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1.
Rested upon Box‐Behnken experimental design and response surface method, the joint effect of temperature, salinity and pH on the fertilization and hatching in Nile tilapia was studied under laboratory conditions. Results showed that the linear and quadratic effects of temperature, salinity and pH on fertilization and hatching were all statistically significant (P < 0.01). Interactions between temperature and salinity, and between temperature and pH on fertilization and hatching statistically differed from zero (P < 0.05). Interaction between salinity and pH on hatching was significant (P < 0.05), but nonsignificant on fertilization (P > 0.05). Regressions of fertilization and hatching towards temperature, salinity and pH were established, with the determination coefficient being 99.17% for fertilization and 99.79% for hatching, and could be used for prediction. By utilizing statistical optimization technique, the optimal temperature/salinity/pH combinations were attained: 27.6°C/9.3 ppt/7.5 for fertilization, at which the maximum fertilization was 87.7%, with the desirability being 92.11%; and 27.1°C/9.2 ppt/7.4 for hatching, at which the maximum hatching rate reached 81.2%, with the desirability as high as 96.74%. It could be said that the fertilization and hatching concurrently culminated at the 27.3°C/9.2 ppt/7.4 combination. It can be envisioned that the application of these results derived would give an impetus to the tilapia seed production efficiency and in turn to the development of tilapia husbandry.  相似文献   

2.
The combined effects of temperature and salinity on the yolk utilization of sac fry in Nile tilapia (Oreochromis niloticus) were investigated using central composite experimental design and response surface approach. Based on the preliminary trials, temperature was determined to range from 22 to 34°C, and salinity ranging from 2 ppt to 10 ppt. The utilization was mensurated in terms of yolk sac volume. Results showed that the linear effects of temperature and salinity on the yolk utilization was significant (P < 0.01); the quadratic effects of and the interaction between the two factors were significant (P < 0.05); temperature was more important than salinity in influencing the yolk utilization. The model equation of yolk sac volume towards temperature and salinity was established. From those high R2 values, the model had excellent goodness of fit to experimental data and could be applied for predictive purpose. What with the production cost, it is suggested that the temperature/salinity combination, i.e. 28–30°C/4–6 ppt, be employed during the period of sac fry rearing, in which the yolk utilization was on average 98.6%.  相似文献   

3.
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4.
Although a stenohaline freshwater fish, the stinging catfish Heteropneustes fossilis, is also available in the freshwater fringes of the coastal areas of Bangladesh, the tolerance of this species to variable environmental salinity has not been thoroughly investigated. Based on median lethal salinity (MLS‐50 96 h), three sublethal salinity levels (3 ppt, 6 ppt and 9 ppt) and a control (0 ppt), each with three replications were selected to observe the effects of mildly brackish conditions on the fish for a period of 90‐day exposure. Better growth and survival were found up to 6 ppt compared with control. Salinity more than 6 ppt appeared unsuitable for H. fossilis fingerling due to increased mortality and reduced growth. To determine biochemical alterations, a few important physiological parameters were observed after 90 days of exposure. Glycogen level of liver and muscle in the fish reared at 9 ppt salinity decreased significantly (P < 0.05) as compared to the control. Glucose level in blood and liver was also found to be increased in fish with increase in salinity. ALP and ATPase activities were reduced significantly in both muscle and liver tissues at higher salinity, indicating the stress mitigation effect. However, all the biochemical parameters were found in normal condition up to 6 ppt compared with control. This evidence suggests that H. fossilis can sustain and grow well below 6 ppt and can be a potential candidate for culture in coastal areas after heavy downpour when the salinities level falls to 6 ppt or lower.  相似文献   

5.
Tilapia juveniles are a very important life stage, and reliably assessing their growth performance is of prime importance in aquaculture production. The suitability of the RNA/DNA as a bioindicator for growth evaluation in tilapia has not yet been reported. In this study, we examined suitability of RNA/DNA ratio for assessing growth of tilapia juveniles and variation in the ratio under the concurrent influences of temperature and salinity using the central composite design and response surface methodology. Results showed that under our experimental conditions, the synergistic effects of temperature and salinity on the RNA/DNA ratio were highly significant (P < 0.01), and the ratio varied with the two factors in a nonlinear fashion; the temperature × salinity interaction was detected at 1% significance level, and had a negative effect on the RNA/DNA ratio particularly at higher temperatures. Temperature was found to have a greater influence on RNA/DNA ratios than salinity. A model of the relation between RNA/DNA, temperature and salinity was developed, with an R2 greater than 98%. The linear relationships of absolute growth, cumulative growth and specific growth of tilapia juveniles to RNA/DNA ratio all showed an R2 of greater than 95%. Our results indicate that the RNA/DNA ratio was a responsive and accurate bioindicator for evaluating the growth performance of juvenile tilapia. These ratio‐based models are neither temperature‐ nor salinity‐dependent, and could be readily applicable to freshwater or brackish water aquaculture within temperature–salinity combinations ranging from 16 to 36°C and 0–16 ppt.  相似文献   

6.
Streptococcus agalactiae is an important pathogen in fish, causing great losses of intensive tilapia farming. To develop a potential live attenuated vaccine, a re‐attenuated S. agalactiae (named TFJ‐ery) was developed from a natural low‐virulence S. agalactiae strain TFJ0901 through selection of resistance to erythromycin. The biological characteristics, virulence, stability and the immunization protective efficacy to tilapia of TFJ‐ery were determined. The results indicated that TFJ‐ery grew at a slower rate than TFJ0901. The capsule thickness of TFJ‐ery was significantly less (p < 0.05) than TFJ0901. When Nile tilapia were intraperitoneally (IP) injected with TFJ‐ery, the mortality of fish was decreased than that injected with TFJ0901. The RPS of fish immunized with TFJ‐ery at a dose of 5.0 × 107 CFU was 95.00%, 93.02% and 100.00% at 4, 8 and 16 weeks post‐vaccination, respectively. ELISA results showed that the vaccinated fish produced significantly higher (p < 0.05) antibody titres compared to those of control at 2 or 4 weeks post‐vaccination. Taken together, our results suggest that erythromycin could be used to attenuate S. agalactiae, and TFJ‐ery is a potent attenuated vaccine candidate to protect tilapia against S. agalactiae infections.  相似文献   

7.
This study assessed the immune response of Nile tilapia (Oreochromis niloticus L.) after feeding on different levels (0.1%, 0.2% and 0.4%) of dietary Indian lotus (Nelumbo nucifera) leaf powder for 45 days. We evaluated both the nonspecific immune response at the end of the feeding period and the resistance to Aeromonas hydrophila. Exposure to Indian lotus resulted in a significant elevation in serum total globulins, serum lysozyme activity, serum killing percentage and the phagocytic activity (p < 0.05). Total serum protein and albumin showed no remarkable variation between tilapia fed on 0.1% Indian lotus and the control group (p > 0.05). In addition, the relative expressions of immune‐related genes, namely interleukin–1β and tumour necrosis factor–α were significantly up‐regulated in tilapia fed on 0.4% Indian lotus as compared to the control group; their expressions were down‐regulated in the other tested groups (p < 0.05). The survival rate of Nile tilapia postchallenge to A. hydrophila reported a significant and dose‐dependent increase in the Indian lotus‐supplemented groups (p < 0.05). Therefore, dietary incorporation of Indian lotus leaves (0.4%, 0.2% and 0.1%) could strengthen the immunity of Nile tilapia and improve its resistance to A. hydrophila infection. Therefore, Indian lotus leaves could serve as potential feed supplements for Nile tilapia.  相似文献   

8.
This study was carried out to evaluate the effects of dietary supplementation of thermotolerant bacterium on growth and immune responses of Nile tilapia (Oreochromis niloticus). Bacillus paralicheniformis SO‐1 was isolated from marine environments and incorporated into four isonitrogenous (300g/kg crude protein; cp) and isocaloric (18 MJ/kg) diets at four concentrations: 0, 5, 10 and 20 g/kg diet. Each diet was fed to triplicate groups of Nile tilapia (41.5 ± 0.5 g average weight) at a daily rate of 3% of their biomass, three times a day for 50 days. At the end of the feeding trial, the growth rates, feed utilization efficiency (feed conversion ratio, protein efficiency ratio, protein productive value), digestive enzymes (protease, amylase and lipase) activities, immunological response (serum lysozyme activity, phagocytic activity, respiratory burst and superoxide dismutase activity) and the expression of immune‐related genes [interleukin‐1 (IL‐1), interleukin‐4 (IL‐4) and interleukin‐12 (IL‐12)] were determined. Growth rates, digestive enzymes activities and immunological parameters were significantly improved (p < 0.05) with increasing supplemental SO‐1 up to 10 g/kg. However, further increase in bacterial concentration to 20 g/kg lead to significant decline in fish performance and immune response (p < 0.05). The expression of IL‐1, IL‐4 and IL‐12 genes was significantly up‐regulated (p < 0.05) in the liver of Nile tilapia fed SO‐1‐treated diets. This study clearly demonstrated that B. paralicheniformis SO‐1 could be considered as an efficient growth promoter and immune‐stimulating probiotic for farmed Nile tilapia.  相似文献   

9.
Aeromonas hydrophila is a pathogen infecting farmed hybrid catfish, Clarias macrocephalus (Günther, 1864) × Clarias gariepinus (Burchell, 1822) which incurs substantial economic losses in Thailand. The study aimed at a genetic tracking of A. hydrophila infection and the in vitro assessment of the efficacy of antibiotics against its virulent strains. Five clinical strains from catfishes and Nile tilapia were employed. They were 3‐passage re‐isolated through healthy hybrid catfish and the cytolytic enterotoxin gene (AHCYTOEN) of individuals was traced. Each of the re‐isolates at a dose of ~6.67 × 105 CFU/g was intraperitoneally injected into ~15 g‐healthy hybrid catfish and their pathogenicity were observed for 7 days. It was found that AHCYTOEN was carried over whereas typical signs of motile aeromonas septicaemia were found in the specimens. The bacterial strains of Nile tilapia origin did not induce mortality but those of catfish origins (80%–100% rate of mortality). The strains were susceptible to the tetracycline antibiotics, and oxytetracycline produced MIC50 and MBC as low as 0.007–0.031 μg/ml and 1–8 μg/ml respectively. As oxytetracycline specifically inhibited pathogenic A. hydrophila in vitro, it is recommended that an appropriate dosage regimen of the drug should be established.  相似文献   

10.
Polymorphisms in the growth hormone (GH) gene that is associated with the growth rate of farmed fish have been the target of many breeding programmes. The present study aimed to identify single nucleotide polymorphisms (SNPs) in GH gene regions to evaluate the association of SNP variations with the growth rate of two Nile tilapia: Oreochromis niloticus (Linnaeus, 1758) strains. The targeted regions were amplified, sequenced, aligned and screened for the presence of SNPs; thereafter, performance tests were used to check for the association between SNPs and weight. Allele and genotype frequencies were estimated for each SNP and genotype. Genotype blocks or sets of SNP genotypes and frequencies were also estimated. Association between SNPs and growth rate was statistically evaluated using a univariate linear mixed model that included both fixed and random effects. A total of 10 SNPs were identified, nine in the proximal promoter and one located in the 5′ UTR, forming 10 genotype blocks. In all weight recordings, five genotype blocks were significantly associated with the highest weights. Single nucleotide polymorphisms 6‐10 were also found to be significantly associated with growth (p‐value < .05). Genotypes with higher additive genetic values for weight were identified in the Chitralada strain, suggesting a possible impact of these additive effects of the GH SNP genotype on the growth rate of Nile tilapia. These findings may be used as part of marker‐assisted selection in tilapia breeding programmes.  相似文献   

11.
Impact of osmoregulation on plasma sex steroid levels and gonadal histo‐architecture was monitored to elucidate the effects of deviation from habitat salinity on gonadal recrudescence in an active reproductive season of an euryhaline fish Etroplus suratensis (pearlspot). Fish were maintained in three different salinities of 0 ppt Fresh Water (FW), 15 ppt Brackish Water (BW) and 30 ppt Sea Water (SW) for a period of 60 days. Plasma osmolality values were found to be significantly highest in SW‐acclimated fish accompanied by highest levels of plasma K? and Cl¯ ions. The progress of gonadal recrudescence was higher in BW followed by FW and SW as evident from the cellular features of gonads and increased level of plasma sex steroids, such as, in case of female and 11‐keto Testosterone and Testosterone in case of males. Plasma cortisol levels were comparatively higher in fish of both sexes in SW group. Significantly high levels of cortisol in SW suggest its role in hypo‐osmoregulation and associated stress. This study clearly reveals that salinity changes during the active reproductive phase can suppress the steroid‐mediated gonad recrudescence maximally under hypo‐osmoregulation in an euryhaline fish.  相似文献   

12.
Streptococcus agalactiae is a Gram‐positive facultative intracellular bacterium that leads to severe economic loss of tilapia worldwide. Previous studies demonstrated that CD40 contributes to host protection against intracellular injection. In this study, CD40 was characterized from Nile tilapia (Oreochromis niloticus), named OnCD40. Sequence analysis showed that open reading frame of OnCD40 was 933 bp, containing a single peptide, a transmembrane domain and four cysteine‐rich domains. The qRT‐PCR revealed that OnCD40 was expressed in all examined tissues with the most abundant ones in spleen and thymus. After S. agalactiae stimulation, the expression of OnCD40 was significantly induced in most of the detected organs. Moreover, OnCD40‐overexpressing fish elicited significant protection against subsequent S. agalactiae challenge; approximately 10000‐fold fewer bacteria were detected in spleen of OnCD40‐overexpressing fish in comparison with control fish. Thus, CD40 had protecting function in Nile tilapia against intracellular pathogens.  相似文献   

13.
In this study, we evaluated the growth, osmoregulation and energy metabolism of the oriental river prawn, Macrobrachium nipponense, reared during 6 weeks with different salinities (0, 8, 14 and 22 g/L). The results showed that the haemolymph osmolality of M. nipponense increased with an increase in ambient osmotic pressure; the isosmotic point was 490 mOs/kg H2O. The prawns showed a higher survival rate, weight gain rate and hepatopancreas index in salinity 14 g/L. Digestive enzymes were all affected by salinity, and the highest activities were observed in the salinity 14 g/L. The mRNA expression of Na+‐K+‐ATPase in gills and p53 in hepatopancreas were the highest in salinity 22 g/L. The expressions of heat shock protein 90 and glutathione S‐transferase genes in hepatopancreas were significantly higher in the salinity 8 g/L. Lipid metabolism‐related genes in hepatopancreas were significantly expressed in the salinity 14 g/L. The glucose‐6‐phosphatase gene in hepatopancreas was highly expressed in the salinity 8 and 22 g/L, and the expression of the ecdysone receptor gene in hepatopancreas was significantly higher in the salinity 14 g/L. The results showed that salinity 14 g/L could promote the growth of M. nipponense. However, higher salinity conditions may cause physiological damage, which provides a theoretical basis for brackish water culture of M. nipponense.  相似文献   

14.
Streptococcus dysgalactiae is an emerging fish pathogen that is responsible for outbreaks of disease on fish farms around the world. Recently, this bacterium was associated with an outbreak at a Nile tilapia, Oreochromis niloticus (L.), farm in Brazil. The aim of this study was to evaluate the genetic diversity, best genotyping method and aspects of molecular epidemiology of S. dysgalactiae infections in Nile tilapia farms in Brazil. Twenty‐one isolates from four farms located in different Brazilian states were characterized genetically using pulsed‐field gel electrophoresis (PFGE), ERIC‐PCR, REP‐PCR and sodA gene sequencing. The discriminatory power of the different typing methods was compared using Simpson's index of diversity. Identical sodA gene sequences were obtained from all isolates, and ERIC‐PCR and REP‐PCR were unable to discriminate among the isolates. PFGE typing detected three different genetic patterns between the 21 strains evaluated; thus, it was the best genotyping method for use with this pathogen. The strains from Ceará State were genetically divergent from those from Alagoas State. The S. dysgalactiae isolates analysed in this study constituted a genetically diverse population with a clear association between geographical origin and genotype.  相似文献   

15.
The present study investigated the effects of argan oil, obtained from Argania spinosa, on pre‐ and post‐challenge immuno‐haematological and biochemical responses of Nile tilapia, Oreochromis niloticus. For this purpose, the fish were fed diets containing 0, 0.5%, 1% or 2% argan oil for 45 days. Following 45 days of feeding, fish were challenged with Lactococcus garvieae and mortality was recorded for 15 days. During the pre‐challenge period, significantly higher respiratory burst activity, total white blood cell (WBC), serum lysozyme activity and myeloperoxidase activity were determined in the argan oil‐fed groups. The serum glucose and cholesterol levels decreased whilst total protein and albumin did not change in the groups fed with argan oil‐supplemented diets. After challenge with Lactococcus garvieae, the percentage survival (%) was found to be the highest in the 1% and 2% argan oil‐supplemented feeding groups. Also, there was a significant increase in weight gain, specific growth rate and feed conversion ratio in those fish fed argan oil. The results of this study indicated that after the supplementation of fish diets with argan oil, especially at 1% and 2% concentrations, the immunological, haematological and biochemical values remained similar in both the pre‐ and post‐challenge periods and the immune response against L. garvieae in Nile tilapia was modulated.  相似文献   

16.
Edwardsiella ictaluri infects several fish species and protection of the all the susceptible fish hosts from the pathogen using a monovalent vaccine is impossible because the species is composed of host-based genotypes that are genetic, serological and antigenic heterogenous. Here, immunoinformatic approach was employed to design a cross-immunogenic chimeric EiCh protein containing multi-epitopes. The chimeric EiCh protein is composed of 11 B-cell epitopes and 7 major histocompatibility complex class II epitopes identified from E. ictaluri immunogenic proteins previously reported. The 49.32 kDa recombinant EiCh protein was expressed in vitro in Escherichia coli BL-21 (DE3) after which inclusion bodies were successfully solubilized and refolded. Ab initio protein modelling revealed secondary and tertiary structures. Secondary structure was confirmed by circular dichroism spectroscopy. Antigenicity of the chimeric EiCh protein was exhibited by strong reactivity with serum from striped catfish and Nile tilapia experimentally infected with E. ictaluri. Furthermore, immunogenicity of the chimeric EiCh protein was investigated in vivo in Nile tilapia juveniles and it was found that the protein could strongly induce production of specific antibodies conferring agglutination activity and partially protected Nile tilapia juveniles with a relative survival percentage (RPS) of 42%. This study explored immunoinformatics as reverse vaccinology approach in vaccine design for aquaculture to manage E. ictaluri infections.  相似文献   

17.
Nile tilapia juveniles (8.35 ± 0.80 g) were fed on four levels (0.0%; 0.5%; 1.0%; 2.0%, 4.0%) of Aurantiochytrium sp. meal (ALL‐G‐RICH?), a source of docosahexaenoic acid (DHA). The 1% Aurantiochytrium sp. meal diet was compared to a control diet, which contained the same amount of DHA as cod liver oil (CLO) at 1.7% diet. Groups of 25 fish were stocked in 100 L tanks and fed twice daily until apparent satiation, for 57 days, at 28°C. Increasing dietary Aurantiochytrium sp. meal reduced the body retention of DHA and n‐3 polyunsaturated fatty acids (n‐3 PUFA) but increased the body retention of alpha‐linolenic (α‐LNA), linoleic (LOA) and n‐6 polyunsaturated fatty acids (n‐6 PUFA). Fatty acid profile in tilapia muscle was affected by increasing dietary inclusions of Aurantiochytrium sp. meal, with an increase in DHA, α‐LNA, n‐3 PUFA and n‐3 long chain‐polyunsaturated fatty acids (n‐3 LC‐PUFA) but a decrease in monounsaturated fatty acids (MUFA), n‐6 PUFA and n‐6 long‐chain polyunsaturated fatty acids (n‐6 LC‐PUFA). There was a larger body retention of DHA, α‐LNA, LOA, n‐3 PUFA and n‐6 PUFA fatty acids and a higher percentage of DHA, n‐3 PUFA and n‐3 LC‐PUFA in muscle fatty acid profile in fish fed on CLO diets than in those fed on 1% Aurantiochytrium sp. Therefore, Aurantiochytrium sp. meal is an alternative source of DHA for Nile tilapia diets.  相似文献   

18.
A disease with white spots in internal organs of Nile tilapia occurred in Zhanjiang, southern China. Multiple, white nodules, 0.8–2.2 mm in diameter, were scattered throughout the liver, spleen and kidney of diseased fish. Signs of nodules reproduced after artificial infection with the isolated strain. Isolated bacteria were Gram‐negative, facultative anaerobic, motile, short rod‐shaped, with a length of 1.2–2.2 μm. Morphological and biochemical tests, as well as phylogenetic analysis, all strongly indicated that the isolate from tilapia is identical to Aeromonas schubertii (A. schubertii) which temporary named LF1708 strain. Antibiotic sensitivity assays showed the LF1708 is sensitive to 24 of 27 tested antibiotics. Pathogenicity test revealed that the isolate at the dose of 3.75 × 106 CFU/g killed 100% of experimental tilapia within 2 days and the dose of 1 × 107 CFU/g killed 100% of experimental zebrafish within 1 day. Histopathology of diseased tilapia infected with A. schubertii showed numerous necrotic lesions widely distributed in spleen, liver and kidney, and infiltration with a large number of bacteria. To our knowledge, this was the first report that associated A. schubertii with mortality in tilapia.  相似文献   

19.
Aeromonas hydrophila and Gyrodactylus cichlidarum are common pathogens that induce significant economic losses in farm‐reared Nile tilapia. Nowadays, the sudden appearance of fish mortalities was exaggerated due to mixed and multiple infections. During summer 2016, mass mortality among earthen pond‐farmed Nile tilapia was reported. Clinico‐pathological, bacteriological and parasitological examinations have been demonstrated. As well, the water quality parameters were assessed. The clinical and histopathological findings of the moribund and recently dead fish were characterized by generalized septicaemic signs. The water quality parameters were significantly elevated over the permissible levels, whereas there was an elevation in nitrite (0.04 mg/L), un‐ionized ammonia (0.8 mg/L), hydrogen sulphide levels (153.1 mg/L) and organic matter content (3.79 mg/L). A. hydrophila was identified based on phenotypic characterization, API 20E features and the homology of 16S rRNA gene sequence analysis. In addition, PCR data confirmed the presence of aerolysin (aerA) and haemolysin (hly) genes in the identified A. hydrophila isolates. Gene sequencing and phylogenetic analysis based on 16S rRNA sequence confirmed that A. hydrophila H/A (accession No. MN726928) of the present study displayed 98%–99% identity with the 16S rRNA gene of A. hydrophila. Furthermore, the monogenetic trematode, G. cichlidarum was identified in the wet mounts from the skin and gills of the examined fish with a high infestation rate. In this context, it was reported that the synergistic co‐infection of A. hydrophila and G. cichlidarum with deteriorated water quality parameters could induce exaggerated fish mortalities during hot weather.  相似文献   

20.
The bee pollen is considered an excellent source of flavonoids, carotenoids, phenolic compounds, sterols and minerals; and possesses the ability to boost the immune system, antioxidant action and other interesting therapeutic effects. This study was carried out aiming to evaluate the inclusion of bee pollen in extruded commercial diets of Nile tilapia fingerlings and its effects on the hepatic‐intestinal histomorphometry and zootechnical performance. A total of 225 tilapia fingerlings (1.25 ± 0.05 g) were distributed in a completely randomized design in 15 tanks (30 L) maintained in a recirculation water system with three treatments (0% or control, 1.5% and 2.5% of bee pollen inclusion) and five replicates. Feeding rates were defined from the weekly biometrics and periodic monitoring of the physical–chemical water quality parameters. The water quality variables remained within the appropriate range for the species throughout the experiment. There was no significant difference for the somatic indexes and zootechnical parameters in this experiment. However, the inclusion of bee pollen in Nile tilapia fingerlings diets showed a linear increase in hepatocyte morphology (p = .0098). For the intestinal variables of villus height a significant linear increase was observed (p < .05) as the pollen inclusion increased. In fish that received 2.5%, the number of goblet cells was significantly higher (p < .001) than control group and 1.5%. In this sense, the inclusion up to 2.5% bee pollen in extruded commercial diets of Nile tilapia fingerlings had a positive impact on hepato‐intestinal histomorphometry without causing negative effects on the zootechnical performance.  相似文献   

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