In this study,we aimed to isolate potential Bacillus strains from the digestive tract of Nile tilapia(Oreochromis niloticus).Through morphological,biochemical,16S rDNA sequencing,and evolutionary relationship assessme...In this study,we aimed to isolate potential Bacillus strains from the digestive tract of Nile tilapia(Oreochromis niloticus).Through morphological,biochemical,16S rDNA sequencing,and evolutionary relationship assessments,we identified the isolated species as Bacillus amyloliquefaciens AV5(OR647358),Bacillus subtilis AV7(LC781790),and Bacillus velezensis AV50(OR647359),designated as AV5,AV7,and AV50 strains,respectively.We evaluated their probiotic potential,including tolerance to high bile salt concentrations,low pH levels,and high temperatures,as well as their adhesion abilities(auto-aggregation and cell-surface hydrophobicity),antimicrobial activity,biosafety,compatibility,hemolytic activity,and antibiotic susceptibility.AV5,AV7,and AV50 strains exhibitedγ-hemolytic activity and resistance to low pH(1)and high bile salt concentrations(0.5%).They demonstrated higher viability after exposure to elevated temperatures(80℃,90℃,and 100℃)and increased cell surface hydrophobicity and autoaggregation.These strains showed positive compatibility,indicating their potential for multispecies use.Strains were susceptible to 17 out of 20 tested antibiotics,and displayed significant antimicrobial activity against Vibrio alginolyticus,Vibrio harveyi,Streptococcus iniae,and Streptococcus agalactiae.Therefore,AV5,AV7,and AV50 are promising probiotic candidates for enhancing the growth and health of aquatic animals,particularly in Nile tilapia(O.niloticus).展开更多
Background Saline-alkaline water aquaculture has become a key way to mitigate the reduction of freshwater aquaculture space and meet the increasing global demand for aquatic products.To enhance the comprehensive utili...Background Saline-alkaline water aquaculture has become a key way to mitigate the reduction of freshwater aquaculture space and meet the increasing global demand for aquatic products.To enhance the comprehensive utilization capability of saline-alkaline water,it is necessary to understand the regulatory mechanisms of aquatic animals coping with saline-alkaline water.In this study,our objective was to elucidate the function of proline metabolism in the alkaline adaptation of Nile tilapia(Oreochromis niloticus).Results Expose Nile tilapia to alkaline water of different alkalinity for 2 weeks to observe changes in its growth performance and proline metabolism.Meanwhile,to further clarify the role of proline metabolism,RNA interference experiments were conducted to disrupt the normal operation of proline metabolic axis by knocking down pycr(pyrroline-5-carboxylate reductases),the final rate-limiting enzyme in proline synthesis.The results showed that both the synthesis and degradation of proline were enhanced under carbonate alkalinity stress,and the environmental alkalinity impaired the growth performance of tilapia,and the higher the alkalinity,the greater the impairment.Moreover,environmental alkalinity caused oxidative stress in tilapia,enhanced ion transport,ammonia metabolism,and altered the intensity and form of energy metabolism in tilapia.When the expression level of the pycr gene decreased,the proline metabolism could not operate normally,and the ion transport,antioxidant defense system,and energy metabolism were severely damaged,ultimately leading to liver damage and a decreased survival rate of tilapia under alkalinity stress.Conclusions The results indicated that proline metabolism plays an important role in the alkaline adaptation of Nile tilapia and is a key regulatory process in various biochemical and physiological processes.展开更多
This study was carried out to evaluate the response of Nile tilapia(Oreochromis niloticus)fingerlings to acute copper sulphate and ferrocene toxicity.Nile tilapia fingerlings weighing 2.3±0.2 g were acclimated an...This study was carried out to evaluate the response of Nile tilapia(Oreochromis niloticus)fingerlings to acute copper sulphate and ferrocene toxicity.Nile tilapia fingerlings weighing 2.3±0.2 g were acclimated and randomly distributed at a rate of 10 fish per 30 L aquarium.Fish were exposed to a range of copper sulphate and ferrocene concentrations of 4 mg/L,8 mg/L,12 mg/L,16 mg/L and 2.5 mg/L,5 mg/L,7.5 mg/L,10 mg/L respectively.Fish not exposed to any toxicant served as control.Mortality was assessed and median lethal concentration(LC50)and median lethal time(LT50)were calculated.The 96-h LC50 values obtained for copper sulphate and ferrocene were 7.49 mg/L(confidence interval CI:6.35 to 8.57 mg/L)and 3.55 mg/L(CI:0.98 to 5.17 mg/L)respectively.The LC50 decreased with time of exposure implying that toxicity increased over time,however,LT50 decreased as concentration increased.The safe concentration for copper sulphate derived was 1.913 mg/L and 1.196 mg/L for ferrocene.Histological analyses were carried out on fish gills and skin.The skin histomorphology showed marked and widespread epidermal loss and widespread mycocytic degeneration in treatments with high concentration for both toxicants.The gill morphology showed moderate to severe hyperplasia of the primary gill epithelia leading to partial or complete loss of the secondary lamellae.展开更多
Assessment of population parameters and genetic diversity is critical for the economic and threatened species,including Oreochromis mossambicus.The morphometric and population parameters data for O.mossambicus were ex...Assessment of population parameters and genetic diversity is critical for the economic and threatened species,including Oreochromis mossambicus.The morphometric and population parameters data for O.mossambicus were extracted based on the available literature from various countries.Phylogenetic and genetic diversity were analyzed based on cytochrome c oxidaseⅠ(COⅠ)sequences of the mitochondrial DNA(mtDNA)gene.The population parameters(asymptotic length(L_(∞)),growth constant(K),growth performance index(Ø),approximate maximum age(t_(max)),standard length(L),and weight(W))results revealed a variation among the populations studied.The result categorized the population into two groups:South African populations located close to Zimbabwe,Mozambique,Namibia,Australia,and China,as GroupⅠ,and the Indian population placed close to Thailand,the Philippines,Indonesia,America,and Mexico as GroupⅡ.The meta-regression results reveal that temperature strongly correlated with weight.In contrast,other population factors showed no significant differences.The haplotype analysis based on COI of mtDNA displayed 21 haplotypes,which revealed low nucleotide(π=0.025)diversity.Haplotype diversity(HD)was 0.65.The haplotype analysis showed that Tajima(D)was negative(-0.82)and Fu’s Fs was positive(2.2),and both tests were not significant(P>0.05),whereas the overall F-statistic(F_(st))value was 0.40(P<0.001).In conclusion,population parameters,and genetic analysis indices a high variation among the O.mossambicus from different locations.Additionally,the population parameters for O.mossambicus in America,Asia,and Australia were more influenced by ecological factors.At the same time,the population parameters in the African continent were influenced more by genetic factors.展开更多
Successful crossbreeding between Oreochromis niloticus and Sarotherodon melanotheron to produce a commercial hybrid has been difficult.The karyotypes and isoenzyme of these two species and their reciprocal hybrids（O....Successful crossbreeding between Oreochromis niloticus and Sarotherodon melanotheron to produce a commercial hybrid has been difficult.The karyotypes and isoenzyme of these two species and their reciprocal hybrids（O.niloticus ♀ × S.melanotheron ♂,S.melanotheron ♀ × O.niloticus ♂,the last not included in the isoenzyme study） were investigated via metaphase chromosomes obtained from head kidney cells and electropherogram of lactate dehydrogenase（LDH） isoenzymes from the liver,kidney,white muscle,heart,and eye balls.The diploid chromosome number（2n=44） and the fundamental number（NF=50） of the four tilapia genotypes were the same.However,the karyotype of O.niloticus had three pairs of sub-metacentric（sm）,twelve pairs of sub-telocentric（st）,and seven pairs of telocentric（t） chromosomes,while S.melanotheron had one pair of metacentric（m）,two pairs of sm,12 pairs of st,and seven pairs of t chromosomes.The reciprocal hybrids both showed a mixed karyotype range between their parents：0.5 pair of m,2.5 pairs of sm,12 pairs of st,and seven pairs of t chromosomes.In view of the electropherogram of isozymes,only the LDH of the kidney showed significant clear bands,with five bands in O.niloticus,three bands in S.melanotheron,and duplicated six bands in the hybrids.The bands varied depending on their activities and mobilities.We considered that the differences in karyotype and isoenzyme were related to the genetic mechanism for post-mating isolation,and provided some additional basic genetic background of their taxonomy.展开更多
[Objective] The research aimed to predict the B cell epitope of DMRT protein in Oreochromis niloticus. [Method] The secondary structure of amino acid sequence of DMRT protein was revealed by Garnier-Robson, Chou-Fasma...[Objective] The research aimed to predict the B cell epitope of DMRT protein in Oreochromis niloticus. [Method] The secondary structure of amino acid sequence of DMRT protein was revealed by Garnier-Robson, Chou-Fasman and Karplus-Schulz methods. The hydrophilicity plot, surface probability and antigenic index were obtained by Kyte-Doolittle, Emini and Jameson-Wolf methods, respectively. Based on the above results, the B cell epitopes for DMRT were predicted. [Result] Both the prediction results from Garnier-Robson, Chou-Fasman methods indicated that the α-helix centers of DMRT protein in O. niloticus were in the N terminal No. 31-56, 68-75, 110-116, 209-211 and 239-243; the β-sheet centers of DMRT protein in O. niloticus were in the N terminal No. 95-99, 177-183, 225-234 and 251-254. With the assistant of Kyte-Doolittle, Emini and Jameson-Wolf methods, the B cell epitopes for DMRT were located in or nearby the N terminal No. 13-16, 35-38, 47-54,84-93, 101-109, 127-156, 166-177 and 198-201. [Conclusion] These results are helpful for preparing the antibody of DMRT protein and revealing the sex determination mechanism of O. niloticus.展开更多
为比较星洲红鱼(Singapore red tilapia)和奥尼罗非鱼(Oreochromis niloticus)的生长和肌肉营养特性,实验利用两种鱼的不同体色将其混养在同一池塘中,在相同的环境条件和养殖管理下研究其生长特性,并分析肌肉营养成分。结果表明:两种罗...为比较星洲红鱼(Singapore red tilapia)和奥尼罗非鱼(Oreochromis niloticus)的生长和肌肉营养特性,实验利用两种鱼的不同体色将其混养在同一池塘中,在相同的环境条件和养殖管理下研究其生长特性,并分析肌肉营养成分。结果表明:两种罗非鱼生长在前60 d无差异,60 d后星洲红鱼的体长、体质量日增长和特定生长率均大于奥尼罗非鱼,且差异显著(P<0.05)。据此得到了星洲红鱼和奥尼罗非鱼的体长(L)、体质量(W)生长与养殖天数(d)的回归方程。星洲红鱼含肉率高于奥尼罗非鱼9.65%(P<0.05),肌肉水分高于奥尼罗非鱼,蛋白质、粗脂肪和灰分含量均低于奥尼罗非鱼,其中脂肪含量差异显著(P<0.05),其他不显著。两种罗非鱼肌肉的氨基酸组成全面,氨基酸组成均符合FAO/WHO的理想模式,除精氨酸含量有差异外,其他氨基酸含量稍有差异但不显著。星洲红鱼和奥尼罗非鱼肌肉EAA/TAA、EAA/NEAA、DAA/TAA和EAAI分别为41.04%和40.95%,70.00%和69.34%,40.71%和39.08%,67.46%和67.08%,差异不显著。星洲红鱼、奥尼罗非鱼肌肉∑SFA和∑UFA分别为28.03%和28.60%,63.87%和61.38%,各脂肪酸含量除C14:0和C18:2外,其他含量差异不显著。研究表明,星洲红鱼和奥尼罗非鱼生长快、营养丰富、食用价值高,是优质淡水鱼类养殖品种,其中星洲红鱼含肉率高,生长快,养殖效益明显。展开更多
To evaluate the potential environmental effects of engineered nano metals,it is important to determine the adverse effects of various nanomaterials on aquatic species.Adult tilapia （Oreochromis mossambicus） were mai...To evaluate the potential environmental effects of engineered nano metals,it is important to determine the adverse effects of various nanomaterials on aquatic species.Adult tilapia （Oreochromis mossambicus） were maintained in 10 L glass aquaria,and exposed to a graded series of synthesized silver nanoparticles （Ag-NPs） at 25,50 and 75 mg/L for eight days.The LC 50 value was 12.6 mg/L.Reduced activities of antioxidant enzymes and the contents of antioxidants were lowered in the gills and liver of fishes treated with AgNPs,which resulted in heavy accumulation of free radicals.Histopathological results imply that the balance between the oxidative and antioxidant system in the fish was broken down during Ag-NPs exposure.The principal concern related with the release of nanomaterials and their smaller particle may change the materials transport and potential toxicity to aquatic organisms compared to larger particles.展开更多
Shelf-life extension of aquatic products is of significant economical importance. To determine the potential effect of chitosan on the shelf-life of filleted tilapia, this study analyzed the bacterial community divers...Shelf-life extension of aquatic products is of significant economical importance. To determine the potential effect of chitosan on the shelf-life of filleted tilapia, this study analyzed the bacterial community diversity in fresh and spoiled tilapia fillets stored at (4 ± 1)℃ and examined the antimicrobial activity of chitosan against relevant bacteria isolates. Results showed that Pseudomonas (20%) and Aeromonas (16%) were abundant in fresh tilapia fillets, whereas Pseudomonas (52%), Aeromonas (32%) and Staphylococcus (12%) were dominant in the spoiled samples. Chitosan showed wide-spectrum antibacterial activity against bacteria isolated from tilapia and 5.0 g L-1 chitosan was selected for application in preservation. We further determined the shelf-life of chitosan-treated, filleted tilapia stored at (4 ± 1)℃ based on microbiological, biochemical and sensory analyses. Results showed that the shelf-life of chitosan-treated, filleted tilapia was extended to 12 d, whereas that of untreated, control samples was 6 d. These indicate that chitosan, as a natural preservative, has great application potential in the shelf-life extension of tilapia fillets.展开更多
In this study, the antibacterial effects of Chinese herbal medicines against Streptococcus iniae in Oreochromis niloticus were investigated by drug sensitiv- ity test. The results indicated that Streptococcus in/ae wa...In this study, the antibacterial effects of Chinese herbal medicines against Streptococcus iniae in Oreochromis niloticus were investigated by drug sensitiv- ity test. The results indicated that Streptococcus in/ae was extremely sensitive to Calla Chinensis, Fructus Hippophae and Fructus Murne, highly sensitive to Sappan Lignum, Pericarpium Granati, Folium Eucalypti and Radix Scutellariae, moderately sensitive to Rh/zoma Coptidis, Radix et Rhizoma Rhei, Flos Caryophyllata, Cortex phellodendri and Rabdosia serra （ Maxim. ） Hara, and insensitive to Herba Portulacae , Herba Houttuyniae , Polygonum hydropiper L. , Herba Menthae , Radix Glycyrrhizae , Pericarpium Citri Reticulatae , Herba Andrographitis and Rhizoma Acori Tatarinowii. Chinese medicinal herbs which Streptococcus iniae was extremely sensitive or moderately sensitive to were selected and prepared into three Chinese herbal medicine formulae for medicated bath of Oreochromis niloticus infected arti- ficially with Streptococcus iniae. The results showed that medicated bath elicited therapeutic effects on infected Oreochromis niloticus. Formula II exhibited the best therapeutic effect with an effective percentage of 90%.展开更多
The effects of phenanthrene（Phe） on hepatosomatic index（HSI） and hepatic enzymatic activities in hybrid tilapia（Oreochromis niloticus ♀× O.aureus ♂） were investigated via the static freshwater exposure at...The effects of phenanthrene（Phe） on hepatosomatic index（HSI） and hepatic enzymatic activities in hybrid tilapia（Oreochromis niloticus ♀× O.aureus ♂） were investigated via the static freshwater exposure at dosage of 50,100,and 400 μg/L for 4-14 d.Compared with the control group,HSI was significantly decreased（P 〈 0.05） at 400 μg/L at day 14.Increased enzymatic activities（P 〈 0.05） were observed for catalase（CAT）,glutathione peroxidase（GPx） and superoxide dismutase（SOD） at either 100 or 400 μg/L at day 8 and 14,as well as for CAT at 50 μg/L at day 14,except for GPx at 400 μg/L at day 8.Ethoxyresorufin O-deethylase（EROD） activity was significantly increased（P 〈 0.05） at all dosage at day 4 as well as at 50 μg/L at day 8,but significantly decreased at either 100 or 400 μg/L at day 14（P 〈 0.05）.Glutathione-S-transferase（GST） activity was not affected.The results suggest that CAT,GPx,SOD and EROD,as well as HSI in tilapia may be used as the biomarkers or indexes for evaluating or monitoring the pollution of polycyclic aromatic hydrocarbons（PAHs） such as Phe.展开更多
The efficacy of Endocrine Disrupting Compounds (EDCs), 17β-estradiol was tested on the fish Oreochromis niloticus in order to understand the intersex relationship of fish, in which sequential hermaphrodism can consis...The efficacy of Endocrine Disrupting Compounds (EDCs), 17β-estradiol was tested on the fish Oreochromis niloticus in order to understand the intersex relationship of fish, in which sequential hermaphrodism can consist of a male changing into a female (protandry) or a female changing into a male (protogyny). The fish were equally divided into 3 groups. The first group was the control group;the second and third groups were treated with 10 and 100 mg L-1 of 17β-estradiol, respectively, for 30 days. The overall result in this experiment had no significant effect on the growth parameters. Among the two treated groups, the low concentration group shows results similar to those of the control groups. The high concentration group shows changes to the male reproductive system with the appearance of the testis-ova present resulting in an intersex condition of the male gonads. With this experiment, it can be concluded that 17β-estradiol at high concentration reveals positive changes towards the male reproductive system of the fish, Oreochromis niloticus.展开更多
In this study,chondroitin sulfate was extracted from Oreochromis niloticus bones(OCS)and isolated to three fractions(OCS-1,OCS-2,and OCS-3).The physicochemical properties and structure characterization including monos...In this study,chondroitin sulfate was extracted from Oreochromis niloticus bones(OCS)and isolated to three fractions(OCS-1,OCS-2,and OCS-3).The physicochemical properties and structure characterization including monosaccharide,disaccharide compositions,molecular weight(Mw)of OCS were determined by HPAEC,HPLC-SAX,HPGPC,FT-IR spectra,and 1D/2D NMR.Moreover,their thermal properties,crystalline structure,and microstructure were also analyzed.Results showed that their Mw were between 10 kDa and 50 kDa.CS-6 was the predominant disaccharide unit in four OCS,and the CS-4/CS-6 ratios were close to CS from shark cartilage.Besides,the results of antioxidant activity showed that different fractions of OCS had a distinct DPPH radical,hydroxyl radical,and ABTS+radical scavenging activity.OCS-1 has the highest scavenging activities in DPPH and hydroxyl radical compared with other fractions,which showed a higher medicinal value.Those findings may lay some theoretical basis for the potential application development of OCS.展开更多
This study aimed to investigate the effects of copper and manganese on hemocyte apoptosis and the antagonism of iron and zinc in Oreochromis niloticus The heavy metal contents in fish blood and feed were determined by...This study aimed to investigate the effects of copper and manganese on hemocyte apoptosis and the antagonism of iron and zinc in Oreochromis niloticus The heavy metal contents in fish blood and feed were determined by atomic absorption spectrophotometry, and the hemocyte apoptosis was determined by flow cytometry. A total of 360 tilapias were selected, and they were divided randomly and evenly into 12 groups. In the challenge groups, the tilapias were fed with con stant-level copper sulfate（0, 200 mg/kg） and manganese sulfate（0, 120 mg/kg）; in the antagonism groups, the tilapias were fed with constant-level zinc sulfate（20320 mg/kg） and iron sulfate（150, 350 mg/kg）. After 20-week aquaculture, the hemocyte apoptosis rates in the copper and manganese groups were significantly increased; with the increased addition levels of iron and zinc, the hemocyte apopto sis rates in the iron and zinc groups were significantly reduced, but they were stil higher than that in the control group. In conclusion, excessive copper and manganese can cause apoptosis in hemocytes of O. niloticus. However, the toxic effects of copper and manganese can be antagonized by iron and zinc.展开更多
Acetylcholinesterase （ACHE） plays an important role in enzyme-based detection of pesticides in the environment. In this paper, ACHE from the Triton X-100 extract of brain tissues of Oreochromis aurea was purified by...Acetylcholinesterase （ACHE） plays an important role in enzyme-based detection of pesticides in the environment. In this paper, ACHE from the Triton X-100 extract of brain tissues of Oreochromis aurea was purified by （NH4）2SO4 fractional precipitation, Sephadex G-100 gel filtration, and DEAE-cellulose ion exchange chromatography. Certain biochemical characterizations of the purified enzyme and inhibition of pesticides on the enzyme were also studied. The specific activity of this purified enzyme was 20.628 U/mg protein, fold of purification was 139, and recovery was 22.1%. The optimal temperature of this enzyme was between 35-40 ℃, and optimal pH was between 7.5-8.0. The Michaelis constant （Kin） for acetylthiocholine iodide was 0.183 mmol/L. The enzyme activity was inhibited by excess substrate, and optimal substrate concentration was 6 mmol/L. Four pesticides （dichlorvos, phoxim, triazophos, and methomyl） exhibited strong inhibitions on this enzyme with IC50 less than 5 μg/mL. This study suggests that Oreochromis aurea （tilapia） could be a good enzyme source for pesticide monitoring in water environments.展开更多
The juveniles of hybrid tilapia （ Oreochromis niloticus x Oreochromis areus） were exposed to ananonia-nitrogen （N） （0, 2.5, 5, 10 and 20 mg/L） for 0, 12, 24, 48 and 72 h to evaluate the effect of ammonia-N stres...The juveniles of hybrid tilapia （ Oreochromis niloticus x Oreochromis areus） were exposed to ananonia-nitrogen （N） （0, 2.5, 5, 10 and 20 mg/L） for 0, 12, 24, 48 and 72 h to evaluate the effect of ammonia-N stress on their non-specific immunity. Results show that the activity of serum lysozyme decreased signifi- candy with extension of stress time （P 〈 0.05）. The total antioxidant capacity （T-AOC） and activity of antioxidase in liver were significantly affected. The activi- ty of T-AOC and total superoxide dismutase （T-SOD） of fish exposed to ammonia-N were initially decreasing then increasing （ P 〈 0.05 ）. Activities of catalase （CAT） and glutathione peroxidase （GSH-Px） were correlated with concentrations of ammonia-N. Fish exposed to lower concentrations （2.5 mg/L or 5 mg/L） showed decreased CAT activity within 24 h （P 〈 0.05 ）, while those exposed to higher concentrations （10 mg/L or 20 mg/L） initially showed increased then decreased activity of CAT. Except for the highest concentration groups, fish exposed to ammonia-N showed inductive activity of GSH-Px （ P 〈 0.05 ）. Under the ex- perimental conditions, non-specific immunity of tilapia was affected by ammonia-N stress, and the impact was increased with increased concentration and extension of time.展开更多
Native polyacrylamide gel electrophoresis have been used to analyze malate dehydrogenase (MDH), acid phosphatase (Acph) and peroxidase (Px) isoenzymes in different tissues (liver, kidney, muscle and heart) of the tila...Native polyacrylamide gel electrophoresis have been used to analyze malate dehydrogenase (MDH), acid phosphatase (Acph) and peroxidase (Px) isoenzymes in different tissues (liver, kidney, muscle and heart) of the tilapia fish, Oreo- chromis niloticus in order to study the tissue specificity of these isoenzymes. Three, two and one fractions have been recorded respectively for the three isoenzymes in different studied tissues. The MDH-1 and MDH-2 have been ex- pressed only in muscle and heart while MDH-3 has been expressed in all studied tissues. The percentage amount of MDH in general varied significantly between muscle and different studied tissues. With respect to acid phosphatase, the percentage amount of the total enzyme showed significant difference between liver and muscle and that this variation may be due to higher gene activity in liver. Peroxidase isoenzyme was recorded in liver and heart only with significant increase in liver. The kidney was the least among the studied tissues in showing gene expression for the studied isoenzymes and therefore, liver, heart and muscle tissues are better applicable in studying the isoenzymatic profiles for fish physiology and systematics.展开更多
Nitrogen (N) and phosphorus (P) wastes produced by Nile tilapia Oreochromis niloticus L. fed Azolla, an aquatic atmospheric nitrogen fixing fern, was evaluated for 90 days in pond experiment. Six isonitrogenous (29.2%...Nitrogen (N) and phosphorus (P) wastes produced by Nile tilapia Oreochromis niloticus L. fed Azolla, an aquatic atmospheric nitrogen fixing fern, was evaluated for 90 days in pond experiment. Six isonitrogenous (29.2% crude protein) and isoenergetic (16.9 Kj·g–1) diets A0, A10, A20, A30, A40 and A50, containing 0%, 10%, 20%, 30%, 40% and 50% of Azolla meal (AM) respectively, as partial fishmeal (FM) substitutes, was provided to experimental fish. The Azolla-free diet A0 served as a control. Fish specific growth rate (SGR) was higher with the control diet, the lower values being obtained in A50-fed fish (P Azolla could be used in diet to sustain Nile tilapia growth and as “environmentally-friendly” ingredient to limit P loss, while providing N to the field, beneficially in tropical marshland pond where this nutrient is already limiting.展开更多
Since amateur fishing in fishponds has been on the increase in Brazil, there is a great concern on the microbiological quality of fish. One hundred and thirty-eight samples were collected during the dry and rainy peri...Since amateur fishing in fishponds has been on the increase in Brazil, there is a great concern on the microbiological quality of fish. One hundred and thirty-eight samples were collected during the dry and rainy periods in ten fish farms. Aeromonas spp. counts and tests for sensitiveness to antimicrobials were performed, coupled to the physical and chemical analyses of water. Tests revealed that 70% of samples were contaminated by Aeromonas spp., with water averaging 2.92 Log CFU/100 mL during the rainy period and 3.16 Log CFU/100 mL during the dry one. Fish contaminated by Aeromonas spp. averaged 2.58 Log CFU/100 mL during the rainy period and 3.53 Log CFU/100 mL during the dry one. Aeromonas spp. samples were multi-resistant to 2 or 8 antimicrobials in 62.5% of the samples. Ampicillin was the antimicrobial with the highest resistance percentage rate. Results showed that fish bred in amateur fish farms constituted a health risk for the population.展开更多
The distribution, abundance and intensity of the annelid worm, Piscicola geometra (leeches) infecting Oreochromis niloticus cultured in a rainforest fish pond, South Eastern Nigeria was studied over a 12 months...The distribution, abundance and intensity of the annelid worm, Piscicola geometra (leeches) infecting Oreochromis niloticus cultured in a rainforest fish pond, South Eastern Nigeria was studied over a 12 months period. Three hundred fish were examined of which 48.3% were infected. Infection occurred throughout the year, with a peak in February. Female fish had a significantly higher intensity of infection( P < 0.05) than males. There was a clear seasonal periodicity in the degree of infection and the distribution of the parasite exhibited an aggregated or contagious model of dispersion. There was a significant positive correlation between the size of the fish and worm burden.展开更多
基金The National Natural Science Foundation of China under contract Nos U20A2065,32073006,and 32002426the Natural Science Foundation of Guangxi under contract No.2020GXNSFAA297243+3 种基金the Natural Science Foundation of Guangdong Province under contract No.2021B0202040002the Science and Technology Plan of Guangdong Province under contract No.2023B0202010016the Youth Science and Technology Innovation Talent of Guangdong TeZhi Plan Talent under contract No.2023TQ07A888the Science and Technology Planning Project of Zhanjiang under contract Nos 2022A01012 and 2022A01006.
文摘In this study,we aimed to isolate potential Bacillus strains from the digestive tract of Nile tilapia(Oreochromis niloticus).Through morphological,biochemical,16S rDNA sequencing,and evolutionary relationship assessments,we identified the isolated species as Bacillus amyloliquefaciens AV5(OR647358),Bacillus subtilis AV7(LC781790),and Bacillus velezensis AV50(OR647359),designated as AV5,AV7,and AV50 strains,respectively.We evaluated their probiotic potential,including tolerance to high bile salt concentrations,low pH levels,and high temperatures,as well as their adhesion abilities(auto-aggregation and cell-surface hydrophobicity),antimicrobial activity,biosafety,compatibility,hemolytic activity,and antibiotic susceptibility.AV5,AV7,and AV50 strains exhibitedγ-hemolytic activity and resistance to low pH(1)and high bile salt concentrations(0.5%).They demonstrated higher viability after exposure to elevated temperatures(80℃,90℃,and 100℃)and increased cell surface hydrophobicity and autoaggregation.These strains showed positive compatibility,indicating their potential for multispecies use.Strains were susceptible to 17 out of 20 tested antibiotics,and displayed significant antimicrobial activity against Vibrio alginolyticus,Vibrio harveyi,Streptococcus iniae,and Streptococcus agalactiae.Therefore,AV5,AV7,and AV50 are promising probiotic candidates for enhancing the growth and health of aquatic animals,particularly in Nile tilapia(O.niloticus).
基金supported by grants from the National Natural Science Foundation of China(No.32172946)the Young Elite Scientists Sponsorship Program by CAST(2022QNRC001)+1 种基金the Shanghai Rising-Star Program(2022)the Fundamental Research Funds for the Central Universities,ECNU。
文摘Background Saline-alkaline water aquaculture has become a key way to mitigate the reduction of freshwater aquaculture space and meet the increasing global demand for aquatic products.To enhance the comprehensive utilization capability of saline-alkaline water,it is necessary to understand the regulatory mechanisms of aquatic animals coping with saline-alkaline water.In this study,our objective was to elucidate the function of proline metabolism in the alkaline adaptation of Nile tilapia(Oreochromis niloticus).Results Expose Nile tilapia to alkaline water of different alkalinity for 2 weeks to observe changes in its growth performance and proline metabolism.Meanwhile,to further clarify the role of proline metabolism,RNA interference experiments were conducted to disrupt the normal operation of proline metabolic axis by knocking down pycr(pyrroline-5-carboxylate reductases),the final rate-limiting enzyme in proline synthesis.The results showed that both the synthesis and degradation of proline were enhanced under carbonate alkalinity stress,and the environmental alkalinity impaired the growth performance of tilapia,and the higher the alkalinity,the greater the impairment.Moreover,environmental alkalinity caused oxidative stress in tilapia,enhanced ion transport,ammonia metabolism,and altered the intensity and form of energy metabolism in tilapia.When the expression level of the pycr gene decreased,the proline metabolism could not operate normally,and the ion transport,antioxidant defense system,and energy metabolism were severely damaged,ultimately leading to liver damage and a decreased survival rate of tilapia under alkalinity stress.Conclusions The results indicated that proline metabolism plays an important role in the alkaline adaptation of Nile tilapia and is a key regulatory process in various biochemical and physiological processes.
文摘This study was carried out to evaluate the response of Nile tilapia(Oreochromis niloticus)fingerlings to acute copper sulphate and ferrocene toxicity.Nile tilapia fingerlings weighing 2.3±0.2 g were acclimated and randomly distributed at a rate of 10 fish per 30 L aquarium.Fish were exposed to a range of copper sulphate and ferrocene concentrations of 4 mg/L,8 mg/L,12 mg/L,16 mg/L and 2.5 mg/L,5 mg/L,7.5 mg/L,10 mg/L respectively.Fish not exposed to any toxicant served as control.Mortality was assessed and median lethal concentration(LC50)and median lethal time(LT50)were calculated.The 96-h LC50 values obtained for copper sulphate and ferrocene were 7.49 mg/L(confidence interval CI:6.35 to 8.57 mg/L)and 3.55 mg/L(CI:0.98 to 5.17 mg/L)respectively.The LC50 decreased with time of exposure implying that toxicity increased over time,however,LT50 decreased as concentration increased.The safe concentration for copper sulphate derived was 1.913 mg/L and 1.196 mg/L for ferrocene.Histological analyses were carried out on fish gills and skin.The skin histomorphology showed marked and widespread epidermal loss and widespread mycocytic degeneration in treatments with high concentration for both toxicants.The gill morphology showed moderate to severe hyperplasia of the primary gill epithelia leading to partial or complete loss of the secondary lamellae.
文摘Assessment of population parameters and genetic diversity is critical for the economic and threatened species,including Oreochromis mossambicus.The morphometric and population parameters data for O.mossambicus were extracted based on the available literature from various countries.Phylogenetic and genetic diversity were analyzed based on cytochrome c oxidaseⅠ(COⅠ)sequences of the mitochondrial DNA(mtDNA)gene.The population parameters(asymptotic length(L_(∞)),growth constant(K),growth performance index(Ø),approximate maximum age(t_(max)),standard length(L),and weight(W))results revealed a variation among the populations studied.The result categorized the population into two groups:South African populations located close to Zimbabwe,Mozambique,Namibia,Australia,and China,as GroupⅠ,and the Indian population placed close to Thailand,the Philippines,Indonesia,America,and Mexico as GroupⅡ.The meta-regression results reveal that temperature strongly correlated with weight.In contrast,other population factors showed no significant differences.The haplotype analysis based on COI of mtDNA displayed 21 haplotypes,which revealed low nucleotide(π=0.025)diversity.Haplotype diversity(HD)was 0.65.The haplotype analysis showed that Tajima(D)was negative(-0.82)and Fu’s Fs was positive(2.2),and both tests were not significant(P>0.05),whereas the overall F-statistic(F_(st))value was 0.40(P<0.001).In conclusion,population parameters,and genetic analysis indices a high variation among the O.mossambicus from different locations.Additionally,the population parameters for O.mossambicus in America,Asia,and Australia were more influenced by ecological factors.At the same time,the population parameters in the African continent were influenced more by genetic factors.
文摘Successful crossbreeding between Oreochromis niloticus and Sarotherodon melanotheron to produce a commercial hybrid has been difficult.The karyotypes and isoenzyme of these two species and their reciprocal hybrids（O.niloticus ♀ × S.melanotheron ♂,S.melanotheron ♀ × O.niloticus ♂,the last not included in the isoenzyme study） were investigated via metaphase chromosomes obtained from head kidney cells and electropherogram of lactate dehydrogenase（LDH） isoenzymes from the liver,kidney,white muscle,heart,and eye balls.The diploid chromosome number（2n=44） and the fundamental number（NF=50） of the four tilapia genotypes were the same.However,the karyotype of O.niloticus had three pairs of sub-metacentric（sm）,twelve pairs of sub-telocentric（st）,and seven pairs of telocentric（t） chromosomes,while S.melanotheron had one pair of metacentric（m）,two pairs of sm,12 pairs of st,and seven pairs of t chromosomes.The reciprocal hybrids both showed a mixed karyotype range between their parents：0.5 pair of m,2.5 pairs of sm,12 pairs of st,and seven pairs of t chromosomes.In view of the electropherogram of isozymes,only the LDH of the kidney showed significant clear bands,with five bands in O.niloticus,three bands in S.melanotheron,and duplicated six bands in the hybrids.The bands varied depending on their activities and mobilities.We considered that the differences in karyotype and isoenzyme were related to the genetic mechanism for post-mating isolation,and provided some additional basic genetic background of their taxonomy.
文摘[Objective] The research aimed to predict the B cell epitope of DMRT protein in Oreochromis niloticus. [Method] The secondary structure of amino acid sequence of DMRT protein was revealed by Garnier-Robson, Chou-Fasman and Karplus-Schulz methods. The hydrophilicity plot, surface probability and antigenic index were obtained by Kyte-Doolittle, Emini and Jameson-Wolf methods, respectively. Based on the above results, the B cell epitopes for DMRT were predicted. [Result] Both the prediction results from Garnier-Robson, Chou-Fasman methods indicated that the α-helix centers of DMRT protein in O. niloticus were in the N terminal No. 31-56, 68-75, 110-116, 209-211 and 239-243; the β-sheet centers of DMRT protein in O. niloticus were in the N terminal No. 95-99, 177-183, 225-234 and 251-254. With the assistant of Kyte-Doolittle, Emini and Jameson-Wolf methods, the B cell epitopes for DMRT were located in or nearby the N terminal No. 13-16, 35-38, 47-54,84-93, 101-109, 127-156, 166-177 and 198-201. [Conclusion] These results are helpful for preparing the antibody of DMRT protein and revealing the sex determination mechanism of O. niloticus.
文摘To evaluate the potential environmental effects of engineered nano metals,it is important to determine the adverse effects of various nanomaterials on aquatic species.Adult tilapia （Oreochromis mossambicus） were maintained in 10 L glass aquaria,and exposed to a graded series of synthesized silver nanoparticles （Ag-NPs） at 25,50 and 75 mg/L for eight days.The LC 50 value was 12.6 mg/L.Reduced activities of antioxidant enzymes and the contents of antioxidants were lowered in the gills and liver of fishes treated with AgNPs,which resulted in heavy accumulation of free radicals.Histopathological results imply that the balance between the oxidative and antioxidant system in the fish was broken down during Ag-NPs exposure.The principal concern related with the release of nanomaterials and their smaller particle may change the materials transport and potential toxicity to aquatic organisms compared to larger particles.
基金supported by the Special Funds for the Basic Research and Development Program in the Central Non-profit Research Institutes of China (No.20603022011005)
文摘Shelf-life extension of aquatic products is of significant economical importance. To determine the potential effect of chitosan on the shelf-life of filleted tilapia, this study analyzed the bacterial community diversity in fresh and spoiled tilapia fillets stored at (4 ± 1)℃ and examined the antimicrobial activity of chitosan against relevant bacteria isolates. Results showed that Pseudomonas (20%) and Aeromonas (16%) were abundant in fresh tilapia fillets, whereas Pseudomonas (52%), Aeromonas (32%) and Staphylococcus (12%) were dominant in the spoiled samples. Chitosan showed wide-spectrum antibacterial activity against bacteria isolated from tilapia and 5.0 g L-1 chitosan was selected for application in preservation. We further determined the shelf-life of chitosan-treated, filleted tilapia stored at (4 ± 1)℃ based on microbiological, biochemical and sensory analyses. Results showed that the shelf-life of chitosan-treated, filleted tilapia was extended to 12 d, whereas that of untreated, control samples was 6 d. These indicate that chitosan, as a natural preservative, has great application potential in the shelf-life extension of tilapia fillets.
基金Supported by Post-award Grant Program from the Department of Science and Technology of Hebei Province(15926620H)Science and Technology Support Program of Qinhuangdao Municipal Science and Technology Bureau(201401A067201402B043)
文摘In this study, the antibacterial effects of Chinese herbal medicines against Streptococcus iniae in Oreochromis niloticus were investigated by drug sensitiv- ity test. The results indicated that Streptococcus in/ae was extremely sensitive to Calla Chinensis, Fructus Hippophae and Fructus Murne, highly sensitive to Sappan Lignum, Pericarpium Granati, Folium Eucalypti and Radix Scutellariae, moderately sensitive to Rh/zoma Coptidis, Radix et Rhizoma Rhei, Flos Caryophyllata, Cortex phellodendri and Rabdosia serra （ Maxim. ） Hara, and insensitive to Herba Portulacae , Herba Houttuyniae , Polygonum hydropiper L. , Herba Menthae , Radix Glycyrrhizae , Pericarpium Citri Reticulatae , Herba Andrographitis and Rhizoma Acori Tatarinowii. Chinese medicinal herbs which Streptococcus iniae was extremely sensitive or moderately sensitive to were selected and prepared into three Chinese herbal medicine formulae for medicated bath of Oreochromis niloticus infected arti- ficially with Streptococcus iniae. The results showed that medicated bath elicited therapeutic effects on infected Oreochromis niloticus. Formula II exhibited the best therapeutic effect with an effective percentage of 90%.
基金supported by the National Natural Science Foundation of China (No. 30570325,30671629)the Science and Technology Project of Guangdong Province (No.2005B20301013, 2006A36502004,2007B090400049)
文摘The effects of phenanthrene（Phe） on hepatosomatic index（HSI） and hepatic enzymatic activities in hybrid tilapia（Oreochromis niloticus ♀× O.aureus ♂） were investigated via the static freshwater exposure at dosage of 50,100,and 400 μg/L for 4-14 d.Compared with the control group,HSI was significantly decreased（P 〈 0.05） at 400 μg/L at day 14.Increased enzymatic activities（P 〈 0.05） were observed for catalase（CAT）,glutathione peroxidase（GPx） and superoxide dismutase（SOD） at either 100 or 400 μg/L at day 8 and 14,as well as for CAT at 50 μg/L at day 14,except for GPx at 400 μg/L at day 8.Ethoxyresorufin O-deethylase（EROD） activity was significantly increased（P 〈 0.05） at all dosage at day 4 as well as at 50 μg/L at day 8,but significantly decreased at either 100 or 400 μg/L at day 14（P 〈 0.05）.Glutathione-S-transferase（GST） activity was not affected.The results suggest that CAT,GPx,SOD and EROD,as well as HSI in tilapia may be used as the biomarkers or indexes for evaluating or monitoring the pollution of polycyclic aromatic hydrocarbons（PAHs） such as Phe.
文摘The efficacy of Endocrine Disrupting Compounds (EDCs), 17β-estradiol was tested on the fish Oreochromis niloticus in order to understand the intersex relationship of fish, in which sequential hermaphrodism can consist of a male changing into a female (protandry) or a female changing into a male (protogyny). The fish were equally divided into 3 groups. The first group was the control group;the second and third groups were treated with 10 and 100 mg L-1 of 17β-estradiol, respectively, for 30 days. The overall result in this experiment had no significant effect on the growth parameters. Among the two treated groups, the low concentration group shows results similar to those of the control groups. The high concentration group shows changes to the male reproductive system with the appearance of the testis-ova present resulting in an intersex condition of the male gonads. With this experiment, it can be concluded that 17β-estradiol at high concentration reveals positive changes towards the male reproductive system of the fish, Oreochromis niloticus.
基金The financially supported by the Program of The National Youth Talent Support Program of China.
文摘In this study,chondroitin sulfate was extracted from Oreochromis niloticus bones(OCS)and isolated to three fractions(OCS-1,OCS-2,and OCS-3).The physicochemical properties and structure characterization including monosaccharide,disaccharide compositions,molecular weight(Mw)of OCS were determined by HPAEC,HPLC-SAX,HPGPC,FT-IR spectra,and 1D/2D NMR.Moreover,their thermal properties,crystalline structure,and microstructure were also analyzed.Results showed that their Mw were between 10 kDa and 50 kDa.CS-6 was the predominant disaccharide unit in four OCS,and the CS-4/CS-6 ratios were close to CS from shark cartilage.Besides,the results of antioxidant activity showed that different fractions of OCS had a distinct DPPH radical,hydroxyl radical,and ABTS+radical scavenging activity.OCS-1 has the highest scavenging activities in DPPH and hydroxyl radical compared with other fractions,which showed a higher medicinal value.Those findings may lay some theoretical basis for the potential application development of OCS.
基金Supported by Scientific Operating Expenses of Hainan Province(11-201410-0009)~~
文摘This study aimed to investigate the effects of copper and manganese on hemocyte apoptosis and the antagonism of iron and zinc in Oreochromis niloticus The heavy metal contents in fish blood and feed were determined by atomic absorption spectrophotometry, and the hemocyte apoptosis was determined by flow cytometry. A total of 360 tilapias were selected, and they were divided randomly and evenly into 12 groups. In the challenge groups, the tilapias were fed with con stant-level copper sulfate（0, 200 mg/kg） and manganese sulfate（0, 120 mg/kg）; in the antagonism groups, the tilapias were fed with constant-level zinc sulfate（20320 mg/kg） and iron sulfate（150, 350 mg/kg）. After 20-week aquaculture, the hemocyte apoptosis rates in the copper and manganese groups were significantly increased; with the increased addition levels of iron and zinc, the hemocyte apopto sis rates in the iron and zinc groups were significantly reduced, but they were stil higher than that in the control group. In conclusion, excessive copper and manganese can cause apoptosis in hemocytes of O. niloticus. However, the toxic effects of copper and manganese can be antagonized by iron and zinc.
基金supported by Huizhou Science and Technology Planning Project Foundation (Grant No.2008P60)
文摘Acetylcholinesterase （ACHE） plays an important role in enzyme-based detection of pesticides in the environment. In this paper, ACHE from the Triton X-100 extract of brain tissues of Oreochromis aurea was purified by （NH4）2SO4 fractional precipitation, Sephadex G-100 gel filtration, and DEAE-cellulose ion exchange chromatography. Certain biochemical characterizations of the purified enzyme and inhibition of pesticides on the enzyme were also studied. The specific activity of this purified enzyme was 20.628 U/mg protein, fold of purification was 139, and recovery was 22.1%. The optimal temperature of this enzyme was between 35-40 ℃, and optimal pH was between 7.5-8.0. The Michaelis constant （Kin） for acetylthiocholine iodide was 0.183 mmol/L. The enzyme activity was inhibited by excess substrate, and optimal substrate concentration was 6 mmol/L. Four pesticides （dichlorvos, phoxim, triazophos, and methomyl） exhibited strong inhibitions on this enzyme with IC50 less than 5 μg/mL. This study suggests that Oreochromis aurea （tilapia） could be a good enzyme source for pesticide monitoring in water environments.
基金Supported by Guangdong Natural Science Foundation(S2013010013693,S2011010003451)Science and Technology Project of Guangdong Province(2013B020307016)Excellent Young Teachers Program of Guangdong(Yq2013152)
文摘The juveniles of hybrid tilapia （ Oreochromis niloticus x Oreochromis areus） were exposed to ananonia-nitrogen （N） （0, 2.5, 5, 10 and 20 mg/L） for 0, 12, 24, 48 and 72 h to evaluate the effect of ammonia-N stress on their non-specific immunity. Results show that the activity of serum lysozyme decreased signifi- candy with extension of stress time （P 〈 0.05）. The total antioxidant capacity （T-AOC） and activity of antioxidase in liver were significantly affected. The activi- ty of T-AOC and total superoxide dismutase （T-SOD） of fish exposed to ammonia-N were initially decreasing then increasing （ P 〈 0.05 ）. Activities of catalase （CAT） and glutathione peroxidase （GSH-Px） were correlated with concentrations of ammonia-N. Fish exposed to lower concentrations （2.5 mg/L or 5 mg/L） showed decreased CAT activity within 24 h （P 〈 0.05 ）, while those exposed to higher concentrations （10 mg/L or 20 mg/L） initially showed increased then decreased activity of CAT. Except for the highest concentration groups, fish exposed to ammonia-N showed inductive activity of GSH-Px （ P 〈 0.05 ）. Under the ex- perimental conditions, non-specific immunity of tilapia was affected by ammonia-N stress, and the impact was increased with increased concentration and extension of time.
文摘Native polyacrylamide gel electrophoresis have been used to analyze malate dehydrogenase (MDH), acid phosphatase (Acph) and peroxidase (Px) isoenzymes in different tissues (liver, kidney, muscle and heart) of the tilapia fish, Oreo- chromis niloticus in order to study the tissue specificity of these isoenzymes. Three, two and one fractions have been recorded respectively for the three isoenzymes in different studied tissues. The MDH-1 and MDH-2 have been ex- pressed only in muscle and heart while MDH-3 has been expressed in all studied tissues. The percentage amount of MDH in general varied significantly between muscle and different studied tissues. With respect to acid phosphatase, the percentage amount of the total enzyme showed significant difference between liver and muscle and that this variation may be due to higher gene activity in liver. Peroxidase isoenzyme was recorded in liver and heart only with significant increase in liver. The kidney was the least among the studied tissues in showing gene expression for the studied isoenzymes and therefore, liver, heart and muscle tissues are better applicable in studying the isoenzymatic profiles for fish physiology and systematics.
文摘Nitrogen (N) and phosphorus (P) wastes produced by Nile tilapia Oreochromis niloticus L. fed Azolla, an aquatic atmospheric nitrogen fixing fern, was evaluated for 90 days in pond experiment. Six isonitrogenous (29.2% crude protein) and isoenergetic (16.9 Kj·g–1) diets A0, A10, A20, A30, A40 and A50, containing 0%, 10%, 20%, 30%, 40% and 50% of Azolla meal (AM) respectively, as partial fishmeal (FM) substitutes, was provided to experimental fish. The Azolla-free diet A0 served as a control. Fish specific growth rate (SGR) was higher with the control diet, the lower values being obtained in A50-fed fish (P Azolla could be used in diet to sustain Nile tilapia growth and as “environmentally-friendly” ingredient to limit P loss, while providing N to the field, beneficially in tropical marshland pond where this nutrient is already limiting.
基金thank CAPES for the award of scholarship to the auhor
文摘Since amateur fishing in fishponds has been on the increase in Brazil, there is a great concern on the microbiological quality of fish. One hundred and thirty-eight samples were collected during the dry and rainy periods in ten fish farms. Aeromonas spp. counts and tests for sensitiveness to antimicrobials were performed, coupled to the physical and chemical analyses of water. Tests revealed that 70% of samples were contaminated by Aeromonas spp., with water averaging 2.92 Log CFU/100 mL during the rainy period and 3.16 Log CFU/100 mL during the dry one. Fish contaminated by Aeromonas spp. averaged 2.58 Log CFU/100 mL during the rainy period and 3.53 Log CFU/100 mL during the dry one. Aeromonas spp. samples were multi-resistant to 2 or 8 antimicrobials in 62.5% of the samples. Ampicillin was the antimicrobial with the highest resistance percentage rate. Results showed that fish bred in amateur fish farms constituted a health risk for the population.
文摘The distribution, abundance and intensity of the annelid worm, Piscicola geometra (leeches) infecting Oreochromis niloticus cultured in a rainforest fish pond, South Eastern Nigeria was studied over a 12 months period. Three hundred fish were examined of which 48.3% were infected. Infection occurred throughout the year, with a peak in February. Female fish had a significantly higher intensity of infection( P < 0.05) than males. There was a clear seasonal periodicity in the degree of infection and the distribution of the parasite exhibited an aggregated or contagious model of dispersion. There was a significant positive correlation between the size of the fish and worm burden.
