How to raise leeches in plastic foam boxes? With breeding techniques

Use water tanks, large plastic buckets, plastic foam boxes, water buckets and other containers to raise leeches; it is simple, flexible, and easy to operate, and can be used when raising a small number of leeches in rural areas. So how do you raise leeches in plastic foam boxes? The following is an introduction to leech breeding techniques.

1. Biological characteristics of leeches

1. Living habits The vast majority of leech species live in freshwater, very few species live in seawater, a very small number live on land, and some species live both in water and on land. The suitable growth temperature is 15-30°C. When the air temperature is below 10°C, they stop feeding, and when the water temperature reaches above 35°C, their growth and development are also affected.

Leeches have broad adaptability to water pH, and their favorite environment is neutral or slightly alkaline water; they do not like living in environments with deeper water and more silt at the bottom. The response of leeches to dissolved oxygen in water is shown in two aspects: on the one hand, they can endure long periods of oxygen deficiency in water; on the other hand, they are also very sensitive to oxygen deficiency in water. When the living environment lacks oxygen, the symbiotic bacteria in the leech body can carry out anaerobic respiration and maintain their life in the short term.

During artificial breeding, as long as the dissolved oxygen in the water is maintained above 0.7 mg/L, their living needs can be met, so fresh water needs to be added frequently during artificial breeding. Leeches in nature do not have high requirements for the environment and water quality, and can grow and develop in ordinary water bodies. Two points should be noted during artificial breeding: first, choose water areas without pollution, chemical fertilizers, or pesticide residues; second, avoid nearby pollution sources. Leeches are omnivorous animals, and their main way of life is sucking the blood or body fluids of animals. They often feed mainly on insects, mollusks, and plankton. Under artificial breeding conditions, they feed on various animal viscera, cooked egg yolk, compound feed, plant residues, freshwater shellfish, miscellaneous fish, earthworms, and so on.

2. Environmental requirements Leeches are relatively sensitive to light and show negative phototaxis, that is, they have an instinct to avoid light, and are especially more sensitive under strong light. When artificially breeding leeches, attention should also be paid to this characteristic, and direct strong light should be avoided as much as possible. In midsummer, when the light is very strong, shade treatment should be carried out on the breeding pond to create a suitable dim-light environment. Leeches have an extremely strong ability to sense water currents and are very sensitive to the size of water flow. They can accurately determine the position of the fluctuation center and respond quickly, swiftly swimming upstream.

3. Strong escape tendency Leeches like to crawl, especially on water-bearing walls, so anti-escape facilities should be well set up around the breeding pond, and anti-escape work should be done even more carefully during storms.

4. Hibernation characteristics In winter, leeches lie dormant in mud. When the water temperature is 10°C, they stop feeding and burrow into the bottom of the water or the soil at the pond edge to hibernate.

5. Regeneration After a leech is cut transversely, two new individuals can regrow from the cut parts. This is the unique regeneration ability of leeches.

2. Simple artificial breeding methods for leeches

1. Source of parent leeches

Source and selection of parent leeches Parent leeches, also called brood leeches, can be purchased from fishery departments or markets, or captured from lakes and rivers. Parent leeches should be large, with a single one above 20 grams, robust, uninjured, and strong in vitality, with clear longitudinal stripes on the back and a pale yellow color. This kind of leech lays many eggs and has a high hatching rate.

2. Purchase time

Purchase time Leeches generally lay eggs twice a year, once in spring and once in autumn. For artificial breeding, it is best to purchase parent leeches in spring. In the middle and lower reaches of the Yangtze River, broodstock is often purchased before May, and no later than May 1. In nature, the time for leeches to lay egg cocoons is usually from late April to late May (average water temperature 20°C). In the Zhoushan area, the earliest leeches lay egg cocoons on April 10, so the best time to purchase broodstock locally should be around April 15.

3. Temporary holding of parent leeches

Temporary holding and disinfection of parent leeches Parent leeches must be temporarily held for a few days, and then disinfected. Disinfection method: take 1 large plastic basin, use 0.5%-1.0% formalin or 0.1% potassium permanganate solution as the bath liquid, put the parent leeches in and bathe them for 5 minutes, then remove them and place them in a container filled with clean water, waiting to be put into the breeding platform.

4. Stocking

(1) Preparation of the breeding platform

The breeding platform, also called the egg-cocoon-laying bed, is specially provided for leeches to enter the mud, build cocoons, and lay eggs. The breeding platform is actually a soil bed built with soil on concrete ground or flat ground, 30 cm high and 120 cm wide, with unlimited length (depending on the number of parent leeches). The area of the breeding platform is prepared at 1.5 kg of parent leeches per square meter of platform surface.

(2) Leech cocoon building

The egg-cocoon-laying bed should be relatively soft soil, with a soil moisture content of 30%-40% (it can be formed into a lump by squeezing with the hand, and disperses with a gentle shake). After parent leeches are put into the cocoon-laying bed, they naturally slowly burrow into the soil, then drill an oblique or vertical tunnel upward, about 1 cm wide and 5-6 cm deep, with 2-4 branches. The front end of the leech faces upward and rests in the tunnel. The single-cell glands in the clitellum secrete a thin mucus, mixed with air to become soap-foam-like, and then secrete another kind of mucus to become the cocoon wall, wrapping around the clitellum to form the egg cocoon.

(3) Leech egg laying

Leech cocoon building and egg laying are completed continuously, and it takes about 30 minutes from cocoon building and egg laying to withdrawal. One leech can lay 2-3 cocoons, and individual ones can lay 4. The sizes of the cocoons vary greatly; the first is the largest, and the last-laid egg cocoon is the smallest. Most cocoons are elliptical or oval, spongy or honeycomb-like, with an average short diameter of 26.5 mm and long diameter of 18.7 mm. The average weight of each egg cocoon is 1.68 grams. There are about 595 per kilogram of cocoons.

(4) Artificial hatching of leech egg cocoons

Hatching containers: plastic buckets, plastic foam boxes, etc.

Operation: mix loose sandy soil and loose loam together as hatching soil, and place it at the bottom of the container with a thickness of 1-2 cm. Then place the egg cocoons with the sharper end facing up neatly on the hatching soil, and cover them with several layers of gauze or cotton cloth and other materials to maintain a certain humidity. To prevent young leeches from escaping, cover the hatching container with 1 layer of 60-mesh nylon sieve silk net, and finally wrap it tightly with plastic film to prevent water in the incubator from evaporating. The indoor temperature is controlled between 20-28°C, with 25°C being the best; the humidity of the hatching soil is between 30%-40%.

Under the above conditions, young leeches can generally hatch after about 25 days. To prevent the hatched young leeches from escaping, a larger water tank or other water-holding container can be placed below the incubator, with an appropriate amount of water in the container to receive the hatched young leeches, and some bamboo strips or wooden sticks placed on the water surface for the young leeches to crawl onto and rest. Most cocoons contain 15-20 young leeches, the most more than 30, and the fewest 12. After all egg cocoons have hatched, they can be taken out and placed in a bamboo basket. Put 1 plastic foam board in the rearing pond, place the basket containing the egg cocoons on the foam board, and the hatched young leeches can directly enter the temporary rearing pond. For ease of observation, fix the foam board in one place to prevent drifting.

Standards for high-quality young leeches: high-quality young leeches should be dark purplish red in body color and strong in vitality. Place the young leeches in a washbasin and touch them with chopsticks; they can respond quickly, the leech body contracts into a ball, and sometimes the tail tip can be seen fanning, with high sensitivity to phototaxis. When young leeches are placed in water for temporary rearing for more than 15 hours, if the survival rate reaches above 95%, it indicates that the quality of the young leeches is relatively good. Newly hatched young leeches are cork-colored, and as the young grow, the body color gradually changes to the body color of adult leeches. During the temporary rearing period, the main management work is feeding and changing water. Because they are young leeches, the management workload is not large.

3. Breeding by the plastic foam box method

1. Box selection

Plastic foam box modification It is best to use a new plastic foam box. If an old one is used, as long as it does not leak water, the openings around it are intact, and it has a box lid, it is also acceptable. Open a 20 cm × 25 cm rectangular opening at the center of the box lid for observation, feeding, water changing, and so on. To prevent leeches from escaping through the opening in the lid, a special funnel-shaped anti-escape net must also be set at the box lid opening. Making method of the anti-escape net: the net is conical. Take 4 mm diameter steel bars to make 1 square frame slightly larger than the lid opening, sew a conical bag with artificial fiber cloth, and sew the bag mouth onto the steel bar frame.

2. Water use

For breeding water, unpolluted river water, well water, or reservoir water can all be used.

3. Stocking seedlings

When stocking seedlings, the amount of water entering the box should not be too much, generally reaching 1/3-1/2 of the box wall height. For box-cultured leech seedlings, young leeches or medium leeches can be stocked. Generally, young leeches are stocked in late May, and medium leeches are stocked in mid-to-late June. Stocking young leech seedlings is relatively difficult to raise, so beginners can choose to stock medium leeches. In the author's trial breeding, artificially bred seedlings were stocked, with 200 young leeches per box. The stocking amount of medium leeches (young adult leeches) is 80-100.

4. Daily management work

(1) Feeding

The main baits are water fleas, aquatic earthworms, spiral shells, field snails, golden apple snails, mussels, river clam meat, and livestock and poultry offal, etc. At the beginning of breeding, feed an amount equal to 12%-15% of the leech weight daily. After 20 days, feed an amount equal to 10%-12% of the leech weight. When feeding leeches below 6 cm in length, the spiral shells must be crushed, and before crushing they must be washed clean, otherwise it is easy to introduce pathogens. For every 500 grams of leeches cultured, 4-5 kg of spiral shells need to be fed.

(2) Changing water

When the water temperature in the box is below 18°C, the amount of water changed is not large. Generally, change water once every two days, and the amount changed is 1/3-1/2 of the total. When the water temperature is above 18°C, gradually increase the amount of water changed as the water temperature rises, that is, from 1/2 to 3/4. In addition, water should be changed once every 10 days, and the temperature difference during water changing should be within ±4°C.

(3) Removing residual bait

3-4 hours after each feeding, residual bait should be removed, especially in the hot midsummer season, to prevent residual bait from fermenting and pathogenic microorganisms from multiplying in large numbers.

(4) Separate rearing

As leeches grow, separate those of similar size into different boxes for easier management.

5. Harvest

Box-cultured leeches grow very quickly. Generally, by early October, when they grow to an average of 40-50 leeches per 500 grams, they can be harvested