What is the development process of freshwater shark larvae?

Badin is also known as freshwater shark, tiger shark, eight treasures, crystal badkin. It is mainly distributed in the inland rivers and lakes of Southeast Asia such as Malaysia, Thailand, Laos, Cambodia, Vietnam and other countries, and is one of the famous freshwater aquaculture high-yield fish with excellent economic characteristics in Southeast Asia.

1. Freshly hatched larvae.

The body of the fish is transparent, the yolk sac is slightly light yellow, peach-shaped, the front end of the heart is oval, uninterrupted contraction and relaxation, the back end is cylindrical, the back end of the yolk sac has a coiled digestive tract, and there are irregular black spots on the surface of the yolk and the lower edge of the trunk.

2. The first day of larvae.

The yolk sac is reduced and egg-shaped, with a clear cloaca visible, but not open outside the body, the eye diameter does not increase significantly, the caudal fin is membranous, the swimming ability is still very poor, and it lies on its side at the bottom of the water.

3. The next day, larvae.

The yolk sac is further reduced, orange petal-shaped, the mouth fissure is slightly opened, the cloaca is close to penetration, the melanin of the eyeball increases, the eye diameter increases significantly, the tail vertebrae are upturned, the tail fin is fan-shaped, the swimming ability is enhanced, and intermittent swimming can be done. The dark spots extend in a chrysanthemum-like shape and spread to the upper margin of the trunk, and the two jaw whiskers are shorter.

4. The larvae on the third day.

The yolk sac is basically gone, the digestive tract is penetrated anteriorly and backward, the intestinal curve is visible and distributed in the digestive cavity, and gently peristalsis rhythmically, a large number of black dendritic structures appear at the junction of the thoracic cavity and the abdominal cavity, which may be a vascular plexus or a plexus, the mouth fissure is completely open, the gill cover on both sides is constantly opening and closing, the gill arches and gill rakers are clearly visible, on the whole, the head is larger, the trunk is slender, with dorsal fin, anal fin, can swim horizontally, and the two jaw whiskers are as long as the middle and back of the body.

5. The larvae on the fourth day.

The ventricles of the head are clearly visible, the canalith is enlarged, it begins to swim constantly in search of food, the ingested food is visible in the intestines, and the lower jaw is growing.

6. The larvae on the fifth day.

The body color gradually deepened, the chrysanthemum-like black spots in the front and back of the dorsal fin increased, the trunk was thickened, the caudal fin was forked, the appearance was basically the same as that of the adult, the dorsal fin and anal fin were further developed, and the other body parts did not change significantly.

The highly differentiated fish are relatively transparent, and then slowly turn pale yellow, shrink continuously, and finally become coiled eggs.

Freshwater sharks are warm-water fish that inhabit the middle and lower layers of the water body under natural conditions and prefer to flock in groups. Because the swim bladder has the effect of assisting respiration, it often swims to the surface of the water to draw water and can breathe oxygen in the air. Cultivation water should be filtered to prevent predators from entering the cultivation pond.

The size of the fry in the same culture pond is consistent. The cement pond can be stocked with 500-1000 freshwater shark fry per cubic meter of water.

At first, it is newly hatched, and the body will be relatively transparent, and then it will take on the shape of an egg. After that, the head will be very clear, and finally the torso will be thicker.

Most shark fertilized eggs develop into fetuses in the mother's womb and eventually give birth to larvae.

When a shark's baby hatches in its belly, it kills the mother shark's womb and eats other siblings or unhatched eggs. It can be seen that this killer instinct is developed from the moment of birth.

Sharks grow quite slowly, during which they catch small fish, mollusks, and crustaceans. Male sharks are considered sexually mature at an average age of 9 years, while females may have to be sexually mature for more than 10 years.

Oviparous, peculiar egg shells, varying in size and shape depending on the speciesThe largest is 30 cm, 14 cm wide and 9 cm high, and is the largest egg in the living fish, the smallest egg is 63 mm long and 37 mm wide, and most species have rectangular egg shells with extended tendrils at the four corners to be wound around seaweed, stones and other objects for hatching.

80% of the species of sharks are below the total length of the body, the vast majority of sharks are small fish, the largest shark is the whale shark, also known as the whale pattern, up to 20m, weighing 7000-8000kg, can be described as the king of fish;

The smallest is the broad-tailed little horn shark (also known as the little sperm shark), the mature male is 15cm, the female is 20cm, and the size difference between the size of the shark is more than 100 times. The Tertiary stratigraphic fossil species of the giant man-eating shark has been discovered, with long teeth and an estimated body length of up to 90 meters, and the American Museum of Natural History exhibits this two-jaw model, which can accommodate six people standing in the mouth.

Tooth form: shark teeth are composed of dentine, bone dentine and enamel, etc., it is evolved from shield scales, the morphology of the teeth is one of the classification basis, shark teeth have many styles, there are comb-shaped teeth, different anterior and posterior teeth, and three three-peaked teeth at the tip;

There are 8 types of multimodal teeth with more than 5-7 cusps, unimodal teeth with 1 large lateral flattening, stone-paved teeth with many small teeth, granular teeth with many fine decimal teeth, and incisor teeth with wide and flat teeth.

Sharks are almost exclusively carnivorous species, with only a few species such as whale sharks and basking sharks feeding on plankton. Carnivorous sharks have a strong bite due to their strong contractile muscles and sharp teeth, and can eat molluscs, crustaceans, large fish and marine mammals, and even attack small boats and eat people.

Shark eggs are fertilized and hatched in the body, and thousands of baby sharks hatch. But instead of living in harmony, these siblings killed each other in their mother's womb. In the end, only the most ferocious one survived and left the mother.

1.Oviparous: Generally adopted by large sharks.

Shark eggs are large and nutritious. The discharged egg is packed in a flat, cushion-shaped sheath that is added around the egg as it passes through the fallopian tubes, the outer skin of the sheath hardens when it enters the water, and each corner of the sheath has a short, hollow horn that allows seawater to enter and give the egg oxygen. There is a limited number of ovulations at a time.

The eggs are in the shape of a cloth bag or spiral, and after they are laid, they are fixed in coral reefs, seabed plants or rock crevices. The empty oocysts of the spiny shark that washed up on the shore are nicknamed the mermaid's purse.

Except for whale sharks, which can produce more than 300 at a time, the rest can produce dozens at most each time, and the least is the fox shark (thresher shark), which only produces two at a time.

3.Viviparous (placental viviparity): Fertilized eggs with horny shells develop in the uterus, and the nutrients needed for growth are obtained from the yolk sac placenta until the young sharks are almost fully formed, giving birth to dozens of eggs at a time.

Most of the sharks in the ocean are viviparous. Most sharks breed seasonally each year, with some large sharks breeding every other year. Most sharks have a gestation period of 8-9 months, and the gestation period of the white-spotted horn shark can even be as high as 24 months.

In general, large sharks produce more small sharks at a time, while small sharks do the opposite. Sharks also grow unusually slowly, not becoming sexually mature until they are 5-10 years old.

The shark is a social animal, he just eats some small fish, well, or nutrition to keep himself from hungry, that's it, but just eats some small fish, and then that's it, and then grows bigger and bigger.

Sharks are an ancient group, no matter how they are defined, at least for most of the dinosaur era, and survived for 66 million years after the extinction of the dinosaurs. Together with its close relative, the ray subclass and its distant relative, the silver shark, make up today's cartilaginous fishes, and they are one of the most dynamic branches of all cartilaginous fish. Sharks have lived in the oceans for hundreds of millions of years, their history will continue, these ancient fish will always be with us, and what we need to do is to protect these creatures that have come from time immemorial.