| The two-headed fiddler ray fetus, as seen from the bottom.
Credit: Leonardo Guida
They say two heads are better than one. That may or may not be true, but at the very least, two heads are more interesting.
While checking up on the pregnant female rays that he was caring for in an aquarium, Australian researcher Leonardo Guida saw that some of the animals had given birth, in April of this year. As he made note of the baby rays, an “oddly shaped, pale object in the water” caught his attention.
The object turned out to be a stillborn ray … with two heads. This is the first two-headed ray or shark discovered in Australia, and one of only a few examples worldwide of this rare birth defect found in sharks and rays, said Guida, who is a doctoral student at Monash University in Melbourne.
The defect arises when the neural tube (like a spinal cord) in a single fertilized egg is duplicated, which can happen as the result of a genetic defect or for other unknown reasons. It can also happen when an embryo begins to divide into two to form twins, but is stopped prematurely. [Cyclops of the Sea: Pictures of a One-Eyed Shark]