Australia is known for its populations of Great White Sharks (Carcharodon carcharias), but this week news broke of a different “white shark”; a male Grey Nurse (or “Sand Tiger,” Carcharias taurus, as we call them stateside) Shark that is entirely white.
An image of the all-white male shark, from The Daily Telegraph.
Normally these sharks, like many others, exhibit the classic “dark on top, white on bottom” counter shading, with some darker spots over the dorsal half of their body, but this one is being heralded as “albino.” Albinism is a genetic disorder by a lack of pigment in the hair, skin, and eyes of mammals, the eyes appearing red because there is no pigment in the eye to “cover up” the blood vessels in the back of the eye (we’d all look this way if we lacked pigment in our eyes, which actually occurs every now and then). What is more likely is that this is a shark exhibiting Leucism, which is caused by a reduction in all kinds of skin pigment (albinism just deals with melanin). While I’m not sure what an albino shark’s eyes would look like, the eyes of the shark in the picture seem to be no different from those of normal sharks, which is characteristic of Leucism rather than Albinism as well. Perhaps the most famous examples of leucism are alligators; they appear to be a creamy-white color with blue eyes, almost like giant versions of a white-chocolate alligator I once received as a treat when I was younger.
Still, the presence of such a shark does raise some interesting questions. It seems to be more skiddish than other sharks of its kind nearby, so did its bright coloring make it more attractive to predators (i.e. larger sharks), requiring it to be more shy? How did it get to grow to such a size if it was so conspicuous? Why hasn’t it been seen previously? Why hasn’t another case been seen previously? We might not be able to get answers to any of these questions, but the presence of a potentially leucistic shark is definitely exciting.