Antiviral Effect of Fucoidan Extracted from the Brown Seaweed,Sargassum wightii,on Shrimp Penaeus monodon Postlarvae against White Spot Syndrome Virus

This study was carried out to determine the effect of seaweed polysaccharide, fucoidan from brown seaweed, Sargassum wightii, on Penaeus monodon postlarvae (PL) against white spot syndrome virus (WSSV). The fucoidan was extracted from S. wightii, and the yield was observed as 2.832 ± 0.204%. Artemia franciscana nauplii were enriched with extracted fucoidan at four different concentrations (100, 200, 300, and 400 mg/L) and fed to shrimp P. monodon PL for 20 d. After feeding experiment, the P. monodon PL were challenged with WSSV, and the mortality percentage was recorded daily up to 21 d. During the challenge test, the control PL showed 100% cumulative mortality within 9 d, but the fucoidan‐enriched Artemia nauplii fed groups of PL exhibited 60–94% cumulative mortality within 21 d. The reduction in mortality percentage of experimental groups of PL over control PL was ranged between 33.71 and 61.65%. The polymerase chain reaction analysis confirmed the concentration‐dependent variation in WSSV infection.     

Encapsulation capacity of Artemia nauplii with customized probiotics for use in the cultivation of western king prawns (Penaeus latisulcatus Kishinouye, 1896)

The encapsulation capacity of Artemia nauplii with customized probiotics Pseudomonas synxantha and Pseudomonas aeruginosa for use in the cultivation of western king prawns (Penaeus latisulcatus) was investigated. Seven trials were conducted to investigate this encapsulation capacity in terms of Artemia survival and probiotic load in Artemia. Newly hatched Artemia nauplii at 250 nauplii mL^?1 were fed individual probiotics at 0, 10³, 10⁵ and 10⁷ colony‐forming units (CFU) per millilitre, and mixtures of these two probiotics (10⁵ CFU mL^?1) at 30:70, 50:50 or 70:30 v/v in a medium of ozonated water (OW), tryptone soya broth (TSB), and a mixture of these media. The appropriate medium for encapsulation of probiotics by Artemia nauplii was the mixture of OW and TSB at 75:25 v/v; whereas, the use of OW or TSB alone was not effective. Artemia nauplii most effectively encapsulated the customized probiotics at 10⁵ CFU mL^?1. The results indicates that the encapsulation of Artemia nauplii is optimized by using a combination of P. synxantha and P. aeruginosa at 50:50 v/v in a media mixture of OW and TSB at 75: 25 v/v. Artemia should be harvested at 48 h when survival is still high (78%) and the probiotic load in Artemia is high (3 × 10⁴ CFU nauplius^?1).     

Effect of hot water extracts of brown seaweeds Sargassum spp. on growth and resistance to white spot syndrome virus in shrimp Penaeus monodon postlarvae

An experiment was conducted to evaluate the effect of a hot water extract of brown seaweeds Sargassum duplicatum and Sargassum wightii on the growth and white spot syndrome virus (WSSV) resistance in shrimp Penaeus monodon postlarvae (PL). Artemia nauplii (instar II) were enriched with both seaweed extracts at various concentrations (250, 500 and 750 mg L^?1) and fed to the respective P. monodon (PL15–35) group for 20 days. A control group was also maintained without seaweed extract supplementation. The weight gain of the experimental groups was significantly higher (0.274–0.323 g) than the control group (0.261 g). Similarly, the specific growth rate was also significantly higher (16.27–17.06%) in the experimental groups than in the control group (16.03%). After 20 days of the feeding experiment, the shrimp PL were challenged with WSSV for 21 days. During the challenge test, the control shrimp displayed 100% mortality within 8 days. In contrast, the mortality percentage of the highest concentration (750 mg L^?1) of seaweed extract enriched Artemia nauplii fed shrimp was 54–79%. Comparatively, low mortality was observed in S. wightii extract‐enriched Artemia nauplii fed shrimp. The polymerase chain reaction analysis indicated the concentration‐dependent infection of WSSV in P. monodon PL.     

A diet of fructose‐enriched Artemia improves the response of juvenile Litopenaeus vannamei shrimp to acute low‐salinity challenge

The Pacific white shrimp (Litopenaeus vannamei), as an economically important species, has been reared in low‐salinity water during the last decade. To investigate how juvenile L. vannamei shrimp fed with fructose‐enriched Artemia respond to acute low‐salinity stress, the shrimp were randomly divided into four treatment groups, three groups were fed with Artemia enriched with either 100, 200 and 300 mg L^?1 of fructose and a control group fed with Artemia with no enrichment for 10 days. The results showed that the 300 mg L^?1 fructose group demonstrated the maximum survival rate and glycogen content. Additionally, the 300 mg L^?1 fructose group showed significantly higher Na⁺/K⁺‐ATPase activity, total antioxidant capacity, and expression levels of Na⁺/K⁺‐ATPase α‐subunit, V‐H ATPase α‐subunit, hexokinase, phosphofructokinase, antioxidants (SOD, CAT, GPX) and Hsp70 mRNA when compared with the control group. Furthermore, after exposure to low salinity, the mRNA levels of phosphofructokinase, V‐H ATPase α‐subunit, GPX, p38, JNK and Rac1 stayed constant in shrimp fed with fructose‐enriched Artemia but changed significantly in the control group. Thus, a diet of fructose‐enriched Artemia can improve the osmoregulation and survival of juvenile L. vannamei shrimp exposed to low salinities.     

Oxygen consumption and ingestion rate of Penaeus setiferus larvae fed Chaetoceros ceratosporum, Tetraselmis chuii and Artemia nauplii

The effects of the density and type of food on oxygen consumption and ingestion rate of larvae of the white shrimp Penaeus setiferus fed diatoms Chaetoceros ceratosporum, flagellates Tetraselmis chuii and Artemia franciscana nauplii were analysed. Diatoms, flagellates and Artemia nauplii were fed at five densities from 10 to 5 × 10³ cells mL^?1, 0 to 4 × 10³ cells mL^?1, and 0.1, 0.5, 1.0, 1.5 and 2 nauplii mL^?1, respectively. In three experiments, two of three types of food were maintained constant at concentrations of 30-40 × 10³ cells mL^?1 (diatoms), 2 × 10³ cells mL^?1 (flagellates) and 1 Artemia nauplii mL^?1. The oxygen consumption in three experiments increased with larval stage, reaching maximum values in Mill except at lower feed concentrations. A maximum ingestion peak in MI was recorded in larvae fed diatoms, whereas that peak was observed in Mil in larvae fed flagellates. The maximum ingestion rate of Artemia nauplii was observed in Mill. Feed concentrations that produced an optimum metabolic rate as a consequence of equilibrium between ingested food and larval stages were obtained with 20 and 30 × 10³ cells mL^?1 of C. ceratosporum, 2 and 3 × 10³ cells mL^?1 of T. chuii, and 1.0 Artemia nauplii mL^?1. These concentrations would be the most suitable for producing P. setiferus postlarvae.     

Use of the microalga Nannochloropsis occulata in the rearing of newborn longsnout seahorse Hippocampus reidi (Syngnathidae) juveniles

The aim of this study was to evaluate the effect of microalgae on the rearing of newborn juveniles of the longsnout seahorse, Hippocampus reidi. Two treatments in three replicates were tested over a 15‐day period: with and without the addition of the microalgae Nannochloropsis oculata at a concentration of 2.02 ± 0.44 × 10⁶ cells mL^?1. At each replicate, beginning on the second day of life, 120 H. reidi juveniles (stocking density of 3 ind L^?1) were fed the offspring of the benthic copepod Tisbe biminiensis (100 copepod cm^?2) together with newly hatched Artemia nauplii (3.8 mL^?1). From the sixth day of life, enriched Artemia metanauplii replaced newly hatched Artemia nauplii. After 15 days, the H. reidi individuals were counted, measured and weighed. Mean survival was significantly greater in the microalgae treatment (76.42 ± 5.07%) than in the treatment with no microalgae (25.44 ± 6.91%). Moreover, total length, height and dry weight were significantly larger in the microalgae treatment. Thus, the addition of microalgae increases the growth and survival of H. reidi juveniles fed T. biminiensis and Artemia. The higher growth and survival of H. reidi juveniles was not related to the larger ingestion rates but probably to the nutritional improvement of the live feeds or to the probiotic effect. The protocol developed for rearing H. reidi juveniles resulted in a high survival, and represents an advance in the farming of this species.     

Vibrio spp. Control at Brine Shrimp,Artemia, Hatching and Enrichment

Experiments were conducted to evaluate different prophylactic methods to control the bacterial load in brine shrimp, Artemia, hatching. The first experiment evaluated three treatments to control Vibrio spp. during the Artemia hatching: microalgae (Chaetoceros calcitrans), probiotic (Bacillus spp.), and antibiotic (Florfenicol). In the second experiment, Artemia metanauplius were enriched in distinct treatments with C. calcitrans, probiotic, and emulsion rich in docosahexaenoic and eicosapentaenoic fatty acids. Enriched Artemia metanauplius and nauplii (control) were offered to white shrimp, Litopenaeus vannamei, postlarvae (PL₇–PL₁₉). Presumptive Vibrio were quantified in Artemia, PL, and rearing water. Microalgae and probiotic were effective to control Vibrio spp. in Artemia nauplii. The enrichment process increased the Artemia bacterial load but did not affect Vibrio load in L. vannamei.     

Inhibitory effects of Bacillus licheniformis (DAB1) and Pseudomonas aeruginosa (DAP1) against Vibrio parahaemolyticus isolated from Fenneropenaeus indicus

In aquaculture industries, there is an urgent need to develop microbial control strategies, to control disease outbreaks. In recent years, probiotics are considered as a valid alternative for the use of antibiotics in aquaculture to prevent high mortality and promote growth. In the present study, seven strains of bacteria such as Bacillus licheniformis (DAB1), Bacillus pumilus (DAB2), Bacillus sp. (DAB3), Pseudomonas aeruginosa (DAP1), Pseudomonas sp. (DAP2), Pseudomonas aeruginosa (DAP3), Pseudomonas aeruginosa (DAP4), and three pathogenic Vibrio parahaemolyticus (DAV1, DAV2, DAV3) were isolated from healthy and diseased Fenneropenaeus indicus collected from the east coast of Tamilnadu, India. The strains were identified by biochemical analysis and 16S rRNA sequence methods. Among the seven probiotic strains tested, the cell-free extract from DAB1 and DAP1 exhibited higher inhibitory activity of V. parahaemolyticus than other isolates under in vitro conditions. The LC₅₀ of DAV1, DAV2, and DAV3 was found to be ～10³ CFU mL^?1. Pathogenicity of three V. parahaemolyticus DAV1, DAV2, and DAV3 showed significant mortalities (40 %) in Artemia nauplii at inoculation densities of 10³ CFU mL^?1 when compared to the controls (unchallenged nauplii). A significant reduction in mortality (P < 0.001) was found by addition of 10⁶ CFU mL^?1 of DAB1 and DAP1 strains in nauplii against the pathogens. In conclusion, the present study result reveals that DAB1 and DAP1 have potential applications for controlling pathogenic V. parahaemolyticus in Artemia culture systems and aquaculture practices.     

Dietary supplementation with the microalgae Parietochloris incisa increases survival and stress resistance in guppy (Poecilia reticulata) fry

Dietary enrichments with the arachidonic acid (ARA)‐rich microalga, Parietochloris incisa, on the survival of guppy (Poecilia reticulata) fry were examined. Diets were applied via Artemia enrichment to fish from two commercial farms for 34 and 36 days of experimental period (trials 1 and 2, respectively). In trial 1, Artemia nauplii were enriched with dry biomass of whole algal cells at 0 (control), 0.1, 0.2 and 0.4 mg mL^?1. Fry fed with Artemia enriched with 0.4 mg mL^?1 demonstrated the lowest mortality rates (24% and 1% in farms 1 and 2, respectively) compared with controls (36% and 13% in farms 1 and 2, respectively). In trial 2, fry were fed with Artemia, enriched with whole algal cells (0.4 mg ml^?1), algal hexane extract (HE; containing primarily ARA‐rich triacylglycerols and β‐carotene; 0.19 mg ml^?1) or the extraction residue (0.28 mg ml^?1). Acute stress (5 min air exposure) was applied after 18 days. The lowest mortality was recorded in the whole alga‐fed group (av. 26% and 2.6% in farms 1 and 2, respectively), with a slightly, but not significantly higher mortality in the HE‐fed group (av. 29% and 6.2% in farms 1 and 2, respectively). Elevated lysozyme was associated with the reduced mortality. Overall, the use of P. incisa as a dietary supplement for guppy fry during their first month of life enhanced their survival and stress resistance.     

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.     

Dietary astaxanthin levels affect colour,growth, carotenoid digestibility and the accumulation of specific carotenoid esters in the Giant Tiger Shrimp,Penaeus monodon

The carotenoid astaxanthin (Axn) plays a vital role in shrimp pigmentation, with direct influence on product quality, and forms a significant cost component of shrimp aquaculture feeds. However, the effects of dietary Axn on other measures of shrimp physiological performance are varied, and the efficiency of carotenoid uptake from the diet and deposition in shrimp tissues is poorly defined. This study fed juvenile shrimp (Penaeus monodon) diets that contained 0, 25, 50 or 100 mg kg^?1 Axn for 6 weeks. Shrimp fed carotenoid‐free diets had significantly reduced colour and growth than those fed carotenoids, but survival was unaffected. Carotenoid digestibility improved as dietary carotenoid levels increased, and was 98.5% in shrimp fed 100 mg kg^?1 Axn. After 6 weeks, whole body carotenoid levels were significantly depleted in 0 or 25 mg kg^?1 fed shrimp, compared with those fed 50 or 100 mg kg^?1 or compared with initial shrimp. This study also showed that Axn monoesters were enriched with saturated fatty acids, whereas Axn diesters were enriched with monounsaturated and polyunsaturated fatty acids. Combined, these studies demonstrate that a total dietary carotenoid intake of between 25 and 50 mg kg^?1 Axn is required for normal shrimp growth and health in P. monodon. Evidence suggests that there is a functional role for the accumulation of carotenoids and the formation of specific Axn fatty acid esters, and these may be linked to the metabolism, storage, mobilization or deposition of Axn within various tissues.     

Enrichment of Artemia nauplii with the probiotic yeast Saccharomyces boulardii and its resistance against a pathogenic Vibrio

Enrichment of Artemia nauplii with a known probiotic yeast Saccharomyces boulardii (SB) and its role in enhancing resistance against the pathogen Vibrio harveyi was investigated. SB was cultured, then fed to instar II Artemia nauplii in three different treatments; 10² (T1), 10³ (T2) and 10⁴ (T3) colony forming units (CFU) per ml in triplicate. The algae Nanochloropsis sp. was used as control diet. Survival and total count of CFU nauplii⁻¹ was observed on different media (Sabouraud, for enumerating yeasts, thiosulphate citrate bile salts sucrose, for enumerating Vibrio and seawater agar, for enumerating total aerobic flora) for each replication. Enhanced survival of nauplii was observed in treatments as compared to control. Results indicated that enrichment of SB in Artemia nauplii proceeded in a linear fashion, and up to 3500 CFU of SB could be detected in one nauplii at 10⁴ CFU ml⁻¹ treatment. No conclusive trend could be observed in the count of Vibrio and total aerobic flora due to treatment. Enriched nauplii were then challenged with the pathogen V. harveyi for 24 and 48 h at a concentration of 6.1 × 10⁶ CFU ml⁻¹. The survival counts at 48 h showed that the resistance of the nauplii was significantly (P < 0.01) improved in those fed with 10⁴ CFU  ml⁻¹ SB (90% survival rate after 48 h of challenge versus less than 40% for the infected control group without SB and treatments T1 and T2). This study shows that SB, which has been used for the first time in an aquatic live feed organism, has a profound beneficial effect on the nauplii by increasing its resistance to a pathogenic Vibrio infection. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of Rearing Density and Feeding Regimes on Growth and Survival of African Catfish,Heterobranchus longifilis (Valenceinnes, 1840) Larvae in a Closed Recirculating Aquaculture System

Heterobranchus longifilis larvae were reared over a 35 d period to evaluate the effects of stocking densities and feeding regimes on growth and survival. In experiment 1, larvae (12.3?±?2.1 mg) were stocked into glass aquaria at densities of 1, 2, 5, 10, 15, 20, and 25 larvae L^?1. Larvae were fed on Artemia nauplii ad libitum. Significant variations in terms of growth performance and feed utilization occurred at all levels of density treatments. Specific growth rate (SGR), body weight gain (BWG), and feed efficiency (FE) of the larvae decreased significantly as density increased. However, survival rate increased with the increase of stocking density. In experiment 2, larvae (13.4?±?1.1 mg) stocked at a density of 15 larvae L^?1, in the same conditions as experiment 1, were fed on three different regimes: Artemia nauplii; 35%?protein beef brain; and 35%?protein commercial catfish feed (CN⁺). SGR, BWG, and coefficient of variation (CV) of larvae fed on Artemia nauplii were significantly higher than those fed on beef brain and CN⁺. The survival rate of larvae fed on beef brain was significantly higher (88.40?±?9.75%) than those of Artemia (69.21?±?6.69%) and CN⁺ (40.40?±?6.22%). The results of this study suggest that the optimum stocking density is 15 larvae L^?1 and the beef brain can be used as alternative feed to Artemia in rearing H. longifilis larvae.     

Water quality,Vibrio density and growth of Pacific white shrimp Litopenaeus vannamei (Boone) in an integrated biofloc system with red seaweed Gracilaria birdiae (Greville)

An indoor trial was conducted for 42 days to evaluate water quality, Vibrio density and growth of Litopenaeus vannamei in an integrated biofloc system (IBS) with Gracilaria birdiae. Four treatments were used, each in triplicate: Control (monoculture shrimp); IBS 2.5 (L. vannamei and 2.5 kg wet weight seaweed m^?3); IBS 5.0 (L. vannamei and 5.0 kg wet weight seaweed m^?3) and IBS 7.5 (L. vannamei and 7.5 wet weight seaweed m^?3). Shrimp individuals (0.34 ± 0.01 g) were stocked at a density of 500 shrimp m^?3. No water exchange was carried out during the experimental period. Molasses was added once a day as an organic carbon source to maintain the C:N ratio at 12:1. The IBS significantly decreased (P < 0.05) dissolved inorganic nitrogen (DIN) ranging from 19% to 34% (3.12–3.83 mg L^?1), NO₃‐N ranging from 19% to 38% (2.40–3.16 mg L^?1), Vibrio density ranging from by 8–83% (0.40–2.20 log 10³ colony‐forming units mL^?1), and FCR ranging from by 20–30% (1.20–1.37), as compared to the control (4.73 mg L^?1, 3.93 mg L^?1, 2.40 log 10³ colony‐forming units mL^?1, and 1.74 respectively). Moreover, the IBS significantly increased (P < 0.05) crude protein in whole body shrimp, ranging from 8% to 13% (13.2–13.7% wet weight basis); as well as final weight, ranging from 25% to 32% (3.90–4.12 g), weekly growth ranging from 25% to 34% (0.59–0.63 g), and shrimp yield by 22–39% (1.72–1.96 kg m^?3), as compared to control (12.1% wet weight basis, 3.12 g, 0.47 g, and 1.41 kg m^?3 respectively). It can thus be concluded that cultivating Gracilaria birdiae in an IBS with L. vannamei can contribute to DIN and NO₃‐N removal, lower Vibrio density, increased crude protein in whole body shrimp, higher growth and yield parameters in shrimp culture.     

Indian Herbal Medications to Replace Antibiotics for Shrimp Penaeus monodon Post Larvae

Herbs with known antibacterial characteristics were chosen and extracted with different polar and non-polar solvents and screened against five different shrimp pathogens: Pseudomonas aeruginosa, Staphylococcus aureus, Aeromonas hydrophila, Vibrio harveyi, and V. parahaemolyticus. Five different diets were prepared by incorporating equal proportions of these five herbal extracts at increasing concentrations: Control (0), HD1 (200), HD2 (400), HD3 (600), and HD4 (800 mg/kg of diet). Diets were individually fed to the Penaeus monodon post larvae (PL 25) for 30 days. At 10-day intervals, post larvae were bath challenged with V. harveyi and observed for pathological signs. Post larvae fed the HD 4 diet enjoyed a 75% improvement in survival over the control group and significantly improved final weights and SGR (P < 0.05). The herbal diets HD1 to HD4 helped to decrease the Vibrio load in P. monodon post-larvae after challenging.     

Nutrient composition of fairy shrimp Streptocephalus sirindhornae nauplii as live food and growth performance of giant freshwater prawn postlarvae

Nutritional efficacy of fairy shrimp (Streptocephalus sirindhornae) nauplii, as a live food, was studied for growth performance and survival rate of giant freshwater prawn (Macrobrachium rosenbergii) postlarvae. A feeding experiment was designed with four different feeds: dry commercial feed, fairy shrimp nauplii, Artemia sp. nauplii and adult Moina macrocopa. Results from the nutritional composition revealed that fairy shrimp nauplii had protein and lipid contents of 54.58 ± 2.8 g kg^?1 and 255 ± 2.8 g kg^?1, respectively. The highest value for an individual amino acid in fairy shrimp was lysine (140.7 ± 1.6 g kg^?1). The essential amino acids content in the whole body of the larval prawns was in the range of 66.7–67.5 g kg^?1. Fairy shrimp nauplii had the highest essential amino acid ratio (A/E) of lysine, similarly, in musculature of prawn larvae. Weight gain and specific growth rate of the postlarvae fed with fairy shrimp nauplii were significantly higher than those fed with Artemia nauplii, adult Moina and dry commercial feed. The presented results suggest that S. sirindhornae nauplii can be used as a nutritionally adequate food for freshwater prawn M. rosenbergii postlarvae.     

Replacement of live food with a microbound diet in feeding Litopenaeus setiferus (Burkenroad) larvae

Microbound feeds have been well accepted by shrimps and farmers in many penaeid shrimp hatcheries. The present study focused on an adequate level of replacement of Artemia nauplii and microalgae by a microbound diet for rearing Litopenaeus setiferus (Burkenroad) larvae. A microbound diet (MBD) consisting of fishmeal, squid meal, shrimp meal, yeast meal and soybean meal was used. The first experiment was designed to obtain the optimum level of MBD to complete the live feeding schedule, from Protozoea (PZ_III) to Mysis (M_III). The experimental levels of the microbound diet tested were 2, 4, 6 and 8 mg MBD L^?1 day^?1. The next step was to determine the Artemia nauplii replacement level from PZ_I to M_III by MBD. These experiments were carried out either in the presence (Experiment 2) or in the absence of algae (Experiment 3). Four replacement levels were tested: 0% (4 mg MBD L^?1 day^?1: 1 Artemia nauplii mL^?1), 40% (5.5 mg MBD L^?1 day^?1: 0.6 Artemia nauplii), 60% (6.5 mg MBD L^?1 day^?1: 0.4 Artemia nauplii) and 100% (8 mg MBD L^?1 day^?1: 0 Artemia nauplii). In all experiments growth, survival, development, quality index (QI) and performance index (PI), were used to determine the optimum concentration of microbound diet. Results showed that 6 mg MBD L^?1 day^?1 can be recommended as a complement to live food for L. setiferus larvae from PZ_III to M_III. In the presence of algae, maximum growth and survival may be obtained in 40–60% (5.5–6.5 mg MBD L^?1 day^?1) of Artemia nauplii replacement levels. In the absence of algae, the Artemia nauplii replacement resulted in slower development, less salinity resistance, lower growth and lower survival than was obtained in larvae fed with algae.     

Dietary choline requirement in slight methionine‐deficient diet for juvenile gibel carp (Carassius auratus gibelio)

A 10‐week feeding trial was conducted in a flow‐through system to determine dietary choline requirement for juvenile gibel carp (Carassius auratus gibelio) (5.5 ± 0.1 g). Purified basal diet was formulated using vitamin‐free casein as protein source. Choline chloride was supplemented to the basal diet to formulate seven diets containing 76.1, 163, 356, 969, 1457, 2024 and 4400 mg kg^?1 choline. Dietary methionine was 0.58%, less than the requirement (0.69%). The results indicated that specific growth rate (SGR) was higher in the fish fed 2024 mg kg^?1 diet than the control group. Feeding rate and feed efficiency were not significantly affected. Protein productive value increased as dietary choline increased from 76.1 to 2024 mg kg^?1 diet and was lower in the fish fed the diet containing 4400 mg choline kg^?1 diet. Serum high‐density lipoprotein cholesterol (HDL‐C) and total cholesterol significantly increased with increasing dietary choline up to 1457 mg kg^?1, and no differences were found with further increase. Fish carcass fat contents decreased significantly with increased dietary choline. Hepatic lipid contents increased with dietary choline up to 1457 mg kg^?1 and then decreased. Quadric regression of SGR and plasma HDL‐C indicted dietary choline requirement was 2500 and 2667 mg kg^?1 diet, respectively.     

Dietary manganese requirement for juvenile cobia,Rachycentron canadum L

A 10‐week feeding trial was conducted to estimate the optimum dietary manganese requirement for juvenile cobia, Rachycentron canadum L. The basal diet was formulated to contain 501 g kg^?1 crude protein from vitamin‐free casein, gelatin and fish protein concentrate. Manganese sulphate was added to the basal diet at 0 (control group), 6, 12, 18, 24 and 36 mg Mn kg^?1 diet providing 5.98, 7.23, 16.05, 23.87, 28.87 and 41.29 mg Mn kg^?1 diet, respectively. Each diet was randomly fed to three replicate groups of cobia for 10 weeks, and each tank was stocked with 30 fish (initial weight, 6.27 ± 0.03 g). The manganese concentration in rearing water was monitored during the feeding period and was < 0.01 mg L^?1. Dietary manganese level significantly influenced survival ratio (SR), specific growth ratio (SGR), feed efficiency ratio (FER) and the manganese concentrations in the whole body, vertebra and liver of cobia. When the dietary manganese level rose from 5.98 mg kg^?1 to 23.87 mg kg^?1, the superoxide dismutase (SOD; EC 1.15.1.1) activities in liver also increased (P < 0.05). But there was no significant change in SOD activities for the groups fed with diets containing manganese level higher than 23.87 mg kg^?1. On the basis of broken‐line regression of SGR, manganese concentration in whole body and vertebra the manganese requirements of juvenile cobia were 21.72 mg kg^?1, 22.38 mg kg^?1 and 24.93 mg kg^?1 diet in the form of manganese sulphate, respectively.     

Effects of supplementation of decapod zoea to Artemia basal diet on fatty acid composition and digestive gland histology in common octopus (Octopus vulgaris) paralarvae

The present study aimed to evaluate the effect of the supplementation of different crab zoeas to enriched Artemia basal diet for Octopus vulgaris paralarvae during the first month of life. Paralarvae were fed using enriched Artemia nauplii alone and Artemia co‐fed either first zoea stages of Grapsus adscensionis or Plagusia depressa. The experiment was carried out over a period of 28 days, in 0.12 m³ tanks with a flow‐through rearing system. Growth in dry weight as well as mantle length and width were assessed weekly. Additionally, prey and paralarvae fatty acid composition and digestive gland (DG) histology were evaluated. Addition of low amounts of crab zoeas (approx. 100 indv. L^?1 day^?1) provided during critical life stages of O. vulgaris proved to be good enough to improve paralarvae growth and survival in comparison with those fed exclusively on enriched Artemia. These results were supported by the finding of a higher number of glycoprotein absorption vacuoles in the DG from paralarvae co‐fed crab zoeas, suggesting a higher feeding activity. In addition, fatty acid analysis of crab zoea showed that these are good sources of dietary arachidonic and eicosapentaenoic acids during the octopus planktonic life stage, whereas the low docosahexaenoic (DHA) content suggests the use of additional DHA sources or higher zoea densities to meet paralarvae nutritional demand to carry out a successful metamorphosis to benthic life.