Viviparous fish. The Blue Shark. Cramp-fish

Most of the fish known to us multiply by spawning, but not all. Some underwater inhabitants, both aquarium and wild, give birth to their offspring. Therefore, many fans of the aquatic fauna are interested in the question of which fish are viviparous and exactly how they multiply.

Sharks

Many sharks are known for being viviparous. For example, such species include tiger, herring, paid shark, hammerhead and others. Also on this list there is a blue shark. The size of this fish usually does not exceed 3.8 meters. But their sexual maturity begins when they reach two meters. In males, this period occurs with a body length of 1.9 meters.

After the mating took place, the female can not become pregnant immediately. Spermatozoa in her body can persist for months, waiting for the period of ovulation. After the ovum females have been fertilized, the period of gestation begins, which can last from 9 months to a year. It is believed that the blue shark refers to the most prolific of all large relatives. The number of fry born in the world varies, and the figure varies from 4 to 120 individuals. Kids are born independent, ready for predatory life, but only half of them reach their maturity, because larger fish are not averse to profit.

Cramp-fish

But this method of reproduction of fish is not only found in sharks. Some types of stingrays are also viviparous, for example, caudex. Usually the female brings one baby, whose length is about 35 centimeters. To the viviparous slopes also include mantas, which bear one more name - sea devils. These large fish also bring one baby, which at birth already reaches a meter, and its weight - 50 kilograms. To the offspring came into the world, the mother seems to shoot his baby, which is rolled into a roll. The crumb immediately spreads its "wings" and swims for the female. During the period of pregnancy this fish shows unprecedented aggression and is able to flood the boat.

How do babies develop in the womb?

It is known that viviparous fish brings already formed baby, but scientists for many years could not understand how the fry get oxygen in the womb if they do not have a placenta and an umbilical cord. But in 2008 the riddle was solved. Okinawa fishermen caught a pregnant sea devil and left him to scientists for research. In order to better study the period of bearing of the fetus in this fish, the researchers improved the ultrasound device a little, after which it began to work in salt water. Observations continued until the birth, which occurred after eight months. One young female has appeared in the world. The newborn weighed 50 kilograms.

Since this viviparous fish was under observation during the entire period of gestation, scientists were able to solve the riddle about how the fetus breathes. Being in the womb, the kid uses his gills and pumps the amniotic fluid through them . For this, he, as an adult, opens and closes his mouth. The water that comes to it passes through a special channel and reaches the valve behind the head (it is not only in the rays, but also in the sharks). Adults do not close their mouths when driving, to immediately filter water and plankton. Cubs in the womb have to use their mouth as a pump. In this way, the fetus can breathe and eat.

Relationship between parents and fry

Since the young immediately after the appearance are ready to lead an independent life, they basically do so. Most of them now do not depend on the mother. And in some cases it is better for them to stay away from their parents. Adult individuals usually do not distinguish their offspring from eating, and if they are hungry, they can profit from their own babies.

Other species of live-born fish

The sharks and stingrays described by us are related to cartilaginous fishes. Among bone fishes more often occur those that spawn by spawning. But nevertheless among them it is possible to meet and viviparous. These include a citmatogaster. This species of fish by some factors is similar to percids, and on other grounds resembles carp. Their habitat is the Pacific Ocean, its northern part.

But viviparous are not only fish, in which fry eat directly from the mother in the womb. The female can carry eggs in the belly. Fry eat from the yolk. When it's time to give birth, the eggs form into the fry and the mother starts to throw them. For example, such a method of reproduction of fish is inherent in the Beldjug. At birth, these fry are already formed. At times the female can bring up to three hundred fish, but it happens portion by piece. The size of each newborn fry is four centimeters.

Among the commercial viviparous fish is the grouper. This is a very prolific species, which is caught in large quantities in the Barents Sea and the Atlantic Ocean. This viviparous fish for one season gives an offspring of several hundred thousand. It larvae, each of which is approximately six millimeters.

The only viviparous fish of Lake Baikal

Baikal is a beautiful and deep-water lake, and it is home to many underwater inhabitants. Among all the diversity here you can find a single viviparous fish, which is called golomyanka. To many, this fact may seem surprising, since usually in the northern latitudes the fish multiply by laying eggs. There are two kinds of golomyans here. The large grows to 25 cm, the small one does not exceed 15 cm. The Golomyanka does not spawn spawn migrations, as it does in other fish that spawn. When the time comes and in the womb of the female the roe turns into fry, the mother rises closer to the surface of the water. Most likely, it is necessary for children to feed on plankton organisms. Viviparous fish golomyanka gives a large offspring depending on the species. Small ones appear at one time not more than 1.5 thousand fish. At large this figure is approximately 2,5 thousand fry. After giving birth, the mother dies. Surprisingly, this species of fish is found only on Lake Baikal. Such a mechanism of reproduction and death is no longer repeated in other underwater inhabitants.

Aquarium inhabitants

But viviparous fishes are found not only among commercial fish species. Many owners of aquariums know that some of their favorites of their fry bear. In general, live birth is inherent in the family of Pecilia, Gudii and some others. Usually these are schooling fish, and they are small in size. Also among them, males are slightly smaller than females, and their coloring seems brighter. When they reach puberty, the anal fin of the male becomes a gonopodia, through which fertilization takes place. Each species has its own distinctive features in the structure of this process. This is necessary in order to exclude the possibility of hybridization. But breeders annually bring out new varieties of decorative fish, which leads to the appearance of unusual colors and shapes. Mostly it concerns guppies. Without selection, decorative viviparous fish quickly loses its color and gradually degenerates.

Development of fry

The period of development from caviar to fry in the womb of a female depends on the family and the type of fish. After fertilization, bearing can last only a week or two. But in some fish this period lasts up to 2.5 months. In most of the calves of the Pecilia family, the young grow large and at the same time much more easily than the caviar itself, whereas in other species the weight of fry considerably exceeds that of fertilized eggs. And due to the fact that the milk from the male can remain in the female for a long period, the eggs can not be fertilized immediately, but after a while and not once. Therefore, even with a single fertilization, the fish can bring offspring several times. It is not difficult to feed it, since the fry immediately manifest activity after the birth. The number of young fish depends on the type of fish and can be as many as one or hundreds.

The content of the lamb

In order to reproduce viviparous fish successfully, it is important to take care of their living conditions. Common aquariums are usually suitable for their maintenance, in which there are vegetative thickets. In addition, neutral water requires regular replacement. Weekly, 15 to 40% of the liquid is replaced. But some species will feel much more comfortable if the water is slightly salty. Such conditions are created mainly for mollies and white whites. For this, a tablespoon of sea salt is added per ten liters. Also, the ideal water temperature for most species usually ranges from 20 to 25 ^° C.

To ensure that the ration of fish is balanced, they need to add vegetable components to the feed. It can be salad, filamentous algae, oatmeal and other food.