Yet the sharks lacked cone cells, which respond individually to light at specific wavelengths. In human eyes, a variety of cone cells helps us to distinguish between colors.

The most affected country in the Southern Cone is Argentina, with the second-highest number of swine-flu-related deaths in the world (after the US) and 70% of the deaths in the Southern Cone.

But no cone cells were observed in 10 of the 17 species, while only one type of cone cell appeared to be present in the other 7.