石門水庫集水區淡水螺川蜷年齡決定與生殖生物學研究

Age Determination and Reproductive Biology of Freshwater Snail Semisulcospira libertine (Prosobranchia: Pleuroceridae) in Shihmen Reservoir Watershed, Northwestern Taiwan

徐正勳(Cheng-Hsuing Hsu)

指導教授 ： 李英周

國立臺灣大學/生命科學院/漁業科學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02981

摘要

川蜷為雌雄異體行卵胎生連續生殖的淡水螺類，為未受汙染水域的指標螺類，廣泛分布於石門水庫集水區內，因此本研究藉由殼體氧穩定同位素推估川蜷年齡，並以胚胎組成探討成熟體形與生殖週期。
本研究採樣分為兩期：2010年7-10月於霞雲溪測點與三民溪測點進行調查；2011年5月-2012年4月期間增加庫志溪與石壁腳溪2測點，合計共4測點，按月調查各測點環境因子與螺貝類組成。選取霞雲溪兩川蜷殼體樣本進行年齡推估工作，並將三民溪與霞雲溪採獲川蜷進一步解剖，辨別性別與分析育幼囊胚胎組成。
研究結果顯示，川蜷密度逐漸下降且三民溪螺類組成改變；霞雲溪殼高為24.95mm 與20.53mm 之川蜷樣本年齡推估分別為19月齡與14.5月齡；兩溪流族群性比皆偏離1:1；霞雲溪雌川蜷50%族群成熟殼高（MH50）為13.5mm，成熟殼寬（MW50）為6.55mm；而三民溪成熟殼高（MH50）為17.84mm，成熟殼寬（MW50）為7.58mm，霞雲溪個體成熟體型較小；霞雲溪川蜷終年具繁殖能力，無明顯生殖高峰與休止期；藉由定齡樣本的成長來推估成熟年齡，兩樣本約於6-12個月間達族群成熟殼高。
殼體氧穩定同位素分析法可應用於淡水螺貝類年齡推定；此外，川蜷密度與螺貝類組成受棲地條件影響，可作為石門水庫集水區內未來生態工程評估、棲地評估與復育的考量物種之一；未來如應用殼體氧同位素法驗證較易操作之年齡形質之有效性，將可廣泛推估各溪流川蜷於原棲地的年齡成長，有助於釐清性比偏差與生殖策略差異之原因。

關鍵字

川蜷 ； 氧穩定同位素 ； 年齡 ； 生殖生物學 ； 石門水庫集水區

並列摘要

Ovoviviparous freshwater snail Semisulcospira libertina (Prosobranchia: Pleuroceridae) were wildly distribution in Shihmen Reservoir watershed, and it was seem as indicator species of un-polluted habitat. In this study, we estimated age of S. libertina through stable oxygen isotope ratios (δ18O) of shell, and determined the reproductive biology by dividing embryo stage from female brood pouch.
The study periods were divided to two stages, we surveyed two streams sampling stations (Hsiayun and Sanmin) from July to October 2010 at first, and then surveyed four streams sampling stations (Kuchi, Hsiayun, Shihbichiao and Sanmin) from April 2011 to May 2012. The freshwater snails sampling and environment monitoring were conducted at each station monthly. The age determination of S. libertina were determined by two shell sample from Hsiayun station. The reproductive biology were determined from S. libertina population from Hsiayun and Sanmin station.
The result revealed that the series of δ18O from two shell samples show the fluctuated pattern both. The shell high of two samples were 20.53mm and 24.95mm, δ18O were determined from -6.17 to -8.12 ‰ and from -6.83to -8.55 ‰, age were estimated about 14.5 months and 20 months respectively. The community composition of freshwater snails changed and population density of S. libertina decline. The sex ratio was severely deviated from 1:1 in all streams, and the female much more than the male. The minimal mature shell high (MH50) and shell width (MW50) of Hsiayun were 13.5 and 6.55mm respectively. The minimal mature shell high (MH50) and shell width (MW50) of Sanmin were 17.84 and 7.58mm respectively. The potential shell size to release juveniles of female S. libertina in Hsiayun stream was smaller than Sanmin stream. We suggested that the different reproductive strategy of S. libertina depended on the different habitat and interspecific competition.
The results suggested that the age of freshwater mollusk living in natural habitat would estimate objectively through determining the δ18O of shell. This method would benefit to the studies among the growth, population dynamic, resources assessing, and medical model species.

並列關鍵字

Semisulcospira libertina ； age ； stable oxygen isotope ； reproductive biology ； Shihmen Reservoir

參考文獻

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