| Summary: | 碩士 === 國立臺灣大學 === 動物學研究所 === 92 === Sturgeons (Order Acipenseriformes), are primitive chondrosteans fish. Although morphologically similar with shark, they were classified to Class Actinopterygii. Acipenseriformes have 2 families, 6 genera and 26 species. All of them are distributed in the temperate areas of Northern Hemisphere. It’s an important aquaculture species in the world. Recently, fertilized eggs and juveniles of the fishes were also imported into Taiwan for the purpose of aquaculture and becoming exotic species. Some species of sturgeons are polypolids. The hybridization is common even between genera Acipenser and Huso. The parents of different species with the same chromosome numbers will produce reproductive offsprings, and thus, genetic introgression among species would easily happen in the nature conditions.
In this study, we use both morphological and molecular (mtDNA Cyt-b) methods to identify the exotic sturgeons in Taiwan and both the phylogeny and the genetic introgression of the fish were analyzed meanwhile. The specimens were collected from 4 different origins: 1) Smuggled sturgeons (Nos. 1-15); 2) Aquaculture specimens from Chupei station of Freshwater Aquaculture Research Center, including A. schrenckii (Nos.18, 21-24), A. gueldenstaedtii (No.16), A. sinensis (No.17), A. baerii (No.19) and one unknown species sturgeon (No. 20); 3) A. schrenckii (No.25) and A. transmontanus (No.26) from aquaculture pond in Fu-San; and 4) Polyodon spathula (No.27) and unknown species sturgeons (Nos.28-31) from Taipei city Zoo. The result indicates that 4 of the smuggled specimens (Nos.1-15) are H. dauricus, and the rest of the specimens are hybrids of H. dauricus (♀) with A. schrenckii(♂) or reverse. No.16 and 19 are pure A. gueldenstaedtii. No.31 is morphologically belonged to A. gueldenstaedtii, but genetically A. baerii. It may be the reason that the A. gueldenstaedtii lived in Volga River was genetically intruded by A. baerii. One (No.17) of the 6 (Nos.17, 18, 21, 23, 24 and 25) specimens with the morphology of A. schrenckii had the same haplotype with the specimen (No. 22) with A. dabryanus morphology. It suggested the high possibility an introgression event of A. schrenckii by A. dabryanus. Other samples can be classified into 3 haplotypes, which are different with those of A. transmontanus or A. schrenckii but they are more close to A. transmontanus by genetic distance. This maybe due to the hybridization by either nature or artificial. The possible pathway of nature hybridization was analyzed from aquaculture, biogeography and geologic events.
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