1. Sand selection. The hatching of crucian carp eggs needs proper temperature, humidity and ventilation. If the sand is too coarse (the particle size is larger than 1mm), although the sand environment in contact with the eggs is well ventilated, its water retention is poor, and it cannot maintain the appropriate humidity of the sand for a long time, which affects the hatching rate. If the sand is too fine (the particle size is less than 0. 1 mm), it is easy to harden, even if its water retention is very good, it will lead to the suffocation and death of eggs. It is ideal to choose sand with a particle size of 0.5~0.6 mm.
2. Disinfect. Put the selected sand into the basin, add clear water to stir, pour out the muddy water, and repeat this for many times to wash away the soil in the sand. The purified sand was soaked in a solution of 20 mg/kg bleaching powder for 2 days for disinfection. Filter out the sand, rinse with cold boiled water to remove the contained drugs, and dry in the sun for later use. You can also spread clean sand and use it after 2~3 days of exposure. The pine and Chinese fir boxes used for incubation should also be cleaned and disinfected.
Step 3 pack. Stir the sand evenly with cold boiled water to a suitable water content, and box it. Carassius auratus eggs have strong resistance to low humidity and weak resistance to high humidity. The water content of sand should be 5% ~ 65438 05%. If it exceeds 25%, the egg is easy to die; If it is less than 3%, the water in the egg will easily evaporate, which will affect the development. If you hold the adjusted sand in your hand, the sand will spread out naturally after landing, or even hold it in a ball, and let it go a little, which proves that the humidity is suitable. Otherwise, it must be readjusted.
The wooden box filled with sand can be large or small, with a depth of 35 cm, and the sand depth is 20 cm after the eggs are arranged.
4. choose eggs. When selecting eggs in the spawning sand bed, it is necessary to check the fertilization of the eggs of Carassius auratus under strong light. If there is a white circle at one end of the egg (which is called the animal pole), it means that it has been fertilized. If there is no fertilization, you should put it back in the sand bed and stay put. A white circle will appear after 24 hours, and then it will be classified as a fertilized egg for incubation, otherwise it should be rejected.
5. Ovulation. Carefully selected fertilized eggs are placed on the sand surface in the box, with the polar face up, and each egg is separated with one finger. In order to make full use of space, ovulation can also be increased to 2 layers, but most of them are discharged 1 layer, which is convenient for management.
After arranging the eggs, cover the eggs with a layer of sand with adjusted humidity, the thickness of which is 2~3 cm higher than the surface of the eggs, and scrape them flat.
Ovulation should pay attention to: ① animals must face up, otherwise it will affect embryo development or turtle can't get out smoothly;
② Eggs placed in batches at different times should be marked separately for easy observation and management;
(3) Because the box is dry around, it should not be too close to the side when ovulating.
6. Keep warm. The optimum sand temperature in incubation period is about 30℃. Below 25℃, embryo development is slow; At 38℃~40℃, the embryo will die within a few hours. In order to keep the best temperature, the temperature is high in summer, and ventilation is needed to cool down; When the temperature is low, close the doors and windows to keep warm.
In the south of the Yangtze River, soft-shelled turtles lay eggs from June to August, with the peak in July. During this period, the indoor temperature will not be as high as 35℃ or lower than 24℃, which is suitable for artificial incubation of eggs.
7. Moisturize. That is to say, during the whole incubation period, the humidity of the sand layer is kept at 5%~ 15%. On a hot and sunny day, the temperature is high and the water evaporates quickly. If the sand is still wet, there is no need to sprinkle water. If the sand near the eggs is dry or even white, you can sprinkle cold boiled water evenly on the sand surface by hand. After a few minutes, when mixing sand, pay special attention not to shake the eggs below, so as not to affect embryo development.
8. Come out of the shell. At about 30℃, the plant pole (opposite to the animal pole) is pink at 5~8 days after ovulation, and it is red-black at 20~25 days, when the young turtle has formed; From 26 to 30 days, dark embryos can be seen in the plants; After 33 days, the whole egg turned white, and the animal and plant poles could not be distinguished. Therefore, the appearance of eggs can basically predict the hatching time of young turtles. After 35 days of incubation, a large flat-bottomed container is buried in the sand in the wooden box, and fine sand with a thickness of 2 cm is placed in the container, and the water level is about 5 cm higher than the surface of the fine sand. After the young turtle breaks out of its shell, it will crawl into the container to have a rest because of its natural hydrophilicity. If the young turtle can't find water after hatching, it will be dried to death.