Effects of Lactic Acid Bacteria and Citrus Essential Oil on the Quality of Vacuum-Packed Sea Bass (Dicentrarchus labrax) Fillets During Refrigerated Storage

The preservative effect of refrigerated and vacuum-packed sea bass (Dicentrarchus labrax) fillets inoculated with four mixtures of lactic acid bacteria (LAB) (Lactococcus lactis, Lactobacillus plantarum, and Carnobacterium piscicola) and incorporated with citrus essential oil (CEO) was evaluated on the basis of microbiological and biochemical analysis.

Initially, sea bass fillets showed high nutritional quality. During refrigerated storage, lipid contents did not show a significant decrease in any fish fillets; meanwhile, important proteolysis was observed in untreated control. In addition, results indicated that both CEO and LAB strains exhibited antimicrobial activity against spoilage, pathogenic, and fungi flora. Moreover, the total volatile bases (TVB-N) values were higher in control fillets, and the lowest TVB-N values were observed in Control CEO and C3 + CEO (30.47 ± 0.00 and 32.29 ± 1.12 mg TVB-N/100 g, respectively). Also, the levels of biogenic amines increased in all fillets without exceeding the upper limit of acceptability except for untreated control (sum of about 1396.63 ppm). Furthermore, this combined treatment ameliorated the muscle liquid-holding capacity, which improves technological properties.

Overall, this treatment may open new promising opportunities for the biopreservation of fish products by enhancing the period of storage of refrigerated and vacuum-packed sea bass fillets.     

Enrichment of C20-22 Polyunsaturated Fatty Acids from Refined Liver Oil of Leafscale Gulper Shark,Centrophorus squamosus

The C_20-22 polyunsaturated fatty acids (C_20-22 PUFAs), mainly eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), were concentrated from the refined liver oil of deep sea leafscale gulper shark, Centrophorus squamosus, by sequential processes of winterization, urea complexation, and argentation chromatography. Winterization at 4°C using acetonitrile as solvent showed significant reduction of the total saturated fatty acid content (12%) with a concomitant increase of polyunsaturated fatty acids (36.3%). The urea complexation process significantly enriched the total polyunsaturated fatty acids (49.5%), with a reduction in saturated fatty acids (83.9%). Silica gel based argentation chromatography further concentrated the esters of C_20-22 PUFA (>99 percent purity). Nuclear Magnetic Resonance spectroscopy was used as a chemical fingerprinting tool to study the enrichment of C_20-22 PUFAs at various stages of the purification process. An increase in the proton signal intensity at the olefinic region (at δ 4–6) and a decrease in the aliphatic signals (at δ 0.5–2) showed that the process successfully enriched the C_20-22 PUFAs.

Abbreviations: PUFA, polyunsaturated fatty acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; FAME, fatty acid methyl esters; SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; NMR, nuclear magnetic resonance; GCMS, gas chromatography mass spectrometry; FFA, free fatty acid.     

Effects of kelp residues fermented with probiotics on the culture of sea cucumber,Apostichopus japonicus

The kelp aquaculture production in China is the largest in the world, and a large amount of kelp residue is produced by kelp processing. Kelp residues contain substantial quantities of crude fibre, protein, and residual alginic acid, and may be used as feedstuff for aquaculture animals. In this study, we used probiotics to ferment kelp residues to improve kelp nutrient content and then fed the fermented kelp to the sea cucumber, Apostichopus japonicus. To study the effect of fermented feed on sea cucumber, its growth performance, digestive enzyme activity, diversity of intestinal microbiota and water quality of the sea cucumber culture water were determined. Growth performance of sea cucumber fed with fermented feed significantly (p < .01) increased when compared with sea cucumber fed with formulated feed. Amylase, cellulose and alginase activities were significantly (p < .01) higher in the fermented feed group when compared with the formulated feed group. The total number and diversity of intestinal microbiota showed a significant increase in sea cucumbers fed with the fermented feed. The water quality of the fermented feed group showed much lower ammonia and nitrite (<0.050 mg/L) levels when compared with the formulated feed group. These results suggest that kelp residues fermented with probiotics enhance the growth, digestive enzyme activities and intestinal microbiota of sea cucumbers and improve the culture water quality. Fermented kelp residues are a new supplementary nutrient source for sea cucumbers and may be applicable to other animal aquacultures.     

Purification and characterization of a cysteine-like protease from the body wall of the sea cucumber <Emphasis Type="Italic">Stichopus japonicus</Emphasis>

The sea cucumber (Stichopus japonicus) is able to undergo autolysis in response to a variety of environmental and mechanical cues. Within the framework of a long-term study of this phenomenon we have purified a protease from the body wall of the sea cucumber by means of ion-exchange chromatography with DE-52 cellulose and gel filtration chromatography with Sephadex G-100. The final enzyme preparation was nearly homogeneous on polyacrylamide gel electrophoresis, and its molecular weight was estimated to be approximately 35.5 kDa. The purified enzyme exhibited a maximum activity for the hydrolysis of casein at pH 7.0 and 50°C and a remarkable stability at pH 4.0–7.0 and 40–60°C. Based on the inhibition and activation profiles obtained with numerous specific protease inhibitors and an activator, the protease purified from the body wall of the sea cucumber was defined to be a cysteine-like protease.     

Effects of dietary protein levels on the activity of the digestive enzyme of albino and normal Apostichopus japonicus (Selenka)

We evaluated the effects of different proportions of dietary protein (5%, 10%, 15%, 20%, 25% and 30% protein) on the activity of digestive enzymes of normal and albino Apostichopus japonicus. The experimental diets were fed for 60 days, the optimal conditions for digestive enzyme activity in sea cucumbers were studied. The optimal temperature for protease was 29.3°C and the optimal pH was 1.8. The optimal temperature for amylase was 34.3°C and the optimal pH was 6.7. The optimal temperature for cellulase was 56°C and the optimal pH was 5.9. The activity of intestinal protease increased at first and then decreased as the proportion of dietary protein increased, reaching the maximum when the proportion of protein was 19.7%. The activity of protease in the intestine of normal sea cucumber was significantly lower than that of albino sea cucumber, and the activity of amylase was significantly higher than that of albino sea cucumber. This study is expected to provide a basis for further explaining the ecological difference of albino and normal A. japonicus.     

Oxidative Stability of Common Kilka (Clupeonella cultriventris caspia) Oil Supplemented with Microwave Extracted Ghure (Unripe Grape) Marc Extract

The objective of this study was to evaluate the effect of microwave extracted Ghure (unripe grape) marc extract on common kilka (Clupeonella cultriventris caspia) oil oxidation during accelerated storage. The antioxidant activity of Ghure marc extract was compared with those of α-tocopherol and BHT. The Ghure marc extract significantly reduced the peroxide and p-anisidine value of kilka oil. Even though the effect of Ghure marc extract on reducing the oxidation of kilka oil was similar to the effect of BHT, it was functionally more effective than α-tocopherol. Generally, Ghure marc extract could be considered as a potential source of natural antioxidants, with inexpensive costs, for improving the oxidative stability of kilka oil.

Abbreviations: AA, Antioxidant activity; AOP, Antioxidant power; AV, p-Anisidine value; CUPRAC, Cupric ion reducing antioxidant capacity; DHA, Docosahexaenoic acid; EPA, Eicosapentaenoic acid; FIC, Ferrous ion chelating; GME, Ghure marc extract; FRAP, Ferrous ion reducing antioxidant power; KO, Kilka oil; IP, Induction period; MAE, Microwave-assisted extraction; MUFA, Monounsaturated fatty acid; PUFA, Polyunsaturated fatty acid; PV, peroxide value; PF, Protection factor; RSA, Radical scavenging activity; SFA, Saturated fatty acids; TFC, Total flavonoid content; TPC, total phenolic content TV, totox value.     

Structural Changes,Volatile Compounds and Antioxidant Activities of Maillard Reaction Products Derived from Scallop (Patinopecten yessoensis) Female Gonad Hydrolysates

In order to improve the utilization of scallop byproducts, scallop female gonad hydrolysates (SFGHs) were prepared using alcalase and ribose at a mass ratio of 1:2 and pH 7.0 (95°C, up to 12 h) to develop heterogeneous Maillard-type antioxidant and flavor compounds. The formation of Schiff’s base as well as modification of the amide bands in Maillard reaction products (MRPs) were investigated using ultraviolet–visible, fluorescence, and Fourier transform infrared spectroscopy. The significant decrease of amino acid residues explained the strong Maillard reactivity of SFGHs. MRPs with enhanced ABTS⁺ radical scavenging capacity over SFGHs promoted the survival of HepG2 cells treated with hydrogen peroxide. Moreover, 19 new volatile compounds were produced by the reaction of SFGHs with ribose. These results suggest that SFGHs–ribose MRPs can be potentially used as antioxidants with flavor properties.

Abbreviations: SFGs: scallop female gonads; SFGHs: scallop female gonad hydrolysates; ABTS: 2?2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid); BHT: butylated hydroxytoluene; Trolox: 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; MRPs: Maillard reaction product; H₂O₂: hydrogen peroxide; HS-SPME/GC/MS: Headspace solid phase micro-extraction/gas chromatography/mass spectrometry.     

Immune responses of the sea cucumber Apostichopus japonicus to stress in two different transport systems

We report the effect of transport stress on the immune responses of the sea cucumber Apostichopus japonicus. The total coelomocytes counts, phagocytosis activity, reactive oxygen species production, acid phosphatase activity, phenoloxidase activity and catecholamine levels were measured in A. japonicus following both damp and water transportation methods. With both transport methods, stress resulted in significant elevation of catecholamine levels. Total coelomocytes counts increased following transportation, whereas phagocytic activity and reactive oxygen species production decreased. Damp transport significantly depressed acid phosphatase and phenoloxidase activity in A. japonicus. However, there were no significant differences in acid phosphatase and phenoloxidase activity after water transportation. These results show that transport stress induces modifications in the immune system of A. japonicus and that damp transport elicited more severe stress than water transport. This study increased understanding of the mechanism of transport stress inducing neuroendocrine responses and immune modification in A. japonicus. The information obtained should be helpful to optimize transport process in sea cucumber culture.     

Effects of l‐tryptophan on the performance,energy partitioning and endocrine response of Japanese sea cucumber (Apostichopus japonicus Selenka) exposed to crowding stress

The effects of dietary tryptophan on growth performance, energy budget and endocrine response of sea cucumber Apostichopus japonicus (Selenka) were studied, to test whether the tryptophan could mitigate the crowding stress response of the sea cucumber. Four density treatments of the sea cucumber (i.e. 4, 8, 16 and 32 individuals per 40 L water, represented as L, ML, MH and H) were fed with diets containing 0 (control), 1%, 3% and 5% l ‐tryptophan, respectively, for 75 days. The results showed that the specific growth rate (SGR) and feed conversion ratio (FCE) of A. japonicus decreased with increasing in the stocking densities but increased after supplementation of 1% and 3% tryptophan. The energy allocation of the A. japonicus was affected significantly by stocking density and dietary tryptophan treatments (p < .05). In general, the energy consumed (C) and energy used for growth (G) decreased with the increasing in the stocking densities. The highest proportion of energy deposited to growth occurred in each 3% treatment (L, 6.38%; ML, 6.12%; MH, 4.56% and H, 4.14%), which were significantly higher than the controls (p < .05) respectively. Higher cortisol, glucose and lactate levels of A. japonicus were recorded in the control treatments of MH and H, but l ‐tryptophan supplementation could reduce the levels of cortisol, glucose and lactate of the test animals. The present results proved that the growth performance of the sea cucumber was inhibited by high stocking densities, while dietary supplementation of tryptophan could significantly mitigate the crowding stress, and improve the growth of sea cucumber.     

An artificial oyster‐shell reef for the culture and stock enhancement of sea cucumber,Apostichopus japonicus,in shallow seawater

Because of its high nutritional value and health benefits, aquaculture production of Apostichopus japonicus in China is the largest of any single species. Therefore, the development of new farming methods is of considerable significance. In this study, discarded oyster shells have been used to create an artificial reef for the culture of this species. The results have shown that from 6th March 2009 to 26th November 2009, the wet weight of sea cucumber increased from 49.57 ± 1.16 to 79.87 ± 1.46 g ind^?1. Between 16th July and 18th October, the specific growth rate and daily weight gain of A. japonicus differed significantly from other periods. Population density was higher within the reef compared with outside the reef area, and the difference was significant (P < 0.01). The maximum distance between A. japonicus individuals within the reef area on 3rd March and 16th July was 65.0 ± 3.3 and 62.9 ± 4.4 cm, respectively, but the difference was not significant (P > 0.05). The diatom species attached to the oyster shells were similar to those found in the stomach content of A. japonicus. In conclusion, the oyster‐shell reef provides a suitable habitat and shelter for the culture of the sea cucumber, A. japonicus.     

Vitamin E requirement of sea cucumber (Apostichopus japonicus) and its' effects on nonspecific immune responses

This feeding trial was conducted to determine the vitamin E requirement of sea cucumber (Apostichopus japonicus) and to study the effects of vitamin E on nonspecific immune parameters. Commercial sea cucumber diets supplemented with 0, 50, 100, 200, 500 or 1000 mg kg^?1 vitamin E were fed to juvenile sea cucumber (7.96 ± 0.01 g) for 60 days. Specific growth rate and total coelomocyte counts were maximized in sea cucumber fed diets supplemented with 100 mg kg^?1 vitamin E. Reactive oxygen species production was maximized at 50 mg kg^?1 vitamin E, whereas superoxide dismutase activity was the highest in sea cucumber fed diets supplemented with 100 mg kg^?1 vitamin E. The vitamin E concentration in the body wall of the sea cucumber increased as the vitamin E level in the diet increased. Analysis of specific growth rate and total coelomocyte counts of the sea cucumber indicated that 88–92 mg kg^?1 vitamin E is required for maximal growth and nonspecific immune responses of A. japonicus and that 114.7 mg kg^?1 vitamin E is required to minimize lipid peroxidation levels.     

Combined influence of water temperature, salinity and body size on energy budget in the sea cucumber Apostichopus japonicus Selenka

The worldwide demand for sea cucumber is outpacing the sustainable harvest capabilities of fisheries. Sea cucumber ranches and farms are striving to supplement wild harvest, but variable temperature and salinity conditions in pond culture systems make sea cucumber production challenging. In this study, we evaluated how water temperature, salinity and body size affected the energy budget of pond-cultured sea cucumber Apostichopus japonicus Selenka. An orthogonal design was used to identify the most suitable conditions for energy consumption and scope for growth (SFG). After the 42-day experimental period, we found that water temperature, salinity and body size significantly influenced energy consumption, while salinity and body size were the main influencing factors on SFG. Based on these results, we suggest that a water temperature of 16 °C and a salinity of 30 g L^?1 are optimal conditions for stocking sea cucumber A. japonicus with a body size of 37.34 ± 4.63 g. As such, the optimum stocking seasons for sea cucumber A. japonicus may be April in the spring and October in the autumn.     

Intra‐specific effects of sea cucumber (Apostichopus japonicus) with reference to stocking density and body size

The present studies deal with the intra‐specific effects of sea cucumber Apostichopus japonicus with unlimited food resources, especially the effects of stocking density on growth variation of the animal and energetic changes of small individuals under the stress of large individuals. The results showed that with the initial body weight of 5.12±0.09–6.11±0.26 g of sea cucumber among the densities of 5, 10, 20, 30, 40 and 50 ind./100 L, the density of 20 ind./100 L was the optimum stocking density because of its highest specific growth rate, crude protein content and crude lipid content in tissue. Individual growth variation of A. japonicus increased with the increase of stocking densities, whereas no significant differences in variation were found when the density was over 30 ind./100 L (P>0.05). The low‐weight individuals under the stress of heavy‐weight individuals exhibited obvious changes in energetics, such as lower ingestion rate, lower energy deposited as growth but higher respiration and excretion. The coefficient of variation in growth of the animals was over 70% due to the simultaneous action of aggression and maybe a factor of chemical mediator, and led to significant changes in the energetics of small‐sized individuals.     

Effect of salinity on growth and energy budget of red and green colour variant sea cucumber Apostichopus japonicus (Selenca)

Sea cucumber, Apostichopus japonicus (Selenca), tolerates salinity fluctuations inhabiting intertide zone. This study deals with growth, food intake, food conversion and the bioenergetic responses of the red variant (wet weight of 2.60 ± 0.11g) and green variant (wet weight of 2.56 ± 0.08 g) A. japonicus to different salinities of 22, 26, 30, 34, and 38 psu at 16.5 ± 0.5°C. The results showed that salinity had a significant effect on specific growth rate (SGR) of both green and red variants A. japonicus (P < 0.05). Both colour variants of sea cucumber had highest SGR at 30 psu, and then decreased when salinity below or above this point. Maximum SGR (the green 1.07 ± 0.08% day^?1, the red 1.14 ± 0.09% day^?1 respectively) is related with maximum food intake (FI) and highest food conversion efficiency (FCE) (P < 0.05) occurring at 30 psu. Only under 22 psu, the green variant grew faster than the red variant (P < 0.05), and under other four salinity treatments there was no significant difference between SGR of two colour variant holothruians (P > 0.05). Values of adaptable salinity scope for green and red variants sea cucumber survival are 18.5~39 psu and 20.9~38.6 psu respectively. The average energy budget formula of sea cucumber at 30 psu was: 100C = 6G +42F +3U+49R (C, energy ingested; G, energy for growth; F, energy loss as faeces; U, energy used for ammonia excretion; R, energy loss for respiration). The sea cucumber had maximum energy ingested (C) and highest proportion of energy for growth (G) at 30 psu, and then decreased when salinity is above or below this salinity. Both red and green variants of A. japonicus deposited for growth were very low, and the energy loss in faeces and energy for respiration accounted for the majority of assimilation energy. The result clearly showed that the optimum condition for farming green and red variants A. japonicus, both with respect growth and energy allocation, is the salinity scope of 26 ~ 30 psu.     

Preliminary Study of the Optimum Dietary Ascorbic Acid Level in Sea Cucumber,Apostichopus japonicus (Selenka)

A 14‐wk feeding trial was carried out to evaluate the optimum dietary ascorbic acid (AA) level in juvenile sea cucumber, Apostichopus japonicus. Sea cucumbers averaging 1.49 ± 0.07 g (mean ± SD) were randomly distributed into 18 rectangular plastic tanks of 20 L capacity in a recirculating system (20 animals per tank). Six semipurified experimental diets were formulated to contain 0 (l ‐ascorbyl‐2‐monophosphate [AMP]; AMP0), 30 (AMP24), 60 (AMP48), 120 (AMP100), 240 (AMP206), and 1200 (AMP1045) mg AA/kg diet in the form of AMP using casein as the main protein source. Sea cucumbers were fed each of the six experimental diets in triplicate groups. At the end of 14 wk of feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of sea cucumbers fed AMP100, AMP206, and AMP1045 were significantly (P < 0.05) higher than those of animals fed AMP0, AMP24, and AMP48. However, there were no significant differences in WG, SGR, and FE among sea cucumbers fed AMP100, AMP206, and AMP1045 and among animals fed AMP0, AMP24, and AMP48. Whole‐body vitamin C concentration increased with AA content of the diets. Broken‐line analysis of WG showed an optimum dietary AA level of 105.3 mg AA/kg diet in sea cucumber. These results indicated that the optimum dietary vitamin C level in sea cucumber in the form of AMP could be greater than 100 mg AA/kg diet but less than 105.3 mg AA/kg diet.     

Feasibility of Offshore Co‐culture of Abalone,Haliotis discus hannai Ino,and Sea Cucumber,Apostichopus japonicus,in a Temperate Zone

Feasibility of offshore co‐culture of abalone and sea cucumber was investigated in Northern China. Survival and growth of abalone, Haliotis discus hannai Ino, and sea cucumber, Apostichopus japonicus, co‐cultured in abalone cages from suspended longlines, in the offshore area, were examined. Abalone and sea cucumbers were co‐cultured at density ratios of both 3:1 and 6:1 for 1 yr. Abalone were fed with fresh kelp and no additional feed was given to sea cucumbers. Survival of abalone and sea cucumber was 100% for all treatments. Abalone and sea cucumber grew well; the body weight (BW) of abalone and sea cucumber was nearly doubled and had reached a commercial size. There were no significant differences in the growth rates for both abalone and sea cucumber between the two density treatments. The specific growth rate of BW of abalone (SGRbw) was highest in June, with a value of 0.536%/d. Growth rate of sea cucumber (SGRsc) was highest in December, reached 1.84%/d, with an annual average SGRsc of 0.182%/d. Results suggested that the offshore co‐culture of abalone and sea cucumber was feasible offshore. The co‐culture of abalone with sea cucumbers may provide an additional valuable crop without additional financial input.     

Effects of dietary heat‐killed Lactobacillus plantarum L‐137 (HK L‐137) on the growth performance,digestive enzymes and selected non‐specific immune responses in sea cucumber,Apostichopus japonicus Selenka

A feeding trial was conducted to evaluate the efficacy of dietary heat‐killed Lactobacillus plantarum L‐137 (HK L‐137) on growth performance, digestive, non‐specific immune and phagocytosis of sea cucumber, Apostichopus japonicus. Sea cucumbers (initial body weight 1.35 ± 0.04 g) were fed diets supplemented with five levels of HK L‐137 (0, 0.005, 0.025, 0.05 and 0.25 g HK L‐137 kg^?1 diets) for 60 days. Results indicated sea cucumbers fed with diets containing 0.05 and 0.25 g HK L‐137 kg^?1 diets showed significantly (P < 0.05) higher body weight gain and specific growth rate than other groups. Sea cucumbers fed with diets containing 0.05 and 0.25 g HK L‐137 kg^?1 diets showed significantly (P < 0.05) higher protease activity than control group. Higher amylase, lysozyme and phagocytic activities were found in 0.25 g HK L‐137 kg^?1 diet group. Higher superoxide dismutase enzyme and alkaline phosphatase activity was found in 0.05 g HK L‐137 kg^?1. While no significant differences (P > 0.05) were found in acid phosphatase activity. These results suggested that dietary supplementation of 0.05 g HK L‐137 kg^?1 diets would have benefit on growth, digestive enzymes and several non‐specific immune parameters of sea cucumber.     

亚硒酸钠对刺参免疫反应中体腔液酶活力的影响

为了合理评价硒对水产养殖刺参的作用,实验检测和观察了室内模拟亚硒酸钠处理及病菌感染条件下刺参体腔液免疫酶的变化、组织病理变化和相对保护率。结果表明,随着亚硒酸钠处理强度的增加,刺参体腔液中超氧物岐化酶(SOD)、谷胱甘肽过氧化物酶(GP-X)、溶菌酶(LYZ)、酚氧化酶(PO)及碱性磷酸酶(ALP)活性升高;在同时感染病菌的情况下,SOD、GP-X及LYZ活性表现为先升高后下降的趋势,PO和ALP活性则持续上升,但随亚硒酸钠浓度升高,ALP活性增加的幅度减少,而较高亚硒酸钠浓度时累计发病率上升,相对保护率下降。研究结果表明,适宜浓度的亚硒酸钠可增强刺参对病菌感染的免疫力,而病菌感染可以加剧亚硒酸钠胁迫对刺参造成的免疫功能损伤,所以适度利用硒可减轻刺参养殖病害的发生。     

Dietary supplements of guanosine improve the growth,non‐specific immunity of sea cucumber,Apostichopus japonicus Selenka,and its resistance against Vibrio splendidus

The growth response, non‐specific immune activities and disease resistance were measured in sea cucumber, Apostichopus japonicus Selenka (initial average weight 6.80 ± 0.10 g), when fed diets supplemented with graded levels of guanosine from the guanosine‐5’‐monophosphate disodium (GMP) at 0 (control), 0.3, 0.6 and 1.2 g/kg for 8 weeks. The results showed that GMP supplemented at 0.6 and 1.2 g/kg significantly enhanced the growth of sea cucumber. Sea cucumber fed a diet with 0.6 g/kg of GMP had significantly higher intracellular superoxide anion production, nitric oxide synthase activity, lysozyme activity and the total superoxide dismutase (T‐SOD) activity than those in control group (p < .05). Increased lysozyme activity and T‐SOD activity were also found in sea cucumber fed GMP at 1.2 g/kg. Moreover, there was significantly lower cumulative mortality after the disease challenge in sea cucumber fed the diets with 0.6 and 1.2 g/kg GMP than that in control and 0.3 g/kg GMP groups (p < .05), and no significant difference was observed between 0.6 and 1.2 g/kg GMP groups. These results suggested that feeding GMP at a dose of 0.6 g/kg could enhance growth, non‐specific immunity of sea cucumber as well as its resistance against Vibrio splendidus.     

Effects of Dietary Yeast Polysaccharides on the Immune Responses of Apostichopus japonicus to a Sudden Drop in Temperature

The effect of yeast polysaccharides (YSPs) on immune function was evaluated in sea cucumber, Apostichopus japonicus, exposed to two protocols of acute decrease in temperature (T5 group: 20 C → 15 C → 10 C → 4 C; T10 group: 20 C → 10 C → 4 C). Juvenile sea cucumbers were fed an artificial diet containing 0.5% YSP. The phagocytic rate and index and the activities of lysozyme, acid phosphatase, and alkaline phosphatase were measured 24 h after each drop in temperature. The immune indices generally decreased in animals fed the basal diet (BD) in both temperature‐change protocols. Supplementing the feed of A. japonicus with YSPs led to increases in most indices compared with those fed the BD, except for the phagocytic index at 10 C in the T5 group. Therefore, the addition of YSPs to the BD improves the immunocompetence of A. japonicus during exposure to a rapid decrease in temperature.