Believe it or not, there are blue blooded animals. Humans (and mammals in general) have red blood because of the presence of Iron. Logically speaking, since these animals do not have red blood, they must have some other element flowing through their body right? The secret element is copper… An animal which has blue blood is called a teuthida, and has copper flowing through it, giving it a shade of blue!
Octopuses, squids, cuttlefish and nautilus, and horseshoe crabs all are blue blooded sea-animal. Their blood contains the copper-rich protein hemocyanin for transporting oxygen. Unlike hemoglobin, which contains iron, hemocyanin is an oxygen carrying molecule with copper at its center. Hemocyanin is dissolved in blood plasma instead of being carried within red blood cells and gives the blood a bluish color.