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1.
This paper reports on an experiment to determine growth and survival of blacklip pearl oyster, Pinctada margaritifera (L.), larvae fed a 1:1 mixture of Isochrysis aff. galbana clone T-ISO and Pavlova salina at six different densities (1, 2, 5, 10, 20 and 30 × 103 cells ml-1. Larval growth and survival were assessed every four days over a 20–day period. Exponential and logistic regression models were fitted to the growth and survival responses, respectively. Overall growth of larvae fed 5 × 103 cells ml-1 was significantly greater (p > 0.01) than growth of larvae reared at other algal densities. The optimal food ration for maximum larval growth was 20 × 103 cells ml-1, which resulted in larvae with antero-posterior shell length of 230 m after 20 days. These larvae were significantly larger (p > 0.05) than those in all other treatments at the end of the experiment. Survival of larvae fed 0, 1 and 2 × 103 cells ml-1 was significantly lower than that of larvae in all other treatments at the end of 15 days (p > 0.01). Maximal survival (8%) over the 20 day period was shown by larvae fed 10 × 103 cells ml-1, while lower survival was shown by larvae fed 2 × 103 cells ml-1 (2%) and 1 × 103 cells ml-1 (0%).  相似文献   

2.
The effect of 5-hydroxytryptamine (5-HT) on larval development of the giant freshwater prawn, Macrobrachium rosenbergii, was investigated. Four days after hatching, larvae were exposed to 5, 50 or 100 μg/ml 5-HT in 12 ppt commercial seawater for a period of 2 or more days. Continuous exposure to 50 μg/ml or 100 μg/ml 5-HT over 2 days reduced the survival significantly and all larvae died by 13 days post-hatch (after 9 days of exposure). On the contrary, there was no significant difference in the survival of larvae exposed to various concentration of 5-HT for 2 days compared to that of the control. Exposure to 5-HT for 2 days stimulated growth and developmental rate of the larvae. Furthermore, pigmentation of the exoskeleton was also induced within 1 h of exposure. The larvae exhibited bright-orange color on their eyestalks, cephalothoraxes and abdomens. Exposure to 100 μg/ml 5-HT for 2 days produced the highest growth, developmental rate and the strongest pigmentation. The average body lengths 25 days post-hatch of larvae exposed to 50 μg/ml and 100 μg/ml 5-HT for 2 days were 3.5 ± 0.6 mm and 4.3 ± 0.7 mm, respectively, compared to 2.8 ± 0.4 mm that of the control. Furthermore, the rate of transformation of larvae to postlarvae during 30–40 days post-hatch was significantly higher in those exposed to 50 μg/ml and 100 μg/ml 5-HT compared to that of the control. The present study indicates that brief exposure of early stage larvae to 50–100 μg/ml 5-HT enhances growth, developmental rate and pigmentation of the giant freshwater prawn larvae.  相似文献   

3.
To determine the optimal salinity, stocking density, and algal density for hatchery culture of the Iwagaki oyster Crassostrea nippona larvae, three experiments with salinities of 14, 18, 22, 26, 30, and 34 practical salinity unit (PSU); stocking densities of 0.5, 1, 2, 4, 8, and 12 larvae ml?1; and algal densities of 10, 20, 40, and 100?×?103 cells ml?1 were designed, which included the developmental stages from newly hatched D-larvae to pediveligers. Results showed that larval growth of C. nippona was the fastest at a salinity of 26 PSU, and when salinity was adjusted to a level that was lower or higher than this salinity, survival and growth rate of larvae declined (P <?0.05), resulting both in a decreased mean shell length and a high mortality. Larval growth decreased significantly with increasing stocking density. Larvae reared at 4 larvae ml?1 had the smallest shell length (198.9 μm) and lowest survival rate (7.9%), whereas larvae reared at 0.5 larvae ml?1 had the largest shell length (245 μm) and highest survival rate (66.3%) on day 13. And the shell length of larvae reared at 0.5 and 1 larvae ml?1 was significantly (P?<?0.05) larger than the values in other treatments, except those reared at 2 larvae ml?1 (P?>?0.05). When feeding the single-algal diet of Isochrysis galbana (clone T-ISO), the shell length of larvae increased markedly as the algal density was increased. Larvae reared at the highest algal density (100?×?103 cells ml?1) had the largest mean shell length; however, under the conditions of our experiment, there was no significant difference (P?>?0.05) in growth and survival rates between the treatments at algal densities of 40?×?103 and 100?×?103 cells ml?1. For a large-scale culture, based on the results of this study, a salinity of 26 PSU, stocking density of 0.5–1 larvae ml?1, and algal density of 40?×?103 cells ml?1 are recommended for an early development of C. nippona.  相似文献   

4.
Pharmacokinetics and residue elimination of marbofloxacin (MBF) were studied in crucian carp (Carassius auratus, 250±30 g) kept at two water temperatures of 15 and 25 °C. Marbofloxacin concentrations in plasma and tissues were analysed by means of high‐performance liquid chromatography using an ultraviolet detector. The limits of detection were 0.02 μg mL?1, 0.02 μg g?1, 0.025 μg g?1, 0.02 μg g?1 and 0.025 μg g?1 in plasma and muscle, skin, liver and kidney respectively. Fish were administered orally at a single dosage of 10 mg kg?1 body weight in the PK group. The data were fitted to two‐compartment open models at both temperatures. At 15 °C, the absorption half‐life () and distribution half‐life (t1/2α) of the drug were 0.36 and 4.48 h respectively. The corresponding values at 25 °C were 0.23 and 0.87 h respectively. The elimination half‐life (t1/2β) was 50.75 h at 15 °C and 25.05 h at 25 °C. The maximum MBF concentration (Cmax) differed little between 15 (6.43 μg mL?1) and 25 °C (8.36 μg mL?1). The time to peak concentration was 1.74 h at 15 °C and 0.78 h at 25 °C. The apparent volume of distribution (Vd/F) of MBF was estimated to be 1.36 and 0.87 L kg?1 at 15 and 25 °C respectively. The area under the concentration–time curve (AUC) was 301.80 μg mL?1 h at 15 °C and 182.80 μg mL?1 h at 25 °C. The total clearance of MBF was computed as 0.03 and 0.05 L h?1 kg?1 at 15 and 25 °C respectively. After repeated oral administration at a dosage of 10 mg kg?1 body weight per day for 3 days, the results showed that the elimination half‐lives () of MBF from all tissues at 15 °C were longer than that at 25 °C. Therefore, water temperature is an important factor to be considered when deciding a reasonable withdrawal time.  相似文献   

5.
The toxicity of formalin and trifluralin to the larval stages of the mud crab Scylla serrata was compared in a static bioassay. Prophylactic doses of 5, 10, 15, 20 and 25 μg L−1 formalin and 0.05, 0.1, 0.2, 0.4 and 0.8 μg L−1 trifluralin were used. Toxicity was assessed on the basis of survival of larvae after 24, 48, 72 and 96 h exposure to the test chemicals and metamorphosis to the next larval stage. Result shows that larval survival in all stages was significantly reduced at concentrations of 20 and 25 μg L−1 formalin whereas larvae were able to tolerate all trifluralin treatments. However, larvae became more tolerant to high formalin concentrations as the larval stage progressed. Survival was better at 5, 10 and 15 μg L−1 formalin and in all trifluralin treatments than the control in almost all the larval stages. Faster metamorphosis was observed at 5 and 10 μg L−1 formalin and 0.05, 0.1 and 0.2 μg L−1 trifluralin concentrations. Doses of formalin and trifluralin obtained from the toxicity experiments were applied as prophylaxis to newly hatched larvae in white plastic basins. Prophylactic doses of 5 and 10 μg L−1 formalin and 0.05 and 0.1 μg L−1 trifluralin applied every other day were found to be effective in enhancing survival and larval development to megalopa compared with control. However, no megalopae survived to crab instar in all formalin treatments. Although the use of fungicides in rearing systems resulted in higher survival compared with controls, other strategies (i.e. maintenance of good water quality and hygienic practices in the hatchery) should be further investigated as an alternative to the use of chemicals in hatcheries.  相似文献   

6.
Filtered sea water was seeded with one of five oyster-pathogenic bacteria to obtain a final concentration of 105 cells/ml. UV irradiation at a dose of 93 312–155 520 μW s?1 cm?2 rendered the contaminated sea water safe for rearing fertilized eggs of Crassostrea virginica. Fertilized oyster eggs were reared until the larvae began to set in filtered, UV-irradiated sea water and in filtered, non-UV-treated sea water. The data suggest that when a pathogenic bacterium is present the potential for disease is much greater in non-UV-treated sea water.  相似文献   

7.
Minimum inhibition concentrations (MICs) were determined for Furanace (Dainippon Pharmaceutical Co. Ltd.) against 17 strains of pathogenic vibrios isolated from marine fish and salmonidae. All the strains tested were sensitive to Furanace, the highest MIC being 3.1 μg/ml for one strain and the remainder being < 1.6 μg/ml. Plaice (Pleuronectes platessa L.), Dover sole (Solea solea (L.)) and brill (Scophthalmus rhombus (L.)) rapidly took up Furanace from low-concentration baths (5–10 μg/ml) at 9.5–11.5°C. Uptake varied between species at these temperatures and in most cases blood levels above 1 μg/ml were achieved after 1 hour's exposure. Two hours after exposure over 70% of the Furanace had been eliminated from the blood.  相似文献   

8.
Total lipids, lipid classes and their associated fatty acids were measured in developing eggs, yolksac larvae and starving larvae (from fertilized egg to day 9 after hatch) of the common dentex Dentex dentex (L., 1758). The larvae of common dentex during lecitotrophia and subsequent starvation consumed 1.6 g of total lipid per larvae per day. The overall decrease was mainly due to utilization of the major neutral lipids, TAG and SE (0.5 and 0.6 g larvae–1 day–1, respectively) which was 3.4-fold greater than that of the the major phosphoglycerides (primarily PC by 0.2 g larvae–1 day–1). There was net synthesis/conservation of PE during the first half of the study period before it decreased rapidly (0.2 g larvae–1 day–1) during the second half. PUFAs were principally catabolized (468.6 ng larvae–1 day–1), primarily 22:6(n-3), 20:5(n-3) and 20:4(n-6) (221.8, 58.5 and 12.1 ng larvae–1 day–1, respectively). Saturated and monounsaturated fatty acids were also utilized (227.2 and 256.7 ng larvae–1 day–1, respectively), principally 16:0 and 18:1(n-9) that were both consumed at 149.8 and 156.7 ng larvae–1 day–1, respectively. The rank order of utilization of fatty acids (ng larvae–1 day–1) by D. dentex larvae from total lipids, PC and TAG coincided with the order of abundance of the different fatty acids in the respective lipid fractions. However, in PE, the most abundant fatty acid, DHA, was relatively conserved and 16:0, the second most abundant fatty acid, was catabolized to the greatest extent. D. dentex showed a pattern of lipid metabolism during early development similar to that of marine larval fish from temperate waters whose eggs contain high levels of total lipids, including an oil globule, and which preferentially utilize neutral lipids as the primary energy source.  相似文献   

9.
This study aims to evaluate the efficacy of Streptococcus agalactiae vaccine preparations, administered to tilapia broodstock, in preventing streptococcosis, through specific and non-specific immunity being transferred to the offspring. The study was conducted in two phases. The first was the vaccination of the broodstock using a whole-cell vaccine, an extracellular product (ECP) vaccine, and a combination of the two with a ratio of 1:1. The vaccines were administered to the broodstock 2 and 3 weeks before spawning. The second phase was the challenge test for larvae produced by vaccinated broodstock, and larvae from the unvaccinated control broodstock, through immersion in a suspension of 107 cfu mL?1 pathogenic S. agalactiae for 30 min, at ages 7, 14, 21, and 28 days post-hatching. The parameters evaluated were the broodstock’s blood profile, antibody-lysozyme (in broodstock, eggs, and larvae), and the larvae’s relative percent survival. Treatment with the combined vaccine administered 3 weeks before spawning resulted in the broodstock having significantly better antibody levels, lysozyme activity, and hematology profiles, compared to the other treatments (p?<?0.05). In addition, the larvae produced by broodstock subjected to this treatment, when challenged with the pathogenic S. agalactiae at ages 7, 14, 21, and 28 days, had RPS values of 95.24, 83.33, 72.22, and 56.02%, respectively. It was concluded that the administration of the “whole-cell/ECP” combination vaccine preparation to tilapia broodstock in the 3 weeks before spawning can increase specific and non-specific immunity in the broodstock and protect the larvae from S. agalactiae infection.  相似文献   

10.
The dietary value of dried, commercial Chlorella was compared with that of living marine Chlorella, and yeast, in relation to growth of the rotifer Brachionus plicatilis raised individually and by batch culture methods.A concentration of 50 μg/ml of dried Chlorella powder is near an optimal density for rotifer growth. The dried material in suspension is less effective for growth than living marine Chlorella, although it is much more effective than a suspension of yeast at the same density (50 μg/ml).In batch culture (12-l glass vessel), the rotifers grew from an initial inoculation of 13.2 individuals/ml to a density of 434 individuals/ml by the 16th day. About 107 rotifers could be removed from one batch culture in five harvests in the 41-day experimental period.The results indicate that dried Chlorella powder is an effective food for the rotifer Brachionus plicatilis.  相似文献   

11.
The changes in proximate composition, amino acid (total and free) and fatty acid content of artificially propagated trout cod, Maccullochella macquariensis larvae from five mothers hatched, weaned and reared separately, each in two groups, one fed with Artemia naupli and the other starved, for 15 days (after yolk resorption), are presented. There was no significant change in the proximate composition of fed larvae with devlopment, but in starved larvae the protein (linearly) and lipid (curvi-linearly) content decreased significantly as starvation progressed. The essential amino acids (EAA) and non- essential amino acids (NEAA) found in highest amounts in trout cod larvae were lysine, leucine, threonine and arginine, and alanine, serine and glutamic acid, respectively. In fed larvae the total amino acid (TAA), TEAA and TNEAA content did not vary significantly as development progressed. In starved larvae the TAA, EAA and NEAA content, as well as all the individual amino acids decreased significantly (P<0.05) from the levels in day of hatch and/or yolk-sac resorbed larvae. The greatest decrease occurred in the TEAA content (7.38±0.76 at day of hatch to 1.96±0.09 15 day starved in moles larva–1; approximately a 74% decrease), whereas the decrease in TNEAA was about 38%. Unlike in the case of TAA distinct changes in the free amino acid (FAA) pool were discernible, from day of hatch and onwards, in both fed and starved trout cod larvae. In both groups of larvae the most noticeable being the decrease of % FEAA in TFAA, but not the % FAA in TAA. Four fatty acids together, accounted for more than 50% of the total in each of the major fatty acid categories in all larvae sampled; 16: 0, 18:1n-9, 22: 6n-3 and 20: 4n-6, amongst saturates, monoenes, n-3 PUFA and n-6 PUFA, respectively. Twelve fatty acids either decreased (14: 0, 16: 1n-7, 20: 1n-9, 20: 4n-6, 20: 5n-3, 22: 5n-3 and 22: 6n-3) or increased (18: 2n-6, 18: 3n-3, 18: 3n-6, 18: 4n-3 and 20: 3n-3) in quantity, after 15 days of feeding, from the base level in day of hatch and/ or yolk- sac resorbed larvae. The greatest increase occurred in 18: 3n-3 from 6.4±0.1 to 106.2±13.1 g mg lipid–1 larva–1, and the greatest decrease occurred in 22: 6n-3 (181.2±12.4 to 81.4±6.2 g mg lipid–1 larva–1). In starved larvae, at the end of 15 days, all the fatty acids, except 18: 0, 20: 3n-3 and 20: 4n-6, decreased significantly (P<0.05) from the levels in day of hatch and/or yolk- sac resorbed larvae.  相似文献   

12.
α-Cypermethrin (Cyp) is a synthetic insecticide used to control pests in agricultural crops and to protect human health against noxious insects; this toxic can reach aquatic systems through ground infiltration or by runoff and could affect the aquatic biota. The present study was aimed at evaluating the acute toxicity of Cyp on zebrafish (Danio rerio) exogenous feeding larvae of 10 and 20 days post-fertilization (dpf), and of sublethal concentrations on only 10-dpf larvae. Proteins, lipids, carbohydrates, glycogen concentration, and total energy contents, as well as malondialdehyde (MDA) quantification, through thiobarbituric acid reactive substances, as a lipid peroxidation biomarker, were assessed in free-feeding larvae exposed to sublethal Cyp concentrations. The LC50 for 10-dpf larvae was 1.94 µg L?1, and these were more sensitive than 20-dpf larvae (3.56 µg L?1). The amount of protein, carbohydrates, and glycogen were not significantly affected (p > 0.05), but sublethal Cyp concentrations exposure caused decrement in lipids from 9.05 to 3.74 µg larva?1, as well as a reduction in MDA and in the total energy content, which affected significantly the development of this fish. Although Cyp is considered an insecticide of reduced residual effect in the environment, the present study revealed that relatively low Cyp concentrations produced significant toxic effects on exogenous feeding fish larvae, a situation that could contribute to increase deaths during this already critical developmental stage in which high mortality is observed frequently.  相似文献   

13.
The spatfall prediction techniques used in Hiroshima Bay, Japan, are described. Data are given for the 1977 season. Plankton hauls from seven stations showed successive high peaks of small, medium and large larvae during early August. Small larvae (< 150 μm diameter) peaked at an average of 1,782 larvae per tonne of sea water (m3) on 10 August; medium larvae (151–250 μm) at 1,258/m3 peaked on 12 August as did large settling larvae (251–300 μm) at 350/m3. A small spatfall occurred on 14, 16 and 18 August when an average of 65, 64 and 65 spat per shell, respectively, attached on collectors during 2 days' immersion.A second, much bigger peak of small larvae built up from 16 August to reach an average maximum of 4,702 larvae/m3 on 24 August. Medium larvae peaked at 754 larvae/m3 on 28 August. A red tide then appeared consisting of vast numbers of a dinoflagellate tentatively identified as Gymnodinium simplex, and the anticipated main spatfall did not occur. The effects of red tides are discussed. By 17 September water conditions had improved and an estimated 50–100 spat were reported attached per shell on the collectors. This is about half the 200 spat per shell considered by the industry to be a good set.  相似文献   

14.
Two experiments were conducted to investigate the efficacy of three androgens applied through immersion treatments on the sex ratio of Nile tilapia (Oreochromis niloticus L.) fry. In experiment 1, 14 days post‐hatching (DPH) larvae were exposed to a single immersion treatment in 17α‐methyltestosterone (MT), 17α‐methyldihydrotestosterone (MDHT) or 17α‐ethynyltestosterone (ET) at 200, 600 and 1800 μg L?1 over 4 h (130 larvae per treatment). In experiment 2, Nile tilapia larvae were exposed to the higher androgen concentration (1800 μg L?1) applied as either a single immersion (14 DPH) or double immersion (10 and 14 DPH) over 4 h (125 larvae per treatment). Change in sex proportion within each experiment as well as between experiments was analysed by the chi‐square test. In experiment 1, MT, MDHT and ET were equally effective in significantly increasing the proportion of males when applied at 1800 μg L?1 (86.0%, 90.0% and 86.7% respectively). At 200 μg L?1 none of the androgens altered sex ratio. At 600 μg L?1, only MDHT slightly, but significantly skewed the sex ratio towards males (73.0%). In experiment 2, a single immersion treatment at 14 DPH (1800 μg L?1) significantly increased the proportion of males, but at this time the response was significantly hormone dependent (MDHT, 100.0%; MT, 91.6%; ET, 76.9%). When compared with a single immersion, two‐immersion treatments significantly increased the proportion of males in the MT‐treated group (from 91.6% to 98.3%), decreased the proportion of males in the MDHT group (from 100.0% to 93.4%) and had no significant effect the ET‐treated group (change from 76.9% to 82.5%). The overall comparison of the sex ratio among same treatments from different experiments (a single immersion in 1800 μg L?1) was not significantly different.  相似文献   

15.
In this study, a 25-day experiment was performed to evaluate the survival and development of Portunus trituberculatus larvae under different light intensities (0, 61.55, 93.57, 124.31, 195.31, 248.51, and 310.95 μmol m−2 s-1). The newly hatched larvae were cultured in 1-L beakers at a density of 100 individuals/L, with four replicates per treatment. Full-spectrum light-emitting diode (LED) strip lamps were used as the light source. The larvae were fed with Artemia nauplii until all the larvae metamorphosed to young crabs or died, and survival and development of the larvae were recorded. The results showed that P. trituberculatus zoeae were not able to complete the entire larval cycle in the absence of light. In the dark treatment, the survival rate of the larvae decreased sharply in Z3 and reached 0.8 % in Z4, and all the larvae failed to develop to the megalopa stage. In the light treatment, no significant differences were observed in the survival rates of the Z1, Z2, and Z3 larvae under different light intensities (P > 0.05). However, the highest survival rates were detected for Z4 larvae and megalopae at 195.31 and 124.31 μmol m−2 s-1, respectively, indicating a decline in the light requirement. Although the Z2 and Z4 larvae were found to develop faster at a light intensity of 195.31 μmol m−2 s-1 (P < 0.05), no significant differences were found among the treatments at the end of the experiment (P> 0.05). In conclusion, the results show that P. trituberculatus needs more lighting than other crab species, and the light requirement declines as the zoeal and megalopal larvae develop into young crabs.  相似文献   

16.
The ingestion of an inert feed as a sole food source was investigated in larval silver sea bream (Sparus sarba) fed an alginate-based microparticulate diet. Using the auto-fluorescent properties of pigments associated with the alginate base, ingestion and gut content were investigated over a 6 h experimental period in fed and unfed larvae. By extracting and measuring chlorophyll a (Chl a) and phaeopigment content of feeding larval fish and relating this to standardized Chl a and phaeopigment content of the diet, relative to diet weight, it was determined that individual fed 7-day old larvae had a maximum gut content of 1.05±0.09 g diet while 14-day old fed fish had a maximum gut content of 3.17±0.90 g diet. On average, the gut content of 14-day old fish was 2.89 times greater than the gut content of 7-day old fish. The dry weight of larval sea bream increased from 43±4.2 g at day 7 to 134.3±20.4 g at day 14 indicating that growth of fish fed this inert feed was substantial. Gut pigment dynamics suggested that Chl a was degraded to phaeopigments by 7-day but not 14-day old larvae and the individual gut dietary content varied considerably in 14-day old fish. The maximum Chl a and phaeopigment content in larval sea bream was 0.4 ng ind–1 and 0.55 ng ind–1 for 7-day old fish and 1.54 ng ind–1 and 2.81 ng ind–1 for 14-day old fish respectively. The present method may potentially allow simple and direct assessment of larval fish feed ingestion in both an experimental and commercial setting.  相似文献   

17.
In the present study, cellulase, protease, lipase and amylase activities were performed to investigate the effects of Lactococcus lactis subsp. lactis CF4MRS bioencapsulation of Artemia franciscana. Our results show that cellulase activities (total cellulase—FPase activity, exoglucanase and endoglucanase—CMCase activity) were significantly higher (P < 0.05) in A. franciscana tissue homogenates compared to those in the control group after 8 h of L. lactic bioencapsulation. Notably, an exception case was found in β-D-glucosidase activity, whereby the cellulase activity was not significantly different (P > 0.05) compared to the control group. Administrations of L. lactis at cell concentration of 108 CFU mL?1 showed considerable improvement of other important enzymatic activities such as amylase, protease and lipase in A. franciscana. The amylase/protease ratio in probiotic-treated A. franciscana was recorded at 0.343, approximately two times higher than those without probiotic administration (0.184). In contrary, amylase/lipase ratio showed half of a reduction (0.330) in L. lactis-administrated A. franciscana compared to the control (0.614). Our study suggests that important digestive enzymes, e.g., cellulase, amylase, protease and lipase, can be enhanced through bioencapsulation of A. franciscana with L. lactis subsp. lactis, which could in turn lead to further stimulation of endogenous enzymes in the fish and shrimp larvae.  相似文献   

18.
This study examined the effects of two probiotics (Virgibacillus proomii and Bacillus mojavensis) on the digestive enzyme activity, survival and growth of Dicentrarchus labrax at various ontogenetic stages in three separate experiments. These probiotics were incorporated as single or mixed into fish feed for a period of 60 days. The growth parameters, proximate composition of whole body, digestive enzymes and gut microbiology were monitored at regular. The increments in length and weight and the survival were significantly higher (P < 0.05), and the values of food conversions were significantly lower (P < 0.05) in fishes fed the probiotic. The administration of V. proomii and B. mojavensis in diet resulted in an increase (P > 0.05) in body ash and protein content and in the specific activity of phosphatase alkaline and amylase in the digestive tract of all the fishes. V. proomii and B. mojavensis persisted in the fish intestine and in the feed in high numbers during the feeding period (group 1: 5.8 × 104 CFU/ml, group 2: 9.6 × 104 CFU/ml, and group 3: 9.8 × 104 CFU/ml day 60). The two probiotics V. proomii and B. mojavensis were adequate for improved growth performance and survival and for healthy gut microenvironment of the host.  相似文献   

19.
The combined effects of stocking density and microalgae ration on survival and size of Saccostrea echinata larvae were studied in two‐factor experiments for the major developmental stages: D‐veliger (1‐day posthatch [dph], Experiment 1), umbonate (12 dph, Experiment 2), and eyed (19 dph, Experiment 3) larvae. Larvae were stocked into replicate sets of four 10‐L aquaria with ambient 1‐μm filtered sea water (28 ± 1.5°C and 36 ppt) and cultured for four days at densities of 0.5, 2, 5, 7, or 10 larvae/mL and provided with microalgae rations at each of five densities (cells larvae?1 day?1); 0, 1, 3, 5, or 8 × 103 (D‐veliger larvae, Experiment 1); 0, 5, 12, 18, or 25 × 103 (umbonate larvae, Experiment 2); and 0, 15, 30, 40, or 60 × 103 (eyed larvae, Experiment 3). Microalgae rations for each larval life stage were selected on the basis of increasing food requirement with larval size and comprised a 2:1:1 mixture of Chaetoceros calcitrans, Tisochrysis lutea, and Pavlova spp., calculated on an equal dry‐weight basis. Contour plots were generated from larval survival and larval size (dorso‐ventral measurement [DVM]) data to determine optimal culture conditions. Larvae showed high survival (54–100%) over a wide range of both treatment parameters across all life stages, confirming broad tolerance limits for this species. The interaction effects of larval stocking density and microalgae ration on larval size were significant (p < 0.001) across all life stages. Results indicate that maximum larval size (DVM) is achieved when S. echinata are cultured at: 6–8 larvae/mL and fed 5–6 × 103 cells larvae?1 day?1 for D‐veligers (mean DVM >80 μm), at 2–8 larvae/mL and fed 11–25 × 103 cells larvae?1 day?1 for umbonate larvae (mean DVM > 190 μm), and at 1–4 larvae/mL and fed 15–40 × 103 cells larvae?1 day?1 for eyed larvae (mean DVM >230 μm). Results will help refine current hatchery methods for S. echinata supporting further development toward commercial aquaculture production of this species.  相似文献   

20.
To investigate whether PCB 126 exposure duringembryonic development induces an endocrine stressresponse in larval carp, eggs were exposed,containing 0.01% ethanol (vehicle-control), 10-11,immediately after fertilization, for 48 h to water10-10 or 10-9 mol l-1 PCB in 0.01% ethanol. Eggsincubated in water served as controls. After transferto PCB-free water, mortality, the incidence ofyolk-sac and pe-ricardial oedema, wet and dry weight,rate of skin pigmentation, and whole-body contents ofthe stress hormones ACTH, -MSH and cortisol weredetermined at 48, 96, 144, 168, 192 and 216 hpost-fertilization. Except for the dry weight, allparameters of animals exposed to 10-10 and 10-9 moll-1 PCB increased in a concentration-related manner.However, these changes became evident only at 144 hpost-fertilization, i.e. after resorption of theyolk-sac. Swelling of the yolk sac and pericardiumoccurred, and whole-body ACTH, -MSH and cortisollevels increased. Although animals exposed to 10-10and 10-9 mol l-1 PCB displayed stable but elevatedwhole-body ACTH and -MSH levels until 216 h,whole-body cortisol concentrations gradually decreasedfrom 168 h post-fertilization, and were significantlybelow control values at 216 h post-fertilization.Exposure of the carp embryos to 10-11 mol l-1 PCB only increased whole-body -MSH levels. Increased whole-body ACTH and cortisol levels indicate that PCBinduces a stress response in carp larvae, possiblymediated by a disturbed hydromineral balance (oedema).We further suggest that the PCB-stimulated bodypigmentation is mediated by a stimulation of -MSHsecretion.  相似文献   

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