Cut the earthworm according to different parts and get three different segments, namely headless and tailless, headless and tailless. Regeneration was observed at room temperature in soil. The results show that earthworms have regeneration ability from beginning to end, but the regeneration ability of different segments is different. The tail has the strongest regeneration ability and the fastest regeneration speed, followed by the middle section and the worst head. It was also observed that the earthworm was cut into different numbers of segments.
Key words: "Taiping II" earthworm; Regeneration; livability
Regeneration is the repair and restoration of unnatural parts by individuals or organs, which is considered to be one of the most important mechanisms for organisms to adapt to the environment. It has long been found that broken earthworms have the ability of regeneration and recovery. In 2002, three experts from the Institute of Zoology, Chinese Academy of Sciences (Qi Liping, Ge Feng and Zhou Xiaodong) published "Study on the Regeneration Ability of Earthworms" in the journal of Applied and Environmental Biology. It is pointed out that the regeneration ability of earthworm is related to the cutting position, and the survival rate is positively correlated with the number of body segments, which enriches people's understanding of earthworm regeneration ability. In recent years, with the rise and development of cell biology, molecular biology and neurobiology, it provides a basis for further study on the regeneration mechanism of earthworms.
"Daping No.2" earthworm was fed with cow dung at the temperature of 23℃ ~ 24℃ and the relative temperature of 60%, and the spawning period was 14 ~ 18 days. The larval stage of earthworm is 40 ~ 45 days, and it takes 5 ~ 7 days from reproductive node to spawning. "Daping 2" has very strong reproductive ability and is suitable for long-term experiments. Generally, necrosis and death will not occur after cutting, which ensures the experiment. In this experiment, the mechanism of earthworm regeneration and its adaptability to the environment were preliminarily discussed by cutting different segments of earthworm and the influence of cutting different segments on the survival rate.
1 materials and methods
1. 1 Material source "Taiping No.2" was purchased from Shenzhen Huaqiang North Bait Store, cultured in a 9cm diameter Petri dish, and apple peel was used as feed.
1.2 morphological observation of dissecting microscope Xia "Taiping No.2": the total number of nodes is 85- 1 10, and the reproductive ring has three nodes, which are located in front of the node and about two-thirds behind the reproductive ring. After cutting earthworms according to different requirements, put them in a Petri dish with a diameter of 9 cm for dark culture, and add a small amount of water every day.
1.3 research methods
1.3. 1 Two-stage grouping (1) Take five earthworms, and divide the head and tail into two sections; (2) take five earthworms, starting from the tail end, with a quarter of the strength, and cut them into two sections; (3) take five earthworms, take the girdle as the boundary, and then cut them into a head section and a tail section, so that the head section has no girdle; (4) Take five earthworms, take the girdle as the boundary, and then cut them into head and tail sections, so that the section with the head is the girdle.
(5) Take five earthworms, divide the head and tail into two sections, and don't cut them off; (6) Numbering the earthworm fragments cut in the above (1)-(4), and placing them in a culture dish.
1.3.2 Three-stage grouping (1) Take five earthworms and divide them into three equal parts; (2) taking five earthworms, taking the girdle as the boundary, the girdle and the head as a section, taking a quarter of the body length from the tail end as a section, and taking a section in the middle; (3) Taking five earthworms as a boundary, making a section with no girdle at the head, with a quarter length from the tail end as a section, and a section with girdle in the middle as a section; (4) Take five earthworms, divide them into three equal parts, and don't cut them off; (5) Numbering the earthworm fragments cut in the above (1)-(4), and placing them in a culture dish.
1.3.3 divide five earthworms into four sections, number them separately, and put them in Petri dishes for feeding.
1.3.4 divide five earthworms into five sections, number them separately, and put them in Petri dishes for feeding.
1.3.5 Five earthworms were taken from the blank control group, numbered and kept in Petri dishes.
1.3.6 in the mixed culture group, five intact earthworms and five equally divided earthworms were taken, numbered, and placed in a Petri dish.
2. Results
2. 1 The results show that different segments of earthworm obtained by different cutting methods have different degrees of regeneration, among which the tail has the strongest regeneration ability and the fastest regeneration speed, followed by the middle segment and the head is the worst.
Fig. 1- 1 1-2 regeneration; Figure 1-2, and the regeneration of figure 1-41-3; Fig. 1-3 regeneration1-4;
Figure 1-5 Healing; Figure 1-6 control chart of fresh-cut earthworms
2.2 Survival rate of different segments1The survival rate analysis of three earthworm segments (Figure 2) shows that 1-3 and 1-5 have the highest survival rate, and the fourth group has the lowest survival rate. The general trend is that the more segments, the lower the survival rate. However, there is one obvious exception (1-2
Fig. 2 survival rate chart of different cutting methods
2.3 Relationship between the number of nodes and the survival rate Through the analysis of the survival rate and the number of nodes of earthworms (Figure 3), it is found that the survival rate of earthworms is positively correlated with its node trees, that is, the more nodes, the higher the survival rate of earthworms.
Fig. 3 Relationship between the number of body segments and survival rate
3 discussion
3. 1 overall progress of the experiment: Earthworms drink a little water every day from cutting, and feed apple peel the next day. Their lives and growth are very good. From the seventh day, they began to regenerate. First, a light link appeared in the wound, and then the link became thick and black. At the same time, small yellow teeth appeared in the early stage of wound healing, as shown in Figure 1 and Figure 4. Later, the small teeth became longer and thicker. It took a long time to form the initial resection. The experiment lasted for 20 days and achieved satisfactory results. Many brothers and sisters have done similar experiments before, but they all failed. When we decided on the topic, the teachers told us seriously that this experiment was not easy to do, and many people had failed before. At that time, we were dubious, but we didn't give up and sincerely asked our teachers and brothers and sisters for advice. Finally, we all agree that the possible reason for the failure of the experiment is the cultivation process of earthworm. In the past, most experiments were carried out under soilless culture conditions, and it is very likely that earthworms will die because they do not adapt to this new environment. In view of this, we cultivate in the soil, replenish water regularly, and keep the original ecological environment of earthworms as much as possible. Sure enough, the survival rate of earthworms has been greatly improved. From this, we realize that we should be bold and cautious, dare to innovate and face difficulties bravely.
3.2 The influence of different cutting on earthworms is shown in Figure 2, from which it can be seen that the fewer cutting sections, the higher the survival rate of earthworms. It is also observed in the experiment that the regeneration ability of truncated tail is the strongest, and the regeneration ability of truncated tail is not as obvious as that of truncated tail, while the regeneration ability of truncated two sections is not strong, mostly showing healing. I questioned this. Whether the regenerative tail is rich in nutrition or the cells in the tail are poorly differentiated, and how the body realizes the missing part and regenerates tissue, I have not found the answer in the experiment. I checked the relevant information, and there are different opinions. I hope to improve the experiment in the future and finally uncover the mysterious mechanism of earthworm regeneration.
3.3 Relationship between the number of body segments after shearing and the survival rate As can be seen from Figure 3, the survival rate of earthworms after shearing increases with the increase of the number of body segments, that is, the shorter the body segments, the higher the mortality rate, which may be related to the strong resistance of earthworms and the more nutrients stored, but whether the body segments of earthworms after shearing have heads or tails has nothing to do with the survival rate of earthworms.