近日,，俄克拉何馬大學(xué)的生物學(xué)家Douglas Gaffin等研究人員在Animal Behaviour
雜志上發(fā)表論文"Scorpion fluorescence and reaction to light"蝎子的身體布滿了眼睛,，有的時候甚至可多達(dá)12個,。蝎子的整個外骨骼可能充當(dāng)著一個巨大的光感受器，這是一種原始的“眼睛”,，用來感受月光和星光,。
這一猜想或許能夠幫助解釋為何蝎子在紫外光下會發(fā)出明亮的光芒。Douglas Gaffin說,，這可能是蝎子的一種自我防御措施,，無論它們的體色如何，在它們沒有找到藏身處之前,，這種光芒一直會在紫外光照射下放射出光子,，在陰影下光芒會消失，于是蝎子就可以選擇朝那個方向移動,。
這種機(jī)制被稱為熒光,，但為何蝎子會擁有它仍不得而知?？赡艿脑虬ㄇ笈夹盘?、由日行向夜行進(jìn)化的遺存等,。4.3億年前的蝎子親屬——板足鱟（eurypterids）化石顯示,，這種機(jī)制早已存在。Gaffin注意到一種被稱為荒漠草原蝎（Paruroctonus utahensis）的蝎子甚至在全黑的情況下也能發(fā)光,。Gaffin并不是第一位注意到熒光作用在將紫外光轉(zhuǎn)換為可視的綠光的過程中的作用,。之前曾有研究者將蝎子的眼睛遮蔽，并將熒光色素移除后發(fā)現(xiàn)它們就無法辨清方向了,。而另外的研究表明當(dāng)蝎子身體閃爍綠光時,，其尾部的神經(jīng)也會亮起來。
Gaffin和他的學(xué)生分別在紫外線,、綠光和不可見長波光下觀察蝎子的行為,，同時，他們完全將蝎子的眼睛遮住,，以確認(rèn)外骨骼能否起到感光的作用,。結(jié)果顯示，遮住眼睛的蝎子與紫外光下的蝎子行動方式是一致的。雖然星光要比月光黯淡得多,，但Gaffin認(rèn)為足夠多的熒光色素仍然能夠感受星光,。為了驗(yàn)證這一猜想，他將繼續(xù)做更多的實(shí)驗(yàn),。（生物谷Bioon.com）
doi:10.1016/j.anbehav.2011.11.014
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Scorpion fluorescence and reaction to light
Douglas D. Gaffina, , , Lloyd A. Bummb , Matthew S. Taylora , Nataliya V. Popokinaa , Shivani Manna
Scorpions are largely solitary, nocturnal arachnids that glow a bright cyan-green under UV light. The function of this fluorescence is a mystery. Previous studies of four species from three families have shown that scorpion lateral and medial eyes are maximally sensitive to green light (around 500 nm) and secondarily to UV (350–400 nm). Scorpions are negatively phototactic, and we used this behaviour to assay the responses of desert grassland scorpions, Paruroctonus utahensis, to 395 nm UV light, 505 nm cyan-green light, 565 nm green light and no light within small, circular arenas. Based on the eye sensitivity data, we predicted maximal response to 505 nm, followed by lower responses to 395 and 565 nm. In our experiments, however, scorpions responded most intensely (abrupt bouts of locomotory activity) to 395 nm and 505 nm. Next, we ran trials under 395 and 505 nm on scorpions with their eyes blocked. Scorpions with blocked eyes were much less likely to move under 505 nm than under 395 nm and were much less likely to move under 505 nm than were control animals (those without their eyes blocked). These results suggest an active role for fluorescence in scorpion light detection. Other studies indicate that photosensitive elements in scorpion tails are sensitive to green light. We therefore propose that the cuticle may function as a whole-body photon collector, transducing UV light to cyan-green before relaying this information to the central nervous system. Scorpions may use this information to detect shelter, as blocking any part of the cuticle could diminish the signal.
