of food for 24 h before being bulk weighed and accounted. Five shrimp at intermolt stage C in each tank were used for the body composition analysis. Another 10 shrimp at intermolt stage C in each tank were dissected to obtain muscle, hepatopancreas, and gill, and were stored at -80[degrees]C for biochemical analysis and enzyme essay. Weight gain and survival were calculated to assess the growth performance of shrimp. Weight gain (percent) was calculated as follows:

Weight gain =- X 100, [W.sub.t] - [[W.sub.0]/W0] x 100,

where [W.sub.0] is the initial weight and Wt is the final weight.

Survival rate (percent) was calculated as follows:

Survival rate = [Final shrimp number/Initial shrimp number] x 100.

Whole-Body Proximate Compositions

Each experimental sample consisted of five randomly collected shrimp from each tank, and was analyzed in triplicate for proximate composition following the standard methods (Association of Official Analytical Chemists 2000). Moisture was determined by oven drying at 105[degrees]C to a constant weight. Samples used for dry matter were digested with nitric acid and incinerated in a muffle furnace at 600[degrees]C overnight to determine ash content.

Protein was measured by the combustion method using an FP-528 nitrogen analyzer (Leco). Lipid content was determined by the ether extraction method using the 2055 Soxtec system (Foss, Sweden).

Fatty Acid Analysis

Total lipids of the gill, muscle, and hepatopancreas were extracted in triplicate using chloroform:methanol (2:1, v/v) (Folch et al. 1957). The saponifiable lipids were converted to their methyl esters using the standard boron trifluoride-methanol method (Morrison & Smith 1964). Fatty acid methyl esters were analyzed using an Agilent 6890 gas chromatograph (Agilent Technologies) equipped with a flame ionization detector and an SP-2560 fused silica capillary column (100 m, 0.25 mm i.d., and 0.20-[micro]m film thickness). Injector and detector temperatures were 270[degrees]C and 280[degrees]C, respectively. The column temperature was held at 120[degrees]C for 5 min then programmed to increase at 3[degrees]C/min up to 240[degrees]C, where it was maintained for 20 min. Carrier gas was helium (2 mL/min), and the split ratio was 30:1. Identification of fatty acids was carried out by comparing the sample fatty acid methyl ester peak relative retention times with those obtained for the Sigma-Aldrich (St. Louis, MO) standards. The concentration of individual fatty acids was calculated and expressed as the mass percentage of total identified fatty acids.

Enzyme Activity, Lipoprotein, Total Cholesterol, and Triglyceride Content Determination

Activity assays of all enzymes and lipoproteins tested in this study were determined using an enzyme-linked immunosorbent assay kit (Xinyu, Shanghai) according to protocols, with specific antibodies corresponding to the parameter. Enzyme activity of FAS, HSL, LPL, ATGL, acyl-CoA, diacylglycerol acyltransferase 2 (DGAT2), ELOVL6, A5FAD. and [DELTA]6FAD are expressed as units per gram protein and were detected in the hepatopancreas. The protein content of each sample was determined using a UV-Vis spectrophotometer (NanoDrop 2000; Thermo Scientific). Total triacylglycerol (TAG) and total cholesterol are expressed as nanomoles per liter hemolymph. The contents of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) are expressed as micromoles per liter hemolymph. The content of very low-density lipoprotein (VLDL) is expressed as micrograms per milliliter hemolymph.

Statistical Analyses

Data are expressed as mean [+ or -] SE and were subjected to 1-way analysis of variance (SPSS for Windows, version 11.5) to determine significant differences among treatments. If a significant difference was identified, differences between means were compared using Duncan's multiple range test. The level of significance was set at P < 0.05.

RESULTS

Weight gain of shrimp at 3 was significantly less than that of shrimp at 17 and 30 (Table 3). There were no differences in shrimp survival and weight gain between salinities of 17 and 30. Whole-body proximate composition (protein, lipid, ash, and moisture) was not affected by salinity (Table 3).

Table 4 shows the fatty acid composition in muscle, gill, and hepatopancreas of the shrimp at different salinities. No differences were found in hepatopancreas 18:2(n-6) (LA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), [SIGMA] saturated fatty acid (SFA), [SIGMA] polyunsaturated fatty acid (PUFA) and [SIGMA](n-6). Shrimp hepatopancreas 18:3(n-3) (linolenic acid [LNA]) at 3 was significantly greater than that of shrimp at 17 and 30. Both [SIGMA](n-3) and [SIGMA] monounsaturated fatty acid (MUFA) of shrimp at 3 were more than those at other salinities, and [SIGMA]MUFA of shrimp at 3 was significantly greater than that of shrimp at 30. Shrimp [SIGMA](n-3) at 3 was significantly more than that of shrimp at 17. With regard to muscle tissue, salinity did not affect LNA, [SIGMA]TMUFA, and [SIGMA]TPUFA contents. The LA and [SIGMA](n-6) of shrimp at 30 were significantly more than those at the other 2 salinities, and those of shrimp at 17 were significantly more than shrimp at 3. However, EPA had the opposite trend compared with LA and [SIGMA](n-6). The DHA of shrimp at 3 was significantly more than that at 17, and [SIGMA](n-3) at 3 was more than that at 30. For gill, a significant difference was found only in [SIGMA]SFA content, which was lower at 3 than at 30.

Table 5 shows lipid metabolites of white shrimp at different salinities. No differences were found in total cholesterol, LDL, and VLDL contents among all treatments, but values of these parameters at 3 were the lowest. The HDL content of shrimp at 3 was lowest and differed from that of shrimp at 30. Total triacylglycerol content of shrimp at 17 was lowest and differed from that of shrimp at 30, but no significant difference between 3 and 30 was found.

No difference was found in activities of FAS, HSL, LPL, ATGL, DGAT2, [DELTA]5FAD, and [DELTA]6FAD (Table 6; (P > 0.05). At the 3 salinity, ELOVL6, HSL, A5FAD, and A6FAD were lowest (P > 0.05), and all enzyme activity values tested in shrimp at 3 were less than in shrimp at 30 (P > 0.05).

DISCUSSION

In the current study, Litopenaeus vannamei at the medium salinity of 17 (in the range of salinity for the optimal growth of L. vannamei) had the best growth performance compared with white shrimp at either low salinity or high salinity. Similar reports have demonstrated that the optimal salinity of L. vannamei ranges from 15-30 for optimal growth performance (Bray et al. 1994, Ponce-Palafox et al. 1997). Similarly, the optimal salinity for the growth of L. vannamei was found to be around 20 (Huang et al. 2004), and much higher or lower ambient salinity would affect shrimp growth negatively (Li et al. 2007). This study further confirms that low salinity can decrease growth performance of L. vannamei, and there is a need to solve this problem and to improve the growth performance of L. vannamei at low inland salinities.

When challenged with ambient salinity stress, a high proportion of the metabolic energy budget (20%-50%) is needed for osmoregulation, leading to low energy available for growth in many fish, such as Spams sarba (Woo & Kelly 1995), Salmo salar (Handeland et al. 1998), Anarhichas minor (Foss et al. 2001), Scophthalmus maximus (Imsland et al. 2001), Pagrus auratus (Fielder et al. 2005), and Spams aurata (Laiz-Carrion et al. 2005). However, previous research in crustacean species has showed only that energy expenditure increases when ambient salinity changes, including Penaeus setiferus (Rosas et al. 1999), Penaeus latisculcalus (Sang & Fotedar 2004), Marsupenaeus japonicas (Setiarto et al. 2004), and Litopenaeus vannamei (Silvia et al. 2004), but a specific discussion of the energy budget used for osmoregulation is not reported in these studies. The current study, there was an extra energy expenditure during osmoregulation that resulted in slow body weight gain at a salinity of 3 (Rosas et al. 1999, Gomez-Jimenez et al. 2004, Setiarto et al. 2004, Li et al. 2007).

The white shrimp Litopenaeus vannamei is a euryhaline decapod species and is generally considered an osmoconformer (Dali et al. 1990, Kirschner 1991). To maintain homeostasis by osmoregulation, shrimp require energy from nutrients via a compensatory process, and lipids play significant roles in this process (Lemos et al. 2001, Luvizotto-Santos et al. 2003, Sang & Fotedar 2004, Palacios et al. 2004b). Therefore, it is reasonable to assume that sufficient energy provided from lipid metabolism can improve osmoregulation efficiency, survival, and growth of cultured shrimp in a low-salinity condition. In the current study, ATGL, LPL, and HSL activities of shrimp at both 3 and 30 were more than those at 17, indicating that lipid mobilization has increased, because ATGL (TAG hydrolysis), LPL, and HSL are crucial enzymes in lipid mobilization by performing the first step in hydrolyzing TAG to generate diacylglycerol and free fatty acid (Osuga et al. 2000, Jenkins et al. 2004, Villena et al. 2004. Zimmermann et al. 2004). Both LPL and HSL are factors in lipolysis. Lipoprotein lipase is a "gatekeeper" for fatty acid uptake (Greenwood 1985), and HSL as the rate-limiting enzyme is thought to break down TAG functionally into diacylglycerol and then into monoacylglycerol (Holm et al. 2000, Lampidonis et al. 2011).

In addition, we observed that lipid synthesis of shrimp at both 3 and 30 was slightly enhanced with increased FAS activity. Total triacylglycerol of shrimp at both 3 and 30 were significantly greater than at the optimal salinity of 17 (Li et al. 2007). Fatty acid synthase and DGAT2 are the key enzymes related to lipid synthesis. Fatty acid synthase is a complex multifunctional enzyme consisting of a protein with 7 catalytic domains and acts on energy homeostasis by catalyzing the synthesis of myristate, palmitate, stearate, and long-chain SFAs (Chirala & Wakil 2004). Diacylglycerol acyltransferase 2 can catalyze the final step in TAG biosynthesis by converting acyl-CoA and DAG in TAG (La Russa et al. 2012, Gong et al. 2013). Therefore, this finding indicates that both high and low salinity can enhance lipid synthesis and stimulate lipolysis capacity.

Lipoproteins function in the transportation of lipids, including PUFAs, that cannot be synthesized de novo and must be obtained from the diet (Teshima & Kanazawa, 1971). In the current study, HDL. LDL, and VLDL shrimp contents at 3 were less than those at 17, indicating that more lipids are used during the process of [beta]-oxidation to supply enough energy for osmoregulation. In addition, among lipids, cholesterol may decrease gill permeability via increasing membrane stability (Coutteau et al. 1996). In the current study, total cholesterol in hemolymph at low salinity was less than in the other 2 groups, and it could likely be used in synthesizing cell membrane of other tissues to improve permeability for regulating osmotic stress.

Previous studies have shown that an (n-3) PUFA-rich diet can improve resistance to osmotic shock in aquatic animals because (n-3) HUFAs, especially DHA, are incorporated primarily in cell membranes and can increase membrane permeability, and hence their fluidity (Martins et al. 2006, Sui et al. 2007). Free fatty acids, especially long-chain PUFAs, have the potential to modulate fatty acid composition on the gill membrane and thus increase enzymatic efficiency (Palacios et al. 2004b, Hurtado et al. 2007). The modification of fatty acid composition in the gills with higher levels of (n-3) PUFAs can result in a larger gill area to enhance the osmoregulatory capacity of shrimp at low salinities, and increase survival (Palacios et al. 2004a). In the current study, in gill, muscle, and hepatopancreas, [SIGMA](n-3) longchain-PUFAs--and DHA, in particular--at 3 were greater than those in the other 2 groups (30 and 17), especially [SIGMA](n-3) long-chain PUFAs in hepatopancreas and DHA in muscle, indicating that white shrimp need more (n-3) long-chain PUFAs at 3. This is in agreement with the finding that a greater DHA content results in better tolerance to low salinity in Chinese mitten crab (Eriocheir sinensis) larvae (Sui et al. 2007).

The pathways from LNA to EPA and DHA involve desaturation at the A6 and A5 positions of the carbon chain, and an intermediate-chain elongation step. However, there is wide variation among aquatic animals in their ability to synthesize HUFAs (Sargent et al. 2002). Shrimp have a limited ability to synthesize (n-6) and (n-3) families of fatty acids de novo, including LA and LNA (Suprayudi et al. 2004). Marine shrimp also have a limited ability to elongate and desaturate LNA to HUFAs, such as 20:4(n-6), EPA, and DHA (Kayama et al. 1980). Because of this, long-chain PUFAs such as fish oil have been added to the diets of marine shrimp. In contrast to marine species, freshwater species have a lower requirement for (n-3) HUFAs and a greater capacity to elongate and desaturate PUFAs from shorter chain fatty acids such as 18:3(n-3) (Sargent et al. 1999). In the current study, ELOVL6, A6FAD, and A5FAD activity was detected in Lilopenaeus vannamei hepatopancreas, and this enzyme activity tended to increase at low salinity. It was also noted that 18:3(n-3) was significantly greater in shrimp hepatopancreas at 3. In shrimp muscle and gill, both DHA and [SIGMA](n-3) long-chain PUFAs at 3 were increased compared with the other 2 salinities. These findings, including the relevant enzyme activity and DHA and EPA accumulation (4.5% 6%) in muscle and hepatopancreas of shrimp fed diets containing extremely low or no DHA and EPA (< 0.1 %), together with the findings of the key genes in the process for lc-HUFA synthesis (K. Chen, E. Li, and L. Chen, unpubl. data) could indicate that, as a marine species, L. vannamei has an ability to synthesize both DHA and EPA from LNA, and ambient low salinity may improve its ability to synthesize more long-chain PUFAs, especially EPA and DHA, to reduce stress at low salinities.

In summary, Litopenaeus vannamei showed a series of physiological responses to ambient salinity challenges (Fig. 1). Gills responded first to osmotic stress as the primary organ for osmoregulation (Pequeux 1995), and [SIGMA]SSFA was used through [beta]-oxidation to supply enough energy for osmoregulation (Deering et al. 1997), resulting in low [SIGMA]SFA in gills, because osmoregulation needs more energy to maintain intracellular and extracellular osmotic equilibrium (Evans et al. 2005, Tseng & Hwang 2008). However, aquatic animals need to produce sufficient energy to cope with longterm stress (not stress limited to the scope of 96 h). Total triacylglycerol, HSL, and ATGL activity was increased in hepatopancreas, which is the main lipid reserve, lipid metabolism, and fatty acid synthesis site in crustaceans (Boer et al. 2007), and more fatty acids were hydrolyzed from monoglycerol, diacylglycerol, and TAG. Those fatty acids were transferred to the gill by lipoprotein to meet the energy requirement for osmoregulation.

Last, 18:3(n-3) and (n-3) long-chain PUFA levels increased in gill, hepatopancreas, and muscle under either hypo--or hyperosmotic stress to limit the salinity impact on Litopenaeus vannamei. During this long-term stress, ELOVL6, [DELTA]5FAD, and 6FAD activity was inhibited as a result of (n-3) long-chain PUFA accumulation in the organism (feedback regulation). In addition, (n-3) series releasing in all tissues would have positive effects during ambient osmotic stress, as reported in other aquatic animals (Palacios et al. 2004a, Martins et al. 2006, Sui et al. 2007). Detained function of (n-3) series in osmotic regulation of aquatic animals needs further investigation.

[FIGURE 1 OMITTED]

ACKNOWLEDGMENTS

This research was supported by grants from the National Natural Science Foundation of China (nos. 31472291 and 31172422), the Special Fund for Agro-scientific Research in the Public Interest (nos. 201003020 and 201203065), the National "Twelfth Five-Year" Plan for Science & Technology Support (no. 2012BAD25B03). the National Basic Research Program (973Program, no. 2014CB138603), and the Shanghai University Knowledge Service Platform Shanghai Ocean University Aquatic Animal Breeding Center (no. ZF1206), and in part by the E-Institute of Shanghai Municipal Education Commission (no. E03009) and the ECNU innovation fund.

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KE CHEN, (1), ERCHAO LI, (1), *, LEI GAN, (1), XIAODAN WANG, (1), CHANG XU, (1), HEIZHAO LIN, (2), JIAN G. QIN, (3), LIQIAO CHEN, (1), *

(1) School of Life Sciences, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China; (2) Shenzhen Base of South China Sea Fisheries Research Institute, S3 Dadui Village, Shenzhen 518121, China; (3) School of Biological Sciences, Flinders University, GPO Box 2100, Adelaide SA 5001, Australia

* Corresponding authors. E-mail: ecli@bio.ecnu.edu.cn (E. Li) and lqchen@bio.ecnu.edu.cn (L. Chen)

DOI: 10.2983/035.033.0317
TABLE 1.

Fatty acid composition (percent by weight of total fatty acids)
and minerals (percent of diet) of the commercial diet used in
this study.

                Feed content

Fatty acid
  14:0              1.89
  16:0             16.63
  18:0              4.36
  24:0              0.51
  [SIGMA]SFA       24.34
  16:1              2.30
  18:l(n-9)c       26.21
  20:ln-9           1.43
  24:ln9            0.23
  [SIGMA]MUFA      30.60
  18:2(n-6)c       28.16
  18:3(n-3)         2.72
  20:5(n-3)         4.16
  22:6(n-3)         7.23
  [SIGMA]PUFA      45.07
  (n-3)            15.31
  (n-6)            29.75
  (n-3/n-6)         0.51
Cations
  [Ca.sup.++]       0.74
  [Na.sup.+]        0.44
  [K.sup.+]         0.91
  [Mg.sup.++]       0.28

MUFA, monounsaturated fatty acid; SFA, saturated fatty acid.

TABLE 2.

Contents of some key minerals in water used in this experiment
(grams per kilogram).

                   Salinity

             3      17     30

Sodium      0.35   4.30   9.28
Magnesium   0.04   0.52   1.12
Calcium     0.01   0.16   0.35
Potassium   0.01   0.16   0.33
Chloride    0.63   7.73   16.70

TABLE 3.

Growth, survival, and whole-body proximate composition (percent live
weight) of white shrimp at different salinities (percent).

Salinity        Survival                Weight gain

30         93.33 [+ or -] 1.67   652.87 [+ or -] 24.27 (a)
17         88.33 [+ or -] 3.00   645.89 [+ or -] 15.61 (a)
3          65.00 [+ or -] 9.61   548.34 [+ or -] 21.95 (b)
P value           0.07                     0.02

Salinity        Moisture               Protein

30         73.61 [+ or -] 1.56   18.04 [+ or -] 0.83
17         72.81 [+ or -] 1.66   19.31 [+ or -] 0.98
3          72.94 [+ or -] 0.22   19.38 [+ or -] 0.18
P value           0.90                  0.42

Salinity          Lipid                  Ash

30         1.36 [+ or -] 0.045   2.83 [+ or -] 0.094
17         1.37 [+ or -] 0.054   2.92 [+ or -] 0.095
3          1.37 [+ or -] 0.069   2.62 [+ or -] 0.067
P value           0.99                  0.12

Values within the same column with different letters represent
significant difference (P < 0.05).

TABLE 4.

Fatty acid composition (percent by weight of total fatty acids) in
muscle, gill, and hepatopancreas of white shrimp grown at
different salinities (percent).

                                  Hepatopancreas

                          30                        17

18:2(n-6)      26.87 [+ or -] 0.38        26.10 [+ or -] 0.66
18:3(n-3)       0.17 [+ or -] 0.02 (a)     0.29 [+ or -] 0.07 (a)
EPA             2.72 [+ or -] 0.11         2.69 [+ or -] 0.07
DHA             6.90 [+ or -] 0.11         6.63 [+ or -] 0.18
[SIGMA]SFA     23.08 [+ or -] 0.06        22.69 [+ or -] 0.75
[SIGMA]MUFA    35.85 [+ or -] 0.45        36.55 [+ or -] 0.13
[SIGMA]        41.08 [+ or -] 0.42        40.76 [+ or -] 0.88
[SIGMA](n-3)   10.95 [+ or -] 0.17 (ab)   10.74 [+ or -] 0.24 (a)
[SIGMA](n-6)   28.40 [+ or -] 0.38        28.17 [+ or -] 0.90
(n-3)/(n-6)              0.4                        0.4

                         Hepatopancreas

                          3              P value

18:2(n-6)      25.91 [+ or -] 0.14        0.34
18:3(n-3)       0.64 [+ or -] 0.10 (b)    0.01
EPA             2.97 [+ or -] 0.07        0.12
DHA             6.84 [+ or -] 0.17        0.48
[SIGMA]SFA     22.63 [+ or -] 0.23        0.76
[SIGMA]MUFA    36.90 [+ or -] 0.15        0.10
[SIGMA]        40.47 [+ or -] 0.38        0.79
[SIGMA](n-3)   11.67 [+ or -] 0.33 (b)    0.01
[SIGMA](n-6)   27.24 [+ or -] 0.08        0.37
(n-3)/(n-6)              0.4

                                     Muscle

                         30                        17

18:2(n-6)      14.72 [+ or -] 0.19 (c)   13.68 [+ or -] 0.07 (b)
18:3(n-3)       0.52 [+ or -] 0.03        0.46 [+ or -] 0.02
EPA            14.52 [+ or -] 0.17 (a)   15.36 [+ or -] 0.23 (b)
DHA             9.27 [+ or -] 0.08        8.88 [+ or -] 0.16
[SIGMA]SFA     32.24 [+ or -] 0.20 (a)   33.24 [+ or -] 0.36 (b)
[SIGMA]MUFA    20.23 [+ or -] 0.15       19.79 [+ or -] 0.19
[SIGMA]        47.53 [+ or -] 0.29       46.97 [+ or -] 0.49
[SIGMA](n-3)   30.47 [+ or -] 0.30       31.11 [+ or -] 0.38
[SIGMA](n-6)        14.720.19 (a)        13.68 [+ or -] 0.17 (b)
(n-3)/(n-6)              2.1                       2.3

                              Muscle

                          3              P value

18:2(n-6)      12.71 [+ or -] 0.31 (a)    0.01
18:3(n-3)       0.46 [+ or -] 0.03        0.27
EPA            16.26 [+ or -] 0.20 (c)    0.01
DHA             9.61 [+ or -] 0.09        0.01
[SIGMA]SFA     33.57 [+ or -] 0.24 (b)    0.03
[SIGMA]MUFA    19.75 [+ or -] 0.21        0.19
[SIGMA]        46.68 [+ or -] 0.22        0.30
[SIGMA](n-3)   32.05 [+ or -] 0.46        0.07
[SIGMA](n-6)   12.71 [+ or -] 0.31 (a)    0.01
(n-3)/(n-6)              2.5

                                      Gill

                         30                         17

18:2(n-6)      14.33 [+ or -] 0.94       13.88 [+ or -] 0.31
18:3(n-3)       0.71 [+ or -] 0.01        0.71 [+ or -] 0.43
EPA            12.69 [+ or -] 0.25       13.22 [+ or -] 0.58
DHA            12.62 [+ or -] 0.31       13.29 [+ or -] 0.26
[SIGMA]SFA     35.02 [+ or -] 0.12 (b)   34.20 [+ or -] 0.24 (ab)
[SIGMA]MUFA    19.51 [+ or -] 0.17       19.62 [+ or -] 0.64
[SIGMA]        45.47 [+ or -] 0.26       46.18 [+ or -] 0.48
[SIGMA](n-3)   29.59 [+ or -] 0.42       30.68 [+ or -] 0.76
[SIGMA](n-6)   14.52 [+ or -] 0.12       14.09 [+ or -] 0.34
(n-3)/(n-6)              2.0                       2.1

                              Gill

                          3              P value

18:2(n-6)      13.69 [+ or -] 0.28        0.25
18:3(n-3)       0.71 [+ or -] 0.40        0.99
EPA            13.32 [+ or -] 0.36        0.55
DHA            13.45 [+ or -] 0.36        0.21
[SIGMA]SFA     33.80 [+ or -] 0.32 (a)    0.03
[SIGMA]MUFA    19.86 [+ or -] 0.42        0.86
[SIGMA]        46.34 [+ or -] 0.17        0.22
[SIGMA](n-3)   31.07 [+ or -] 0.52        0.25
[SIGMA](n-6)   13.85 [+ or -] 0.12        0.31
(n-3)/(n-6)              2.2

Values in the same row with different letters represent a
significant difference (P < 0.05). DHA, docosahexaenoic acid;
EPA, eicosapentaenoic acid; MUFA, monounsaturated fatty acid;
PUFA, polyunsaturated fatty acid; SFA, saturated fatty acid.

TABLE 5.

Lipid metabolism related to biochemical parameters in
hemolymph of white shrimp grown at different salinities.

                               30                        17

TAG (nmol/L)         16.13 [+ or -] 0.52 (a)   13.61 [+ or -] 0.09 (b)
TC (nmol/L)           1.42 [+ or -] 0.05        1.39 [+ or -] 0.08
HDL ([micro]mol/L)    8.47 [+ or -] 0.22 (b)    6.68 [+ or -] 0.25 (a)
LDL ([micro]mol/L)    8.08 [+ or -] 0.20        8.93 [+ or -] 0.97
VLDL ([micro]g/mL)    5.79 [+ or -] 0.25        5.78 [+ or -] 0.31

                                3              P value

TAG (nmol/L)         15.44 [+ or -] 0.40 (a)    0.01
TC (nmol/L)           1.25 [+ or -] 0.03        0.16
HDL ([micro]mol/L)    6.37 [+ or -] 0.06 (a)    0.01
LDL ([micro]mol/L)    6.78 [+ or -] 0.34        0.11
VLDL ([micro]g/mL)    5.42 [+ or -] 0.20        0.56

Values in the same row with different letters represent a
significant difference (P < 0.05). HDL, high-density lipoprotein;
LDL, low-density lipoprotein; TAG, total triacylglycerol; TC,
total cholesterol; VLDL, very low-density lipoprotein.

TABLE 6.

Lipid metabolism related to enzyme activities (in units per
gram protein) in hepatopancreas of white shrimp grown at
different salinities.

                 30                   17

ATGL     2.22 [+ or -] 0.42   1.55 [+ or -] 0.22
HSL      1.17 [+ or -] 0.19   0.67 [+ or -] 0.10
LPL      0.35 [+ or -] 0.06   0.23 [+ or -] 0.03
FAS      1.73 [+ or -] 0.35   1.15 [+ or -] 0.21
DGAT2    2.87 [+ or -] 0.50   2.24 [+ or -] 0.42
ELOVL6   0.22 [+ or -] 0.04   0.16 [+ or -] 0.02
A6FAD    0.95 [+ or -] 0.12   0.66 [+ or -] 0.09
A5FAD    1.07 [+ or -] 0.17   0.75 [+ or -] 0.10

                 3            P value

ATGL     1.73 [+ or -] 0.15    0.312
HSL      0.96 [+ or -] 0.20    0.184
LPL      0.30 [+ or -] 0.05    0.250
FAS      1.17 [+ or -] 0.10    0.233
DGAT2    2.06 [+ or -] 0.16    0.376
ELOVL6   0.16 [+ or -] 0.01    0.169
A6FAD    0.64 [+ or -] 0.04    0.081
A5FAD    0.80 [+ or -] 0.04    0.194

A5FAD, A5 fatty acid desaturase; A6FAD, A6 fatty acid desaturase;
ATGL, adipose triacylglycerol lipase; DGAT2, diacylglycerol
acyltrans- ferase 2; ELOVL6, elongase of very long chain fatty
acids 6; FAS, fatty acid synthase; HSL, hormone sensitive lipase;
LPL, lipoprotein lipase.
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Author:Chen, Ke; Li, Erchao; Gan, Lei; Wang, Xiaodan; Xu, Chang; Lin, Heizhao; Qin, Jian G.; Chen, Liqiao
Publication:Journal of Shellfish Research
Article Type:Report
Date:Dec 1, 2014
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