探討發光二極體（LED）對白棘三列海膽胚胎發育及行為之影響

Abstract

本研究目的為探討不同波長之發光二極體 (LED) 對白棘三列海膽(Tripneustes gratilla) 的胚胎發育、遮蔽行為 (covering behavior)、翻正行為 (righting behavior) 以及趨光性 (phototaxis) 之影響。實驗用海膽分為三組不同波長處理，分別為白光（全光譜）、紅光（波長：630nm）及藍光（波長：450nm）。胚胎發育實驗是將人工授精後的受精卵於LED下照射培養，並分別於24及48小時記錄胚胎發育各階段的個體數量，結果顯示在授精後24小時，波長450nm組有較高比例的胚胎進入錐形期 (Prism)，而在授精後48小時，波長450nm組也有較高比例的胚胎進入四腕期 (4-arm pluteus)，但死亡率亦較高；全光譜組和630nm組的發育速度則無明顯差異。遮蔽行為是海膽利用管足抓取物品覆蓋在自身上的行為，實驗將海膽在三組LED光譜下照射60分鐘後，觀察海膽抓取壓克力片覆蓋於自身上的數量，結果顯示在波長450nm組，海膽抓取的壓克力片數量最多，即遮蔽行為最為明顯，其次是全光譜組，而在波長630nm組，最不易觸發海膽的遮蔽行為；另外，白色海膽（黑色素較少）的遮蔽行為較黑色海膽更為明顯。翻正行為指的是海膽利用管足和棘刺將自身翻至反口面朝上之行為，本實驗分別在三組LED光譜下倒置海膽，並觀測其翻正的所需時間，結果顯示450nm組的翻正所需時間較長，推測因光波長450nm的刺激性較強，對海膽造成的壓力較大，因此翻正速度較慢。在趨光實驗的結果中顯示了海膽在光波長450nm環境下的負趨光性最為顯著，其次是全光譜，而在波長630nm的光照射下的海膽並無特定趨光或負趨光的行為，此結果再次顯示了海膽對於波長450nm的光較敏感且排斥。本次實驗證實了波長450nm的光環境會加速海膽胚胎的發育，但對於海膽的刺激性亦較高，會促使其產生遮蔽、排斥的行為。

In the present study, we reported that the effects of different wavelength (white: full spectrum; blue LED, peak at 450nm; red LED, peak at 630nm) on embryo development, covering behavior, righting behavior and phototaxis of collector urchin (Tripneustes gratilla). 450nm treatment significantly enhanced embryo development at 24hr and 48hr after fertilization, however, it made the death rate higher than the other two treatments. The growth rate of full spectrum and 630nm treatments was lower than 450nm treatment but had relatively lower death rate. Covering behavior means that sea urchins cover themselves with small rocks, shells and algal fragments. We performed experiments to examine how the sea urchin’s covering behavior is affected by different wavelength of LED. The study found that urchins covered most under the 450nm treatment, but covered least under the 630nm treatment. In addition, we found that white urchins (less pigmented) covered more than black urchins under all different LED conditions. Also, urchins needed longer time on righting behavior under 450nm treatment and showed the most significant negative phototaxis. By contrast, urchins under the full spectrum and 630nm treatments needed less time on righting behavior, and showed less negative phototaxis (full spectrum) or even phototaxis (630nm). In summary, the 450nm LED could enhance the development of sea urchin embryos, meanwhile, it has more irritability to urchins that makes them want to cover themselves or escape.