草鱼、鲢和瓦氏黄颡鱼幼鱼感应流速的比较

在21±1℃水温下,使用自行制作的鱼类游泳行为测试槽,采用流速递增的方法测定了草鱼(Ctenopharyngodon idellus)(体长9.64±3.12 cm,体重20.97±16.71 g)、鲢(Hypophthalmichthys molitrix)(体长10.60±3.45 cm,体重24.37±18.61 g)和瓦氏黄颡鱼(Pelteobagrus vachelli)(体长11.54±1.46 cm,体重20.98±6.94 g)幼鱼个体的感应流速.结果表明:草鱼、鲢和瓦氏黄颡鱼幼鱼的感应流速分别是(8.21±0.68)、(6.74±0.84)和(33.11±3.06) cm·s-1,相对感应流速分别是(0.91±0.22)、(0.67±0.15)和(2.9±0.29) BL·s-1;鲢和草鱼幼鱼的感应流速差异不显著(P＞0.05),但瓦氏黄颡鱼比草鱼和鲢幼鱼感应流速大近4倍,差异显著(P＜0.05);因此,草鱼和鲢幼鱼较瓦氏黄颡鱼幼鱼对流速的感应更敏感.本实验结果可为设计鱼道、确定拖网速度等提供一定的科学指导.     

Intensive culture of grass carp and hybrid grass carp larvae

Intensive culture of grass carp and hybrid grass carp (Ctenopharyngodon idella x Aristichthys nobilis ) larvae was conducted under Florida (U.S.A.) conditions. The influence of different rearing facilities (indoor tanks, outdoor tanks and cages) and different methods of fish feeding using live zooplankton and artificial food was tested. High survival (86–100%) and satisfactory grass carp growth (47–56 mg) were obtained in the outdoor tanks and cages during the 10–day experiment. It is believed, that the technique described can be used after some improvements for commercial–scale grass carp larvae rearing. Low survival (1–3%) was obtained in the hybrid culture experiment even though satisfactory growth rates (84–212 mg) were obtained after 13 days. High mortality was attributed to genetic abnormalities caused by hybridization. The hybrid does not appear to be a promising fish for culture.     

Purification, N-terminal sequence determination and enzymatic characterization of antiquitin from the liver of grass carp

Aldehyde dehydrogenase (ALDH) is a superfamily of enzymes catalyzing the conversion of various aldehydes to the corresponding acids using the coenzymes NAD+ or NADP+. While mammalian ALDHs have been studied extensively, the non-mammalian ALDHs, notably those of teleostean origin, remain relatively unexplored. In our previous study on grass carp (Ctenopharyngodon idellus) liver ALDH, a significant amount of the ALDH activity did not adsorb on the alpha-cyanocinnamate Sepharose column which binds ALDH2. The objective of the present study was to purify the ALDH which accounts for this unadsorbed activity. Further chromatography on Affi-gel Blue agarose, followed by size exclusion on Superdex 200 successfully isolated this aldehyde-oxidizing activity. The protein was a homo-tetramer with a subunit molecular mass of 58 kDa. N-terminal sequencing of the first 21 amino acid residues, followed by blastp analysis on the NCBI database revealed the protein as antiquitin. The optimal pH for the oxidation of acetaldehyde was 9.5. At this pH, the Vmax and the Km values for acetaldehyde were 1.95 U/mg and 2.00 mM, respectively.     

Cloning of the grass carp growth hormone cDNA

We have constructed a cDNA library in lamda gt11 using mRNA isolated from the pituitary glands of the grass carp (Ctenopharyngodon idellus). Based on the published sequence of the rainbow trout growth hormone cDNA, we synthesized two oligonucleotide probes. One of these hybridized strongly with a specific mRNA fragment from the grass carp pituitary. Using this probe, we have isolated six positive clones carrying an insert of approximately 1.2 Kb. By restriction enzyme digestion, all the clones were determined to be identical. Sequence determination on one of them indicated that it has an open reading frame coding for 210 amino acids. Both the nucleotide and translated amino acid sequence are highly homologous to those of the salmon growth hormone and the common carp. A putative signal peptide consisting of hydrophobic amino acids can be identified at the 5' end of the sequence. A polyadenylation signal, ATTAAA, was also present 12 base upstream from the poly A tail.     

Reproductive condition and occurrence of intersex in bighead carp and silver carp in the Missouri River

Little is known about the reproductive biology of the exotic bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix in the Missouri River. In order to fill this gap in understanding, herein is described the reproductive condition of these Asian carps. Evidence is presented which indicates that bighead and silver carp in the Missouri River have a protracted spawning period that extends from early spring through fall and some individual bighead and silver carp are spawning multiple times during a reproductive season. Although bighead and silver carps are successfully maturing and spawning in the Missouri River some reproductive abnormalities such as intersex, atresia, and sterility were observed. Knowledge of the reproductive activity of these invasive carps may be useful to resource managers tasked with their control. Furthermore, the reproductive abnormalities observed should be considered when evaluating the environmental condition of the Missouri River relative to supporting a healthy fish fauna.     

The influence of grass carp on habitat structure and its subsequent effect on the diet of tench

Ecological studies were carried out in shallow experimental sites in the Lancaster Canal to evaluate potential interactions between grass carp and feeding habits of tench.
Grass carp, through moderate weed consumption, produced better conditions for the exploitation of benthic organisms by the benthophagous tench, because tench (>35 cm fork length) were able to search for food in the open areas created. This also enabled the fish to make use of zooplankton, mainly the large species Eurycercus lamellatus whose restricted phytophilic habitat made it vulnerable to predation. Epibenthic animals, in particular gastropods and Asellus aquaticus , suffered principally from the predation, which caused severe reduction of them in the site totally depleted of vegetation. In this site, tench utilized a diet in which red chironomids were the dominant prey group together with a large amount of fine detritus.
It is suggested that a moderate control of vegetation in temperate climates, using the grass carp as the biological agent, could be a satisfactory management technique for the improvement of aquatic habitats.     

二龄草鱼脾脏、肝脏组织高表达甘露糖结合凝集素mRNA

Innate immunity is expected to be very important in fish. Mannose-bingding lectin (MBL) participates in the innate immune system as an activator of the complement system and as an opsonin after binding to certain carbohydrate structures on microorganisms. In this experiment, total mRNA was isolated from spleen, liver, gills, thymus, head kidney and kidney of adult and immature grass carp Ctenopharygodon idllus. The cDNA of MBL was obtained by RT-PCR using total mRNA from the spleen of carp as template. Such cDNA was labled with ^32p and used as probe for Northern analysis, and autoradiographic signals were quantified by densitometry analysis. The results showed that MBL was high expressed in the spleen and liver and low in gills, thymus, head kidney and kidney of adult grass carp, and MBL was much lower expressed in spleen and liver of immature grass carp than those of adult grass carp. The results might partially explain why immature grass carp are vulnerable to grass carp hemorrhage virus (GCHV) whereas adult grass carp are not.This suggested that MBL mav be an imoortant anti-GCHV factor [Acta Zoologica Sinica 50 (1): 137 - 140. 2004].     

Isolation and characterization of 17 polymorphic microsatellites in grass carp

Here we report the isolation and characterization of 17 polymorphic loci isolated from a partial genomic DNA library of grass carp (Ctenopharyngodon idellus) enriched for CA repeats. We tested variability of these microsatellites on 24 unrelated individuals collected in China. All microsatellites were polymorphic. The average allele number was 7.9 per locus, ranging from four to 13. The observed heterozygosity was from 0.46 to 0.88 with an average of 0.71, whereas the average expected heterozygosity was 0.78. Sixteen of the 17 microsatellites conformed to Hardy–Weinberg equilibrium, and inherited independently. These microsatellites can be used to study genetic diversity and population structure of wild populations, and facilitate selective breeding of cultured broodstocks.     

A 15 nucleotide deletion mutation in coding region of the RIG-I lowers grass carp (Ctenopharyngodon idella) resistance to grass carp reovirus

RIG-I (Retinoic acid-inducible gene I) is a pivotal receptor that detects numerous RNA and DNA viruses and plays crucial roles in the induction of type I interferons. In the present study, a deletion mutation in CiRIG-I (Ctenopharyngodon idella RIG-I) coding region was detected, its association with resistance/susceptibility to grass carp reovirus (GCRV) was examined, and possible mechanism was analyzed. A 15-bp deletion mutation was found, and the mutation results in a deletion of five amino acids. To investigate the genotypes and alleles, the relevant PCR products were electrophoresed on 2.5% agarose gel. Three genotypes and two alleles were discovered. The general allele was named as A and the deletion mutation allele was named as B. The deletion mutation cancels a predicted phosphorylation site and changes the secondary structure and the probability of peroxisomal targeting signal 1 in CiRIG-I. To explore the correlation between these genotypes and the resistance of grass carp to GCRV, a challenge experiment was carried out. The cumulative mortality in genotype AA (40.70%) and AB (52.73%) was significantly lower than that in genotype BB (71.43%) (P = 0.032). The result demonstrated that genotype AA and AB were resistant to GCRV, while genotype BB was susceptible. The 15-bp deletion mutation lowers the resistance of grass carp to GCRV. This result might provide a potential genetic marker for further investigation of selective breeding of resistant grass carp to GCRV.     

Purification and characterization of grass carp mitochondrial aldehyde dehydrogenase

The molecular biology and enzymology of aldehyde dehydrogenase (ALDH) have been extensively investigated. However, most of the studies have been confined to the mammalian forms, while the sub-mammalian vertebrate ALDHs are relatively unexplored. In the present investigation, an ALDH was purified from the hepatopancreas of grass carp (Ctenopharygodon idellus) by affinity chromatographies on alpha-cyanocinnamate-Sepharose and Affi-gel Blue agarose. The 800-fold purified enzyme had a specific activity of 4.46 U/mg toward the oxidation of acetaldehyde at pH 9.5. It had a subunit molecular weight of 55000. Isoelectric focusing showed a single band with a pI of 5.3. N-terminal amino acid sequencing of 30 residues revealed a positional identity of approximately 70% with mammalian mitochondrial ALDH2. The kinetic properties of grass carp ALDH resembled those of mammalian ALDH2. The optimal pH for the oxidation of acetaldehyde was 9.5. The K(m) values for acetaldehyde were 0.36 and 0.31 microM at pH 7.5 and 9.5, respectively. Grass carp ALDH also possessed esterase activity which could be activated in the presence of NAD(+).     

Comparison of early developmental stages and adults of grass carp, Ctenopharyngodon idella, and hybrid carp (female grass carp × male bighead Aristichthys nobilis)

Hybrid carp and grass carp from the zygote to the prolarval stage and adults were compared to establish distinguishing characteristics. Zygote diameter, yolk sac and embryo length were not different between the fishes. Body pigmentation patterns showed distinct separation among the prolarvae of the hybrids and grass carp. Total and preanal myomeres were higher in grass carp larvae than in the hybrids. The grass carp and hybrid larvae also differed in 38% of the proportional morphometric characters.
Average meristic counts of adults were significantly higher in hybrids compared with grass carp. Adults of the two fishes showed significant differences in 63% of the proportional morphometric measurements. Gill raker counts showed no overlap and lateral line scales were smaller and more numerous in the hybrid adults.