Albino animals lack the brownish-black pigment melanin.
Leucistics, like this alligator, have two recessive genes that produce a white color. The 150-pound reptile in the pool at the Otto Borchert Family Special Exhibits Building is one of only 14 such alligators known in the world, according to Craig Berg, curator of reptiles and fish at the zoo. The Ghost is not an albino, Berg said, but a creature even more unusual, a leucistic. Instead of lacking the brownish-black pigment melanin, as albino animals do, leucistics have two recessive genes that produce a white color. No basking in the sunshine for the Ghost, a.k.a.