Study On The Biological Characteristics And The Genetic Diversity Of Red Bighead Carp(Aristichthys Nobilis)

After the years been artificial breeding, the bighead carp (Aristichthys nobilis) had substantial decline in germplasm resources and significant reduction of genetic diversity. Purification and rejuvenation of the bighead-carp germplasm is an urgent task. Red bighead carp is a new type of special bighead crap be selected and bred by our laboratory form wild bighead crap in recent years and those red bighead carp been named XiangYun Golden Bighead-carp. That bighead crap in red color has fast growth, is good breeding species and valuable experimental material. At the same time we had gotten the offspring of those red bighead crap be bred by parthenogenesis. Three kinds of bighead crap——the normal bighead crap in black color (BC), XiangYun Golden Bighead-carp(RBC) and the offspring of those red bighead crap be bred by parthenogenesis(GRBC) were collected for use. The study is focus on the difference between three kings of bighead crap on morphological features and molecular biology.The ordinary regulations and T value test were chose to study their morphological features. The results showed notable difference on the lateral-line scale, number of vertebra of the three stocks. The RBC and the gRBC almost had same morphological features. The difference of the ratio of head- length to snout- length, body-length to body-highness and caudal- peduncle- length to caudal- peduncle- highness between BC and RBC with gRBC was obvious.Genetic variation was comparatively analyzed between the Red bighead carp (RBC) population and the bighead carp (BC) population of aquaculture strains originating from xiangjiang river used as the control, using random amplified polymorphic DNA (RAPD) assay and microsatellite analysis. The specific fragments for RBC and BC population was detected by S20 and S46 respectively. The average genetic distances of BC ranged from 0.04 to 0.13 with a mean of 0.075. And the average genetic distances of RBC ranged from 0.02 to 0.35 with a mean of 0.139. The average genetic distances estimated by Lynch's index of BC population were significantly lower than those of RBC population. Where as the average genetic distances between BC and RBC ranged from 0.06 to 0.37 with a mean of 0.123. The mean number of alleles per microsatellite locus (1.89) in BC population was considerably lower than that (2.44) in RBC population. The average observed (0.34) and expected heterozygosis (0.39) in BC population were lower than those (0.54 and 0.51, respectively) in RBC population, indicating that the RBC presented higher genetic diversity than the BC. The results from RAPD assay and microsatellite analysis were in agreement with each other, that is to say, the BC presented lower level of polymorphism than RBC. Furthermore, as expected, microsatellite analysis revealed more detailed information on genetic diversity than RAPD assay. The complete mitochondrial DNA sequences from two kinds of of bighead carp (RBD and *RBD) were determined. The result showed that the complete mitochondrial DNA sequences of two kinds of bighead carp (RBD and *RBD) are resemble. The genome is a circular molecule with 16618 bp in length, and the overall base composition included 31.64% of Adenine (A),27.10% of cytosine (C),15.94% of Guanine (G), 25.32%, of thymine (T), and with 56.96% the A+T content.