Administration of the hot-water extract of Spirulina platensis enhanced the immune response of white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus

White shrimp Litopenaeus vannamei which had been injected with the hot-water extract of Spirulina platensis at 6, 10, and 20 μg g^?1, or immersed in aerated seawater containing extract at 200, 400, and 600 mg L^?1 were challenged with Vibrio alginolyticus at 1.5 × 10⁶ or 1.4 × 10⁶ colony-forming units (cfu) shrimp^?1, and then placed in seawater. Survival rates of shrimp that received the extract of S. platensis at 6–20 μg g^?1, and those of shrimp immersed in seawater containing the extract at 400 and 600 mg L^?1 were significantly higher than those of control shrimp after 24–96 and 48–96 h, respectively. In a separate experiment, the hyaline cell (HC) count, granular cell (GC, including semi-granular cell) count, total haemocyte count (THC), phenoloxidase (PO) activity, respiratory burst (RB), superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, and lysozyme activity were measured when shrimp were injected with the extract at 6, 10, and 20 μg g^?1, and immersed in seawater containing the extract at 200, 400, and 600 mg L^?1. These parameters directly increased with the concentration, and significantly increased when shrimp were immersed in the seawater containing the extract at 0.5–4 h. L. vannamei that received all doses of the extract via injection or via immersion all had increased phagocytic activity and clearance efficiency to V. alginolyticus at 12–72 h and 3–4 h, respectively. It was concluded that L. vannamei that received the hot-water extract of S. platensis had enhanced innate immunity and increased resistance against V. alginolyticus infection.     

Innate immunity of the white shrimp Litopenaeus vannamei weakened by the combination of a Vibrio alginolyticus injection and low-salinity stress

White shrimp Litopenaeus vannamei were reared at a salinity of 35‰ without a Vibrio alginolyticus injection (unchallenged group), and other shrimp were reared at 35‰, injected with tryptic-soy broth (TSB)-grown V. alginolyticus at 1.8 × 10⁵ colony-forming units (cfu) shrimp^?1 (challenged group), and then examined for the hyaline cell (HC) count, granular cell (GC, including semi-granular cell) count, total haemocyte count (THC), phenoloxidase (PO) activity, respiratory burst (RB) and superoxide dismutase (SOD) activity after transfer to 35‰ (control), 25‰, 20‰, and 15‰ for 1, 6, 12, 24, 72, and 120 h. Results indicated that the haemocyte count, PO activity, RB, and SOD activity of unchallenged shrimp and challenged shrimp that were transferred to low-salinity levels all began to significantly decrease at 6, 6, 6, and 1 h, respectively, and reached the lowest levels at 12 h. HC, GC, the THC, PO activity, RB, and SOD activity of unchallenged shrimp that were transferred to 15‰ decreased by 53%, 41%, 49%, 68%, 39%, and 62%, whereas those parameters of challenged shrimp that were transferred to 15‰ decreased by 79%, 78%, 79%, 82%, 54%, and 72%, respectively after 12 h compared to control shrimp. These immune parameters began to recover after 24–72 h for both unchallenged shrimp and challenged shrimp. We concluded that the innate immunity was weakened in white shrimp L. vannamei that received combined stresses of a V. alginolyticus injection, and low-salinity transfer. It was also concluded that shrimp with respectively 21%, 18%, 46%, and 28% lower THC, PO activity, RB, and SOD activity of the original values would be killed due to decreases in their immunity, and resistance to V. alginolyticus infection. Shrimp farming should be maintained at a constant high salinity level to prevent exacerbated decreases in innate immune parameters of shrimp when infected by a pathogen coupled with low-salinity stress leading to mortality.     

White shrimp Litopenaeus vannamei that received the hot-water extract of Gracilaria tenuistipitata showed earlier recovery in immunity after a Vibrio alginolyticus injection

White shrimp Litopenaeus vannamei which had been immersed in seawater containing the hot-water extract of Gracilaria tenuistipitata at 0 (control), 200, 400, and 600 mg L^?1 for 3 h, were challenged with Vibrio alginolyticus at 4.6 × 10⁶ colony-forming units (CFU) shrimp^?1 and then placed in normal seawater (34‰). The survival rates of shrimp immersed in 200, 400, and 600 mg L^?1 of the hot-water extract were significantly higher than those of control shrimp over 48–120 h. In another experiment, L. vannamei which had been immersed in the hot-water extract at 0, 200, 400, and 600 mg L^?1 for 3 h, were challenged with V. alginolyticus at 4.0 × 10⁶ CFU shrimp^?1, and the immune parameters examined included the haemocyte count, phenoloxidase (PO) activity, respiratory burst (RB), and superoxide dismutase (SOD) activity at 12–120 h post-challenge after shrimp had been released into normal seawater. Shrimp not exposed to the hot-water extract or V. alginolyticus served as the background control. Results indicated that the haemocyte count, PO activity, RB, and SOD activity of shrimp immersed in 600 mg L^?1 were significantly higher than those of control shrimp at 12–72 h post-challenge. Results also indicated that total haemocyte count (THC), PO activity, RB and SOD activity of shrimp immersed in 400 and 600 mg L^?1 of the hot-water extract returned to the background values at 96, 48, 48, and 72 h, whereas these parameters of control shrimp returned to the original values at >120, >120, 96, and 96 h post-challenge, respectively. It was therefore concluded that L. vannamei that had been immersed in seawater containing the hot-water extract of G. tenuistipitata exhibited protection against V. alginolyticus as evidenced by the earlier recovery of immune parameters.     

Fucoidan effectively provokes the innate immunity of white shrimp Litopenaeus vannamei and its resistance against experimental Vibrio alginolyticus infection

In this study, we examined the effect of fucoidan on the immune response of white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus infection. Fucoidan induced degranulation, caused changes in the cell morphology, and increased activation of prophenoloxidase (proPO) and the production of superoxide anions in vitro. Shrimp that received fucoidan via immersion at 100, 200, and 400 mg l^?1 after 3 h showed haemocyte proliferation and a higher mitotic index of haematopoietic tissue. In another experiment, the haemocyte count, phenoloxidase (PO) activity, and respiratory bursts (RBs) were examined after the shrimp had been fed diets containing fucoidan at 0 (control), 0.5, 1.0, and 2.0 g kg^?1 for 7–21 days. Results indicated that these parameters directly increased with time. The immune parameters of shrimp fed the 1.0 g kg^?1 diet were significantly higher than those of shrimp fed the 2.0 g kg^?1 diet after 14 and 21 days. Phagocytic activity and the clearance efficiency against V. alginolyticus were significantly higher in shrimp fed the 1.0 g kg^?1 diet compared to those of shrimp fed the 0, 0.5 and 2.0 g kg^?1 diets. In a separate experiment, shrimp that had been fed diets containing fucoidan for 21 days were challenged with V. alginolyticus at 10⁶ colony-forming units shrimp^?1. Survival rates of shrimp fed the 1.0 and 2.0 g kg^?1 diets were significantly higher than those of shrimp fed the 0 and 0.5 g kg^?1 diets for 96–120 h. We concluded that fucoidan provokes innate immunity of shrimp as evidenced by haemocyte degranulation, proPO activation, and the mitotic index of haematopoietic tissue, and that dietary administration of fucoidan at 1.0 g kg^?1 enhanced the immune response of shrimp and their resistance against V. alginolyticus infection.     

The VP37-binding protein F1ATP synthase β subunit involved in WSSV infection in shrimp Litopenaeus vannamei

To investigate the interaction between white spot syndrome virus (WSSV)-VP37 and gill membrane proteins (GMPs) of Pacific white shrimp (Litopenaeus vannamei), the VP37 protein was expressed and purified, and a distinct 53 kDa VP37-binding protein band was identified in GMPs by virus overlay protein binding assay and GST pull-down assay. By electroelution, the VP37 binding protein was purified and identified as F₁ATP synthase β (F₁ATPase β) subunit by Mass Spectrometry. The purified F₁ATPase β subunit was used to immunize BALB/C mice to produce monoclonal antibodies (Mabs). After cell fusion, sixteen hybridomas secreting Mabs against F₁ATPase β subunit of L. vannamei were screened by enzyme-linked immunosorbant assay (ELISA), three of which designated as 1D5, 1E8 and 2H4 were cloned by limiting dilution and further characterized by indirect immunofluorescence assay (IIFA) and western blotting. The results of IIFA showed that specific fluorescence signals located at the peripheral zone of the gills of L. vannamei. Western blotting demonstrated that three Mabs reacted specifically with the 53 kDa protein band in GMPs of L. vannamei. By IIFA, the Mabs could also cross-react with the gill cells of three other WSSV-susceptible shrimps Fenneropenaeus chinensis, Penaeus monodon and Marsupenaeus japonicus. Furthermore, the three anti-F₁ATPase β subunit Mabs could partially block the binding of WSSV to GMPs by ELISA in vitro, and also exhibited direct anti-WSSV activity in shrimp by neutralization assay in vivo. These findings suggested that F₁ATPase β subunit involved in WSSV infection in L. vannamei.     

Immune responses of Litopenaeus vannamei to thermal stress: a comparative study of shrimp in freshwater and seawater conditions

The effects of hypothermal (22–16?°C) and hyperthermal (22–28?°C) stress on the immune system responses of the shrimp Litopenaeus vannamei cultured in either freshwater or seawater were measured and compared. The following immune system indicators were measured for comparison: total hemocyte count (THC), activity of phenoloxidase (PO), nitric oxide synthase (NOS), superoxidase (SOD), and malondialdehyde (MDA) content. Thermal stress significantly decreased THC in both freshwater and seawater shrimp within 6–12?h (P?0.05). After hypothermal stress, all shrimp had a significantly lower THC level than their prechallenge levels (P?0.05). Under both types of thermal stress, the activity of PO, NOS, and SOD first increased and then decreased. After 48?h of thermal stress, shrimp PO and NOS activity decreased in both freshwater and seawater. After 48?h of thermal stress, the reduction in the SOD activity in the hemolymph of freshwater shrimp was greater than that in seawater shrimp. During exposure to stress, the MDA content in freshwater shrimp was significantly higher than in seawater shrimp, which demonstrated that lipids in freshwater shrimp were more susceptible to peroxidation than those in seawater shrimp, particularly at low temperatures. Large temperature fluctuations, particularly sudden cooling, should be avoided when rearing L. vannamei because of high rates of lipid peroxidation and decreased immunity. These effects are more marked in freshwater than in seawater.     

Effects of phosphatidyl serine on immune response in the shrimp Litopenaeus vannamei

Phosphatidyl serine plays an important role in animal innate immunity. Given its important functions, numerous investigations have been carried out on its immunological function in many animals. However, studies of phosphatidyl serine in the white shrimp Litopenaeus vannamei, an economically important animal, are rare. In this paper, we demonstrated influences of injecting phosphatidyl serine (PS) on immune response including some parameters from pro-phenol oxidase activating system (pro-PO system) and hemocyanin-derived phenol oxidase activity (Hd-PO) along with antibacterial and bacteriolytic activities in the white shrimp Litopenaeus vannamei with different PS concentrations (5, 10 and 20 μg mL^?1). The results showed that PS could affect immune response of L. vannamei significantly (P<0.05), including total hemocyte counts (THC), PO activity from hemocyte, phenol oxidase (PO) activity from plasma, hemocyanin concentration, Hd-PO activity as well as antibacterial and bacteriolytic activities in the plasma. Among the lines, 20 μg mL^?1 PS had the strongest effect on the above parameters, whereas 5 μg mL^?1 had the least effect. The experimental results indicated that PS was able to activate exocytosis of pro-PO and formation of Hd-PO in white shrimp after injection, further regulating the immune process reflected by variation of antibacterial and bacteriolytic activities in a certain way.     

Hyperglycemic and osmotic effects of dopamine and recombinant hormone CHH-B1 in the Pacific white shrimp Litopenaeus vannamei

The effects of dopamine (DA) on crustacean hyperglycemic hormone (CHH) release and osmoregulation were investigated in the white shrimp Litopenaeus vannamei. Application of 2 μg of the recombinant CHH-B1_His hormone or 2?×?10^?6 mol L^?1 of DA to intact shrimp caused an increase in the hemolymph glucose levels 1 h post-injection, suggesting that DA might stimulate hyperglycemia through CHH release from the sinus glands. This assumption was supported by similar experiments using bilaterally eyestalk-ablated shrimp. Additionally, rCHH-B1_His restored the osmoregulatory capacity (OC) of shrimp under hyperosmotic conditions to basal values 2 h post-injection, whereas DA led to an OC decrease in shrimp at all sampling times. These neuroendocrine factors may be involved in the control of metabolism and osmoregulation in L. vannamei and could be important for its adaptation to different environmental conditions.     

Effects of the probiotic,Bacillus subtilis E20, on the survival,development, stress tolerance,and immune status of white shrimp,Litopenaeus vannamei larvae

In this study, the probiotic, Bacillus subtilis E20, isolated from the human health food, natto, was used for white shrimp, Litopenaeus vannamei, larvae breeding to improve the larval survival rate and development by adding probiotic to the rearing water at (control), 10⁸, and 10⁹ cfu L^?1 salt water once every 3 days during the 14 days of breeding experiment. Thereafter, stress tolerance and immune status of postlarvae were evaluated. Shrimp larval development was significantly accelerated after adding the probiotic to the larval rearing water at a level of 10⁹ cfu L^?1. The survival rate of larvae was significantly higher in the treatment with 10⁹ cfu L^?1 compared to the control and the treatment with 10⁸ cfu L^?1 after all larvae had metamorphosed to postlarvae. Adding the probiotic to the shrimp larvae rearing water produced a weak inhibition of bacterial growth by an analysis of the total bacterial count and presumptive Vibrio count. For stress tests, no postlarvae died when they were reared in water in which the temperature was decreased from 30 to 2 °C at a rate of 0.1 °C min^?1. Postlarvae had significantly lower cumulate mortality in the treatments with 10⁸ and 10⁹ cfu L^?1 compared to the control when they were suddenly exposed to fresh water and 60‰ salt water. A significant decrease in the cumulative mortality of postlarvae treated with the probiotic at a level of 10⁹ cfu L^?1 was recorded after the sudden transfer to 300 mg L^?1 nitrite-N compared to the control and treatment with 10⁸ cfu L^?1. The analysis of immune-related gene expressions showed that the gene expression of prophenoloxidase I, prophenoloxidase II, and lysozyme of larvae were significantly increased after being reared in probiotic-containing water at the levels of 10⁸ and 10⁹ cfu L^?1. However, no significant difference in serine proteinase or glutathione peroxidase gene expressions was recorded in this study. It is therefore suggested that 10⁹ cfu L^?1 of probiotic, B. subtilis E20 adding to rearing water for shrimp larva breeding.     

A thioredoxin response to the WSSV challenge on the Chinese white shrimp, Fenneropenaeus chinensis

Thioredoxin (TRX) is involved in cell redox homeostasis. In addition, it is responsible for maintaining proteins in their reduced state. In our study, a Fenneropenaeus chinensis thioredoxin (FcTRX) gene was identified from the Chinese white shrimp. The full length of FcTRX was 777 bp, including a 60 bp 5′ untranslated region (UTR), a 318 bp open reading frame (ORF) encoding a 105 amino acids protein, and a 399 bp 3′ UTR. FcTRX contained a TRX domain with a conserved motif of Cys-Gly-Pro-Cys (CGPC). No signal peptide was predicted by SMART analysis. The molecular mass and pI of FcTRX were 12 kDa and 4.62, respectively. FcTRX is a widely distributed gene, and its mRNA is detected in hemocytes, hearts, hepatopancreas, gills, stomach, and intestine from an unchallenged shrimp. The expression level of FcTRX was the highest in hepatopancreas, where it was down-regulated to the lowest level at 12 h white spot syndrome virus (WSSV) challenge. In the gills, it went up to the highest level at 6 h. Western blot showed that FcTRX protein in hepatopancreas challenged with WSSV was down-regulated from 2 h to 12 h and then restored to the level similar to that of unchallenged shrimp at 24 h. In the gills challenged with WSSV, the FcTRX protein was up-regulated from 6 h to 24 h. Our research indicated its possible role in the anti-WSSV innate immunity of shrimps.     

Dietary administration of zingerone to enhance growth, non-specific immune response, and resistance to Vibrio alginolyticus in Pacific white shrimp (Litopenaeus vannamei) juveniles

Zingerone, one of the active components of ginger, is a phenolic alkanone with antioxidant and anti-inflammatory properties. The effects of zingerone supplementation on the growth, immunity, and disease resistance of Pacific white shrimp (Litopenaeus vannamei) juveniles were studied. Four experimental diets, including a control diet (without zingerone enrichment) and 1, 2.5, and 5 mg zingerone (kg diet)⁻¹ were used. After 56 days of culture, shrimp fed diets supplemented with 1, 2.5, and 5 mg zingerone (kg diet)⁻¹ had significantly greater weight gain and feed efficiency than the controls. Furthermore, after 56 days of culture, shrimp fed all doses of the zingerone diet had higher survival rates compared to the controls after 24-72 h of challenge by the pathogen, Vibrio alginolyticus. Significantly increased phenoloxidase levels were found in shrimp fed the zingerone diets at all doses, and respiratory bursts, lysozyme and phagocytic activities of shrimp fed 2.5 and 5 mg zingerone (kg diet)⁻¹ also significantly increased. Neither the total hemocyte count nor superoxide dismutase activity of the experimental and control groups revealed significant differences at any dose. The results indicate that zingerone can be recommended as a supplement to shrimp feed to increase growth, immunity, and disease resistance against the pathogen, V. alginolyticus. Use of zingerone as appetizer and immunostimulant in shrimp is promising.     

Effects of Copper on Hemocyte Apoptosis,ROS Production,and Gene Expression in White Shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

Copper, a common chemical contaminant in aquatic environment, is known to be toxic to aquatic life at high concentrations. In the present study, we evaluated the apoptotic cell ratio and ROS production in hemocytes of the white shrimp Litopenaeus vannamei exposed to 1 or 5 mg L^?1 Cu for 0, 3, 6, 12, 24, and 48 h. The expression changes of antioxidant biomarker genes, i.e., copper-zinc superoxide dismutase (Cu-Zn SOD) and catalase (CAT), apoptosis-related genes, i.e., caspase-3 and inhibitor of apoptosis protein (IAP), and a specific biomarker gene of heavy metal pollution, i.e., metallothionein (MT), were also determined in hemocytes. Significant increases in ROS production were observed in both treatment groups at each time points. The apoptotic cell ratios were significantly increased at 6–48 h among shrimp exposed to 1 mg L^?1 Cu and at each time points in 5 mg L^?1 Cu group. These results indicated that Cu would induce oxidative stress and apoptosis in the hemocyte of L. vannamei. Quantitative real-time PCR analysis revealed that the relative expression levels of Cu-Zn SOD, CAT, caspase-3, IAP, and MT were upregulated in a dose-dependent and time-dependent manner, suggesting the involvement of these genes in stress response against Cu exposure.     

Noradrenaline modulates the immunity of white shrimp Litopenaeus vannamei

The total haemocyte count (THC), phenoloxidase activity, respiratory burst, superoxide dismutase (SOD) activity, phagocytic activity and clearance efficiency in response to pathogen Vibrio alginolyticus were measured when the white shrimp Litopenaeus vannamei (18.4 +/- 1.2 g) were injected individually with noradrenaline at 10(-8), 10(-7) and 10(-6) mol shrimp(-1). For the shrimp that received noradrenaline at 10(-8), 10(-7) and 10(-6) mol shrimp(-1), the THC decreased by 15%, 21% and 32%, phenoloxidase activity decreased by 15%, 31% and 31%, respiratory burst decreased by 13%, 21% and 32%, and SOD activity decreased by 46%, 56% and 55%, respectively, after 2 h. The phagocytic activity and clearance efficiency of shrimp that received noradrenaline at either dose decreased significantly after 2 h. The THC, phenoloxidase activity, respiratory burst, SOD activity, phagocytic activity and clearance efficiency returned to normal values after 4, 4, 8, 24, 16 and 8 h, respectively, in the shrimp that received noradrenaline at either dose. In another experiment, L. vannamei which had received noradrenaline at 10(-8), 10(-7) and 10(-6) mol shrimp(-1) were challenged after 1h by injection with V. alginolyticus at 1.0 x 10(5) colony-forming units (cfu)shrimp(-1) and then placed in seawater of 20 per thousand. The cumulative mortality of shrimp that received noradrenaline at either dose was significantly higher than that of shrimp that received saline after 4 h, and at the termination of the experiment (48 h after the challenge). It is therefore concluded that noradrenaline administration at 10(-6) mol shrimp(-1) or less causes immune modulation of L. vannamei.     

Immune responses of Fenneropenaeus chinensis against white spot syndrome virus after oral delivery of VP28 using Bacillus subtilis as vehicles

The protective efficacy of oral administration of VP28 using Bacillus subtilis as vehicles (rVP28-bs) in shrimp, Fenneropenaeus chinensis, upon challenge with white spot syndrome virus (WSSV) was investigated. The calculated relative percent survival (RPS) value of rVP28-bs fed shrimp was 83.3% when challenged on the 14th day post-administration, which is significantly higher (p < 0.001) than that of the group administered recombinant Escherichia coli over-expressing rVP28 (rVP28-e21). After immunization, activities of phenoloxidase (PO), superoxide dismutase (SOD) and inducible nitric oxide synthase (iNOS) in hemolymph were analyzed. It was found that the supplementation of rVP28-bs into shrimp food pellets resulted in the most pronounced increase of iNOS activity (p < 0.001), but had the least influence on activities of PO and SOD. Besides, in the shrimp orally administered with rVP28-bs, the caspase-3 activity was one-fifth that of the control, though the signs of apoptosis (chromatin margination, nuclear fragmentation and apoptotic bodies) could not be observed by transmission electron microscope (TEM). These results suggest that by oral delivery of rVP28-bs, shrimp showed significant resistance to WSSV and an effect on the innate immune system of shrimp. The remarkably enhanced level of iNOS after rVP28-bs administration might be responsible for antiviral defense in shrimp.     

Effects of dominant microalgae species and bacterial quantity on shrimp production in the final culture season

The dominant microalgal species, quantity of heterotrophic bacteria and Vibrio in the intestines and gills of Litopenaeus vannamei (Pacific white shrimp), positive detection rate of white spot syndrome virus (WSSV), and water quality indices were investigated at the final culture stage (88th day in culture season). Correlation of microalgal community, bacteria quantity, and shrimp production were analyzed by statistical analysis methods. Every 10 days, probiotics were used in groups A, B, and C, consisting of Bacillus, photosynthetic bacteria (PSB), and equal parts Bacillus and PSB, respectively. The results showed that production (25597.33?±?928.46 kg ha^?1) and survival rate (77.06?±?9.00 %) was the highest in group C, but positive detection rate of WSSV was the lowest. The microalgal community of group C was significantly dominated by Chlorella pyrenoidosa, with an average density and dominance of (289.52?±?142.10)?×?10⁷ cells L^?1 and 0.878?±?0.161, respectively. The correlation analysis indicated a significant negative correlation between Cyanophyta dominance and shrimp production (P?<?0.05), while the relationship between production and Vibrio quantity was not significantly correlated (P?>?0.05). Accordingly, microalgal dominant species should be controlled as a key factor in the shrimp culture season; in particular, the dominance of Cyanophyta should be restricted to a low level. Meanwhile, the combined use of Bacillus and PSB probiotics was considered an effective solution to optimize microalgal communities and controlling the cell density of Cyanophyta.     

Effects of dopamine on the immunity of white shrimp Litopenaeus vannamei

The total haemocyte count (THC), phenoloxidase activity, respiratory burst, superoxide dismutase (SOD) activity, phagocytic activity and clearance efficiency in response to pathogen Vibrio alginolyticus were measured when the white shrimp Litopenaeus vannamei (20.0+/-1.5 g) were injected individually with dopamine at 10(-8), 10(-7) and 10(-6)mol shrimp(-1), respectively. For the shrimp that received dopamine at 10(-7) and 10(-6)mol shrimp(-1), the THC decreased by 25% and 39%, phenoloxidase activity decreased by 15% and 32%, respiratory burst decreased by 21% and 36%, and SOD activity decreased by 50% and 63%, respectively, after 4 h. The phagocytic activity and clearance efficiency of shrimp that received dopamine at either dose decreased significantly after 2 h. The THC, phenoloxidase activity, respiratory burst, SOD activity, phagocytic activity and clearance efficiency returned to normal values after 16, 8, 8, 24, 16 and 4 h, respectively, for the shrimp that received dopamine at either dose. In another experiment, L. vannamei which had received dopamine at 10(-8), 10(-7) and 10(-6)mol shrimp(-1) were challenged after 1 h by injection with V. alginolyticus at 1.0x10(5) colony-forming units (cfu) shrimp-1 and then placed in seawater of 20 per thousand. The cumulative mortality of shrimp that received dopamine at either dose was significantly higher than that of shrimp that received saline after 8 h, and of shrimp that received saline at the termination of the experiment (48 h after the challenge). It is therefore concluded that dopamine administration at 10(-6)mol shrimp-1 or less causes immune modulation of L. vannamei.     

Potential probiotic Lactobacillus plantarum VSG3 improves the growth,immunity, and disease resistance of tropical freshwater fish,Labeo rohita

The study evaluated the effects of dietary doses of Lactobacillus plantarum VSG3 on the growth performance, immunity, and disease resistance of Labeo rohita juveniles against Aeromonas hydrophila infection. Fish (mean body weight 60 g) were fed with diet containing 0 (control), 10⁶, 10⁸, 10¹⁰ cfu g^?1 L. plantarum VSG3 for 60 days. Various growth and immune parameters were examined at 30 and 60 days of post-feeding. Fish were challenged with A. hydrophila 60 days post-feeding and mortalities were recorded over 10 days post-infection. Results showed that administration of VSG3 for 60 days had significant effects (P < 0.05) on the specific growth rate (SGR) and feed utilization efficiency of L. rohita. Dietary administration of L. plantarum VSG3 significantly increased the serum lysozyme and alternative complement pathway (ACP) activities, phagocytosis and respiratory burst activity in L. rohita throughout the experimental period. The highest superoxide dismutase (SOD) activity (P < 0.05) was observed in the fish group fed diet containing VSG3 at 10⁸ cfu g^?1. The serum IgM levels were significantly higher in the experimental groups compared to the control group after 30 days of feeding; but, the result was opposite after 60 days of feeding. Further, fish fed the diet containing 10⁸ cfu g^?1 L. plantarum VSG3 had significantly higher (P < 0.05) post-challenge survival rate (77.7%). These results collectively suggest that dietary supplementation of L. plantarum VSG3 at 10⁸ cfu g^?1 to L. rohita is optimal for enhancing the growth, immunity, and disease resistance against A. hydrophila infection.     

Shrimp that have received carrageenan via immersion and diet exhibit immunocompetence in phagocytosis despite a post-plateau in immune parameters

The effect of carrageenan on the immune response of white shrimp Litopenaeus vannamei, was studied in vitro and in vivo. Shrimp haemocytes receiving carrageenan at 1 mg ml⁻¹ experienced change in cell size, reduction in cell viability, increase in PO activity, serine proteinase activity, and RB in vitro. Shrimp received carrageenan via immersion at 200, 400 and 600 mg L⁻¹ after 3 h and orally at 0.5, 1.0 and 2.0 g kg⁻¹ after 3 weeks showed higher proliferation of haematopoietic tissues (HPTs) together with increases in haemocyte count and other immune parameters. Shrimp that fed a diet containing carrageenan at 0.5 g kg⁻¹ after 3 weeks significantly up-regulated gene expressions of several immune-related proteins. The immune parameters of shrimp that received carrageenan via immersion and orally increased to a plateau after 3 h and after 3 weeks, but decreased after 5 h and 6 weeks, respectively. Phagocytosis and clearance of Vibrio alginolyticus remained high in shrimp that had received carrageenan via immersion after 5 h and orally after 6 weeks, respectively. Resistances of shrimp against V. alginolyticus and white spot syndrome virus were higher over 24–144 h and 72–144 h, respectively in shrimp that received carrageenan at 600 mg L⁻¹ via immersion after 3 and 5 h. It was concluded that carrageenan effectively triggers an innate immunity in vitro, and increases mitotic index of HPT, immune parameters, gene expressions and resistance against pathogens in vivo. Shrimp received carrageenan via immersion and orally exhibited immunocompetence in phagocytosis and clearance of V. alginolyticus, and resistance to pathogen despite the trend in immune parameters to recover to background values.