近日，俄克拉何马大学的生物学家Douglas Gaffin等研究人员在Animal Behaviour
杂志上发表论文"Scorpion fluorescence and reaction to light"蝎子的身体布满了眼睛，有的时候甚至可多达12个。蝎子的整个外骨骼可能充当着一个巨大的光感受器，这是一种原始的“眼睛”，用来感受月光和星光。
这一猜想或许能够帮助解释为何蝎子在紫外光下会发出明亮的光芒。Douglas Gaffin说，这可能是蝎子的一种自我防御措施，无论它们的体色如何，在它们没有找到藏身处之前，这种光芒一直会在紫外光照射下放射出光子，在阴影下光芒会消失，于是蝎子就可以选择朝那个方向移动。
这种机制被称为荧光，但为何蝎子会拥有它仍不得而知。可能的原因包括求偶信号、由日行向夜行进化的遗存等。4.3亿年前的蝎子亲属——板足鲎（eurypterids）化石显示，这种机制早已存在。Gaffin注意到一种被称为荒漠草原蝎（Paruroctonus utahensis）的蝎子甚至在全黑的情况下也能发光。Gaffin并不是第一位注意到荧光作用在将紫外光转换为可视的绿光的过程中的作用。之前曾有研究者将蝎子的眼睛遮蔽，并将荧光色素移除后发现它们就无法辨清方向了。而另外的研究表明当蝎子身体闪烁绿光时，其尾部的神经也会亮起来。
Gaffin和他的学生分别在紫外线、绿光和不可见长波光下观察蝎子的行为，同时，他们完全将蝎子的眼睛遮住，以确认外骨骼能否起到感光的作用。结果显示，遮住眼睛的蝎子与紫外光下的蝎子行动方式是一致的。虽然星光要比月光黯淡得多，但Gaffin认为足够多的荧光色素仍然能够感受星光。为了验证这一猜想，他将继续做更多的实验。（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.
