| Anguilla is of great commercial importance and medicinal value. So it has been capturedand cultivated in many parts of the world. Our country is the largest producing country ofAnguilla. Its export value stays in the first place of the aquaculture products. However, thegermplasm resources are limited and unstable because of the overexploitation along the coast ofChina. Thus, new Anguilla species have been introduced from abroad for aquaculture. Theintroduction caused confusion of the classification of Anguilla. In our study, we used AFLP,COⅠand COⅡ molecular technologies to indentify the germplasm resource of several Anguilla.We also analyzed its tolerance to ultimate high and ultimate low water temperature which couldbe used as based information for the extension aquaculture of the new Anguilla species.1．Our research aimed to analyze the tolerance to ultimate high and low water temperatureon five species of Genus Anguilla elver(Anguilla japonica, A. anguilla, A. rostrata. A. bicolorPacifica and A. mormorata). Natural water temperature was used as initial temperature, and weincreased/decreased1℃every four hours in high-temperature/low-temperature experiment. Theresults showed that five Anguilla species are different in the tolerance to the ultimate watertemperature. In the high temperature experiment,the highest mortality of A. japonica, A. rostrata,A. anguilla, A. bicolor Pacifica and A. mormorata was observed in39℃,38℃,37.5℃,39℃,38℃, respectively. However, the endurance ability in the high-temperature experiment areinsignificant. In the low temperature experiment, A. japonica and A. rostrata are insensitive tolow temperature for they can survive in the mixture of ice and water. Among the rest threespecies, the highest mortality of A. anguilla, A. mormorata and A. bicolor Pacifica was observedin2℃,5℃,10℃, respectively.2．Amplified fragment length polymorphism (AFLP) has been used to analyze the geneticdiversity and differentiation of six Anguilla species (e.g. A.japonica, A. Anguilla, A. rostrata, A.bicolor Pacifica, A. mormorata and A.Mossambica). Our study showed that the genetic diversityamong six Anguilla species was high. A total of519bands were amplified by eight pairs ofAFLP primer combinations. The percentage of polymorphic loci was from54.62%(A. bicolorPacifica) to63.85%(A. anguilla), The number of alleles per locus （A）was from1.5462to1.6385, with an average of1.5918. The effective number of alleles per locus （Ae）was from1.2657to1.3289, with an average of1.3040. And the mean of Shannon’s Information index was0.2810, ranging from0.2520to0.3066, the mean of Nei’s gene diversity was0.1837, ranging from0.1632to0.2002. Our study also showed that the genetic distance between A. Anguilla andA. rostrata was the lowest (D=0.0543), followed by that between A. bicolor Pacifica and A.mormorata (D=0.1253). The cluster analysis showed that six Anguilla species clustered into twomajor groups. A. rostrata, A. Anguilla and A. Mossambica clustered into one group and the restclustered into the other one. Besides, five specific loci using E-AAG/M-CGT andE-AAG/M-CTT primer combinations could be applied to indentify six Anguilla specieseffectively.3．Mitochondrial cytochrome oxidase subunit Ⅰ(COⅠ) fragments and Mitochondrialcytochrome oxidase subunit Ⅱ (COⅡ) fragments were amplified among six Anguilla species.The sequence of COⅠ gene is652bp in length, and the difference of the sequence of COⅠgene is105bp among six Anguilla species. Among them,18are transversion and87aretransition. The sequence of COⅡ gene is412bp in length, and the difference of the sequence ofCOⅡ gene is46bp among six Anguilla species. Among them,6are transversion and40aretransition. In the COⅠ and COⅡ gene among the six Anguilla species, the contents of A, T, Gand C were similar, and the content of A+T is larger than that of G+C. |
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