1. Copper-containing proteins found in the blood of certain arthropods and mollusks that function similarly to hemoglobin in transporting oxygen throughout the body.
Usage: plural form; technical/scientific term; also spelled hemocyanins in American English

Examples

• Haemocyanins are responsible for oxygen transport in horseshoe crabs and octopuses.
• Unlike hemoglobin, haemocyanins contain copper atoms at their active sites.
• The blue color of octopus blood comes from the haemocyanins dissolved in it.
• Scientists study haemocyanins to understand alternative respiratory pigments in invertebrates.
• Haemocyanins are less efficient at oxygen binding than mammalian hemoglobin in warm environments.