A Fish with Three Hearts: Cuttlefish

It is said to be a royal among sea animals because it has blue blood, literally. And the cuttlefish has a large heart. Actually, it is not one but three hearts.

And it is not even a fish but belongs to the same family as the squid and the octopus. They are called the cephalopods, which literally translated means head-foot.

The blood of the cuttlefish is blue because of the huge amount of copper in it. While it uses two of its hearts to pump blood into the gills (the lung of the fish) where it absorbs oxygen, the third heart pumps blood into the other organs.

With their flattened bodies, cuttlefish are well suited to life on the sea bed, where they hunt for molluscs and small fish. They have a chalky internal shell called cuttlebone that often gets washed ashore. The cuttlebone has a use: it is fed to canaries and parrots.

The cuttlefish is a master at camouflage; it can change its colour to match its background and hide from its predators. This is done by adjusting the size of the pigment sacs in its skin.

The pigment sacs are small bags in which the cuttlefish carries several colours. If the attacking animal still manages to detect the cuttlefish, it ejects a black liquid blinding the attacker temporarily while it escapes.

228 words | 2 minutes
Readability: Grade 8 (13-14 year old children)
Based on Flesch–Kincaid readability scores

Filed under: planet earth
Tags: #heart, #pigments

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