My Science School

The blue-ringed octopus may look cute and harmless at the first glance. But take care; it is an extremely poisonous animal!

These small octopuses are common in coral reefs and tide pools of the Pacific and Indian Oceans. They usually stay hidden in crevices, shells or marine debris, their tan-coloured body blending in with the surroundings. But the ‘true colour’ of this shy little thing comes out when threatened by somebody. Bright blue rings appear all over its body as a warning signal, which have given it the name.

If a human is bitten by the blue-ringed octopus it can cause respiratory distress and paralysis and other symptoms too, like nausea, blindness and heart failure.

The venom is not just to fight the enemies, it helps in feeding too. These octopuses usually hunt small crabs and shrimp, but will also eat molluscs and small fish. The octopus delivers the paralyzing venom into the prey. The venom is produced by its saliva, which also contains digestive enzymes. So the flesh of the prey is partially digested before the octopus sucks it out. The blue-ringed octopus is not hurt by its own venom.

Urchin usually means a young child who is raggedly dressed and behaves badly. But sea urchins get their name from an old meaning of this word - the hedgehog. Sea urchins have a globular body that is full of spines, like a hedgehog.

The sea urchins belong to a group called echinoderms, or spiny-skinned marine invertebrates. The largest of this species are the red sea urchins, whose outer skeleton can have a diameter of more than 18 cm and spines, a length of up to 8 cm. They are a colourful sight under the sea, varying between a uniform red and dark burgundy, crawling slowly over the sea bottom using their spines as stilts.

The sea urchins are among the longest-living animals, with a life span of over 100 years. But that does not mean that they don't face any danger in the sea. They are eaten by some fish like the wolf eels, sea stars, crabs etc. Large adults, of course, are often left alone by these predators. But sea otters eat even the largest sea urchins, cracking them on rocks. Young sea urchins usually seek shelter under the spines of the adults, and emerge only when they reach approximately 5 cm in diameter.

Picture Credit : Google