Most fish lay eggs, and it is fertilized outside of their body. Fish that spawn, are called oviparous. But some fish give birth to live fry. Such fish are called viviparous.
To live-bearing are guppies, sword fish. The eggs of these fish are fertilized inside the mother’s body and develop there until the fry. At a certain time they are born. This happens 21 days after fertilization.
The number of eggs, fertilized and deferred, differs greatly depending on the type of fish. Some fish lay eggs and abandon her, without showing her any more interest. This is a fish that produce huge amounts of eggs. Those fish that look after their young, they lay only a few eggs.
Caviar can be of two types. One kind of eggs floats on the water surface, the other sinking. The caviar, which floats, is called pelagic. It is usually tiny, bright and contains a lot of protein. Caviar, which is sinking, is called Donna. It is usually harder and more protein in it. Continue reading
Hundreds of thousands of years ago, long before the appearance on Earth of man, the oceans already swam fish. At that time they were the most highly developed creatures.
Since then, they began to develop a variety of ways so that now only some species only vaguely resemble the first primitive ocean fishes.
As a rule, fish has an elongated and tapering shape. People have copied it in the construction of ships and submarines, as it is the best adapted to movement in water.
Most fish use their tail as a motor. With the help of fins and they control their movements. Except for one species of fish, all the others breathe by means of gills. Fish swallows mouth water that passes through the gills and out through the hole. Water also contains oxygen, and it through the gills into the blood of fish, as the air through the lungs in the blood of man. Continue reading
Sponges that are sold in stores and are used for washing dishes or cleaning the kitchen, not real. They are made from synthetic materials, although very similar to a real sponge and easy to use.
But these sponges appear in the sea, not in a chemical laboratory. For a long time many were convinced that they know all about sponges. It was believed that this plant, until in 1825 a man by the name of Robert Grant proved that sponges were animals!
It considered the sponge in water through a microscope. And saw trickles of water, which went in through one hole and out through another. Still, for many years, scientists did not know what kind of animal. Thought it was a tiny single-celled creatures that live together in one big colony.
We now know that sponges are the dried skeletons of marine animals belonging to the class of “porous”. This is a pretty significant group of animals. Although sponges are one of the lowest forms in the animal Kingdom, their structure is quite complicated. Continue reading