These phenomena have puzzled alien breeding enthusiasts, including me, for many years. I have been thinking about what caused these defects, and I have also done some analysis and testing mainly for short heads.
1 Considering that the seedlings hide in the cracks of rocks in the wild state, long-term external force will affect the shape of the seedlings' skulls, but the artificial environment lacks this behavior, resulting in the lack of skull extrusion and other defects.
Conclusion: In the artificial environment, the shelter was built with stones and tiles, and the seedlings were allowed to drill into the rock pile under the condition of imitating the wild environment to test the previous guess.
Conclusion: Failure ... Shortness and other defects still appear, and the external force has limited effect on the head bone morphology, and there is no obvious improvement.
The theory that the external force of water flow affects the development shape of skull is basically consistent with the theory 1. Most of the time, the fish head is facing the direction of water flow, and the deformed mouth is below the fish body. The main behavior is to use the sediments at the bottom of the river, such as stones, wood and other substances that adsorb the most at the bottom of the river. The current will impact the fish, and the long-term external force of the current will make the skull longer.
Conclusion: failure ... adding waves to the fish tank to increase water flow has not improved.
3. Incomplete nutrition of the bait leads to short head deformity. The phenomenon of short head deformity of heteromorphic seedlings mainly occurs in several fixed varieties, such as L600 and L046. In recent years, I have deliberately kept the bred L600 dwarf seedlings for breeding, and the feed is taken out regularly for observation. It was found that the head of short-headed seedlings became hard when it was 8 cm soft and 10 cm, indicating that the real cause of short-headed seedlings was slow calcification of the head. It is not directly proportional to the growth rate of fish, that is to say, the larvae cultivated in artificial feed are rich in bait, and the nutrients in the bait are enough to promote growth, and the growth of fish is accelerated, but the speed of bone calcification cannot keep up with the growth rate, leading to deformity.
Conclusion: By changing the formula of fry feed and increasing nutrient sources to promote the absorption of calcium, phosphorus and magnesium, the bone calcification rate of fry is accelerated, and the bone calcification rate is directly proportional to the growth rate of artificially raised fish. Through the test, the expected effect has been achieved.