EVERYDAY SCIENCE

Detailed explanation-1: -Furthermore, the blood in human veins is also not blue. Blood is always red. Blood that has been oxygenated (mostly flowing through the arteries) is bright red and blood that has lost its oxygen (mostly flowing through the veins) is dark red.

Detailed explanation-2: -Indeed, most mammal, fish, reptile, amphibian, and bird blood is red because of hemoglobin, whose protein is made of hemes, or iron-containing molecules that fuse with oxygen.

Detailed explanation-3: -Can you guess what animals might have blue blood? Lobsters, crabs, pillbugs, shrimp, octopus, crayfish, scallops, barnacles, snails, small worms (except earthworms), clams, squid, slugs, mussels, horseshoe crabs, most spiders.

Detailed explanation-4: -Blood does change color somewhat as oxygen is absorbed and replenished. But it doesn’t change from red to blue. It changes from red to dark red. It is true that veins, which are sometimes visible through the skin, may look bluish.