Some tiny crustaceans living in clear-water alpine ponds high in Washington state’s Olympic Mountains have learned how to cope with the sun’s damaging ultraviolet rays without sunblock — and with very little natural pigmentation to protect them. In fact, in laboratory tests these water fleas, about the size of fruit flies, withstood UV rays much better than the same species of flea taken from a pond less than a mile away, where the water was murkier and thus offered protection.