Difference in light perception capability and spectral response between juveniles and sub-adults of the whiteleg shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> as determined by electroretinogram

In this study, we determined light perception capability in juveniles and sub-adults of L. vannamei by means of electroretinogram (ERG) measurements. Eyes were assumed to be dark-adapted when the response magnitude had stabilized after 70–80 min under dark conditions. ERG responses elicited by mono-wavelength (336–694 nm) stimuli of equal intensity were determined in individual dark-adapted specimens. Relative spectral response curves determined from the amplitudes of on and off relative responses were found to be significantly different in juveniles and sub-adults. Both maximum on relative spectral response magnitudes were observed at 544 nm, but the on relative spectral response magnitudes of sub-adults to 518 nm were higher than for juveniles, and the on relative spectral response magnitudes of sub-adults to 568 nm were lower than for juveniles. The on and off relative spectral response curves of juveniles were steeper than those of sub-adults, while the on relative spectral response magnitude of juveniles was lower than that of sub-adults from 336 to 544 nm. The off relative spectral response magnitude of juveniles was higher than that of sub-adults from 518 to 597 nm.     

Comparison of flavor components in shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> cultured in sea water and low salinity water

To compare the flavor components of shrimp Litopenaeus vannamei cultured in sea water and low salinity water, the chemical composition of muscle was analyzed, muscle extracts prepared, and their sensory components and sensory properties were assessed. Shrimp cultured in sea water had a higher content of crude protein, lower moisture, and a higher flesh pH compared to the low salinity samples (P<0.05), whereas no significant differences were found in crude lipid and ash. The free amino acid composition of muscle extracts and the amino acid composition of peptides from shrimp cultured in sea water and low salinity water were similar, that is, the former had a very high content of glycine, arginine, proline and alanine, and the latter a very high content of glutamate, glycine, arginine, proline and alanine. The major components of nucleotides were adenosine monophosphate and inosine monophosphate, and the major components of organic acids were acetic acid and malic acid. Extracts from shrimp cultured in sea water had enhanced umami, sweetness and overall flavor, and less of an earthy-musty taste compared to samples cultured in low salinity water (P<0.05). Aftertaste did not differ between the two shrimp extracts (P>0.05).     

Genetic diversity status of Pacific white shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>) using SSR markers in Iran

Genetic diversity is vital for the maintenance of genetic pool in cultured shrimps. In order to estimate the current status of genetic diversity in Litopenaeus vannamei shrimp in Iran, as an exotic species, a total of 45 individuals from Amiri and Gorgeaj farms in Jask port of Hormozgan province and one hatchery in Gomishan city of Golestan province, were detected using four microsatellite loci. The number of alleles per locus was 5–10, and the mean effective number of alleles (N _e) across populations and loci ranged from 4.834 to 5.148. The overall mean observed heterozygosity (H _o) ranged from 0.450 to 0.479, which was lower than the expected one (0.789–0.794). There was nothing remarkable about any of the allele frequencies across populations or loci. The mean inbreeding coefficient (F _IS) and pairwise genetic differentiation (F _ST) among populations were 41.6 % and 0.133, respectively. The three studied populations departed from Hardy–Weinberg equilibrium (HWE). Analysis of molecular variance revealed 14 % variability among and 86 % within populations. However, considering departing from HWE and the high F _IS and F, the moderate pairwise F _ST values, importance of introducing genetically diverse broodstock and monitoring to control inbreeding is discussed.     

The effectiveness of commercial probiotics in northern white shrimp <Emphasis Type="Italic">Penaeus vannamei</Emphasis> ponds

ABSTRACT:   The effectiveness on water quality, population density of bacteria, and shrimp production in ponds treated with commercial probiotics was tested in Penaeus vannamei ponds in Hai-yan, China. Six ponds with replicates for treatment and control were used. Results showed that the probiotics could improve the population density of beneficial bacterial flora, reduce concentrations of nitrogen and phosphorus, and increase yields of shrimp. The average counts of Bacillus sp., ammonifying bacteria, and protein mineralizing bacteria were found to be significantly higher in treated ponds compared to control ponds ( P  < 0.05). In control ponds, an increase in presumptive vibrios was observed and the average density was up to 2.09 × 10³ cfu/mL, whereas that was only 4.37 × 10² cfu/mL in treated ponds ( P  < 0.05). The use of probiotics also significantly increased dissolved oxygen ( P  < 0.05) and reduced dissolved reactive-phosphorus, total inorganic nitrogen and chemical oxygen demand ( P  < 0.05). An average of 8215 ± 265 kg shrimp/ha was obtained in treated ponds with a feed conversion ratio (FCR) of 1.13 ± 0.05 and survival rate of 81.00 ± 6.25% compared with 4985 ± 503 kg shrimp/ha, 1.35 ± 0.12 and 48.67 ± 3.51%, respectively, in control ponds. This indicates that the addition of the commercial probiotics had a noticeable influence on water quality of shrimp ponds and shrimp production.     

Effect of microencapsulated thyme essential oil on white spot virus-infected <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

The present work was performed to investigate if feeding Litopenaeus vannamei with microencapsulated thyme essential oil (TEM, 1.05 g thyme essential oil per 100-g powder) adsorbed on commercial pellet feed was able to protect shrimps against white spot syndrome virus (WSSV) disease. Five treatments were tested: uninfected shrimp fed with commercial pelleted feed (T_C, negative control), WSSV-infected shrimp fed with commercial pelleted feed (T₁, positive control), WSSV-infected shrimp fed with commercial pelleted feed with 0.1% TEM (T₂), WSSV-infected shrimp fed with commercial pelleted feed with 0.5% TEM (T₃), and WSSV-infected shrimp fed with commercial pelleted feed with 1% TEM (T₄). At 72 h post infection, phenoloxidase activity of shrimps treated with 1% TEM did not show significant differences with T_C values but it was significantly higher than that of the other treatments (T₁, T₂, and T₃). Moreover, shrimps treated with T₄ presented absence of clinical signs of WSSV infection and their survival rate was significantly higher than that of T₁, T₂, and T₃ treatments. Therefore, 1% TEM seemed to protect shrimps against WSSV symptoms. Using microencapsulated thyme essential oil may help to fight against WSSV in shrimp farms.     

Pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin in Pacific white shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> after multiple-dose oral administration

The present study was designed to explore pharmacokinetics (PK) of enrofloxacin and its metabolite ciprofloxacin in Pacific white shrimp Litopenaeus vannamei after multiple-dose oral administration of enrofloxacin (30 mg/kg dose per 12 h and continuous feeding for 3 days). Enrofloxacin and ciprofloxacin concentrations in hemolymph, hepatopancreas, and muscle of the shrimp were simultaneously determined by high-performance liquid chromatography. PK parameters were analyzed based on statistical moment theory. Meanwhile, the relationship of pharmacokinetics/pharmacodynamics (PK/PD) was established based on drug concentration of hemolymph and in vitro antibacterial activity (MIC value). Results showed faster absorption of enrofloxacin in hemolymph (T_max?=?1 h) and muscles (T_max?=?1 h) than that in hepatopancreas (T_max?=?3 h) after the first oral administration. In multiple-dose oral administration, slight accumulation of enrofloxacin occurred in the hemolymph and hepatopancreas, while in the muscle, enrofloxacin concentration showed a significant decline following multiple administration. Tissue distribution of enrofloxacin and ciprofloxacin both followed the order hepatopancreas?>?hemolymph?>?muscle, with significantly higher ciprofloxacin concentration in hepatopancreas than in hemolymph (approximately 10-fold) and muscles (approximately 50-fold), indicating that the hepatopancreas is the main organ involved in metabolism of enrofloxacin in Pacific white shrimp. After multiple-dose administration, C_max/MIC and AUC_0–24/MIC values showed that the therapeutic regimen in this study could be remarkably effective in prevention and treatment of Vibrio infection in Pacific white shrimp.     

Carbonic anhydrase and Na/K-ATPase activities during the molt cycle of low salinity-reared white shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

Changes in hemolymph osmolality, ion concentrations, and enzymatic activities of carbonic anhydrase (CA) in the gills and epidermal tissue, and Na/K-ATPase in the gills during the molt cycle were investigated in the white shrimp Litopenaeus vannamei. Hemolymph osmolality was high in the intermolt and early premolt stages, but started to decrease prior to ecdysis through to postmolt stages A and B. Changes in Na⁺ and Cl⁻ ion concentrations paralleled those in hemolymph osmolality. CA activity levels in the anterior and posterior gills were low at intermolt stage C₀ and premolt stage D₀, and maximum at premolt stage D₃. In the epidermal tissue, activity was relatively high at intermolt stage C₀ and premolt stage D₀, but fluctuated towards premolt stage D₃ and postmolt stage A. On the other hand, Na/K-ATPase activity in the gills decreased between intermolt stage C₀ and premolt stage D₂, but increased at premolt stage D₃ and postmolt stage A. The changes in patterns of CA activity during the molt cycle suggest that CA may be involved in supplying counter-ions for Na⁺ and Cl⁻ uptake during molting. Branchial Na/K-ATPase appears to be involved in producing local osmotic gradients in order to support water influx across the epithelium.     

Spatial learning-induced <Emphasis Type="Italic">egr</Emphasis>-<Emphasis Type="Italic">1</Emphasis> expression in telencephalon of gold fish <Emphasis Type="Italic">Carassius auratus</Emphasis>

The immediate-early gene (egr-1) expression was used to examine the neuron’s response in telencephalon of goldfish during spatial learning in small space. Fishes were pre-exposed in the experimental apparatus and trained to pick food from the tray in a rectangular-shaped arena. The apparatus was divided into identical compartments comprising three gates to provide different spatial tasks. After the fish learned to pass through the gate one, two more gates were introduced one by one. Fish made more number of attempts and took longer time (P < 0.05) to pass through the first gate than the gate two or three. This active learning induces the expression of egr-1 in telencephalon as established by western blot analysis. Subsequently, the fish learn quickly to cross the similar type of second and third gate and make fewer errors with a corresponding decline in the level of egr-1 expression. As the fish learned to pass through all the three gates, third gate was replaced by modified gate three. Interestingly, the level of egr-1 expression increased again, when the fish exhibit a high exploratory behavior to cross the modified gate three. The present study shows that egr-1 expression is induced in the telencephalon of goldfish while intensively acquiring geometric spatial information to pass through the gates.     

Contribution of bioflocs to the culture of <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> post-larvae determined using stable isotopes

The aim of this study was to use preselected quality indicators for Litopenaeus vannamei post-larvae and the stable isotopes technique with δ¹³C and δ¹⁵N to determine the influence of bioflocs in shrimp feeding during the nursery phase, between PL1 and PL30. A control treatment (CT) with water renewal was compared to a biofloc treatment (BT) that received organic carbon fertilizations. Different types of commercial feed (Stresspak and Flake-INVE?, PL40-GUABI?), microalgae (Chaetoceros muelleri) and Artemia sp. nauplii were used as food sources. The physical and chemical parameters of water and ammonia were monitored daily, and nitrite, nitrate and alkalinity were measured weekly. Suspended solids and the microorganisms of bioflocs were characterized. At the end of the experiment, fifteen shrimps of each replicate were collected to evaluate nine larvae quality indicators. Isotopic values of ¹³C and ¹⁵N of food sources and shrimp tissues were collected on days 10, 20 and 30, and a Bayesian model of isotopic mixture measured the contributions of these sources to the shrimp biomass. Salinity, alkalinity and nitrite differed significantly between the treatments but were appropriate for post-larvae production. The larvae quality conditions in the CT treatment were ranked as “good,” whereas the BT conditions were considered “excellent” according to the analysis of larval quality parameters. The stable isotopes analysis showed that the PL40 GUABI? feed was the most important food source throughout the experimental period in the CT. In the BT (10th and 20th days), the bioflocs and commercial feeds (Flake-INVE?, PL40-GUABI?) did not present significant variations in their contribution ratios; however, on the 30th day, the contribution of the PL40-GUABI? feed was higher when compared to bioflocs. In general, the commercial feed played a more important role as a food source for Litopenaeus vannamei larvae during the nursery phase, although the consumption of bioflocs led to a better larvae quality.     

The effects of cyclical temperature changes on growth and physiological status of <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

The purpose of this study was to investigate the growth and physiological status of Litopenaeus vannamei subjected to one constant temperature (25°C) and four cyclical temperature change regimes (25 ± 1°C, 25 ± 2°C, 25 ± 3°C and 25 ± 4°C). The growth rates of shrimp at 25 ± 2°C or 25 ± 3°C were significantly higher than that at a constant temperature of 25°C. On the other hand, the growth rate in 25 ± 4°C regime was significantly lower than those in other regimes. The daily feed intake rate of shrimp at 25 ± 4°C was the lowest, and the food conversion efficiency was also significantly lower than those at 25 ± 2°C and 25 ± 3°C, respectively. The food conversion efficiency at 25 ± 2°C or 25 ± 3°C was significantly higher than those in other regimes. Thus, it can be inferred that the growth enhancement in the test shrimp at the suitable diel fluctuating temperatures was due to high food conversion efficiency. Studies of the physiological parameters showed that at 25 ± 4°C, the hemolymph glucose content of the test shrimp was the lowest, while the activity of PK in hepatopancreas was the highest, which indicated that the test shrimp at 25 ± 4°C was in a stressed condition. The hemolymph glucose content of the test shrimp at 25 ± 3°C was the highest, and the activity of HK in hepatopancreas was the lowest. These results indicated that the test shrimps at 25 ± 3°C were not in a stressed condition. Compared with the constant temperature regime, the expression of HSP70 in any of the four cyclical temperature change regimes was not significantly increased. The reason for this might be that the fluctuation amplitude of ± 4°C did not induce the increased expression of HSP70.     

Effect of VP28 DNA vaccine on white spot syndrome virus in <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

White spot syndrome virus (WSSV) occurs worldwide and causes high mortality and considerable economic damage to the shrimp farming industry. Considering the global environmental, the economic and sociological importance of shrimp farming, and the constraints of high intensity cultivation, development of novel control measures against the outbreak of WSSV become inevitable. In this study, we have explored the protective efficacy of DNA vaccination and tissue distribution of the recombinant plasmid in immunized Litopenaeus vannamei. The VP28 gene was cloned in the eukaryotic expression vector pVAX1, and the construct vector was named as lpv28. The protective effect of lpv28 against WSSV was evaluated in L. vannamei by injecting lpv28 construct and later challenging with WSSV. Expression of these proteins from the recombinant plasmids was confirmed in vitro by RT-PCR and Western blot analysis. The result of vaccination trials showed that a survival rate in shrimp vaccinated with lpv28 was 52.5% at most compared to control groups (100% mortality). The immunological parameters analyzed in the vaccinated and control groups showed that the vaccinated groups owned a high level of lysozyme, alkaline phosphatase, and total superoxide dismutase when compared to the control group. Furthermore, protein expression analysis indicated that VP28 can be detected in gill, muscle and head soft tissue of the shrimps in the immunized group after 14th day injection. Thus, the result indicated that DNA vaccination strategy has a potential utility against WSSV.     

Use of a <Emphasis Type="Italic">Noctiluca</Emphasis>-killing bacterium <Emphasis Type="Italic">Marinobacter salsuginis</Emphasis> strain BS2 to reduce shrimp mortality caused by <Emphasis Type="Italic">Noctiluca scintillans</Emphasis>

The ability of an algicidal bacterium Marinobacter salsuginis strain BS2, isolated from shrimp pond water, to reduce shrimp mortality was investigated under laboratory conditions. When two species of shrimp (Penaeus monodon and Litopenaeus vannamei) (body length 1.5–1.8 cm) were cultured together with the dinoflagellate Noctiluca scintillans, nearly 80 % of the shrimps died within 7 days. However, when bacterial strain BS2 was also added to the culture, N. scintillans was killed within 48 h, and shrimp survival rates on the 7th day improved from 23 to 87 % for both P. monodon and L. vannamei. The bacterium BS2 alone had no effect on shrimp condition. Under conditions of increased dissolved oxygen, the effect of using BS2 was greater, and shrimp survival rates improved even more dramatically, from 26 to 98 %. These studies provide the first evidence that the use of killing bacteria, isolated from shrimp culture water, can suppress harmful algal blooms (HABs) and thus restore the efficiency of shrimp production. The control of HABs in this way in shrimp culture farms would be a major benefit for shrimp production.     

Antibacterial effect of medium-chain fatty acid: caprylic acid on gnotobiotic <Emphasis Type="Italic">Artemia franciscana</Emphasis> nauplii against shrimp pathogens <Emphasis Type="Italic">Vibrio harveyi</Emphasis> and <Emphasis Type="Italic">V. parahaemolyticus</Emphasis>

The present study was carried out to determine the antibacterial effect of caprylic acid in the culture system of Artemia franciscana nauplii inoculated with shrimp pathogens Vibrio harveyi and V. parahaemolyticus. To begin with, the antibacterial effect of different concentrations (1, 10 and 100 mM) of caprylic acid against V. harveyi and V. parahaemolyticus was assessed through bacterial growth study. This indicated that at 100 mM concentration, the growth of the pathogens was completely inhibited within 5 h, whereas, in 1.0 and 10 mM concentrations, effective inhibition was observed with the extension of time. Subsequently, the influence of pH variation on the growth inhibitory effect of 10 mM caprylic acid against V. harveyi and V. parahaemolyticus at different pH (5–7) was also made through bacterial growth study. At pH 5, the pathogen growth was very less, compared with pH 6 and 7. The Artemia nauplii (instar II) reared in 10 mM caprylic acid supplemented medium were challenged with V. harveyi and V. parahaemolyticus, and the mortality was recorded at an interval of 6 h up to 60 h. In this study, the mortality of Artemia nauplii reduced to 20.61 and 16.30% in V. parahaemolyticus and V. harveyi challenged groups, respectively. The present results provide evidence for the potential antibacterial activity of caprylic acid in aquaculture against luminescent vibrios.     

Characterization of <Emphasis Type="Italic">kiss2</Emphasis> and <Emphasis Type="Italic">kissr2</Emphasis> genes and the regulation of kisspeptin on the HPG axis in <Emphasis Type="Italic">Cynoglossus semilaevis</Emphasis>

Reproduction allows organisms to produce offspring. Animals shift from immature juveniles into mature adults and become capable of sexual reproduction during puberty, which culminates in the first spermiation and sperm hydration or ovulation. Reproduction is closely related to the precise control of the hypothalamic–pituitary–gonadal (HPG) axis. Kisspeptin peptides are considered as the important regulator of HPG axis in mammalian. However, the current understanding of kisspeptin in flatfish is not comprehensive. In this study, we cloned and analyzed the kiss2 and kissr2 genes in Cynoglossus semilaevis. Interesting alternative splicing in the 5′-untranslated regions (UTR) of the Cskissr2 gene was found. The expression profiles of Cskiss2 and Cskissr2 showed relative high messenger RNA (mRNA) levels at the late gastrula stage during embryonic development, at total length = 40 mm during early gonadal differentiation, and in the brains and gonads of all investigated tissues. These results suggested that the kisspeptin system participated in embryogenesis and in the regulation of gonadal differentiation and development. Considering that the control and regulatory mechanisms of kisspeptin in the central reproductive axis are still unclear, we documented that the intramuscular injection of kisspeptin caused different sGnRH and cGnRH mRNA levels in a dose- and tissue-dependent manner. The mRNA expressions of FSH and LH were stimulated in the ovary and were inhibited in the testis under the kisspeptin treatments. These results provided foundations for understanding the roles of kisspeptin in the neuroendocrine system in fish. The manipulation of the kisspeptin system may provide new opportunities to control the gonadal development and even reproduction in fish.     

Cloning and characterization of <Emphasis Type="Italic">Bax1</Emphasis> and <Emphasis Type="Italic">Bax2</Emphasis> genes of <Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis> and evaluation of transcript expression in response to grass carp reovirus infection

Multidomain proapoptotic Bcl-2-associated X (Bax) protein is an essential effector responsible for mitochondrial outer membrane permeabilization, resulting in cell death via apoptosis. In this study, two Bax genes of grass carp (Ctenopharyngodon idellus), designated as CiBax1 and CiBax2, were isolated and analyzed. The obtained CiBax1 cDNA is 2058 bp long, with a 579 bp open reading frame (ORF) coding a protein of 192 amino acid residues. The full-length cDNA of CiBax2 is 1161 bp, with a 618 bp ORF coding 205 amino acids. Both CiBax1 and CiBax2 are typical members of Bcl-2 family containing conserved Bcl and C-terminal domains, and they share conserved synteny with zebrafish Bax genes despite the grass carp Bax mapping to different linkage groups. Phylogenetic analysis showed that CiBax1 was clustered with Bax from most teleost fish, and CiBax2 was close to Bax2 from teleost fish but far separated from that of Salmo salar. Quantitative real-time PCR analysis revealed broad expression of CiBax1 and CiBax2 in tissues from healthy grass carp, but the relative expression level differed. The mRNA expression of CiBax1 and CiBax2 was both upregulated significantly and peaked in all examined tissues at days 5 or 6 post-infection with grass carp reovirus. Subcellular localization indicated that CiBax1 protein was localized in both nucleus and cytosol, while CiBax2 protein only in cytosol. Moreover, CiBax2, but not CiBax1 was colocalized with mitochondrion under normal condition. Taken together, the findings would be helpful for further understanding of the function of Bax in teleost fish.     

Biofloc management with different flow rates for solids removal in the <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis> BFT culture system

Different water flows for solids removal in the Litopenaeus vannamei BFT system were evaluated. One control (no solids removal) and two treatments using different water flows, high (3945 L h^?1—HF) and low (1750 L h^?1—LF), were used with no water replenishment after each process, and the total dry weight of the solids was measured. L. vannamei (0.18 ± 0.06 g; 350 individuals m^?2) were stocked in 35-m^?3 tanks. For 17 weeks, the physical and chemical parameters were maintained within the recommended. To keep the total suspended solids concentrations at approximately 500–600 mg L^?1, clarifying was performed. The average water volume flowed by clarifiers was significantly different (p < 0.05) between HF (205 ± 34 m³) and LF (114 ± 24 m³). There was a significant decrease (p < 0.05) in the final tank volume in HF (28.09 ± 0.92 m³) and LF (28.62 ± 1.38 m³) due to the clarifying. Before clarifying (initial sample) and at the end of experiment (final sample) were not significantly different (p > 0.05) for crude protein, moisture or ash. The crude lipid of the LF in the final period was significantly lower (p < 0.05) compared to others in both periods. The survival, productivity and food conversion ratio were significantly better (p < 0.05) in the HF and LF treatments compared to those of the control. The best shrimp performance was obtained with solids removal. The lower flow in the clarifier facilitated particle settling, allowing adjustment of the flow.     

Effect of lignite fulvic acid on growth,antioxidant ability,and HSP70 of Pacific white shrimp, <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

This study was conducted to evaluate the effects of fulvic acid (0, 0.3, 0.6, 0.9, and 1.2%) as feed additive on growth, feed utilization, antioxidant ability, and HSP70 in hemolymph and hepatopancreas of juvenile white shrimp Litopenaeus vannamei (average weight 2.5 g) reared under experiment conditions. Shrimp were stocked at a density of 625 shrimps m^?3 for 60 days in net cages submerged in recirculating tanks. At the end of the experiment, specific growth rates and survival rates of shrimp in treatment groups fed with 0.6, 0.9, and 1.2% fulvic acid were higher compared to that of the control group. Shrimp fed 0.6, 0.9, and 1.2% fulvic acid had significantly lower feed conversion rates than those fed control diet. The optimum dietary fulvic acid requirement for juvenile shrimp based on weight gain was 0.897%. Furthermore, superoxide dismutase activity and peroxidase activity increased significantly, while malonaldehyde content decreased in the hemolymph and hepatopancreas of shrimp fed 0.9 and 1.2% dietary fulvic acid. Glutathione content increased obviously in hemolymph of shrimp fed 0.6, 0.9, and 1.2% fulvic acid. In hepatopancreas, glutathione content was significantly higher in shrimp supplemented with 1.2% fulvic acid. HSP70 decreased obviously in hemolymph of shrimp fed 0.9 and 1.2% fulvic acid, while shrimp fed with 0.6 and 0.9% fulvic acid showed lower HSP70 level in hepatopancreas. The results of this study demonstrated that dietary fulvic acid could improve survival rates, growth, feed utilization, antioxidant capability, and stress resistance of juvenile L. vannamei reared under intensive stocking conditions.