Rearing the spotted seahorse Hippocampus kuda by feeding live and frozen copepods collected from shrimp ponds

This study evaluated the use of live and frozen copepods collected from shrimp ponds for rearing juveniles of the spotted seahorse Hippocampus kuda. Protein and HUFA contents in frozen copepods were all higher than in Artemia nauplii, the conventional live food for seahorse juveniles. The results of this study showed that copepods can be used as feed for rearing seahorse fry and juvenile. The spotted seahorse showed obvious preference for live copepods and rarely fed on dead copepods on the tank bottom. Furthermore, the combination of frozen copepods and live Artemia nauplii resulted in highest growth and highest survival of the experimental seahorses. Further research on possible effects of DHA:EPA ratio on survival and growth of young H. kuda is recommended.     

Selection of lactic acid bacteria as candidate probiotics for Vibrio parahaemolyticus depuration in pacific oysters (Crassostrea gigas)

The application of probiotics in food is now widespread and is widely accepted by consumers. Lactic Acid Bacteria (LAB) were isolated from traditional salted fish and then characterized by its ability to inhibit Vibrio parahaemolyticus growth using minimal inhibitory concentration tests. Five out of these strains were identified as Lactobacillus delbrueckii, Lactobacillus casei and three Lactobacillus gasseri by PCR using 16S and 23S rRNA genes. Antibiofilm activity of Lactobacillus spp. extracts were also tested in 96 polystyrene plates. A potential antibiofilm effect was demonstrated as most LAB. Although most LAB extract were able to eradicate pre‐formed biofilm, results demonstrated that five Lactobacillus spp. exhibited a stronger inhibitory effect against V. parahaemolyticus in infected oysters. Vibrio parahaemolyticus viable cells number declined from 10⁶ UFC to 10⁴ UFC after 3 days of incubation with Lactobacillus spp. Probiotic applications, in biological control of seafood associated pathogens can be an alternative solution, providing consumer with a product of good quality owing to the use of non‐toxic compounds. Based on our results, LAB could be used as a bioprotective culture in oyster's depuration to prevent V. parahaemolyticus growth.     

Experimental evidence on prevention of infection by the ectoparasitic protozoans Ichthyobodo salmonis and Trichodina truttae in juvenile chum salmon using ultraviolet disinfection of rearing water

In northern Japan, juvenile chum salmon Oncorhynchus keta (Walbaum) are released from hatcheries to enhance the fishery resource. Infections with ectoparasitic protozoans, particularly the flagellate Ichthyobodo salmonis and the ciliate Trichodina truttae, occasionally cause severe mortality among hatchery‐reared juveniles. This study examined the susceptibility of the two parasites to wide‐ranging UV irradiation (experiment 1) and then investigated whether UV disinfection of the rearing water using a commercial device was useful for preventing infections among juveniles in a small‐scale rearing system over a 28‐day period (experiment 2). In experiment 1, parasite mortality reached 100% with UV irradiation doses of ≥9.60 × 10⁵ μW s/cm² for I. salmonis and ≥8.40 × 10⁵ μW s/cm² for T. truttae. In experiment 2, disinfection of the rearing water at a UV irradiation dose of 2.2 × 10⁶ μW s/cm² succeeded in complete prevention of both parasites in the juvenile salmon. These results elucidate the minimum dose of UV irradiation for inactivation of I. salmonis and T. truttae, and demonstrate the usefulness of water disinfection using a commercial UV irradiation device to prevent infections by these parasites in hatchery‐reared juvenile chum salmon.     

Effect of starvation on survival and biochemical profile of newborn juvenile lined seahorses,Hippocampus erectus (Perry, 1810)

This study assessed the effect of starvation on survival and nutritional status of newborn juveniles H. erectus (<10 days) to optimize rearing protocols, thereby helping to reduce wildlife exploitation. Maximum starvation time (MST) was estimated through the survival of juveniles continuously starved from birth. Resistance to starvation and the effect of food re‐introduction after 1, 2, 4 and 6 days of starvation on survival and metabolite concentrations (total proteins, total lipids, acylglycerides, cholesterol, glucose) were also determined. Survival amongst continuously starved animals decreased from 6.6 ± 0.5 to 0% from days 9 to 10 of starvation. Seahorses under different starvation–refeeding treatments all had 100% survival up to day 5 of experiments. After 10 days, however, a 4‐day starvation period followed by refeeding showed negative effects with <50% survival. During continuous starvation, lipids were the first energy reserve used to maintain basal metabolism, followed by proteins. Except for cholesterol, all metabolite concentrations differed between continuous starvations and feeding. Despite high seahorse survival after 5 days in the absence of food, the recovery of the metabolic status is possible after a starvation period of no more than 2 days, since irreversible physiological changes compromising the ultimate survival of the organisms take place after this time.     

Effect of low salinity on the expression profile of Na+/K+‐ATPase and the growth of juvenile chub mackerel (Scomber japonicus Houttuyn)

Chub mackerel (Scomber japonicus Houttuyn) is one of the most commercially important scombroid fish used as a food resource. Recently, there has been a demand for efficient rearing methods of this fish for a full‐life cycle aquaculture. In the present study, we evaluated the physiological responses in the juvenile S. japonicus to different ambient salinities. A significantly higher gain of the body mass was observed in the juveniles reared in 24 g/L and 13 g/L seawater than in those reared in natural seawater (34 g/L) within 40 days of the experimental period without affecting mortality. A principal enzyme for osmoregulation, Na⁺/K⁺‐ATPase, was expressed in the ionocytes located in the gill filaments of the juveniles. The number and the cell size of ionocytes and the enzymatic activity of Na⁺/K⁺‐ATPase in the gills decreased within 10 days after the low‐salinity challenge, which implies the reduction of the energy‐consuming active ion secretion under the low‐salinity environment. The physiological capacity for adaptation to low‐salinity seawater in chub mackerel could be basic knowledge to carry out culturing of these fish in coastal sea pens where ambient salinity fluctuates. The improvement of the growth performance by rearing in low‐salinity seawater will contribute to the efficient production of the seed juveniles for aquaculture.     

Effects of dietary probiotic Lactobacillus plantarum and whey protein concentrate on the productive parameters,immunity response and susceptibility of Nile tilapia,Oreochromis niloticus (L.), to Aeromonas sobria infection

Immunostimulatory feed supplements have an increasingly interest in aquaculture management. Generally, an individual supplement was used in fish diets but it is expected that the use of multi‐supplements may show synergistic enhancements in fish performance, health, and immunity. Therefore, the present investigation was carried out to evaluate the use of dietary probiotic Lactobacillus plantarum and whey protein concentrate (WPC) in practical diets for Nile tilapia, Oreochromis niloticus. Hence, probiotic L. plantarum, WPC and their mixture were incorporated into a basal fish diet (300 g/kg crude protein) as follows: T1 = a basal control diet, T2 = a basal diet containing L. plantarum, T3 = a basal diet containing 1.0 g WCP/kg diet and T4, T5 or T6 = basal diets containing probiotic L. plantarum + 1.0, 2.0 or 3.0 g WCP/kg diet, respectively. Fish (15.2 ± 0.6 g) were fed on one of the tested diets up to apparent satiation twice a day for 60 days. After that, fish were intraperitoneally injected with pathogenic bacteria Aeromonas sobria and fish mortality was observed for 10 days postchallenge. Fish growth and feed intake were significantly improved by dietary probiotic L. plantarum (T2) and/or WPC (T3) over the control group (T1), and highest fish performance was observed in T5–T6 fish groups. Similarly, highest values of haematocrit, glucose, total proteins, albumin, and globulin were significantly observed in T5–T6 fish groups. Likewise, fish fed dietary probiotic L. plantarum (T2), WPC (T3), and their mixture (T4–T6) showed antioxidants and immune‐stimulating activities better than the control group. Fish fed the control diet were more susceptible to A. sobria infection showing highest fish mortality (75.0%). Meanwhile, dietary probiotic L. plantarum (T2), WPC (T3), and their mixture (T4–T6) enhanced significantly the fish resistance to A. sobria infection resulting in maximum values of relative percent of fish survival (73.3%–80.0%) in T5–T6 groups. The present investigation recommended the use of probiotic L. plantarum with 2.0 g WPC/kg diet to improve the growth, antioxidant, immunity responses and tolerance of Nile tilapia to A. sobria infection.     

Antifungal effect of Origanum onites essential oil as an alternative to formalin in the artificial incubation of narrow‐clawed crayfish (Astacus leptodactylus Eschscholtz, 1823)

As alternative to formalin, the antifungal effect of a plant product [Origanum onites L. (Lamiaceae) oil] was investigated for use in the artificial incubation of narrow‐clawed crayfish (Astacus leptodactylus Eschscholtz) eggs. For this purpose, this study was conducted as two experiments. In experiment I, the eggs were artificially incubated for 40 days. In experiment II, juveniles were cultured to determine effects of O. onites oil on juveniles for 30 days. The experimental groups were as follows: formalin (3500 ppm for 15 min), O. onites oil (300 ppm for 15 min, 700 ppm for 2 min and 1000 ppm as a dip treatment 15 split‐second) and a control (no treatment). In the experiment I, the highest hatching rate (86%) and survival rate of stage II juveniles (80%) were observed in 1000 ppm dip group. These results were similar to that of formalin group (85% and 79%) respectively. The control group exhibited the lowest hatching rate (49%) and stage II rate (42%) compared with the 1000 ppm dip group and 3500 ppm formalin treatments. However, other concentrations (300 and 700 ppm) of O. onites showed toxic effects on the eggs and there was no hatching. In the experiment II, the survival rate and growth performance of the crayfish juveniles were similar in all groups. This study indicated that the 1000 ppm O. onites dip treatment could be a good alternative to formalin for improved egg hatchability in the artificial incubation of crayfish eggs.     

Testing the yield of a pilot‐scale bubble column photobioreactor for cultivation of the microalga Rhodomonas salina as feed for intensive calanoid copepod cultures

A dual column photobioreactor (PBR) (2 × 47 L) with mixed CO₂/air bubbling was tested for cultivation of the microalga Rhodomonas salina as food for live feed copepods. In the continuous growth phase, the cell density was relatively stable at 2.40 ± 0.13 × 10⁶ cells/ml at an average dilution rate of 0.46 ± 0.02 per day throughout the 30‐day experiment. The produced algae had a high content of both total fatty acids (TFA) and free amino acids (FAA). Especially, the harvested algae contained a high proportion of poly‐unsaturated fatty acids that made up 80% of the TFA and of essential amino acids (35% of all FAA), implicating desirable components as feed for copepods. The current PBR was sufficient to feed a culture of the calanoid copepod Acartia tonsa at a density of 2,500 adult/L in ca. 500 L culture with a daily yield of approximately 17 × 10⁶ eggs. To be able to sustain the integrated copepods production, the suggested volume of the algae cultures should be ca. 20% of the copepod culture volume.     

Synergistic effect of sodium selenite and Pediococcus acidilactici on growth,intestinal bacterial counts,selenium bioavailability,hepatic enzymes and non‐specific immune response in rainbow trout (Oncorhynchus mykiss)

Lactic acid bacteria (LAB) have a crucial role in inorganic selenium metabolism as well as their known desirable effects on fish. In this study, the synergistic effects of dietary sodium selenite and Pediococcus acidilactici on growth performance, intestinal bacterial counts, selenium bioavailability, hepatic antioxidant enzyme thioredoxin reductase activity and hepatic glycolytic enzyme activity that is hexokinase, phosphofructokinase and pyruvate kinase, and non‐specific immune response such as serum lysozyme and complements C₃, C₄ and ACH₅₀ activity in rainbow trout (Oncorhynchus mykiss) were investigated. Thus, a 3 × 3 factorial design experiment was conducted with nine purified diets including three levels of sodium selenite (0, 1 and 2 mg/kg) and three levels of P. acidilactici (0, 7 and 9 log CFU/g). After 8 weeks of feeding, weight gain and specific growth rate were increased by increasing dietary sodium selenite and P. acidilactici levels compared to control (p < .05), whereas feed conversion ratio and condition factor was decreased by increasing dietary sodium selenite and P. acidilactici amounts in comparison with control (p < .05). Survival rate was not significantly affected among the experimental treatments (p > .05). Total cultivable bacterial populations after 4 and 8 weeks of the feeding trial were not significantly different among the dietary treatments, while LAB levels were higher in P. acidilactici‐fed groups than in control and selenium‐fed groups (p < .05). Selenocysteine, methylselenocysteine and selenomethionine levels in the intestine of rainbow trout were increased by increasing the sodium selenite and P. acidilactici levels (p < .05), and selenocysteine was found the most selenium species in the trout intestine. The quantity of total selenium in the whole body, intestine, blood, liver and muscle of rainbow trout were increased by increasing the amounts of sodium selenite and P. acidilactici compared to control (p < .05). Hepatic thioredoxin reductase and hexokinase activity were increased by increasing dietary selenium and P. acidilactici levels in comparison to control (p < .05), whereas phosphofructokinase and pyruvate kinase activity in the liver of rainbow trout were not significantly different between the dietary treatments. Serum lysozyme, complements C₃, C₄ and ACH₅₀ activity were enhanced by increasing dietary selenium and P. acidilactici levels compared to control (p < .05). The most synergistic effects of dietary supplements on growth and metabolism of rainbow trout were obtained at 2 mg/kg sodium selenite and 7 log CFU/g P. acidilactici. The findings revealed the synergistic effect of dietary selenium and P. acidilactici on growth and metabolism in rainbow trout (O. mykiss).     

Growth parameters of whiteleg shrimp Litopenaeus vannamei and red seaweed Gracilaria corticata in integrated culturing method under zero water exchange system

Growth parameters of whiteleg shrimp Litopenaeus vannamei and red seaweed Gracilaria corticata were measured using integrated culturing method under zero‐water exchange system in a 45‐day period. A 2 × 3 factorial design was used with two levels of shrimp stocking densities and three levels of seaweed weight densities. G. corticata was cultured on a net tied to a round polyethylene frame. Culture tanks were filled with 750‐L filtered seawater. A 40‐W compact fluorescent lamp was hung over each tank to provide adequate and sufficient light for seaweed growth. Growth parameters of shrimp and seaweed such as specific growth rate (SGR), weight gained (WG) and average daily growth (ADG) were computed based on the initial and final weight of shrimp and seaweed. The maximum and minimum SGR of L. vannamei (1.97 and 1.69%/day) were observed in treatment S₁A₃ (25 shrimp/m² and 400 g seaweed/m²) and S₂A₁ (50 shrimp/m² without seaweed) respectively. The best survival rate (94.67 ± 1.33%), WG (129.9 ± 2.9%) and feed conversion ratio (1.67 ± 0.04) were also observed in treatment S₁A₃. The SGR of G.corticata in the treatment S₁A₃ (1.97 ± 0.00%/day) was significantly higher, compared to others. Strong positive correlations were obtained between the density of G. corticata and the growth parameters of L. vannamei. The red seaweed G. corticata could boost the growth parameters, survival rate and total production of L. vannamei under zero‐water exchange system.     

Virulence of Flavobacterium psychrophilum isolates in rainbow trout Oncorhynchus mykiss (Walbaum)

Flavobacterium psychrophilum, the causative agent of bacterial cold‐water disease (BCWD) in freshwater‐reared salmonids, is also a common commensal organism of healthy fish. The virulence potential of F. psychrophilum isolates obtained from BCWD cases in Ontario between 1994 and 2009 was evaluated. In preliminary infection trials of rainbow trout juveniles, significant differences (0% to 63% mortality) in the virulence of the 22 isolates tested were noted following intraperitoneal injection with 10⁸ cfu/fish. A highly virulent strain, FPG 101, was selected for further study. When fish were injected intraperitoneally with a 10⁶, 10⁷ or 10⁸ cfu/fish of F. psychrophilum FPG 101, the 10⁸ cfu/fish dose produced significantly greater mortality (p < 0.05). The bacterial load in spleen samples collected from fish every 3 days after infection was determined using rpoC quantitative polymerase chain reaction amplification and by plate counting. Bacterial culture and rpoC qPCR were highly correlated (R² = 0.92); however, culture was more sensitive than the qPCR assay for the detection of F. psychrophilum in spleen tissue. Ninety‐seven per cent of the asymptomatic and the morbid fish had splenic bacterial loads of <2.8 log₁₀ gene/copies and >3.0 log₁₀ gene copies/reaction, respectively, following infection with 10⁸ cfu/fish.     

Evaluation of Lactobacillus plantarum as a water additive on host associated microflora,growth, feed efficiency and immune response of giant freshwater prawn,Macrobrachium rosenbergii (de Man, 1879)

A 90‐day experiment was conducted by rearing 1020 prawn juveniles (0.54 ± 0.03 g) in water supplemented with three different concentrations of probiotic bacteria viz. T1 (10⁷ cfu L^?1), T2 (10⁸ cfu L^?1), T3 (10⁹ cfu L^?1) and the control (C) (unsupplemented water), to evaluate probiotic effect of Lactobacillus plantarum. In the present study, the growth parameters (WG%, SGR) and feed utilization parameters (FCR, PER) significantly improved (P < 0.05) in T3. The growth and feed utilization parameters though improved marginally in T1 and T2, the difference was not significant (P > 0.05) compared to the control. The gastro‐intestinal Lactobacillus sp. count increased significantly (P < 0.05) in all the treatment groups, whereas the decrease in harmful bacteria was significant (P < 0.05) in T3 compared to the control. Similarly, the Lactobacillus sp. count in culture water increased significantly (P < 0.05) in all the experimental groups, whereas the decrease in harmful bacteria was significant (P < 0.05) in T2 and T3. The immune parameters (THC, PO and RB activity) and clearance efficiency significantly improved (P < 0.05) in T3 with concurrent decrease (P < 0.05) in cumulative mortality against Aeromonas hydrophila challenge. However, water quality did not improved (P > 0.05) in any of the treatment groups. The results indicate that Lactobacillus plantarum at a minimum concentration of 10⁹ cfu L^?1 could be used as water additive to confer its probiotic effect in prawn, Macrobrachium rosenbergii. Moreover, future studies with higher probiotic concentrations should be conducted for its efficient commercial scale field application.     

Periphyton characteristics influence the growth and survival of Holothuria scabra early juveniles in an ocean nursery system

Floating hapas (fine mesh net enclosures) are a cost‐effective ocean nursery system to culture post‐metamorphic Holothuria scabra to release size. The growth of periphyton biofilm on hapas is a natural food source for early juveniles. This study investigated the effects of periphyton quality (i.e. chlorophyll‐a, phaeopigment, total biomass, autotrophic index or AI), water quality (nutrients, chlorophyll‐a) and environmental parameters (temperature, rainfall) on the temporal variation in the growth and survival of early juvenile (~3 mm) H. scabra reared in floating hapas. Five trials where the juveniles were reared for 60 days each in the eutrophic coastal waters of Bolinao, the Philippines were conducted during different months over 2 years. Significant differences in the growth and survival of juveniles among trials were found. Absolute growth rates (AGR) ranged widely (0.01–0.09 g/day). Trials with high AGR of juveniles (0.07–0.09 g/day) during the first 30 days of rearing had significantly higher chlorophyll‐a (chl‐a) in biofilm (15.9–27.5 mg/m²) and lower AI. Conversely, during the subsequent 30 days, trials with high AGR of juveniles (0.06–0.11 g/day) had significantly lower chl‐a and higher AI. Multivariate analyses showed that chl‐a in biofilm, AI and nutrients in the water column are good indicators of periphyton quality and juvenile growth rates in floating hapas. Further, this study validates the expansion of the feeding mode of juveniles from primarily grazing on microalgae, to feeding on detritus and heterotrophs as they grow. These results are important in optimizing ocean nursery systems.     

Effect of Lactobacillus plantarum and Jerusalem artichoke (Helianthus tuberosus) on growth performance,immunity and disease resistance of Pangasius catfish (Pangasius bocourti,Sauvage 1880)

This study evaluated the effects of Jerusalem artichoke (JA) and Lactobacillus plantarum singly or combined on growth, immunity and disease resistance of Pangasius bocourti. In the first experiment, different concentrations of JA (0, 5, 10, 20, 40, 80 and 160 g kg^?1) were administered to determine an optimal concentration on growth of P. bocourti. In the second experiment, the optimal concentration of JA (5 g kg^?1) was combined with 10⁸ cfu g^?1 L. plantarum. In the final experiment, five randomly selected fish from the second experiment were challenged with Aeromonas hydrophila. Treatments for second and third experiments were 0 g kg^?1 JA (Diet 1), 5 g kg^?1 JA (Diet 2), 10⁸ cfu g^?1 L. plantarum (Diet 3) and 5 g kg^?1 JA + 10⁸ cfu g^?1 L. plantarum (Diet 4). Fish fed 5 g kg^?1 JA or 10⁸ cfu g^?1 of L. plantarum significantly improved specific growth rate (SGR), feed conversion ratio (FCR), serum lysozyme activity and postchallenge survival rate (PCSR). Dietary in the combination of JA and L. plantarum showed significantly enhanced SGR, FCR, serum lysozyme, phagocytosis, respiratory burst activities and PCSR compared with control and individual applications. Dietary JA and L. plantarum significantly stimulated growth, immunity and disease resistance of P. bocourti.     

The effect of lactic acid bacteria administration on growth,digestive enzyme activity and gut microbiota in Persian sturgeon (Acipenser persicus) and beluga (Huso huso) fry

The aims of this study was to assess the effect of two lactic acid bacteria (LAB), Lactobacillus curvatus and Leuconostoc mesenteroides, originally isolated from gastrointestinal (GI) tract of beluga (Huso huso) and Persian sturgeon (Acipenser persicus), respectively, on growth, survival and digestive enzyme (amylase, lipase and protease) activities and the population level of LAB in the GI tract. The treatments included 10 different groups; control, separate supplements of L. curvatus and Leu. mesenteroides at three different counts [2 × 10⁹, 5 × 10⁹ and 9 × 10⁹ colony forming units (CFU) per gram food] and three combinations of the two LAB (2 × 10⁹ + 2 × 10⁹, 5 × 10⁹ + 5 × 10⁹ and 9 × 10⁹ + 9 × 10⁹ CFU per gram food). The bacteria used in this study were added in lyophilized form to chopped Chironomidae. In the beluga study, highest specific growth rate, survival and improved intestinal enzyme activities were noted in the rearing group fed 9 × 10⁹ L. curvatus per gram food. In Persian sturgeon, the inclusion level of 2 × 10⁹ Leu. mesenteroides had similar positive effect. The ability of LAB to colonize the digestive tract seems to involve host specificity, and our bacteriological results are relevant to initiate future probiotic studies in sturgeons and future directions will be discussed.     

The use of Pseudoalteromonas sp. F15 in larviculture of the Yesso scallop,Patinopecten yessoensis

A 49‐day rearing trial was conducted to investigate the effects of Pseudoalteromonas sp. F15 on growth, survival, digestive and immune‐related enzyme activities in larval and juvenile Yesso scallop, Patinopecten yessoensis. Larvae (Day 2 post‐fertilization) (d2 PF)) were provided with a diet only of microalgae (control) and supplemented with F15 at final concentrations of 1×10⁴ and 1×10⁶ cells/mL, respectively. Results indicated that the specific growth rates and survival rates of umbo larvae (d13 PF), crawling pediveliger larvae (d28 PF) and juveniles (d51 PF) fed the F15 supplementation diets at 10⁴ and/or 10⁶ cells/mL were significantly higher than those fed the diet of microalgae. Larvae and juveniles fed 10⁴ and/or 10⁶ cells/mL F15 supplementation diets showed a significant increase in pepsin, amylase and cellulase activities compared with the control group. The lysozyme, superoxide dismutase and catalase activities of larvae and juveniles fed the F15 supplementation diets at 10⁴ and/or 10⁶ cells/mL significantly increased compared to those fed the diet of microalgae. In addition, F15 protected juveniles against challenge with Vibrio splendidus. These data suggest that F15 can be useful in scallop larviculture.     

Effects of plant oligosaccharides derived from dragon fruit on growth,reproduction and survival of freshwater crustacean Daphnia magna

The freshwater crustacean Daphnia is widely used as live food for ornamental fish. To increase production, food supplementations are required when culturing Daphnia. Here, we aimed to clarify the effects of plant oligosaccharides derived from dragon fruit (DFO) on growth rate, egg production, number of first clutch juveniles and survival of Daphnia supplemented with five different concentrations of DFO, that is 0, 1, 3, 9, 27 mg/L. The results showed the growth and reproduction of Daphnia were enhanced when supplemented with DFO. Growth rate of Daphnia supplemented with 9 mg/L DFO was the highest among all treatments. The time that Daphnia produced the first clutch eggs was shorter in high concentration of DFO (3, 9, 27 mg/L). The number of juveniles in the first clutch increased in treatments of higher concentration of DFO (3, 9, 27 mg/L). These results suggest that plant oligosaccharides derived from dragon fruit increase growth and fecundity of Daphnia. Survival rates of Daphnia were 100% except for the treatment supplemented with 27 mg/L of DFO in which the survival rate was reduced to 87%. To our knowledge, this is the first functional evidence demonstrating that oligosaccharides derived from dragon fruit enhance growth and fecundity of Daphnia.     

Isolation and identification of Vibrio campbellii as a bacterial pathogen for luminous vibriosis of Litopenaeus vannamei

Outbreak of luminescent disease was reported from Litopenaeus vannamei shrimp farms in Zhangpu County, Southern China during May–July 2011. The clinical signs included fluorescent, less food consumption and high mortality. Bacteria were isolated from the infected shrimps. The pathogen, a luminescent bacterium named VH1 was identified as Vibrio campbellii based on MLSA analysis (16S rDNA, rpoD and toxR). The haemolysin (hly) gene specific in V. campbellii was detected in strain VH1. Pathogenicity test using immersion infection confirmed that strain VH1 was virulent to L. vannamei postlarvae and juveniles, and the LC₅₀ value was 1.55 × 10⁶ CFU mL^?1 and 1.7 × 10⁶ CFU mL^?1 respectively.     

Effects of dietary supplementation of probiotics on the growth,activities of digestive and non‐specific immune enzymes in hybrid grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀)

Effects of Bacillus cereus BC‐01, Lactobacillus acidophilus LAG01, Clostridium butyricum CBG01 and their combinations as supplementation on the growth performance, digestive enzyme activities and serum non‐specific immunity of hybrid grouper (Epinephelus lanceolatus ♂×E. fuscoguttatus ♀) were assessed. Seven different diets, that is one control diet (basal feed without any probiotics, CT) and six treatment diets containing single B. cereus (Bs), L. acidophilus (Ls) and C. butyricum (Cs) at 1.0 × 10⁹ cfu/kg feed, and also their combinations in equal proportion at 1.0, 2.0 and 3.0 × 10⁹ cfu/kg feed (BLC1, BLC2 and BLC3) were prepared respectively. After 60‐day feeding trial, the final weight, specific growth rate,food consumption, food conversion efficiency and apparent digestibility coefficient of fish in Ls and BLC3 were significantly higher compared with the control (p < .05). The activities of pepsin and trypsin in the intestine of fish for Ls and BLC3 were significantly higher relative to the control (p < .05). Relative to controls, significantly enhanced amylase and lipase activities in proximal intestine except for Cs and BLC1 and lipase activities in distal intestine except for Cs were observed (p < .05). Meanwhile, activities of superoxide dismutase in the serum of fish for all treatments, lysozyme and catalase in Ls and BLC3, and glutathione peroxidase except for Cs were significantly enhanced (p < .05). Based on the above, dietary supplementation of single L. acidophilus at 1.0 × 10⁹ cfu/kg or combination of three strains at 3.0 × 10⁹ cfu/kg for hybrid grouper is recommended.