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
Watching fish in an aquarium, you’d think they never rest or sleep. In the understanding of man, they are in constant motion. However, like all animals, fish periods of active behavior alternate with phases of slowing of physical functions – this is the dream fish.
Dream fish is different from our understanding of sleep. Structural features and habitat not allow the fish to fall into a state in which they would be completely disconnected from reality. In such a state is immersed most mammals during sleep. The fish also during sleep, the brain activity remains unchanged, – they are not able to fall into a state of deep sleep.
This feature and may cause the issue: how do aquarium fish sleep?
Studying the behavior of aquarium fish, you will notice that at certain times the fish are almost motionless, transfixed in the water. This is the sleeping fish. During sleep, the fish usually drift without active movement. But the slightest influence of external factors leads fish into an active state. Continue reading