台灣東北部卯澳灣海域白尖紫叢海膽（Echinostrephus aciculatus）骨片生長和年齡決定之研究

Abstract

本研究選取台灣東北部卯澳灣海域之白尖紫叢海膽（Echinostrephus aciculatus）為研究對象，從2005年四月至2006年三月間每月採樣一次，進行以下實驗：（1）分析殼徑和間歩帶骨片數目之關係（2）分析不同月別樣本殼徑長、冠狀骨片乾重之變化（3）分析海膽的一系列間歩帶骨片圍肛區、腰帶區和圍口區水平成長軸的同位素值變化（4）分析兩隻海膽的圍口區骨片之水平和垂直成長軸氧同位素值變化（5）藉由分析氧同位素值之變化和氣溫之變化呈現反比，回推海膽年齡。 結果顯示白尖紫叢海膽的殼徑和間步帶骨片數目間、殼徑和體高間及體高和間步帶骨片間呈現正相關關係。比較殼徑長，得知3,4月之殼徑最大，逐月減小至11月；比較冠狀骨片乾重也是3,4月最重，7月最輕。以此推論白尖紫叢海膽在7月前完成繁殖和變態定著期，再加入新的族群。分析採樣的其中一隻海膽（殼徑50.47mm）之圍肛區、腰帶區和圍口區間步帶骨片水平成長軸氧同素值變化分析結果顯示出不同的變化趨勢，表示其出現的時間點不同。另分析兩隻海膽（殼徑54.7mm、50.47mm）之圍口區的骨片水平成長軸和垂直成長軸之氧同位素值變化分析結果呈現出以中央為對稱的變化趨勢。以氧同位素值和氣溫呈負相關推測出水平成長軸方向和垂直成長軸方向皆有兩處生長點，且由生長點向內和外長出新的骨質;水平方向的生長，向內和向外的生長速率較相近，而垂直方向之生長速度，向內生長的速率高於向外生長的速率。如此推測出海膽骨片具有環狀形成層，向內和外推擠出新的骨質。最後，從水平成長軸之氧同位素值變化和氣溫呈負相關回推編號05041604海膽年齡約為4.9月。碳同位素值變化顯示其與氣溫變化並沒有明顯的負相關或正相關。

Echinostrephus aciculatus, the most dominant species in Maoaw Bay of the Northeastern Taiwan, was surveyed in this study. From April 2005 to March 2006, samples were taken every month to conduct the following experiment. First, the researcher measured the shell diameter and the plate of interambulacral zone to analyze the relation between. Second, the researcher compared the shell diameter and the dry weight of the coronal plate. Third, the researcher analyzed and compared the stable carbon and oxygen isotope ratios in horizontal growth axle of the periproct, the ambitus and the peristome of the interambulacral zone of two sea urchins. Then, the researcher analyzed the stable carbon and oxygen isotope ratios in the horizontal and vertical growth axle of the peristomes’ plates of two samples. Last, the researcher derived the age of sea urchins by analyzing the inverse relation between isotope ratios and temperatures. Results showed that positive correlation existed among the shell diameter, the plate of the interambulacral zone and the height of sea urchins. As to the shell diameter, samples collected during March and April reached the maximum, with a decreasing trend to the minimum in November. As to the dry weight, the maximum fell on samples collected during March and April while the minimum in July, which showed that Echinostrephus aciculatus had completed reproduction as well as larvae settlement and metamorphosis by July and then joined to a new colony. By analyzing the stable carbon and oxygen isotope ratios of the periproct, the ambitus and the peristome of the interambulacral zone of a sample collected in April, 2005, the researcher derived different values of plates of different areas, and inferred the difference in growing time. Moreover, a trend of mirror symmetry was observed when the researcher analyzed the stable carbon and oxygen isotope ratios in the horizontal and vertical growth axle of the peristomes’ plates of two samples (No. 05041604 and No. 05041659). This finding, combined with the inverse relation between isotope ratios and temperatures, drew the inference of two growth zones in horizontal and vertical axle with both inward and outward bone regeneration. The rates of inward and outward regeneration were similar in horizontal axle while in vertical axle the rate of inward regeneration was higher than that of outward regeneration. In this way, it was inferred that the plates had the circular cambium, from which bone regenerated inward and outward. The researcher then inferred the sample No. 05041604 to be 4.9 months old from the inverse relation between isotope ratios and temperatures. Besides, the carbon isotope ratio didn’t show any significant positive or negative correlation with the temperature.