Anarctic icefish are the subject of study in the war against a host of bone diseases. It turns out that these fish, who live their entire lives in southern waters whose surface doesn't go above freezing, have some interesting traits. They have no red blood cells--a liability in freezing temps. And, they've largely shed their skeletal system. Their native frigid waters are energy poor, and since bone is dense, not having much in the way of bone allows them to use less energy to maintain their bouyancy. Clever little icefish.