In the animal world, if several male animals try to pair with the same female, in order to get her limited egg, there will be fierce competition between their sperm, and the longer sperm will look more competitive.

In the animal world, if several male animals try to pair with the same female animal, in order to get her limited egg, there will be fierce competition between their sperm, and the longer sperm will look more competitive. Zurich and Stockholm University researchers conducted a study that found that different sizes of animals have different sperm lengths. The larger the animal, the more important the sperm count is than the length of the sperm. Therefore, the sperm of elephants is shorter than that of mice.

Sperm is probably the cells with the most variations, and they change with size and shape. Sperm is divided into animal sperm and plant sperm. Animals have male cells during sexual reproduction, male animals' germ cells, male gametes in heterogeneous reproduction , and haploid germ cells produced by sperm organs.

1677, Levenhoek observed sperm from humans and some higher animals, so far, most of which are tadpoles -shaped. Since the 1950s, rapid progress has been made in understanding the biological properties of sperm. Taking mammals as an example, the structure of sperm can be divided into three parts: head, neck and tail. The head is mainly composed of the nucleus and acrosome, which are spherical, long cylindrical, spiral, pear-shaped and axe-shaped, etc. These shapes are determined by the shapes of the nucleus and acrosome. This part of the neck is the shortest. It is located behind the head and is cylindrical or funnel-shaped, also known as the connecting section. The tail part is 3 parts: middle section, main section and last section. The main structure is the axis that runs through the center.

Since scientists discovered sperm 350 years ago, they have become one of the most interesting research objects. But why are there such a big difference between sperm in different species? In fact, they also undertake the same job! That is to fertilize the egg. Longer sperm tends to do this job better. Interestingly, rodents, such as mice and voles sperm are more competitive than large animals. Rodents have twice as long sperm as carnivores, ungulates, primates and whale . The reason is still in controversy.

Controversy 1: Consideration of sperm count and length Researchers from Zurich and Stockholm University compared the effects of sperm on evolution in 100 mammals and found that there is a close relationship between sperm size and number, that is, the longer a single sperm, the fewer sperm will be produced by the testicles.

Controversy 2: It is related to animal volume. On the above study, the researchers used the meta-analysis method. The researchers concluded that those animals that ejaculate more sperm than monogamous animals when ejaculate. They also found that the size of an animal does have an effect on the length and number of sperm. The larger the animal is, the greater the pressure when ejaculation, and the number of sperm is more important than length. Because female animals have a large amount of female reproductive genitalin, and sperm is diluted or missing.

Species with larger size, sperm length or movement speed, if can work, it depends on the number of sperm to get close to the egg. For smaller species, sperm movement distances and small losses are fully utilized. Therefore, more complex sperm forms can be found in small animals' bodies. However, not in large animals. For example, the sperm of the fruit fly is the longest, not the whale. The sperm of the whale is shorter than a tenth of a millimeter and is one thousandth of the sperm of the fruit fly.