臺灣長牡蠣（ Crassostrea gigas Thunberg ) 基礎生物學的研究

Abstract

臺灣的牡蠣產量主要來自養殖，而以長牡蠣（ Crassostrea gigas Thunberg , 1793）為養殖對象，其產量為臺灣貝類總產量之首， 1993 年牡蠣產量佔總漁獲量的1.94 % ，為臺灣最重要的經濟貝類。 臺灣長牡蠣之解剖學研究，確定了四個採樣地區（新竹香山、雲林台西、嘉義布袋以及屏東東港）的種類同為長牡蠣，但其生長之各地區間存在生殖生態上的差異。 利用組織學方法，觀察長牡蠣生殖細胞及生殖腺發育情形，以瞭解其生殖特徵，並進行生殖線分期月別變化、生殖期的判定等研究 ，以建立本省長牡蠣生殖生態的基礎資料。經由 G / B ?（生殖線厚度／內臟團厚度）判定生殖期，結果得到香山地區只有一個生殖週期 7一9 月（ 0.3－0.44 ) ，而其他地區則大約分有春、秋兩個生殖季節，臺西和布袋地區的生殖期均相同，在 2一4 月（0 .29－0.43）和 7－9月（0.23－0 .44）兩期，東港則略為不同，在 l－4 月（0.25－0.35）及 8－10 月（0.25－0.38）兩期。在環境的不同下可能會造成生殖週期的改變或族群遺傳的分化，故本研究以 PCR－RFLP 應用在粒線體DNA ( Mitochondrial DNA ）的方法加以分析各地區間的族群關係，結果發現此四個地區的長牡蠣為同源的族群，族群遺傳並未發生變異，因此在臺灣長牡蠣的資源管理上，可視為同一個族群管理。至於其間產卵期上的差異推測可能是水溫造成的影響。

The major cultured oyster in Taiwan is the Pacific oyster Crassostrea gigas Thunberg, 1793. The annual yield of C. gigas is always the highest among those of all economic shellfishes. The reproductive ecology of C. gigas in Shunsun, Taishi, Budai and Tongkang areas was studied by comparing their G/B (width of gonad/width of body) ratio and gonads’ histology during the year. There exists the ecological difference in water temperature and salinity. According to the annually fluctuation of G/B ratio and the developmental rhythm of gonad, it is suggested that the spawning period of C. gigas in Shunsun is from July to September (0.3-0.44); Taishi and Budai, from February to April (0.29-0.43) and July to September (0.23-0.44); and Tongkang, from January to April (0.25-0.35) and August to October (0.25-0.38). There is no difference between the mtDNAs’ PCR-RFLP data of the oysters from four sites. Therefore, it is suggested that cultured C. gigas in Taiwan can be treated as a single population. The different spawning periods of the oysters from different sites were the result of the different ecological factor as water temperature.