Starfish are some of the most mysterious creatures of the underwater world. These are invertebrate animals belonging to the type of echinoderms. Why echinoderms? And all the matter is that these creatures have very hard skin, and on the outside it is covered with spines or needles, which are plates of calcium carbonate.
Starfish appeared on the planet for a long time, more than 250 million years ago. A brightly colored star-shaped (up to 50 rays) or pentagonal body has a length of one centimeter to one meter. There are about 1.5 thousand species of sea stars, they live at depths of up to 10 kilometers. The life cycle of these creatures lasts about 35 years. They can be found in all oceans of our planet, however, they prefer coral reefs, coastal areas and warm shallows more. In fresh waters they are not found. Most of these creatures grow up to 20 cm, however, there were such individuals, whose length reached 3 meters.
It turns out that sea stars know how to walk. If you look at their lower part, you can see thousands of leg-tubes, which in turn also have suckers, with which the stars move. Also, limbs are used for breathing and catching food.
These creatures during food can not swallow food, because their stomach can turn inside out and penetrate into the shells of animals that the star wants to eat. After this process, from soft tissues there is only a liquid solution, which they can then simply draw into themselves. Food of sea stars are worms, crustaceans, mollusks and sea urchins. Delicacies on their “dinner table” are oysters and mussels.
There are only three kinds of these unique creatures: ordinary stars, feather stars (up to 50 wriggling rays) and fragile stars (discard their rays in case of danger). Fragile stars, like chameleons, are able to grow their rays. As already mentioned, the body of stars consists almost 80% of calcium carbonate. Accordingly, each beam is viable and extremely quickly regenerates. Often these marine creatures multiply also by division in half. Fabrics in the places where the star will disconnect, first become very soft, and then disintegrate. Subsequently, all the “fallen off” parts grow in both individuals.
But the most surprising thing in these sea creatures is that they can, if necessary, change their gender. Of course, for this, certain conditions must be met: food availability, temperature and others. When all conditions are favorable for reproduction, many males change their sex and start laying eggs.
Starfish have no circulatory system. Its very successfully replaced the water-vascular system. It works very interestingly: this sea creature pumps itself with water through the surface of its skin, and its legs-suckers spread it all over the calf. The water is removed in the same way – the skin. With all this, the stars have a heart that makes 6-7 beats per minute. But there is no brain for these creatures.
It turns out that the stars of the sea have eyes and not a pair, like us, people. Each individual has the same number of eyes as the rays. At the tip of each ray is an eye, in appearance a red spot. They see, of course, not very well, but at least they distinguish between darkness and light.