My Science School

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.

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Did you know that animal activists have categorized the Bengal tiger as an animal superstar? The tiger is listed under a special category called the ‘charismatic megafauna’ which uses the animal’s popular appeal as an instrument for environmental change.

Few animals exude power and grace like the tiger. Vividly coloured in yellow to burnished-orange with vertical black stripes and white underparts, the tiger is a solitary predator. It is the largest of the big cats and can reach a length of 10 feet and weigh as much as 260 kg. It is nocturnal and preys on buffalo, deer, wild boar and other large mammals. Tigers possess the longest canines and the strongest teeth of any big cat and usually kill with a powerful bite on the neck. They have retractable claws and can even climb trees in pursuit of their prey.

The Royal Bengal tiger is native to the Indian subcontinent with about 70 percent of the world’s population found in India. Historically this apex predator was hunted for sport and for trophies like its teeth and skin. Tiger parts are also used in traditional Chinese medicine. Rampant killing of this magnificent animal as well as habitat loss from human encroachment led to its rapid decline.

From as many as 100,000 tigers in the 1900s, the numbers reduced to 20,000 in the next 25 years. By 1965 the tiger population in India was on the brink of extinction. This led to tiger protection laws being passed in 1971 and the launch of Project Tiger in 1973. Due to persistent conservation efforts, today India’s tigers number around 3000.

However, further increase of the tiger population needs a corresponding increase in forest area. A single tiger needs a territory of around 100 sq km to operate and unless existing forest reserves are extended, an increasing tiger population cannot be contained.

This iconic and ultimate predator is the national symbol of our country. The IUCN lists the Royal Bengal tiger as ‘Endangered’ on its Red List.

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Yes, they do! In fact the rougheye rockfish are among the longest-lived marine fish species, some of them recorded as old as 205 years. They grow very slowly, and mature late in life.

Does the name of this fish strike you as strange? They really have ‘rough eyes’, because of spines along the lower rim of the eyes. They are also nicknamed ‘blacktip’ rockfish because their pectoral fins have black ends.

The rougheye rockfish live in the Pacific Ocean, from northern Japan and the Bering Sea to southern California. They usually live at depths between 170 to 660 metres, near the seafloor around caves, crevices and boulder fields. They feed mostly on shrimp, but also go for crabs, tiny crustaceans and other fish. The females usually spawn between February and June, releasing larvae from their ovaries. These fish grow to a maximum length of about 97 cm, and their record weight is 6.7 kg.

For most part of the year, the larger fish remain solitary or roam in small groups, but during some periods, the rougheye rockfish form schools.

For most part of the year, these fish remain solitary, but during some periods, the rougheye rockfish roam around in schools (group).

Picture Credit : Google