The blood of a lobster is typically blue. This distinctive color arises from the presence of hemocyanin, a copper-containing protein that functions similarly to hemoglobin in human blood. While hemoglobin transports oxygen in vertebrates, hemocyanin serves the same purpose in many invertebrates. When hemocyanin is oxygenated, it turns a blue color, which explains the bluish tint of lobster blood. This adaptation allows lobsters to thrive in their underwater environment, efficiently transporting oxygen in colder temperatures and lower oxygen levels often found in deep-sea habitats.