The internal structure of the earthworm is repeated and repeated. Look how you cut the earthworm, just cut it to its heart, then neither of them can live. If you cut exactly to the part that separates the repetitions, then both segments can live.
Earthworms themselves are eukaryotic cell organisms
To be precise, it is not necessarily necessary to grow into two, earthworms are a relatively higher species in the link animal phylum, the structure is more complex than many link animals, the emergence of digestive system and circulatory system, is the premise of the development of vertebrates!
It also has dorsal blood vessels, if it loses too much blood when cutting, it may not be able to become two, there are many external factors that can affect its growth, if it is in temperature, PH and sterilization conditions, it is possible to survive!
Just like the tissue culture of plants, of course cutting off earthworms and tissue culture is not a principle, but the lower the organism can be expressed, the greater its ability to develop into the same independent individual.
Earthworms are low-grade animals that are born with a head and tail, mouth, stomach, intestines, and anus. Their bodies are made up of two tubes with two pointed ends set together. The outer layer is a body wall connected by a ring, which contains many muscular systems composed of mesoderm cells. There is a digestive tract in the body, which runs from beginning to end in the middle of a layer of diaphragm. Between the inner and outer layers of the tube, the body cavity fluid is filled, and there is a small hole in the ventral surface of each diaphragm, which becomes the channel for the body cavity fluid to pass through the body.
If the earthworm is cut into two segments, the muscle tissue on the cross-section immediately strengthens the contraction, and a part of the muscle tissue dissolves rapidly to form a new cell mass. At this time, the white blood cells in the blood gather on the cutting surface at the same time, forming a special embolism that causes the wound to close rapidly. Its mesoderm cells are very strong.
3, the study of the regenerative ability of earthworms:
If an earthworm is cut into three pieces, can the middle one survive?
The Akako Aikatsu worm was cut off from a specific part, and 18 treatment body segments of three types, nameless and tailless, headless and tailless, were obtained, and their regeneration was observed in an artificial climate chamber at 20 °C. The results showed that the body segment of the earthworm after shear treatment began to regenerate at about 10 days, and it had regeneration ability from beginning to end; however, the regeneration ability of earthworms in different body segments was different, and the regeneration speed of the body segment with head and tail and headless body segment was faster than that of the headless and tailless body segment. Among them, the head and tail of the headless and tailless earthworm body segment can regenerate, but the speed of tail regeneration is significantly higher than that of the head. The number of earthworm body segments left after shearing has a great impact on the survival rate of earthworms. The more body segments remaining, the lower the mortality rate of the earthworm segment, and the two were positively correlated.
(But there is also a theory that not every earthworm has this ability.)
Among them is the regeneration of ciliates and planarians. Moreover, it is mentioned that the regenerative capacity of coelenterates and planarians decreases from the front of the body to the posterior end, along the body axis: the oral or head is the strongest, the reverse end or tail is the weakest, and the nervous system of the head of the planarian is concentrated and the metabolic rate is the highest. There are many undifferentiated, embryonic cells at the end of the mouth of planarian heads and coelenterates, which may be the reason for the strong regenerative ability of the head. The regenerative ability of the earthworm's head is also stronger than that of the posterior body segments, such as cutting the earthworm into two segments and then removing the abdominal nerve, the earthworm loses the ability to regenerate. These experiments all show that nerves play an important role in regeneration.
5, further test the regeneration ability of earthworms:
Earthworms have a strong regenerative ability, after the body is cut off, in the place of the broken will give birth to embryo-like tissue, and soon the lost part will be compensated for, growing into a new earthworm. The strong regenerative ability is to cut off the front end of the earthworm five to eight nodes, if the earthworm is cut off above the nine nodes, the regeneration ability is very slow, and the reproductive organs cannot be restored. If the earthworm is cut off after the fifteenth section, the head cannot be regenerated, and only a tail body with a missing head will grow, becoming a two-tailed perverted earthworm.
How long can the two tails (does the caudate have a tail physiological structure) survive without eating? Or do you eat with a perverted tip of the mouth?
6, someone has done such an experiment, the two earthworms are cut off the front end and the back end, connected can grow into a new earthworm, more people have ingenious ideas, in the front half of an earthworm side-by-side connected to the rear end of two earthworms, so that a first two tails of the earthworm grew.