Why the clear eyes?

Posted by Nature View (Park City, Utah, United States) on 6 July 2007 in Animal & Insect and Portfolio.

This is the 3rd different Hemigrapsus nudis photograph that I have posted over the past week or so - all 3 were different crabs of the same species found in the same intertidal area.

However, the above crab is different in that it has clear eyes as opposed to black eyes. Can anyone hazard a guess as to what is different about this crab? The answer is actually pretty cool.