Wild Grass Carp Research Articles

Lipid-Lowering Effects of Lotus Leaf Alcoholic Extract on Serum, Hepatopancreas, and Muscle of Juvenile Grass Carp via Gene Expression.

Compared with wild grass carp (Ctenopharyngodon idellus), intensively cultured fish displayed disordered lipid metabolism, showing excess lipid deposition in the hepatopancreas and muscle. Lotus leaf prevents fat accumulation in humans and may have similar effects on fish. This study explored the regulatory mechanisms by which the dietary addition of an alcoholic extract of lotus leaf (AELL) reduced lipid deposition in the hepatopancreas and muscle of juvenile grass carp. The fish (average initial weight: 34.00 ± 0.40 g) were fed four experimental diets containing different AELL levels (0, 0.07, 0.14, and 0.21%) for 8 weeks. Serum components, lipid droplet size, triacylglycerol (TAG) content, enzymatic activities, and mRNA levels of genes related to lipid metabolism in the hepatopancreas and muscle were analyzed. The results show that dietary AELL supplementation significantly reduced the TAG content and lipid droplet area in the histological sections as well as the fatty acid synthase (FAS) activity in both the hepatopancreas and muscle but enhanced the activities of lipoprotein lipase (LPL) and carnitine palmitoyltransferase I (CPT1) in both tissues. In addition, dietary AELL supplementation decreased the mRNA expression of genes involved in fatty acid uptake (cd36, fatp1/fatp4/fatp6, fabp10/fabp11, acsl1/acsl4) and de novo lipid synthesis (pgd, g6pd, and fasn) as well as the transcription factors pparg and srebf1 in the hepatopancreas and muscle but increased the mRNA levels of genes relating to lipid catabolism (cpt1a, lipe, pnpla2, lpl), lipid transportation (apob), and the transcription factor ppara in both tissues. In conclusion, dietary AELL supplementation reduced lipid accumulation in the hepatopancreas and muscle by affecting the gene expression of proteins with known effects on lipid metabolism in juvenile grass carp.

Identifying sources and year classes contributing to invasive grass carp in the Laurentian Great Lakes

Relative contributions of aquaculture-origin and naturally-reproduced grass carp (Ctenopharyngodon idella) in the Laurentian Great Lakes have been unknown. We assessed occurrence and distribution of aquaculture-origin and wild grass carp in the Great Lakes using ploidy and otolith stable oxygen isotope (δ18O) data. We inferred natal river and dispersal from natal location for wild grass carp using otolith microchemistry and estimated ages of wild and aquaculture-origin fish to infer years in which natural reproduction and introductions occurred. Otolith δ18O indicated that the Great Lakes contain a mixture of wild grass carp and both diploid and triploid, aquaculture-origin grass carp. Eighty-eight percent of wild fish (n = 49 of 56) were caught in the Lake Erie basin. Otolith microchemistry indicated that most wild grass carp likely originated in the Sandusky or Maumee rivers where spawning has previously been confirmed, but results suggested recruitment from at least one other Great Lakes tributary may have occurred. Three fish showed evidence of movement between their inferred natal river in western Lake Erie and capture locations in other lakes in the Great Lakes basin. Age estimates indicated that multiple year classes of wild grass carp are present in the Lake Erie basin, recruitment to adulthood has occurred, and introductions of aquaculture-origin fish have happened over multiple years. Knowledge of sources contributing to grass carp in the Great Lakes basin will be useful for informing efforts to prevent further introductions and spread and to develop strategies to contain and control natural recruitment.

Distribution of ancient α1 and α2 domain lineages between two classical MHC class I genes and their alleles in grass carp.

Major histocompatibility complex (MHC) class I molecules play a crucial role in the immune response by binding and presenting pathogen-derived peptides to specific CD8+ T cells. From cDNA of 20 individuals of wild grass carp (Ctenopharyngodon idellus), we could amplify one or two alleles each of classical MHC class I genes Ctid-UAA and Ctid-UBA. In total, 27 and 22 unique alleles of Ctid-UAA and Ctid-UBA were found. The leader, α1, transmembrane and cytoplasmic regions distinguish between Ctid-UAA and Ctid-UBA, and their encoded α1 domain sequences belong to the ancient lineages α1-V and α1-II, respectively, which separated several hundred million years ago. However, Ctid-UAA and Ctid-UBA share allelic lineage variation in their α2 and α3 sequences, in a pattern suggestive of past interlocus recombination events that transferred α2+α3 fragments. The allelic Ctid-UAA and Ctid-UBA variation involves ancient variation between domain lineages α2-I and α2-II, which in the present study was dated back to before the ancestral separation of teleost fish and spotted gar (> 300 million years ago). This is the first report with compelling evidence that recombination events combining different ancient α1 and α2 domain lineages had a major impact on the allelic variation of two different classical MHC class I genes within the same species.

Characterization of 36 insert/deletion mutations by STR genotyping method in grass carp, Ctenopharyngodon idella

Grass carp is one of the most important freshwater aquaculture fish in China. Though a few molecular markers had been reported, it was not enough for grass carp germplasm improvement and protection. In order to verify the effectiveness and practicability of insert/deletion mutations reported in grass carp genome, 85 insert/deletion mutations were randomly selected and analyzed. After simple sequence analysis and attempting primer design, 49 markers were removed due to being simple sequence repeats or unable to design primer for them. Finally, 36 insert/deletion mutations were successfully characterized by STR genotyping method in 32 wild grass carp (collected from Pearl River). The mean effective number of alleles (Ne), observed heterozygosity (Ho), expected heterozygosity (He) and polymorphic information content (PIC) were 1.4976, 0.3190, 0.2970 and 0.2349, respectively. Among all the 36 insert/deletion mutations, three deviated significantly from Hardy–Weinberg equilibrium (P < 0.05). In addition, three pairs of loci (ID-13F with ID-24H, ID-20F with ID-21H and ID-39F with ID-64H) had significant linkage disequilibrium (P < 0.05). Those insert/deletion mutations may lay the foundation for germplasm improvement and protection in grass carp.

Differences in anti-predator behavior and survival rate between hatchery-reared and wild grass carp (Ctenopharyngodon idellus)

Grass carp Ctenopharyngodon idellus , is the primary freshwater species produced in China. Because natural populations have shrunk in the wild, restocking programs using hatchery-reared fish have emerged. Artificial rearing could affect fish anti-predator behavior, thus decreasing their survival in the wild. The impact of artificial rearing on C. idellus 's behavior remains unknown because empirical studies are scarce. In this study, we compared anti-predator behavior and survival rate between hatchery-reared and wild C. idellus . Both hatchery-reared and wild C. idellus displayed clear anti-predator behavior when exposed to visual and odor cues of a predator. However, hatchery-reared C. idellus showed significantly lower aggregation index (reflecting shoaling behavior), inspection rate and spent less time in risky area compared to their wild counterparts. When directly exposed to predators, more hatchery-reared C. idellus were predated. This raises concerns about the efficiency of restocking programs and highlights the need to adjust artificial rearing and stocking conditions of C. idellus to produce fish that are better adapted to natural conditions.

Confronting species distribution model predictions with species functional traits.

Species distribution models are valuable tools in studies of biogeography, ecology, and climate change and have been used to inform conservation and ecosystem management. However, species distribution models typically incorporate only climatic variables and species presence data. Model development or validation rarely considers functional components of species traits or other types of biological data. We implemented a species distribution model (Maxent) to predict global climate habitat suitability for Grass Carp (Ctenopharyngodon idella). We then tested the relationship between the degree of climate habitat suitability predicted by Maxent and the individual growth rates of both wild (N=17) and stocked (N=51) Grass Carp populations using correlation analysis. The Grass Carp Maxent model accurately reflected the global occurrence data (AUC=0.904). Observations of Grass Carp growth rate covered six continents and ranged from 0.19 to 20.1gday(-1). Species distribution model predictions were correlated (r=0.5, 95% CI (0.03, 0.79)) with observed growth rates for wild Grass Carp populations but were not correlated (r=-0.26, 95% CI (-0.5, 0.012)) with stocked populations. Further, a review of the literature indicates that the few studies for other species that have previously assessed the relationship between the degree of predicted climate habitat suitability and species functional traits have also discovered significant relationships. Thus, species distribution models may provide inferences beyond just where a species may occur, providing a useful tool to understand the linkage between species distributions and underlying biological mechanisms.

Genetic variations of body weight and GCRV resistance in a random mating population of grass carp.

The grass carp (Ctenopharyngodon idellus) is an important species in freshwater aquaculture both in China and on a global scale. Variety degeneration and frequent diseases have limited the further development of grass carp aquaculture. Thus, new and improved varieties are required. Here, we identified and assessed the body weight and disease resistance in a random mating population of 19 ♀ × 22 ♂ grass carp, which were derived from different water systems. In both the growth experimental group of 10,245 fish and grass carp reovirus (GCRV)-infected group with 10,000 fish, 78 full-sib families were statistically analyzed for body weight and GCRV resistance. The findings showed that body weight traits had low heritability (0.11 ± 0.04, 0.10 ± 0.03 and 0.12 ± 0.05), GCRV resistance traits had high heritability (0.63 ± 0.11); body weight was higher in 3 families, whereas GCRV resistance was significantly greater in 11 families. Our results confirmed that the natural germplasm resources of wild grass carp were genetically diverse. Breeding of GCRV resistant varieties of grass carp have better genetic basis. This study provides the basis for constructing basal populations for grass carp selective breeding, quantitative trait loci (QTL) and genome-wide association studies (GWAS) analysis.

Genetic variation analysis of wild populations of grass carp (Cteno-pharyngodon idella) using microsatellite markers

Twelve microsatellites were used to analyze the genetic diversity and genetic structure of eight wild populations of grass carp, among which six populations from Yangtze River (Hanjiang, Wujian, Jiujiang, Shishou, Mudong, and Wanzhou), one population from Pearl River and Heilongjiang River for each, Zhaoqing, and Nenjiang, respectively. Twelve markers showed highly polymorphic and all the eight populations contained high genetic variations. The variations of six populations of Yangtze River and Zhaoqing population of Pearl River were higher than Nenjiang population of Heilongjiang River. Bottleneck analysis revealed that four populations (Zhaoqing, Nenjiang, Mudong, and Wangzhou) had experienced a recent genetic bottleneck, and the effective population size was reduced. Pairwise FST and AMOVA analysis detected significant genetic difference among populations. The pairwise population genetic distances and the UPGMA tree demonstrated that the genetic distances between six populations of Yangtze River and Zhaoqing population were closer and clustered together earlier, as compared to those populations with Nenjiang population. The genetic structure simulation analysis suggested that there were five logic populations of all individuals. The genetic structures of Zhaoqing and Nenjiang populations were shown with independent separation, but the genetic structures of populations from Yangtze River were shown with fuzzy distribution. The high diversity was found in the wild grass carp from three major watersheds in China, which would supply a basis for future genetic improvement. However, the bottleneck effect of some populations should be taken into account in the practical breeding programs.

Induced Gynogenesis in Grass Carp (Ctenopharyngodon idellus) Using Irradiated Sperm of Allotetraploid Hybrids

Grass carp (Ctenopharyngodon idellus) eggs were activated by UV-irradiated diploid sperm of allotetraploid hybrids derived from red crucian carp (♀) × common carp (♂) and then duplicated by cold shock in 4-6°C water for 10-12 min. Different cold shock initiation times resulted in two types of diploid gynogenetic grass carp: meiotic gynogenetic (meiG) and mitotic gynogenetic (mitG). Over a 5-year period, a total of 17,170 meiG and 1,080 mitG fry were produced and 6,862 meiG and 372 mitG grass carp survived. The gynogenetic fish were confirmed by morphological characteristics, chromosome examination, and microsatellite DNA analysis. The morphological traits of the gynogenetic grass carp were similar to those of wild diploid grass carp. Normal gynogenetic fish were identified as diploid with 48 chromosomes by chromosomal metaphases examination, while nonviable abnormal embryos were detected as haploid with 24 chromosomes. Microsatellite DNA analysis indicated that after one generation of gynogenesis, the genetic purity of meiG and mitG grass carp was significantly increased over that of wild grass carp. In addition, both meiG and mitG grass carp groups were 100% female, and 88% of these showed normal ovary development. Thus, the sex determination mechanism in female grass carp was homogamety. The ability to establish pure all-female groups of meiG and mitG grass carp should be a valuable contribution to both fish genetics and grass carp breeding.