What are the methods for introducing and breeding leeches?

I. Artificial introduction. Artificial introduction is a measure whereby the breeder purchases seed leeches from farmers or farms (bases) that have already succeeded in breeding them. When introducing them, the species should be selected carefully, and species that meet the standards for Chinese medicinal materials should be strictly chosen for breeding, so as to reduce blindness and unnecessary economic losses. At present, the most widely bred species are the Japanese medical leech, the wide-body golden thread leech and the tea-colored leech. However, no matter which leech is chosen for breeding, the original farm must be investigated and analyzed, and compared with one's own already-built farm, to reach a conclusion on whether it is suitable for breeding. In terms of individual selection, attention should be paid to choosing individuals that are lively and robust, with full bodies, smooth body surfaces, and both luster and elasticity. Healthy bodies not only have a high survival rate and strong resistance to diseases and insect pests, but also have vigorous reproductive capacity. When introducing them, it is best to select excellent species from nearby units. If introducing them from other places, it is best to contact the relevant scientific research departments, seek their opinions, and obtain guidance and help, so as to reduce unnecessary losses.

II. Field collection. (1) Collection environment and time. Every kind of animal has its own established living environment; leaving the suitable living environment conditions, or a sudden change in the environment, will cause massive death, or even extinction. The living environment of leeches was also fixed only after long-term evolution, inheritance and adaptation, so collection should be based on the living habits of leeches. The collection environment and sites are the places where wild leeches frequently appear, such as places with relatively strong water flow. The best collection time is during the peak activity period of leeches, such as 8-10 a.m. and 4-6 p.m. (2) Collection methods and tools used. There are many and varied methods and tools for collecting leeches, and one should adapt to circumstances, choosing and innovating on one's own. Generally, two methods can be used: direct artificial collection and food-lure collection. Using food as a lure is a method of collecting leeches that saves manpower and time; it involves setting traps to capture them according to the leech's active season, living patterns, activity time and blood-sucking habits. Based on the habit of medical leeches liking to suck the blood of vertebrates, dry bones of large livestock can be smeared with fresh pig blood (for the tea-colored leech, cow blood should be used) as a lure; when large numbers of leeches crawl onto the bones, the bones can be scooped out with a fishnet, separating the bones from the leeches. Of course, when using food to lure the wide-body golden thread leech, the bodies of mollusks can be used as bait; when large numbers of leeches arrive, they can be caught with a fishnet. III. Selecting the superior and eliminating the inferior. Whether introducing excellent species for breeding or collecting wild leeches from the field as a seed source, there is the issue of selecting the superior and eliminating the inferior, and in the breeding process this is even more important. The actual purpose of artificially breeding leeches is to reproduce leeches, that is, to obtain large numbers of offspring and achieve high yield, thereby obtaining better economic benefits. To achieve high yield and better economic benefits in artificial leech breeding, excellent species are the key, the internal cause. The quality of the species directly affects the growth, development and reproductive performance of the leeches. Among the large numbers of leeches collected, their health and developmental conditions will not be exactly the same, so it is necessary to select superior species with relatively strong adaptability, fast growth and a high egg-laying rate in order to improve economic benefits. IV. Collecting leech egg cocoons for artificial incubation. Leech egg cocoons are generally collected in mid-to-late April each year; after discovering small holes with a diameter of about 1.5 cm in moist soil such as ditches, riverbanks and lakesides, one can dig inward along the small holes and collect foam-like leech egg cocoons. When collecting egg cocoons, be very careful and do not clamp or pick them with force, otherwise the embryos inside the egg cocoons will be damaged. The collected egg cocoons should be promptly and gently placed into an incubator. The incubator can be an ordinary plastic basin, box or other container, and its size should be determined by the number of eggs placed. First put a layer of sandy soil 1-2 cm thick in the incubator; the water content of the sandy soil should be between 40% and 50%. Place the egg cocoons in the incubator in neat rows with the end having the small hole facing up, then cover the surface with a layer of moist gauze or several layers of gauze to increase the humidity inside the incubator. On the outside of the incubator, wrap it tightly with a plastic bag (a food plastic bag can be used) to prevent evaporation of water inside the incubator. In this way, after about 20 days, young leeches can hatch naturally. Collecting leech egg cocoons for artificial incubation is also a simple and easy method of obtaining a large number of seed sources. V. Issues to note in collection and introduction. (1) Keep records of collection and introduction. When collecting leeches in the field, carry a notebook with you, and record in detail all matters related to the collection, such as the time, place, water area and surrounding environment of collection. If the collected leeches are selected as superior and used as seed leeches for breeding, the records can be referred to in order to create suitable living conditions for them. Through the records, one can also grasp the occurrence numbers and generational occurrence patterns of wild leeches, so as to sum up experience and improve understanding. (2) Disinfection treatment. Whether introduced seed sources or seed leeches collected from the field, disinfection treatment must be carried out to avoid infection with diseases, which could cause all previous efforts to be wasted or even total loss. The disinfection treatment methods are as follows. 1. Isolation breeding   Place newly introduced or field-collected seed sources into separate breeding ponds; after observing for several days, if there is no death or phenomena such as loss of appetite, wilting, darkening of body posture, or loss of luster and elasticity, and the excrement is normal, and it is confirmed that there are no pathological signs, they can be placed into normal breeding ponds or mixed with other leeches. 2. Drug treatment   Before placing them into the isolation breeding pond, the leeches should be washed once with a 0.5%-1% formalin disinfectant solution. Other disinfectant solutions can also be used for washing; the purpose is to eliminate the pathogens of the leeches.