1. A copper-containing protein found in the blood of certain arthropods and mollusks that functions similarly to hemoglobin in carrying oxygen throughout the body.
Usage: technical; biology; also spelled hemocyanin in American English

Examples

• Haemocyanin gives the blood of octopuses and crabs a blue color rather than red.
• The haemocyanin molecule contains copper atoms at its active sites.
• Unlike hemoglobin in vertebrates, haemocyanin is not contained within blood cells but dissolved freely in the hemolymph.
• Researchers study haemocyanin to understand how different organisms evolved oxygen-transport mechanisms.
• The efficiency of haemocyanin in binding oxygen varies depending on the species and environmental conditions.