Erythrocytes (Red Blood Cells)
Humans and other vertebrates have erythrocytes that carry oxygen. Human erythrocytes are biconcave and lack a nucleus, maximizing surface area for gas exchange. Other vertebrates also have red blood cells, though their shapes and structures vary across groups.
Leukocytes (White Blood Cells)
Humans and vertebrates share various leukocytes, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. These cells detect and eliminate pathogens and damaged cells.
Platelets (Thrombocytes)
Humans and mammals possess platelets for blood clotting. Other vertebrates such as birds, reptiles, amphibians, and fish use different clotting mechanisms and do not have platelets analogous to those in mammals.
Nucleated Red Blood Cells
In embryonic development and certain conditions, humans and some vertebrates like amphibians and fish can produce nucleated red blood cells, unlike mature circulating erythrocytes.
Hemoglobin
Most vertebrates, including humans, use hemoglobin to carry oxygen. Some vertebrates, such as certain fish, use different respiratory pigments like hemocyanin or chlorocruorin.