Breeding and hatching of Rana chensinensis in South China-- Reproductive technique

The technique of reproduction and hatching is one of the key techniques for the culture of Rana chensinensis in the south. Generally speaking, in the first ten days of March, before the water temperature rises to 10 ℃, it is necessary to make preparations before reproduction, disinfect the established spawning pool ditch and hatching pool (which can use the original hibernating pool, spawning pool, hatching pond and feeding pond), and inject clear water to adjust the water temperature by adjusting the water level and light. When everything is ready, the Chinese forest frog can be put into the spawning incubator.

It is easy for Rana chensinensis to lay eggs and hatch tadpoles, but without good breeding techniques, it is difficult to achieve the ideal result that the spawning rate and hatching rate are more than 90%. Therefore, the problem of breeding and hatching technology must not be ignored.

1. Breeding technology

(1) Disinfection pairing: after removing the Chinese forest frog from the overwintering pond, the frog was first bathed with 5 × 10-6 potassium permanganate solution for 5 minutes, and then moved into the spawning pond. The density of the frog in the spawning pond was about 30 pairs / m2, the water level was kept at 10: 15 cm, and the water temperature was 10: 15 ℃. After hugging the Chinese forest frog, if it suddenly cools down in the weather, it will lead to the postponement of spawning, and the right Chinese forest frog may hibernate together again, and because of breeding in the south, in order to achieve a high maturity rate of commercial frogs that year, the sooner the better, the better. It's best to lay eggs in a plastic greenhouse.

(2) spawning: when introduced in spring, breeding frogs can normally hold each other and lay eggs within 3-5 days after entering the spawning pond. In the case of high temperature, they often lay eggs within 1-16 hours after entering the spawning pond. Therefore, when breeding frogs are introduced in spring, they should be prepared to put them in the spawning pool at any time, so as not to miss the opportunity to lay eggs and lead to premature or difficult delivery of Chinese forest frogs.

After the Chinese forest frog moves to the south, due to the insufficient depth of overwintering or the great change of air temperature in spring and man-made disturbance, dystocia often occurs, that is, the female frog can drop the eggs normally, and the female and male frogs can hold each other normally, but the female frogs can not lay their eggs because of endocrine disorders. Most of them will die as a result, and there is no good rescue at present.

(3) Postpartum dormancy: under normal circumstances, Chinese forest frogs mostly lay eggs in the early morning, and the eggs just laid are the size of eggs, so don't rush to fish them out at this time. Before the egg mass is swollen by water absorption, the premature removal of the egg mass will affect fertilization and hatching, but the breeding frogs after spawning can be harvested, separated from male and female, and placed in postpartum dormancy places with good ecological environment, light shelter and dampness. Otherwise, the death rate will be too high because of the high temperature in the south, the short dormancy period of frogs, and even no dormancy. At this time, it is necessary to pick up the dead frogs in time, disinfect the breeding places and supply adequate bait.

(4) the ratio of male and female frogs: according to the natural and usual breeding rules, the pairing ratio of female and male frogs is 1 ∶ 1, and the male frogs are required to increase by 10%. According to the spawning experiment of forest frog for many years, Fengkang Company has proved that the ratio of female to male frog can be 70 ∶ 30. Due to the warm temperature in spring in the south, the female frog can lay eggs alone without cuddling to the male frog after the egg development and maturity, as long as the sperm excreted by the male frog is normal and healthy, within 10 hours of sperm survival, the eggs laid by the uncuddled female frog can combine with sperm in water, complete in vitro fertilization and hatch. Because a female frog can lay 1,300 eggs to 2,300 eggs, while a male frog produces millions or tens of millions of sperm, which is far more than the number of eggs, and the breeding frogs paired in the spawning pool can not lay eggs at the same time, it is possible to increase the number of female frogs in the spawning pool to ensure that there are sufficient eggs combined with sperm to produce as many fertilized eggs as possible.

The conditions for the success of this kind of experiment are that the spawning pool is flat, the water temperature is 10: 18 ℃, and the water is absolutely clean and not flowing. The male-to-female ratio of 70 ∶ 30 coincides with the female mutagenesis rate of 70% and male 30%, which is conducive to the full implementation of female mutagenesis for mass spawning and hatching in the future without worrying about the low proportion of male frogs.