| The number of Chinese alligators in Changxing Nature Breeding Research Center for Chinese alligator is 459, including 7 of FO generation animals, 214 of F2 generation animals and 238 of F2 generation animals. As the startup of the reintroduction-planning project for the Chinese alligator captive population, the selection of founder animals and reintroduction sites for the reintroduction population becomes urgent.By using mitochondrial DNA and microsatellite as genetic markers, we did comprehensive research on genetic diversity of Chinese alligator Changxing captive population. In addition, the metal background of Changxing Nature Breeding Research Center and the planning reintroduction site (Taohua Gou) were surveyed by using atomic absorption spectrophotometer. All the study carried here will in turn be helpful for establishing scientific strategy for founder animal and reintroduction site selection for the reintroduction program.1. The analyses of mitochondrial DNA control region non-repetitive sequence variation indicated that Chinese alligator Changxing captive population shared a single mitochondrial haplotype, which revealed little genetic diversity within the population. Variable number tandem repeats (VNTRs) are present in the control region of mitochondrial DNA of Chinese alligator. Length polymorphism and sequence variations existed in the mtVNTR region, which is the sole source for mtDNA control region variations in the captive population.2. The mtVNTRs contained 676-785 base pairs, made up by 5 distinct motifs repeated 31~36 times in 32 individuals examined. The motifs were 21~22 nts in length, with high sequence similarity between each other and with those of the American alligator (Alligator mississippiensis), indicating origination of the mtVNTRs from a single ancestral duplication unit in both species. The 5' and 3' portions of the repetitive sequences in the Chinese alligator were very much conserved among the individuals, while those in the middle showed a higher degree of sequence variation, which was called "edge effect". The results shownhere might be the evolution characteristics of mtDNA control region in the Chinese alligator Changxing population.3. MtVNTRs in the Chinese alligator are extremely variable, varying between generations. 17 VNTR types, of which, 6 from the second generation and 12 from the third generation were identified from the samples. Analysis of the multiple VNTR types showed a high level of stochastic mutation within each generation. The suitability of the mtVNTRs as a marker to monitor the genetic differentiation of the Chinese alligator was also discussed. It is possible that due to the short period of time in the captive breeding, the length polymorphism that has been generated is still waiting for homogenization and fixation in the population to take place. Results indicated that mtVNTRs alone might not be an adequate marker to monitor genetic differentiation within a population.4. In this study, the extent of genetic variation in the captive alligators from Changxing Breeding Research Center was investigated using microsatellite markers derived from American alligators. Out of 22 loci employed, 21 were successfully amplified in the Chinese alligators. Eight of the 22 loci were found to be polymorphic with a total of 26 alleles present among 32 animals scored, yielding an average of 3.25 alleles per polymorphic locus. The expected heterozygosity (HE) ranged at a moderate level from 0.4385 to 0.7163 in this population.5. The ability to detect shared genotypes and multiple paternity were evaluated for those markers. Results suggested that when the polymorphic loci were combined, the individual identity probability and multiple paternity dection probability are 0.995 and 0.9245, respectively. Therefore, the microsatellite markers could be utilized to genetic pedigree construction for the Chinese alligator Changxing captive population. In addition, it could be helpful in the selecting of proper individuals for the reintroduction program.6. Concentrations of a number of metals, including As, Fe, Ca, Mn, Cu, Zn, Pb, Cd, Cr and Hg were determined in the samples of water and soils from the Changxing Chinese alligator Breeding Research Center, in order to evaluate the metalbackground of this reservation. Results showed that except Hg, the concentrations of other toxic heavy metals in water were below the limitations of "Surface Water Quality Type II (GB3838-2002)". And excepet Cd, the quality of soil in this breeding center was content with the criterion of "Soil Quality Type I (GB15618-1995) ". With no records of heavy metal lethal contamination in the Changxing alligator population and no history background of hea\ry metal contamination in the field where the breeding center located in, we concluded that the metal environment of Changxing Chinese alligator Breeding Research Center could meet the requirements of animal growth and propagation. Howevei:, actions should be taken to reduce the concntration of the over-criterion heavy metals.7. The concentrations of a series of metals (As, Fe, Ca, Mn, Cu, Pb, Cd, Cr, Zn and Hg) were examined in the tissues of Chinese alligators to elucidate the background distribution of these metals in the alligator body. Generally, within the body compartments, metal concentrations were high in liver, kidney and heart, and low in pancreas and gonad. Study of metal levels in the feces of Chinese alligator suggested that Chinese alligators could reduce body burden of toxic substances by excreting them to feces. According to the body metal accumulations in the America alligator, we therefore concluded that the metal concentrations in Chinese alligators Changxing population are within the normal range, and they couldn't bring any harms to the animals.8. In order to develpe a non-lethal monitoring method for detecting heavy metal contaminations, we determined the correlation of metal concentrations between three egg compartments and wanted to test whether eggshell or egg membrane could be used as surrogates to measure heavy metal load in the egg contents. Of the ten elements analyzed, concentrations of iron, copper and zinc in the shell membrane were highly correlated with the levels in egg contents, whereas no metal was significantly correlated between eggshell and egg contents. It suggested that only the shell membrane could be a useful bioindicator for Fe, Cu and Zn concentration in the eggs of Chinese alligator.9. Concentrations of a number of metals, including As, Fe, Ca, Mn, Cu, Zn., Pb, Cd,Cr and Hg were determined in the samples of water and soils of Taohua Gou, in order to evaluate the environment quality of the reintroduction site for Chinese alligator Changxing population. Results showed that except Hg, the concentrations of other toxic heavy metals in water were below the limitations of "Surface Water Quality Type II (GB3 83 8-2002)". And excepet Cd and Pb, the quality of soil in this breeding center was content with the criterion of "Soil Quality Type I (GB15618-1995 )". However, actions should be taken to reduce the over-criterion heavy metals before reintroduction.10. Based on the mtDNA and microsatellite analysis results, we conclude thai: Chinese alligator Changxing captive population has very low genetic diversity, but still possesses moderate heterozygosity and remains a degree of rare genes. With the wild alligators critically being in danger and under the background that the genetic diversity for the whole Chinese alligator being extremely low, we should theasure the genetic variation of Changxing alligator population. The current Changxing alligator captive population added an important resource to the reintroduction program.
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