利用遺傳標記及形態鑑定台灣的外來種鱘

Species Identification of the exotic Sturgeons in Taiwan by genetic marker and morphology

何杰騰(Jie-Teng He)

指導教授 ： 曾萬年

國立臺灣大學/生命科學院/動物學研究研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.02097

摘要

鱘 (sturgeons) 為古老的軟骨硬鱗魚類，其外形與鯊魚相近，卻是屬於條鰭魚綱 (Actinopterygii)、軟骨硬鱗亞綱 (Chondrostei)、鱘形目 (Acipenseriformes)。鱘形目共有2科6屬26種，其自然的地理分佈域，僅限於北半球的大西洋及太平洋東西兩岸的溫帶地區。由於鱘的經濟價值高，亞熱帶地區也出現人工繁養殖的鱘。臺灣非鱘的原產地，近年來也自國外引進鱘之幼魚或受精卵孵化後養殖，成為新的外來種。鱘具有多倍體特徵，其中鱘屬 (Acipenser) 及鰉屬 (Huso) 雜交的情形非常普遍，染色體倍數相同的親代雜交產生的子代具有繁殖力，因此在自然情況下或人為移殖時很容易造成基因滲入現象 (introgression)。
本研究以分子遺傳學方法 (mtDNA Cyt-b) 輔以形態學方法鑑別台灣引進的鱘種類，並探討鱘的類緣關係以及因雜交而造成的基因滲入現像。研究材料取自四個地點：1)海巡署在雲林箔子寮港查獲的走私鱘 (Nos.1-15)，2)竹北淡水繁養殖研究中心所飼養的史氏鱘 (Nos.18, 21-24)、俄羅斯鱘 (No.16)、中華鱘 (No.17)、西伯利亞鱘 (No.19)、及未知種鱘 (No.20)，3)福山養鱒場所飼養的史氏鱘 (No.25) 及高首鱘 (No.26)，以及4)台北市立動物園所飼養的匙吻鱘 (No.27) 及未知種鱘 (Nos.28-31)。結果發現Nos.1-15鱘標本中4尾為鰉，其餘為鰉 (♀) ×史氏鱘 (♂) 或相反的雜交組合；Nos.20, 28, 29和30為商業養殖用的歐洲鰉 (♀) ×小體鱘 (♂) 的雜交品系“Bester”；Nos.16和19為純種的俄羅斯鱘，No.31的外部形態屬於俄羅斯鱘，卻帶有西伯利亞鱘的基因，原因可能是伏爾加河的俄羅斯鱘受西伯利亞鱘基因滲入的影響；同理，形態為史氏鱘的標本 (Nos.17, 18, 21, 23, 24, 及25) 中，No.17的基因型與形態為達氏鱘的No.22相同，均為達氏鱘的基因單型，顯示史氏鱘祖先曾發生過達氏鱘的基因滲入事件。其餘標本的基因則分為三個基因單型 (haplotypes)，這三單型既不是高首鱘也非史氏鱘的基因型，但遺傳距離與高首鱘較近，推測其原因可能是人為或自然雜交所造成的。並從人工養殖選種證據，以及從生物地理學及地質事件等其他文獻的側面證據，探討自然雜交發生的可能路徑。

關鍵字

雜交 ； 鱘 ； 鰉屬 ； 鱘形目 ； mtDNA Cyt-b ； 形態學 ； 基因滲入 ； 鱘屬

並列摘要

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.

並列關鍵字

genus Huso ； mtDNA Cyt-b ； morphology ； Sturgeons ； hybridization ； genetic introgression ； genus Acipenser ； Acipenseriformes

參考文獻

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