RED eyes are often a sign of too many late nights, but one worm has another
excuse. The grasshopper parasite Mermis nigrescens uses haemoglobin,
the oxygen-carrying chemical that colours blood red, to absorb stray light in
its eyes.
Adult females emerge from the soil by crawling towards the light. To find the
direction of the brightest light, their eyes are shaped like a tube. One end is
transparent, while haemoglobin on the sides of the tube, like blinkers, absorbs
any light entering at an angle to avoid confusing the worm (Journal of
Biological Chemistry, vol 275, p 4810).
Luc Moens from Antwerp University in Belgium and his colleagues say this is
the first example of haemoglobin having an optical function. They think it鈥檚 the
result of a chance mutation. 鈥淓volution often makes use of whatever is
available,鈥� says Moens.
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