Effect of dietary protein and energy levels on growth,oxygen consumption,haemolymph and digestive gland carbohydrates,nitrogen excretion and osmotic pressure of Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles (Crustacea,Decapoda; Penaeidae)

The influence of protein and energy levels on growth rate, survival, pre- and post-prandial oxygen consumption, ammonia excretion, haemolymph glucose (HG), glycogen in digestive gland and osmotic pressure (OP) in white shrimp Litopenaeus vannamei (Boone) and L. setiferus (Linne) juveniles was studied. Diets containing a high-quality protein at a protein/energy (P/E) ratio of 16, 26, 31 and 36 mg kJ⁻¹ were fed at 20% of shrimp body weight of two sizes: < 1 g and > 1 g. Both species showed a optimum P/E ratio of 36 mg kJ⁻¹ (33–44% protein and 6–23% carbohydrate) in juveniles < 1 g. For shrimp > 1 g, L. setiferus showed a higher growth rate in the diet with 16 mg kJ⁻¹ (27% protein; 32% carbohydrate) and L. vannamei between 26 and 36 mg kJ⁻¹ (33–44% protein and 6–23% carbohydrate). In both experiments, the growth rate of L. vannamei was 2–3 times that observed in L. setiferus. Routine oxygen consumption and apparent heat increment (AHI) of L. setiferus juveniles was two times higher than that observed in L. vannamei juveniles, which could indicate that L. setiferus has a higher metabolic rate. The O/N ratio varied according to protein level, with higher values (O/N = 180) with a 16-mg kJ⁻¹ diet and lower values (O/N = 73) with a 36-mg kJ⁻¹ diet in L. setiferus juveniles. A similar variation in O/N ratio was obtained in L. vannamei fed with all diets with an interval between 22 and 50. An inverse relation between ammonia excretion and HG, and digestive gland glycogen (DGG) in relation to an increase in the P/E ratio indicate that both shrimp species are well adapted to use carbohydrates and/or proteins from their diet. The higher values of hyper-osmotic capacity (hyper-OC) were observed in L. setiferus < 1 g fed with 36 mg kJ⁻¹ and the lowest in L. vannamei < 1 g fed with 31 mg kJ⁻¹. Intermediate values of hyper-OC were observed in both species fed all diets indicating that osmotic factors of juveniles < 1 g of both species are more affected by the P/E ratio than juveniles > 1 g. All results showed that juveniles > 1 g of both species are less dependent of P/E ratio than juveniles < 1 g. Litopenaeus vannamei is a most tolerant shrimp species with a high capacity to use a wide range of dietary P/E ratios for growth, which may be due to its lower energy requirements. Litopenaeus setiferus showed a lower capacity to accept different P/E ratios but the optimum P/E ratio obtained with this species shows that L. setiferus accept diets with a high carbohydrate level as well. These results demonstrate that there are nutritional and physiological differences that explain the differences that have been observed when both species were cultured in commercial ponds.     

Comparative study of the intracellular superoxide anion production in different penaeid species through the NBT‐reduction assay

The capacity of reactive oxygen intermediates production upon haemocyte stimulation is one of the most important immunoparameter utilized to assess the health status in cultivated shrimps. In the present study, we compared oxidative stress potential, by measuring the superoxide anion production in three penaeid shrimps: two wild Atlantic species, the pink shrimp Farfantepenaeus paulensis and the white shrimp Litopenaeus schmitti and one cultivated Pacific species, the white shrimp, Litopenaeus vannamei, through the nitro‐blue‐tetrazolium‐reduction assay. We also proposed an optimized experimental protocol for this assay, that produces rapid and consistent results with low levels of basal superoxide anion (O₂^?) production by unstimulated haemocytes and high levels of this oxygen radical after cell stimulation. Among the different cell elicitors used (zymosan, laminarin, lipopolysaccharide and phorbol myristate acetate), laminarin (β‐1,3‐glucans – 2 mg mL^?1) was the most potent cell activator for the haemocytes of all three penaeids and we recommend this immunostimulant to routinely evaluate shrimp respiratory burst. In general terms, the most elevated levels of O₂^? production, after cell stimulation with microbial components, were detected in L. schmitti. Interestingly, the stimulation profile of the haemocytes of L. vannamei was more similar to F. paulensis, than to L. schmitti, which is more phylogenetically related.     

Inbreeding Effects on Hatchery and Growout Performance of Pacific White Shrimp, Penaeus (Litopenaeus) vannamei

In animal breeding programs, selection coupled with a narrow genetic base can cause high levels of inbreeding to occur rapidly (in one or two generations). Although the effects of inbreeding have been studied extensively in terrestrial animals and to a lesser extent in aquaculture species, little is known about the effects of inbreeding on penaeid shrimp. The objective of this study was to investigate the effects of inbreeding on hatchery and growout performance of the Pacific white shrimp, Penaeus vannamei. The experiment was conducted over 2 yr, and data from two successive generations (G₂ and G₃) of inbred (sibling–sibling mating) and outbred families were analyzed. There were 11 inbred and 12 outbred families in G₂ and 9 inbred and 10 outbred families in G₃. Inbreeding coefficients (F) for outbred and inbred families were 0.00 and 0.25, respectively, for G₂ and 0.00 and 0.375, respectively, for G₃. Growth rates for outbreds and inbreds were similar in both G₂ and G₃. Hatch rate for inbred families was 33.1% lower than for outbred families in G₂ and 47.1% lower in G₃. Inbreeding depression (IBD) (relative change in phenotype per 0.1 increase in F) ± 95% CI for hatch rate was ?12.3 ± 10.1%. Hatchery survival for inbred families was 31.4% lower than for outbred families in G₂ and 38.8% lower in G₃. IBD for hatchery survival was ?11.0 ± 5.7%. Growout survival was 1.9% lower for inbred families than for outbred families in G₂ and 19.6% lower in G₃. IBD for growout survival was ?3.8 ± 2.9%. There was also a significant linear relationship between IBD estimates for survival traits and mean outbred survival. At high outbred survival, IBD was low (e.g., growout survival in G₂), but IBD appeared to become more severe when outbred survival was lower. This suggests that stress (related to environment and/or life stage) may worsen IBD for survival traits. Results also indicate that moderate to high levels of inbreeding (>10%) should be avoided in commercial shrimp hatcheries because the cumulative effect of IBD on hatch rate and hatchery survival will significantly reduce postlarvae production. Thus, IBD can be significant enough to justify the use of inbreeding as a germplasm protection strategy (under certain scenarios) for genetic improvement programs.     

Genetic monitoring of broodstocks of the marine shrimp Litopenaeus vannamei in a closed rearing system in Pernambuco,Brazil

Loss of genetic variability can be detrimental to a population's survival traits and fitness. These effects are likely to be maximized in shrimp closed broodstock rearing systems where post‐larvae are often produced from crosses of breeders collected from an associated grow‐out farm after mass selection. Longtime broodstock management in closed systems is also expected to lead to reduction in or even complete eradication of genetic variability. The present work aimed at monitoring the genetic variability of a Litopenaeus vannamei hatchery in the state of Pernambuco (Brazil), during three successive replacements, using microsatellite markers. No significant genetic diversity losses have been observed through the values of mean heterozygosity (H_o=0.460 and H_e=0.660 in the first sample; H_o=0.420 and H_e=0.620 in the second sample; and H_o=0.600 and H_e=0.660 in the third sample). However, some alleles appear to have been lost after three replacements. The diversity level was considered to be high and is comparable to those reported for wild populations, suggesting that the original imported founder stock of Brazilian L. vannamei is likely to have had a high genetic diversity, possibly due to multiple origins.     

Biotic communities and feeding habits of Litopenaeus vannamei (Boone 1931) and Litopenaeus stylirostris (Stimpson 1974) in monoculture and polyculture semi-intensive ponds

Zooplankton, macrozoobenthos and feeding habits of Litopenaeus stylirostris and L. vannamei in monoculture and polyculture semi‐intensive experimental ponds were evaluated. Zooplankton was more abundant in monoculture of L. stylirostris (1002±670 organisms (org.) L^?1) than in monoculture of L. vannamei (470±37 org. L^?1), and polyculture (321±188 org. L^?1). The main zooplanktonic groups were polychaeta larvae, nauplii, copepods and polychaeta. Macrozoobenthos was more abundant in polyculture (6898±11 137 org. m^?2) compared with monoculture of L. stylirostris (3201±350 org. m^?2) and L. vannamei (2384±3752 org. m^?2). The main benthic groups were copepods, polychaeta, ostracods, nematodes and insects. Differences in feeding habits were found between species and regimes. Litopenaeus vannamei showed to be a more voracious species and fed mostly on organic detritus and benthos in both culture regimes. Litopenaeus stylirostris had a more restricted sources of feed in the ponds. The major component in the stomach content of both species was detritus. Macroalgae, sand, exuvia, formulated feed, prey and microalgae were minor components for both species (<7%). Ingestion of formulated feed was <4% for L. stylirostris and was not detected for L. vannamei. The stomach repletion rates were larger for L. vannamei (55.6% and 48.8%) than for L. stylirostris (43.75% and 44.89%). Litopenaeus stylirostris grew better in polyculture (10.3±3.4 g) that in monoculture (9.0±3.8 g). Litopenaeus vannamei grew better in monoculture (16.1±4.8 g) than in polyculture (13.4±4.5 g). For both species, feed conversion ratio was lower in polyculture.     

MONO- AND POLYCULTURE OF Penaeus vannamei AND P. stylirostris IN PONDS

Polyculture of fish has been shown to be an effective means of increasing production beyond that achieved in monoculture, but little research has been conducted to evaluate the effect of polyculture on production of shrimp species. This research was designed to investigate performance of Penaeus vannamei (v) and P. stylirostris (s) in monoculture (treatments 100v and 100s) as well as in polyculture at various species ratios (75v:25s, 50v:50s, and 25v:75s) at a constant density of 1.8 × 10⁵ /ha. Shrimp were stocked into fifteen 0.1-ha ponds at the Texas A&M University Mariculture Facility for 123–134 days. Results indicate a higher mean survival rate (73 vs 22%) but lower mean growth rate (0.09 vs 0.14 g/day) of P. vannamei than P. stylirostris. Survival rates of neither species differed significantly among treatments. Final weight of each species significantly decreased with increasing density of the same species but significantly increased with increasing density of the other species. Best growth of both species occurred in the 75v:25s treatment. Observed differences in distribution and diel activity of the two species within ponds may partly explain the compatability of these two species in polyculture. Production rates (range, 690 to 2,180 kg/ha) and value (range, US$2,720 to US$5,740/ha) among treatments generally increased with increasing composition of P. vannamei; however, no significant difference in mean value was detected between the 100v and 75v:25s treatments. As a secondary objective of this study, performance of shrimp (25v: 75s treatment) in a single-phase pond system was compared to that in a three-phase (nursery, intermediate, and grow-out) system. Survival, growth, production, and value were found to be similar between systems.     

Genetic variability in four hatchery strains of coho salmon, Oncorhynchus kisutch (Walbaum), in Chile

Coho salmon, Oncorhynchus kisutch (Walbaum), is intensively cultured in Chile. An increasing proportion of the eggs necessary to sustain the culture are locally produced by some hatcheries. However, there is no information about the origin or the genetic variability in these strains. The present study analysed allozymic variability and its distribution within and between some commercial strains of coho salmon in southern Chile. The genetic variability was estimated using horizontal starch gel electrophoresis. Samples of coho salmon were obtained randomly from four Chilean hatcheries. Twenty‐five enzymatic systems were examined, representing 51 enzymatic loci. Eight loci showed variability in at least one strain, which represented a total polymorphism (P) of 15.7%. Only the PGM‐1* locus was variable in all strains. The remaining loci were fixed in at least one strain. Total heterozygosity (H_T) and within population heterozygosity (H_S) were 0.35% and 0.36% respectively. The index of genetic diversity (G_ST) was 1.5%. The results confirm previous reports of low genetic variability in cultured strains of coho salmon in Chile, below that observed in their native range, which suggests loss of the genetic variability caused by genetic drift or other causes in these strains.     

The effect of Ibuprofen on female and male reproduction of the open thelyca marine shrimp,Litopenaeus

A research was designed to explore the effect of ibuprofen (IBU) as an intervening agent for prostaglandin biosynthesis on male and female reproduction of three species of Litopenaeus. Ovarian maturation was studied in L. stylirostris and L. vannamei injected periodically with IBU at 0.01 and 0.1 μg g^?1 body weight (b.w.) and treated for unilateral eyestalk ablation. IBU at 0.1 μg induced a statistically (P < 0.05) higher rate of L. vannamei females with developing ovaries (45 ± 19%) as compared with controls (12 ± 8%) during 5 weeks; L. stylirostris did not activate vitellogenesis under this experimental protocol. IBU was also evaluated for male sexuality in L. occidentalis, L. stylirostris and L. vannamei. Periodic injections of IBU had no effect on sperm counts and spermatophore weights; however, sperm abnormalities in IBU 0.1 μg treated L. occidentalis and L. stylirostris were very low. In L. stylirostris, the renovation of normal spermatophores was remarkably improved in IBU treated males as compared with controls, but in L. vannamei spermatophore deterioration was not affected. The findings of this research support the hypothesis that prostaglandins are involved in penaeid reproduction playing a negative physiological role; however, altered steroidogenic pathways could also be involved.     

Effect of cyclical feeding on compensatory growth,nitrogen and phosphorus budgets in juvenile Litopenaeus vannamei

This study assessed the effect of cyclical feeding on compensatory growth, nitrogen (N) and phosphorus (P) budgets of juvenile Litopenaeus vannamei. A 36‐day growth trial was performed with four different feeding protocols. The control group (S0) was fed to satiation twice every day during the whole experimental period; treatment groups S1, S2 and S3 were fed by the 9, 5 and 3 cycles of 1:3, 2:5 and 3:9 (fasting days:feeding days) respectively. Fasting in S1, S2 and S3 groups did not change the specific growth rate in wet weight (SGR_w), but the feed conversion efficiency (FCE) and protein efficiency ratio (PER) were significantly increased (P < 0.05) in comparison with control. The N and P consumed per unit wet weight gain of shrimp in S1, S2, S3 groups were significantly lower (P < 0.05) than control group by 15.39%, 15.96%, 19.33% for N, and 15.16%, 15.98%, 19.26% for P respectively. The total discharge of N and P (including N and P discharged by faeces (F_N/P), non‐faecal excretions (U_N/P) and exuviations (E_N/P); ) was significantly lower (P < 0.05) in the experiment groups by 19.91–22.07% for N and 18.68–26.37% for P respectively. Overall, the results suggest that the L. vannamei can reach completely compensatory growth, and the total discharge of N and P per unit wet weight gain of L. vannamei significantly decreased by cyclical feeding, which could have a positive effect on the reduced of environmental N and P loading due to the cultured of L. vannamei.     

Moult cycle of laboratory-raised Penaeus (Litopenaeus) vannamei and P. monodon

This study was carried out to gather quantitative data on the moult cycle and stages in laboratory-raised shrimp, kept at a constant temperature of 27°C. The stages of the moult cycle were differentiated and characterised by microscopic analysis of cuticle, epidermis and moulting processes in the uropods of P. vannamei and P. monodon. Five major moult stages were defined: early- and late post-moult (A and B), inter-moult (C) and early- and late pre-moult (D1 and D2). Total moult cycle duration was around 5 and 6.5 days for 2-g P. vannamei and P. monodon and 11 and 12 days for 15-g P. vannamei and P. monodon, respectively. Overall, the relative duration of the moult stages within the cycle was 5–10% for A, 9–16% for B, 12–20% for C, 28–36% for D1 and 30–38% for D2 stage. It was concluded from this study that the pre-moult stages comprised the dominant phase of the cycle and that P. monodon moulted at a significantly slower rate than P. vannamei, under the given conditions. Without the use of invasive techniques, the moult process was charted in laboratory-raised shrimp in Europe, providing a tool for taking into account this important physiological factor in further experiments.     

Preliminary Comparisons of the Native Penaeus setiferus and Pacific P. vannamei White Shrimp for Pond Culture in South Carolina, USA

Two pond experiments were conducted at the Waddell Mariculture Center to compare production characteristics of the native Penaeus setiferus and Pacific P. vannamei white shrimp in South Carolina. In 1985, 7–9 day old postlarval P. setiferus were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1, one 0.25, and one 0.5 ha ponds. Both species were stocked at 12 shrimp/m². The shrimp were fed a 25% protein commercial food and harvested by draining after 147 d. Sarvival in all ponds was > go%, but growth and production of the P. setiferus were considerably lower than values obtained for P. vannamei: 12.8 g and 1,555 kg/ha/crop for P. satiferus versus 19.7 g and 2,477 kg/ha/crop for P. vannamei. In 1989, duplicate 0.1 ha ponds were stocked with P. setiferus and P. vannamei at 60 shrimp/m², and two additional 0.1 ha ponds were stocked with P. setiferus at 40/m². The P. setiferus postlarvae were produced at the Waddell Center from captive-reared and wild South Carolina brood stock. Rearing procedures involved paddlewheel aeration (10 hp/ha), regular water exchange (averaging 16–21%/d in all ponds), and use of a 40% protein feed. Due to the availability of postlarvae, the various treatments were stocked at different times. Both P. setiferus treatments were reared for 145 d, while the P. vannamei were reared for 165 d. P. setiferus at the 40/m² density attained mean size, survival, and standing crop biomass at harvest of 13.5 g, 97.5% and 5,259 kg/ha/crop, respectively. The 60/m²P. setiferus treatment was stocked 2 wk earlier and yielded 15.2 g mean weight, 87.5% survival, and 7,995 kg/ha/crop at harvest. The P. vannamei 60/m² treatment, which was stocked 3 wk earlier than any of the P. setiferus, produced mean size, survival and standing crop biomass at harvest of 17.1 g, 69.5% and 7,187 kg/ha/crop. Both survival and production levels would have been higher had not one replicate experienced a partial mortality due to a feeding accident. The 1989 study yielded what is thought to be the highest production levels yet achieved with P. setiferus in pond culture. These results suggest that P. setiferus may be a viable alternative to P. vannamei for intensive cultivation in the continental U.S. when P. vannamei are unavailable. Further evaluation of this potential is needed.     

EFFECT OF LIGHT INTENSITY AND MALE AND FEMALE EYESTALK ABLATION ON REPRODUCTION OF Penaeus stylirostris AND P. vannamei

This 97-day study, conducted during midwinter using a recirculating water system, was designed to evaluate the effect of light intensity and male and female eyestalk ablation on reproduction of P. vannamei and P. stylirostris. Four light intensities were established using various levels of fluorescent lighting (bright, 14.7 μEm^-2s^-1; moderate, 4.4 μEm^-2s^-1; dim, 0.6 μEm^-2s^-1; and dark, 0.0 μEm^-2s^-1) and the fifth consisted of artificial lighting supplemented with natural light through a translucent skylight (skylight, 4.7–9.3 μEm^-2s^-1). Unilateral eyestalk ablation was performed on all male P. vannamei in one of each pair of tanks within a treatment. In addition, half of the females in each tank were unilaterally ablated. Ovarian maturation, spawning, molting rate, and survival were monitored daily within each tank. Growth and gonad development were measured at termination. The optimum light intensity for P. stylirostris appeared to be lower than that for P. vannamei. P. stylirostris matured and spawned more frequently in the skylight and dim treatments than in the moderate, dark, and bright treatments. P. vannamei matured and spawned more frequently in the skylight, bright, and moderate treatments than in the dim and dark treatments. Natural light supplementation beneficially affected reproduction of both species. Male eyestalk ablation increased gonad size and doubled mating frequency of P. vannamei in comparison to unablated controls. This is the first documentation of increased penaeid shrimp reproduction by unilateral eyestalk ablation of males. Even more significant may be recognition that male gonadal development is a limiting factor in reproduction of shrimp in captivity.     

Evaluation of cholesterol additions to a soyabean meal-based diet for juvenile Pacific white shrimp, Penaeus vannamei (Boone), in an outdoor growth trial

Cholesterol is considered a required nutrient for penaeid shrimps, but an optimal level has not been defined. A 68-day grow-out trial was conducted in 1300-L outdoor tanks in Hawaii, USA, to determine the cholesterol level required in a soyabean meal-based diet for juvenile Pacific white shrimp, Penaeus vannamei (Boone). Test feeds were prepared by adding six cholesterol levels (1.0-10.2 g kg^?1, as-fed basis) to a standard diet high in plant-protein meals, starch and flour. These feeds were provided to the shrimp three times daily. Harvest weights and weekly growth increments varied significantly among diets. The 2.3 g kg^?1 and 4.2 g kg^?1 cholesterol diets yielded better growth than the 1.0 g kg^?1 and 10.2 g kg^?1 diets. Survival and feed conversion ratios did not vary significantly among diets. Significant dietary cholesterol effects on growth of P. vannamei in conditions resembling commercial grow-out indicate that its inclusion in practical diets at more accurately defined levels is necessary. Optimal cholesterol levels for juvenile shrimp may be lower than those now utilized, and may vary relative to the contribution of free sterols from natural foods in shrimp ponds.     

实时荧光定量PCR检测凡纳滨对虾和罗氏沼虾卵黄蛋白原mRNA在卵巢和肝胰腺中的表达

卵黄磷蛋白作为卵黄蛋白的主要成分, 可为甲壳动物胚胎和早期幼体发育提供能量, 为研究其来源及合成规律, 实验应用SYBR GreenⅠ荧光定量PCR法检测了凡纳滨对虾和罗氏沼虾性腺不同发育时期卵巢和肝胰腺两种组织中卵黄蛋白原mRNA的表达水平。结果发现,凡纳滨对虾和罗氏沼虾的卵巢和肝胰腺中都有卵黄蛋白原mRNA的表达。随着卵巢的发育, 凡纳滨对虾卵巢中卵黄蛋白原mRNA的相对表达量在前5个阶段不断增加, 分别为1.1, 5.9, 10.4, 26.9, 85.0, 恢复期急剧减少, 为1.6。肝胰腺中的相对表达量也不断增加, 分别为1.3, 3.3, 7.1, 37.3, 51.6, 恢复期急剧减少, 为1.0。罗氏沼虾肝胰腺中卵黄蛋白原mRNA的相对表达量在前四个阶段不断增加, 分别为3.4, 12.6, 15.2, 38.9, 抱卵期急剧减少, 为2.9;而卵巢在整个发育过程中对卵黄蛋白原合成的贡献比较小, 分别为1.0, 1.3, 1.7, 4.8, 1.5。研究表明, 两种虾类的肝胰腺和卵巢均具合成卵黄蛋白的功能, 而且在不同的卵巢发育阶段呈现明显的规律性。     

Trypsin enzyme activity during larval development of Litopenaeus vannamei (Boone) fed on live feeds

Larval stages of the Pacific white shrimp, Litopenaeus vannamei (Boone) were fed standard live diets of mixed microalgae from the first to the third protozoea (PZ1 to PZ3), followed by Artemia nauplii until post‐larvae 1 (PL1). Trypsin enzyme activity for each larval stage was determined using N‐α‐p‐toluenesulphonyl‐l ‐arginine methyl ester (TAME) as a substrate. Results were expressed as enzyme content to assess ontogenetic changes during larval development. Tissue trypsin content (IU µg^?1 DW for each larval stage) was significantly highest at the PZ1 stage and declined through subsequent stages to PL1. This contrasts with previously observed patterns of trypsin development in Litopenaeus setiferus (Linnaeus) and other penaeid genera, which exhibit a peak in trypsin activity at the third protozoea/first mysis (PZ3/M1) larval stage. Litopenaeus vannamei larvae transferred to a diet of Artemia at the beginning of the second protozoea (PZ2) stage were significantly heavier on reaching the first mysis stage (M1) than those fed algae, while survival was not significantly different between treatments. At both PZ2 and PZ3 stages, trypsin content in larvae feeding on Artemia was significantly lower than in those feeding on algae. The rapid decline in trypsin content from PZ1 and the flexible enzyme response from PZ2 suggest that L. vannamei is physiologically adapted to transfer to a more carnivorous diet during the mid‐protozoeal stages.     

凡纳滨对虾和罗氏沼虾肠道微生物及抗生素抗性基因多样性分析

探究凡纳滨对虾和罗氏沼虾肠道微生物及抗生素抗性基因(antibiotic resistance genes, ARGs)种类的差异。通过高通量测序和变性梯度凝胶电泳(denaturing gradient gel electrophoresis, DGGE)技术分析2种虾肠道微生物群落结构差异和微生物多样性,并运用PCR方法检测了2种虾肠道细菌常见38种ARGs的携带情况。结果显示,获得凡纳滨对虾和罗氏沼虾肠道细菌有效序列分别为42 795和40 713条,物种注释单元(operational taxonomic unit, OTU)数目分别为124和82,分类地位明确的细菌种类分别隶属5个门、17个属和5个门、16个属。凡纳滨对虾肠道细菌的优势类群为变形菌门,所占比例为75.45%,优势菌属为副球菌属(25.83%)和不动杆菌属(25.24%);罗氏沼虾肠道细菌的优势类群是厚壁菌门(49.74%),优势菌属为乳球菌属(49.01%)和弧菌属(29.98%)。凡纳滨对虾肠道细菌(2.19)Shannon指数高于罗氏沼虾肠道细菌(1.78),表明前者肠道细菌多样性大于后者。DGGE图谱的分析结果与高通量测序一致,2种虾肠道细菌种类差异很大。PCR结果显示,凡纳滨对虾肠道细菌携带15种ARGs,罗氏沼虾肠道细菌携带14种ARGs。本实验表明凡纳滨对虾肠道细菌的群落种类多样性、OTU丰富度、物种总数和ARGs种类均高于罗氏沼虾肠道细菌,为后续肠道微生物资源的挖掘提供了理论依据。     

A description of the ovarian development stages of penaeid shrimps from the coast of Pakistan

In this study, four species of penaeid shrimp from Pakistan's inshore waters were studied. These were Penaeus penicillatus (Alcock), Penaeus merguiensis (de Man), Metapenaeus affinis (Milne Edwards) and Parapenaeopsis stylifera (Milne Edwards). During maturation, shrimp ovaries pass through a series of colour changes. The various colours observed in the ovaries of the four species of penaeid shrimps were translucent, white, cream, yellow, green‐yellow, green‐white, light green and dark green. The different type of oocytes observed in histological sections of the penaeid ovaries are as follows: chromatin nucleolar oocytes, perinucleolar oocytes, yolkless oocytes, yolky oocytes and oocytes with cortical bodies. The ovarian developmental stages recognized in these shrimps are: undeveloped, developing, nearly ripe, fully ripe, resorbing and resorbing/ developing. The ovarian developmental stages were similar in all the four species with the exception of the fully ripe stage. In the fully ripe stage of P. penicillatus and P. merguiensis, the cortical bodies were present at the periphery in two shapes; spherical as well as rod‐like. On the other hand, in the fully ripe stage of M. affinis and P. stylifera, the cortical bodies were present only at the periphery and were only spherical. A relationship between colour of ovaries and histological stages of ovarian development was established. A female shrimp with a dark‐green ovary is an indication of the ready‐ to‐spawn condition. In P. merguiensis and Penaeus penicillatus, respectively, 100% and 88.1% females with dark‐green ovaries had oocytes with cortical bodies, whereas in M. affinis and P. stylifera, respectively, 50% and 28.6% females with dark‐green ovaries had oocytes with cortical bodies.     

The Effect of Low Salinity Water with Different Ionic Composition on the Growth and Survival of Litopenaeus vannamei (Boone, 1931) in Intensive Culture

The effects of four different ionic composition low salinity water (T₁, T₂, T₃, and T₄), on growth and survival of Litopenaeus vannamei marine shrimp juveniles were investigated. Shrimp culture in seawater (T_m) was used as control treatment. The results indicated that there were no significant difference (P < 0.05) in growth, survival, production, and feed conversion ratio (FCR) of L. vannamei juveniles reared in the different treatments, but significant differences (P < 0.05) were observed between each of them when compared with seawater (T_m). After 84 days, culture shrimp grew from 0.02 to 7.58 g in T₁. The lowest growth rate was attained in T₃ (0.57 g/week), in which potassium and calcium ions concentrations were the lowest (0.58 and 28.00 mg/L, respectively). The recorded survival rate (76.35% to 79.55%) is considered well for the 84 days growout period, although it was 7.6% lower than that recorded in the control treatment. Although there were no significant differences (P < 0.05) in growth with respect to the ionic composition of the four treatments, there was a trend of increasing growth in relation with the ionic ratio found in the seawater (T_m). This aspect should be evaluated more closely in future research.     

Infection of IHHN virus in two species of cultured penaeoid shrimp Litopenaeus vannamei (Boone) and Litopenaeus stylirostris (Stimpson) in Ecuador during El Niño 1997–98

Infectious hypodermal and haematopoietic necrosis virus (IHHNV) was first noted in blue shrimp Litopenaeus stylirostris (Stimpson) in mid-1981. Since that time, at least 12 species of penaeoid shrimp have been reported to be infected with IHHNV. Pacific white shrimp Litopenaeus vannamei (Boone) represents a shrimp species highly refractory to the disease, whereas L. stylirostris was highly susceptible to the disease. Since the beginning of the shrimp farming industry in Ecuador, viral diseases have been observed in L. vannamei and L. stylirostris. Of these, L. vannamei represents ≈ 80% of cultured shrimp. Histopathology, ultrastructure and in situ DNA hybridization confirm the presence and assess the prevalence of IHHNV in pond-reared shrimp, and especially in abnormally small animals of both species. Although IHHNV may be considered enzootic in cultured L. vannamei in Ecuador, we did not find high prevalence (Cowdry A bodies) in specimens of diseased pond shrimp before 1996. From that time to 1998, a higher prevalence of IHHNV has been observed in both species. The epizootic of the IHHNV disease has been related to the oceanographic and climatological conditions caused by El Niño. In addition, it has been suggested that large quantities of wild shrimp post-larvae of both species that were stocked in shrimp farms, infected as latent carriers in 1997, from which the virus could spread to a larger population of these shrimp in 1998.     

Oral Administration of Hot‐water Extract of Tropical Brown Seaweed,Sargassum cristaefolium,to Enhance Immune Response,Stress Tolerance,and Resistance of White Shrimp,Litopenaeus vannamei,to Vibrio parahaemolyticus

The efficacy of hot‐water extract of tropical brown seaweed, Sargassum cristaefolium (SCE), supplemented in diets on immune response, stress tolerance, and disease resistance of Litopenaeus vannamei to Vibrio parahaemolyticus was evaluated. Shrimp were fed diets containing graded levels of SCE (0, 250, 500, 750, and 1000 mg/kg). The results showed that shrimp fed all diets containing SCE had significantly higher (P < 0.05) immune response in total hemocyte count (THC), differential hemocyte count (granular and hyaline cells), and phagocytic activity than those of shrimp fed the control diet. Similarly, in low dissolved oxygen stress tolerance test and the challenge test with V. parahaemolyticus, survival rates of shrimp fed all diets containing SCE were significantly higher (P < 0.05) (83–93% in stress test and 27–47% in challenge test) than those of shrimp fed the control diet (77 and 3.3%, respectively). These results suggest that oral administration of SCE at 500 and 750 mg/kg can be effectively used to enhance immune response, stress tolerance, and resistance of white shrimp, L. vannamei, against V. parahaemolyticus infection. These findings also confirm that using dietary SCE as immunostimulant is effective at increasing the nonspecific immune system in penaeid shrimp, L. vannamei.