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ABSTRACT: The Japanese eel has dramatically declined in Asia since the 1970s. Over the past two decades, glass eel productivity in Taiwan
has decreased, but is highly variable among each year catch, though the cause for this is unknown. The impact of both population
decline and instability on genetic diversity, however, is unknown. In this study, we investigated changes in allele frequencies
of Japanese eel recruitment events over the past 20years using six polymorphic microsatellite DNA loci. Specimens of glass
eels were collected yearly from a single location in northern Taiwan from 1986 to 2007. Overall genetic differentiation among
all samples was very low but significant (F
ST=0.002, P=0.002), and only 2 out of 120 pairwise tests were significant. The relationship between genetic and temporal distance showed
a slight but insignificant correlation (R
2=0.03, P=0.0504). There were no overall significant differences in allelic richness (P=0.35) or genetic heterozygosity (P=0.73) among annual recruitment events. No apparent loss of genetic diversity and occurrence of a genetic bottleneck for
eel populations were observed. Estimates of the effective population size (N
e) generally exceeded 500, although confidence intervals were very wide. While El Niño /Southern Oscillation (ENSO) events
had little impact on genetic diversity, they may account for the annual fluctuation in glass eel catch. These results indicate
long-term stability of genetic diversity in the Japanese eel with little evidence for sweepstakes recruitment.
Marine Biology 01/2008; 155(6):613-621. · 2.28 Impact Factor
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ABSTRACT: We cloned the complementary deoxyribonucleic acid (cDNA) of the heat shock cognate 70 (hsc70) gene of tiger shrimp (Penaeus monodon). It was 2207 bp long and included a 1959-bp coding region, a 40-bp flanking region at the 5' end, and a 208-bp flanking region at the 3' end. The deduced, 652-amino acid sequence had a molecular mass of 71 481 Da and an estimated isoelectric point (pI) of 5.2. Based on phylogenetic analysis, the gene is clustered with the hsc70 proteins of invertebrates and vertebrates. In native gel electrophoresis, recombinant P. monodon hsc70 expressed in an Escherichia coli system is tightly associated with carboxymethylated alpha-lactalbumin (CMLA), which indicates that hsc70 probably functions as a chaperone. In an in vitro adenosine triphosphatase assay, recombinant hsc70 hydrolyzed adenosine triphosphate to adenosine-5'-diphosphate and increased hydrolysis activity by binding to unfolded peptide, CMLA. In situ hybridization using an antisense riboprobe revealed that the hsc70 gene was active in most tissues of unstressed shrimp. The expression of hsc70 messenger ribonucleic acid (mRNA) in hemocytes increased 2- to 3-fold at the first hour after shrimp experienced heat shock and 0.5-hour recovery. Hsc70 mRNA decreased gradually to the background level. Cloning and characterizing the P. monodon hsc70 gene is the first, crucial step in studying the relationship of heat shock proteins with the stress or immune responses of shrimp.
Cell Stress and Chaperones 02/2004; 9(4):332-43. · 3.01 Impact Factor
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ABSTRACT: To understand the changes of serum levels of sex steroids in the wild Japanese eel Anguilla japonica during silvering process, eels collected from the Kaoping River of Taiwan from August 2000 through June 2001 were examined. The maturational stages of female eels before and during silvering were divided into four stages: juvenile, sub-adult, pre-silver and silver stages based on skin coloration and oocyte diameter. Male eels were investigated only in the silver stage. Radioimmunoassays were employed to measure serum levels of estradiol-17beta (E(2)) and testosterone (T). The mean liver mass of the female eels increased significantly during silvering, but the mean hepatosomatic index remained constant. In contrast, mean ovarian mass and gonadosomatic index increased significantly during silvering. Serum concentrations of E(2) in females increased significantly during silvering (P<0.05), while E(2) was undetectable in silver males. The mean serum T concentrations increased significantly in females (P<0.05) during silvering, with lowest mean values in the juvenile stage and highest mean value in the silver stage. The mean serum T level in the silver males was significantly lower than in silver females (P<0.05). In conclusion, both serum E(2) and T concentrations increased with ovarian development of wild Japanese eels during silvering, while serum E(2) was undetectable in the silver male eels. The findings support the idea that androgen, but not estrogen, plays a major role in silvering process of the eels in both sexes.
Comparative Biochemistry and Physiology Part B Biochemistry and Molecular Biology 01/2004; 136(4):913-20. · 1.92 Impact Factor
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ABSTRACT: The effectiveness of dietary beta-1,3-glucan (BG), derived from Schizophyllum commune, in modulating the non-specific immunity of the grass prawn Penaeus monodon and its resistance to white spot syndrome virus (WSSV) were investigated. Juvenile P. monodon (6.5+/-0.4 g) were fed for 20 days on a series of test diets containing graded levels of BG (0, 1, 2, 10, 20 g kg(-1)diet) and were then challenged by injection of WSSV. The haemolymph total haemocyte count (THC), phagocytosis (PI), phenoloxidase (PO), superoxide anion (O(2)(-)) and superoxide dismutase (SOD) production were measured at days 0, 1, 3, 6, 9, 12 and 24 after challenge, and shrimp survival rate was also recorded. All the shrimps fed on diets containing BG no more than 1 g kg(-1)died by day 12. Conversely, the survival rate of shrimp fed with the diet containing 10 g kg(-1)BG was significantly higher (P<0.05) by day 9 than that of the other groups. When screened by the WSSV PCR diagnostic procedure, the percentages of surviving juveniles of the BG 2, 10, 20 g kg(-1)groups that were 2-step WSSV negative, were 55, 65 and 65%, respectively. The haemolymph THC, PO, O(2)(-)and SOD production of the 2, 10 and 20 g kg(-1)BG diet groups dropped drastically immediately after the WSSV challenge but subsequently returned to normal. Therefore, oral administration of BG at an optimal level of 10 g kg(-1)diet for 20 days effectively enhanced the immune system and improved the survival of WSSV-infected P. monodon.
Fish & Shellfish Immunology 11/2003; 15(4):297-310. · 3.32 Impact Factor
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ABSTRACT: The complete complementary DNA (cDNA) encoding pituitary gonadotropin II-beta subunit (GTH II-beta) of Japanese eel Anguilla japonica was cloned and sequenced, and the profiles of pituitary glycoprotein hormone alpha subunit (PGH-alpha), GTH I-beta, and GTH II-beta mRNA transcript levels at different stages of ovarian development before vitellogenesis in the wild females were investigated. The maturity of female eels was divided into four stages: juvenile, sub-adult, pre-silver, and silver stages based on ovarian development and skin color. The GTH II-beta cDNA was cloned by reverse transcription and polymerase chain reaction (RT-PCR) amplification from total pituitary RNA. The full length GTH II-beta cDNA was obtained using 5(')- and 3(')-rapid amplification of cDNA ends. The cloned eel GTH II-beta cDNA consists of 646 bp nucleotides, including 53 bp nucleotides of 5(')-untranslated region (UTR), 423 bp of open reading frame, and 170 bp nucleotides of 3(')-UTR followed by a poly(A) tail. It encodes a 140-amino acid precursor molecule of GTH II-beta subunit with a putative signal peptide of 24 amino acids and a mature peptide of 116 amino acids. RT-PCR analysis showed that the pituitary transcript levels of alpha subunit steadily increased during eel silvering. The expression of GTH I-beta and II-beta mRNA levels, however, varied in different ovarian developmental stages. The mRNA expression of both GTH I-beta and GTH II-beta were detectable in juvenile stage. The expression levels of GTH II-beta mRNA, but not GTH I-beta, were significantly increased in sub-adult stage. The transcript levels of GTH I-beta and II-beta subunits further increased in pre-silver and silver stages. We demonstrated for the first time that the differential transcription patterns of pituitary PGH-alpha, GTH I-beta, and GTH II-beta mRNAs occur during silvering of the wild female Japanese eels.
General and Comparative Endocrinology 09/2003; 133(1):8-16. · 3.27 Impact Factor
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ABSTRACT: The cyano-metabolite of furazolidone (FZ), 3-(4-cyano-2-oxobutylidene amino)-2-oxazolidone, was isolated from the mixture of FZ incubated with the post-9000 g hepatic supernatant of grouper. Its structure was confirmed by mass spectrometric and nuclear magnetic resonance spectroscopic studies. Thereafter, the disposition of the cyano-metabolite in the orange-spotted grouper (Epinephelus coioides) after oral and bath treatment with FZ was investigated. Qualitative and quantitative analyses of cyano-metabolite in the fish were performed by high-performance liquid chromatography. Mean recoveries of the metabolite in serum, muscle, liver and kidney were 99.8 +/- 4.1, 98.6 +/- 3.5, 53.1 +/- 7.4 and 64.0 11.4%, respectively. Cyano-metabolite was mainly distributed in the serum and muscle rather than in the liver and kidney. After oral treatment of FZ, the peak cyano-metabolite concentrations, 167.2 ng x ml(-1) in serum and 283.2 ng x g(-1) in muscle, were reached at 5.1 and 6.7 h, respectively. The elimination half-life of cyano-metabolite was 4 h. During 24-h bath treatment of FZ, the maximum concentrations of cyano-metabolite, 258 ng x ml(-1) in serum and 204 ng x g(-1) in muscle, were found at 0.25 and 6 h, respectively. The half-life of cyano-metabolite was 0.5 h after transferring the fish to fresh seawater.
Food Additives and Contaminants 04/2003; 20(3):229-36. · 2.13 Impact Factor
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ABSTRACT: Fertilized oyster eggs, S-rotifer (Brachionusrotundiformis) and SS-rotifer (Brachionus sp.),were tested either solely or in combination fortheir suitability as feed for early stage grouper (Epinephelus coioides) larvae. Sizes ofS-rotifers ranged between 143-224 m lorica lengthwith mean 18221m, and SS-rotifersbetween 122-176mlorica length with mean 15413m. Theresults indicated that both fertilized oyster eggs andSS-rotifers were suitable as feed at F1 (first feedingday). However, poor growth was recorded when providing oyster eggs solely for the periodsF1-F3. Although growth of larvae at F6 had nodifference between the sole SS-rotifers and the oystereggs additionally provided for F1-F3, better survivalof larvae at F15 was obtained when providingcombinations of SS-rotifers with oyster eggs for F1-F3.Besides, better growth and survival of larvae at F15was found when providing S-rotifers enriched withKirin yeast for F7-F15. The highest survival andfastest growth of larvae at F15 was found whenproviding oyster eggs for F1-F3, SS-rotifers forF1-F6, S-rotifers for F7-F15, both rotifers enrichedwith Kirin yeast, and Isochrysis for F1-F15.Total fatty acid (TFA), EPA, DHA content, and DHA/EPA(D/E) ratio of larvae changed with their sizes andcorresponded to that of their feeds. The F15 larvaehaving a higher TFA grew faster, having higher DHA orEPA survived better.
Hydrobiologia 11/1997; 358(1):301-304. · 1.78 Impact Factor
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ABSTRACT: Collection and culture of live foods to be used instudies of feeds for rearing finfish and shellfishlarvae in Taiwan began in 1982. Today, 31 species (49strains) of microalgae, three species (nine strains)of rotifers, one cladoceran and one copepod are holdas start culture. Microalgae are collected from localwaters and obtained from foreign collection centers.The most common genera are Chlorella,Nannochloropsis, Tetraselmis, Chaetoceros, Skeletonema, Isochrysis, and Pavlova. Someinteresting genera such as Ellipsoidion,Nannochloris, Synechococcus, and Alexandriumare also included. Three types of rotifers, i.e. L, S,and SS-type, which are classified as Brachionusplicatilis, B. rotundiformis, and Brachionus sp. are found in Taiwan waters. Among therotifers, six strains have been isolated and cultured.Another L-type strain and two SS-type strains wereobtained from foreign sources. The cladoceran Diaphanosoma aspinosum and copepod Apocyclopsroyi are the most common species used in aquaculture.Studies of live foods including their morphology,culture techniques, fatty acid composition andnutritional value as feeds have been undertaken.
Hydrobiologia 11/1997; 358(1):37-40. · 1.78 Impact Factor
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01/2002;
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ABSTRACT: The gonadal development of Japanese eel Anguilla japonica during silvering was examined via gonadal histology and morphometric characteristics. Specimens were collected from the Kaoping River of Taiwan between November 1998 and November 2001. Female eels predominated, constituting 87.6% of the sex-determined eels. The degree of gonadal development was assessed by skin coloration, with female eels divided into yellow, pre-silver, and silver phases. Males were divided into yellow and silver phases because of small sample size. Silver phase eels predominated in the winter. Mean (±S.E.) total length of silver-phase eels was significantly larger in females (642.2±10.4) than males (564.8±14.6) (p<0.001). The mean (±S.E.) gonadosomatic index (GSI) of females increased significantly from 0.27±0.01 for yellow phase, to 0.55±0.03 for pre-silver and 1.32±0.07 for silver phase. Oocyte development progressed from the chromatin nucleolus stage in the yellow phase eel, through the peri-nucleolus stage in the pre-silver phase eel and to the oil-drop stage in the silver phase eel. Spermatogenesis was active for silver phase males which had a larger mean GSI (0.15±0.01) than yellow phase males (0.07±0.02), but the gonadal development of males was slower than that of females. GSI, ocular index (OI), and fin-index (FI) were positively correlated, and gut-index (GI) was negatively correlated with total length in both sexes. Residual analysis of the regression of the indices GSI, OI, FI, and GI on TL indicated that the variation of the indices with growth was greatly influenced by the developmental phase of the eel. On the other hand, OI and FI were positively correlated and GI was negatively correlated with GSI, irrespective of eel phases. These results suggested that the skin coloration, OI, and FI were reliable criteria in selecting mature eel brooders for artificial propagation purposes.
Aquaculture.
