"從台灣產雜斑蓮花青螺Lottia luchuana (Pilsbry, 1901)之 族群動態、生態生理與活動型態探討台灣潮間帶貝類的壓力適應"

Abstract

潮間帶生物面臨許多環境壓力，且其分布受到生理忍受力所限制。因此，環境壓力嚴重影響潮間生物之存活。雜斑蓮花青螺Lottia luchuana (Pilsbry, 1901)是台灣東北角及東部沿岸廣泛分布的一種笠貝，其分布於中高潮帶岩岸，以刮食藻類維生。夏季的高溫與低潮的乾燥壓力以及冬季連續降雨時造成的生理壓力皆會影響此種笠貝的存活、臨死反應、以及行為。因此，本研究就此笠貝之族群動態、滲透壓調節、與活動型態做綜合性的研究，以了解潮間帶笠貝如何適應高溫、乾燥與降雨的環境。 首先對L. luchuana進行兩年的族群動態研究，以了解L. luchuana在潮間帶環境壓力下之生活史策略。另選擇東北角兩個樣點分別在冬夏季透過不同天氣狀況下野外採集與實驗室測量外套腔液和血淋巴液的滲透壓，了解其在不同天氣壓力下，以及離水時間長短之滲透壓的變化。此外也透過24小時逐時連續偵測、15天每日觀察和半年內每月的潮帶分布調查來了解L. luchuana的高低潮、大小潮與季節性週期的活動情形。 實驗結果發現，L. luchuana在族群以及個體層次上皆展現良好的適應能力。在族群上，L. luchuana會隨著浪的高低有季節性垂直遷移，使其能維持在浪打得到的情況之下以減低環境壓力造成之成體死亡率。L. luchuana在台灣東部的新族群加入時間較長，從冬天12月延續到隔年3月，而成體族群的數量呈現穩定的波動。在東北角則是每年冬夏各一次的新族群加入，死亡率低且生長率快，而成體族群的數量在夏季尾聲至秋冬會有下降的趨勢，冬天尾聲又逐漸增加。在個體適應上，生態生理結果顯示L. luchuana外套腔液和血淋巴液之滲透壓在一般溫和天氣狀況下是呈正相關的，然而在受到降雨以及長時間強力太陽照射影響時，血淋巴會維持在穩定範圍內而不隨外套腔液升高或降低，顯示血淋巴有被調節的能力，以在極端環境壓力下有較高的忍受力。從活動行為的結果發現，L. luchuana沒有隨每天潮水漲落之規律活動。反之L. luchuana選擇大部分時間為靜止狀態，並於大浪影響下發生覓食活動以減少覓食時環境壓力的影響。本研究顯示Lottia luchuana可以透過生理以及活動行為的調節以展現高度的環境忍受力並適應中高潮帶之生活。

Intertidal species face many environmental stresses. In the intertidal environment, species live close to the habitats which fit their physiological limits. Physical stress, therefore, severely affects the survival of intertidal organisms. At present, little is known about ecophysiology of intertidal species in Taiwan coast. The intertidal limpet Lottia luchuana is widely distributed on the mid and high shores in north-eastern and eastern coasts of Taiwan. The intense heat and desiccation in summer and heavy rain in winter can impose serious physiological stress to affect the survival, sublethal response and behavior of the limpets. An integrated approach to understand the population dynamics, osmotic regulation and activity pattern of L. luchuana is essential to study how the limpets can adapt to the stressful environments in the intertidal. In this study, we investigated the population dynamics of L. luchuana for two years on the eastern and north-eastern shores of Taiwan, to see the pattern of life history under such stressful environment. In addition, we conducted a series of osmolality examinations of the haemolymph and mantle water of L. luchuana under different weather conditions, both in summer and winter, and investigated the diurnal, spring-neap tide, and seasonal activity pattern on north-eastern coast. Results indicated L. luchuana presented good ability in adaptation for stressful intertidal both in population and individual levels. In population level, L. luchuana exhibits seasonal shift of vertical distribution to reduce physical stresses. The juvenile recruits during Dec. to Mar. on eastern coasts, with low mortality and high growth rate. In north-eastern shores, the new recruitments exhibit in summer and winter respectively, and the population density of adults decline after summer season. In individual level, results showed there is a high correlation in mantle and haemolymph osmolality in benign conditions. However, under heavy rain and intense solar radiation, haemolymph seems to be more constant than mantle. It is likely that there is an osmotic regulation in haemolymph to tolerate the environmental stress on L. luchuana. Also, we found that the limpets stay stationary in most of the time and the activity is only stimulated by tide and wave awash. Limpets did not follow a vertical movement with the rising and ebbing tides. This study shows L. luchuana adapt well to live in mid-high shore of the intertidal and demonstrate good environmental tolerance by physiological and behavioral regulation.