Question

Why the blood of some molluscs and crustencens (crab) is blue in colour​

Answer 1

Answer:

the blood of some molluscs and crustencens (crab) is blue in colour because they don't have hemoglobin like us which gives red colour to our blood

Hope it helps

Answer 2

Answer:

Hemocyanins are copper-containing respiratory pigments found in many mollusks (some bivalves, many gastropods, and cephalopods) and arthropods (many crustaceans, some arachnids, and the horseshoe crab, Limulus). They are colourless when deoxygenated but turn blue on oxygenation.