Detailed Explanation of Artificial Breeding Techniques and Biological Habits of Leeches

   The leech, also known as the medicinal leech, bloodsucker, or water worm, is a valuable traditional Chinese medicinal material. Its saliva contains a blood-clotting substance called hirudin, and it also contains heparin, antithrombin, and other compounds. It can treat stroke, amenorrhea, paraplegia, angina pectoris, unexplained swelling and pain, tumors, cervical lymphatic tuberculosis, and more. Hirudin can keep venous blood vessels unobstructed after transplant surgery. In addition, a honey extract of leeches can treat corneal ulcers and corneal opacities. It is mainly used in clinical practice and for export to earn foreign exchange. Domestic demand alone reaches 5,000 tons per year, but due to the widespread use of chemical fertilizers and pesticides, combined with predatory harvesting of leeches in recent years, wild resources are dwindling day by day and are far from meeting the demand for medicine and export. Artificial breeding is imperative.
 I. Biological Habits
1. Habitat environment. Most leeches inhabit freshwater ditches, rice paddies, lakes, and marshes. They are especially fond of living in ponds rich in organic matter, slow-flowing streams, and courtyard ponds.
2. Types of leeches. In zoology, leeches belong to the class Hirudinea of the phylum Annelida. There are several hundred species worldwide, and nearly a hundred species in China. Many species live in freshwater bodies. The main ones used clinically are Hirudo nipponia, Whitmania pigra, the tea-colored leech, and Whitmania acranulata. For artificial breeding, Whitmania pigra and the tea-colored leech are preferable.
3. Activity patterns. Leeches are poikilothermic animals. In winter, they overwinter dormant in the soil. They emerge from dormancy and become active in March to April. When the temperature is low (water temperature below 10°C), they often hide in mud balls formed by withered grass and silt tangled together at the water's edge. When the temperature is high (water temperature above 15°C), they often emerge from the mud balls, stretch their bodies in activity, and float quietly in the water. When moving in water, they often swim forward with a wave-like motion. After leaving the water, they crawl forward in a looper-like fashion.
4. Feeding habits. Leeches live by sucking blood or coelomic fluid. They have extremely strong tolerance to starvation; after one blood meal, they can live for more than half a year. They mainly feed on aquatic plankton, small insects, mollusks, and decaying organic matter.
5. Reproduction. Leeches are hermaphroditic, mating with other individuals, with internal fertilization. Leeches possess both male and female reproductive organs.
#Mating: Leech mating is similar to that of earthworms. During mating, the head ends point in opposite directions, and each individual's male reproductive organ faces the other's female reproductive pore, completing fertilization and mating.
# Formation of egg cocoons: About 1 month after mating, the clitellum secretes a thin mucus that, mixed with air, becomes soapy foam. Then another type of mucus is secreted, forming a layer of egg cocoon wall around the clitellum. Eggs are produced from the reproductive pore and fall into the cavity between the cocoon wall and the body, and a protein is secreted into the cocoon. The parent gradually wriggles backward and withdraws. The entire egg-laying process takes 30 minutes. Each leech lays 60 to 90 eggs per spawning. The eggs harden after several hours in the soil, the foam of the cocoon wall air-dries, the wall ruptures, leaving only a honeycomb or sponge protective layer composed of pentagons or hexagons.
# Hatching: After the cocoon is produced, if the temperature is suitable, the fertilized eggs develop directly inside the cocoon, hatching after about 16 to 25 days, and can live independently.
# Development: Young leeches have a relatively long growth period, taking from half a year to 3 years to go from juvenile to adult.

 II. Artificial Breeding Techniques

 1. Water body conditions: For artificial breeding, the water body can be large or small, generally 0.5 to 5.0 mu is suitable. Pond depth should be more than 1.5 m, with a water depth of about 1 m, and 10 cm of silt at the pond bottom. Place branches, stones, bricks, and discarded tires, 200 to 300 pieces per mu. Set up inlet and drainage ditches. In the pond, set up earth mounds 20 cm above the water surface, 5 to 8 per mu, each with an area of 1 to 2 sq m. To prevent leeches from escaping due to rainwater overflowing the pond, generally set up escape-prevention ditches or escape-prevention nets around the perimeter. The escape-prevention ditch is 12 cm wide and 8 cm high, with half embedded in the soil. When it rains, sprinkle quicklime into the ditch to prevent leeches from escaping with the water flow. Fifteen days before stocking leeches, use 100 kg of quicklime per mu with a water depth of 20 to 30 cm for thorough disinfection.