Category Sea/Ocean

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.

The box jellyfish feeds on prey like fish and shrimp, but it does not want their escape struggles to damage its delicate tentacles. So the jellyfish uses its powerful venom to stun or kill the prey instantly. The venom of the box jellyfish is among the most deadly in the world, attacking the heart, nervous system and skin cells. Humans struck with this venom sometimes go into shock and drown before reaching shore. The survivors have to endure intense pain for weeks, and carry scars where the tentacles touched. These jellyfish do not fire venom at anything that the tentacles touch. The stinging cells only react to some chemicals on the skin, so there’s no wastage of their weapon!

Also known as sea wasps and marine stingers, these deadly jelly-fish mostly live in the coastal waters near Northern Australia and in the Indo-Pacific. The box jellyfish are so named because of their cube-like shape. This group include various species of various sizes; the largest measuring about a foot across, and with tentacles about ten feet long. Some divers use tight-fitting clothes that cover the whole body to escape their venom.

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The Mediterranean Sea holds a wonder that beats all – something that never dies! It is a jellyfish whose scientific name is Turritopsis dohrnii.

Jellyfish start their lives as larvae, which attach themselves to a suitable place like a rock. Then they are transformed into polyps that have a small body with tentacles. These polyps then clone themselves to form others and create a colony, or a medusa, which is the jellyfish.

When this jellyfish dies, or is physically damaged, the decaying cells form new polyps, and later return to their jellyfish state. This way they could live forever under the right conditions! However, they don’t actually achieve immortality because these tiny wonders are eaten by fish or other animals, or die by other means.

Although the jellyfish has ‘fish’ in its name, it is not fish. It is not made of jelly either. Unlike a fish, it is an animal without a backbone found in oceans and seas around the world. The name jellyfish derives from the jelly-like bodies of these animals. Jellyfish are found in oceans and seas all over the world, in the deepest as well as in shallow water.

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Meet someone whose body tells his own life’s story that runs into centuries! The ocean quahog, a bivalve mollusc that can live more than 500 years, is the longest-lived solitary animal.

The shell of an ocean quahog is a treasure-house of information for scientists. Its shell grows periodically throughout life and the growth patterns visible on the shell function as a calendar. They help not only to tell the age of the animal, but also to know more about the marine environment in the past. For example, scientists would be able to tell from the shell of a quahog, how warm the seas were two centuries ago! The quahogs are the only surviving species of a family of similar claims that had lived during the Dinosaur era!

The ocean quahog (Arctica is landica) lives in the North Atlantic Ocean, buried in sandy sea beds. It feeds on the organic matter it gets by filtering water using its siphon. Interestingly, their feeding activity seems to depend on how much light is available! Thus, in the northern-most regions where they are found, they mostly feed during eight months of the year. During the remaining months, they feed for only a few days.

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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.

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Everybody loves a good pearl. Did you know that the mussel it comes from is admirable, too?

The freshwater pearl mussels are one of the longest-lived invertebrates. Scientists have determined that they can live for up to 210-250 years. Scientifically known as Margaritifera margaritifera, these are bivalve molluscs, meaning they have a compressed body enclosed within a hinged shell. Inside the shell is a thick, iridescent layer called the mother-of-pearl. The freshwater pearl mussels live on the beds of fast-flowing rivers, feeding by taking in water and ingesting any fine organic matter that comes with it.  Just imagine, an adult mussel can filter more water in a day, than what you use for a shower! They live seemingly safe, partly buried in sand or gravel. Yet, they are never safe because of the fine-quality pearls they can produce. Humans have always exploited them in the search for pearls, and these mussels have now become an endangered species.

Picture Credit : Google