福壽螺Pomacea canaliculata (Lamarck, 1819)在台灣之擴散及族群分析

Abstract

福壽螺被引進台灣至少有十五年的歷史，所造成的夢魘及農業與生態上的危害是大家有目共睹的事實。所有的水塘幾乎是福壽螺的天下，稻田、溝渠與水道，處處可見一糰糰粉紅色的卵塊。本文從福壽螺的引進台灣談起，對其特殊的生態習性、棲息環境、飼養所造成的農業災害、食用價值的評估、福壽螺的防治及寄生蟲等方面作全面性的整合與研究。 從解剖學上的研究，可以發現福壽螺為紐舌型齒舌，貝殼斷面可分為三層，分別是：殼皮、稜柱層及珍珠層。福壽螺為雌雄異體，從沒有在同一個個體內發現有雌雄二套生殖系統。福壽螺的外套膜為雙層結構有發達的微血管循環系統，由肺門孔開口於外套腔，除了可在水中以鰓呼吸外，當水中缺乏氧氣時水管可伸到水面，直接從空氣中獲得氧氣，這種習性使福壽螺可在十分惡劣的水質中生存。 在台灣地區福壽螺的貝殼呈現多變的外形，本研究分別針對貝殼的大小、殼毛的有無、貝殼的厚度、殼口顏色、殼面色帶的型式、螺塔的高低、及貝殼外唇前端有否向外延伸翻捲等特徵進行討論，但單從福壽螺的外部形態並不足以顯示族群分化的現象。 本研究再以RAPD技術探討福壽螺族群基因結構，發現福壽螺族群內維持著高度的遺傳變異，這可能是為了適應惡劣的生存環境。地理上較為接近的兩個族群並不一定有較為相近的基因組成。此外，若從枝狀圖來看，即使是分佈於南北兩地的個體，也會被分為同一群（group）。此乃因福壽螺族群並非一步一步漸漸的由南向北擴散，而是在短時間內佔據台灣所有的淡水水域，也就是說福壽螺族群在擴散的過程中並沒有發生基因結構的改變，而是在擴散至全省後，才因下列可能因素造成族群間的差異。 1．分佈在各地的族群各自改變族群內的基因頻度。 2．從南到北擴散之時發生Genetic drift。 3．以上兩種情形同時發生。

The apple snail Pomacea canaliculata had been imported to Taiwan more than 15 years. The seriously agricultural and ecological damage caused by this apple snail, is witnessed by all. P. canaliculata spread almost in all fresh water pool, paddy irrigated canal and other watercourse in Taiwan. Their pink egg sacs were adhered everywhere above 10cm height of the water surface. In this study the imported papers described the apple snail were reviewed, then discuss their special ecological habit, habitat and value of economic utilization. Finally, the prevention and treatment of their agricultural and ecological damage, and the study of their parasite were also reported. In the anatomy study, P. canaliculata. I hold taenioglossa radula, with one central tooth, two lateral teeth and four marginal teeth. The shell of P. canaliculata with three major layers, such as periostracum, prismatic and nacreous layers. Sexes are separate in P. canaliculata, therefore the male and female reproductive system could not been found in the single individual. The mantle roof is developed into a vascularized area and invaginated as a pouch, called pulmonary sac. The mantle edge elongates and rolls up to form a tube for air intake, siphon With the above structure of P. canaliculata may respire aquatically by their gill or aerially by their pulmonary sac. Pomacea canaliculata in Taiwan appears great variance in shell size, shell thickness, band pattern, aperture color, spiral and with shell hairs or not, and outer lip reflexed or not, etc. The shell variations of P. canaliculata maybe cause by their habitat, predator or different sex, and could not respond the population diversity. The population genetic was discussed by using RAPD method. The Taiwanese P. canaliculata keeps great genetic variance within population because of difficult habitat. In the phenogram of the P. canaliculata individuals from north to south of Taiwan, some population even located in vary far distance could groups into more related groups. It is because of rapid spread of P. canaliculata populations from south to north of Taiwan and the populations were not differentiation yet during extended the population. And then the populations becoming difference by the following possibility reason: 1. The genetic frequency of populations becoming difference in different locations. 2. Genetic drift been happenduring population spread. 3. Both of above reason.