Four seas network: there is a folk saying that the mule is called eunuch, which is not rude. The mule has no fertility. Although the mule is also divided into male and female, but because it is a hybrid of horse and donkey, its chromosome cannot match, so its fertility is very low. Let's see the details below!
Mules are the hybrids of horses and donkeys. They are divided into male and female. Male mules and most female mules have no reproductive ability. The reason for the lack of reproductive ability is that the chromosomes are not paired (63), and the reproductive cells cannot divide normally (i.e. meiosis). Female mules have sexual function and * * can conceive embryos, but the most difficult thing is to make female mules pregnant. Strictly speaking, the post natal generations of male and female donkeys are called mules, and the post natal generations of male and female donkeys are called donkeys and mules.
No matter horse or mule, their chromosome numbers are not very normal. This is because the donkey's chromosome 2 is homologous with the horse's chromosome 1, and the donkey 13 is homologous with the horse 11, and the donkey 14 is homologous with the horse 13. Together, donkey 16 and donkey 25 correspond to horse 5, and the harness has 32 chromosomes, while donkey has 31. Although horses and donkeys are closely related, their gametes can not only combine with each other, but also develop into complete individuals. However, the number of chromosomes in their progeny cells is 32 + 31, and one chromosome is always alone.
However, mules are still lucky, because if this is the number of chromosomes in a certain horse cell (called monomer 2N-1 if it is a horse), it is basically unable to survive, and the survival ability of pure haploid is better than that of sexual reproduction diploid species. On the contrary, if it is the chromosome composition of a donkey cell, it will become trisomy, and the redundant chromosome must have three. The 32 + 31 mule is not a real 31 to + 1 relationship. That is to say, in meiosis, it will not simply separate 31 pairs of chromosomes from each other, and then randomly allocate the redundant one. This is the trouble encountered by mules and other hybrid animals. Their chromosomes tend to be randomly separated and freely combined in the process of separation. Because for the three bodies that can survive, although their fertility is lower than normal, it is also quite high. Except for the redundant chromosome, the rest can pair normally and separate from each other.
For the unfortunate mule (take the female mule as an example), what is the chance to generate a normal egg? For example, in an extreme case, its egg contains exactly 31 chromosomes from the donkey, or 32 chromosomes from the horse. Obviously, the probability is quite low (the interested comrades can count it), of course, the actual situation does not need to be so extreme. After all, the mule itself can survive, that is to say, in the egg, it can be a harmonious combination of the chromosomes of the horse and the donkey.
In ancient Chinese books, it is said that the offspring of male horse and female mule is "he", and the offspring of male donkey and female mule is "he". The typical example of female mule's foal in China is the report of Zong Enze and other researchers of Lanzhou Animal Husbandry Research Institute of Chinese Academy of Agricultural Sciences who have carried out systematic research for many years, with a total of about 13 horses.
There are many foreign reports about mules giving birth to Colts. In 1903, there was a case of mules giving birth to Colts in estanz, Africa. In 1913, a female mule and a male donkey copulated and gave birth to a male colt. Then in, she became estrous and mated (still using a male donkey). Another female colt was born. In 1923, a female snail copulated and gave birth to a colt in Morocco with a riding baiber male horse, similar in appearance to her father-- In 1927, a female mule in Nebraska gave birth to a colt by mating with a male donkey. In 1939, a female mule in Arizona gave birth to a colt by mating with a male donkey. It was exactly like a mother mule.