How do leeches grow in plastic foam boxes? Culture technique of attached leech

The use of water tanks, large plastic buckets, plastic foam boxes, buckets and other containers to cultivate leeches is simple, flexible and easy to operate, and can be used when raising a small number of leeches in rural areas. So how do leeches grow in plastic foam boxes? The following is the introduction of leech culture technology.

I. Biological characteristics of leeches

1. Living habits most species of leeches live in fresh water, a few species live in sea water, very few species live on land, and some species live in water and amphibious life. The suitable temperature for growth is 15-30 ℃. When the air temperature is lower than 10 ℃, it will stop feeding and when the water temperature is above 35 ℃, it will also affect its growth and development.

The leech has a wide adaptability to the acidity and alkalinity of the water body, and its favorite environment is neutral or slightly alkaline water, but it does not like to live in an environment 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, it can endure hypoxia for a long time in water; on the other hand, it is very sensitive to hypoxia in water. When the living environment is anoxic, the symbiotic bacteria in the leech can breathe anaerobically and maintain their own life in a short time.

In artificial culture, as long as the dissolved oxygen in the water is more than 0.7 mg / L, it can meet its living needs, so it is often necessary to add fresh water in artificial culture. Leeches in nature do not have high requirements for environment and water quality, so they can grow and develop in general water bodies. When artificial breeding, we should pay attention to two points: one is to choose water without pollution, chemical fertilizer and pesticide residues, and the other is to avoid nearby pollution sources. Leeches are omnivorous animals, which suck the blood or body fluids of animals as the main way of life, and often feed on insects, molluscs and plankton. Under artificial culture conditions, they feed on all kinds of animal viscera, cooked egg yolk, formula feed, plant residues, freshwater shellfish, miscellaneous fish, earthworms and so on.

two。 The leeches are sensitive to the environment and show negative phototaxis, that is, they have the instinct to avoid light, especially when exposed to strong light. In the artificial breeding of leeches, we should also pay attention to this characteristic and avoid direct exposure to strong light as far as possible. When the light is very strong in the midsummer season, the breeding pond should be shaded to create a suitable dark light environment. The leech has a strong ability to sense the flow of water and is very sensitive to the size of the current. It can accurately determine the location of the wave center and react quickly to swim against the current.

3. Escaping leeches like to crawl, especially on walls with water, so it is necessary to do a good job of escape prevention facilities on the edge of the breeding pond, especially when there is a storm.

4. Hibernating characteristics in winter leeches hibernate in the mud, when the water temperature is 10 ℃, they will stop feeding and drill into the bottom or pool soil to hibernate.

5. After the regenerative leech is cut laterally, two new individuals can grow back from the fracture site, which is the unique regeneration ability of the leech.

2. Simple artificial propagation of leeches

1. The source of leeches

The source and selection of leeches, also known as parent leeches, can be purchased from aquaculture departments or markets, or captured from lakes and rivers. Species of leeches require individual size, more than 20 grams per piece, robust, harmless, strong vitality, clear longitudinal lines on the back, yellowish. This kind of leech lays more eggs and has a high hatching rate.

two。 Purchase time

Leeches usually lay eggs twice a year, once in spring and the other in autumn. Artificial breeding leeches had better be purchased in spring. Species are often purchased before May in the middle and lower reaches of the Yangtze River, no later than May 1. In nature, the time for leech oviposition cocoons is usually from late April to late May (the average water temperature is 20 ℃). The earliest time for leech egg laying cocoons in Zhoushan area is April 10, so the best time for local species purchase should be about April 15.

3. Temporary cultivation of leeches

Temporary cultivation and disinfection of leeches the leeches must be temporarily reared for a few days and then sterilized. Disinfection method: take a large plastic basin, the bath solution is 0.5% formalin or 0.1% potassium permanganate solution, put the seed leech into the bath for 5 minutes, fish it out and put it into a container containing clear water, waiting for it to be put into the breeding table.

4. Put in seed

(1) preparation of breeding platform

The breeding platform, also known as the spawning cocoon bed, specially provides leeches into the mud to build cocoons and lay eggs. The breeding platform is actually a border made of soil on cement or flat land, 30 cm high, 120 cm wide and unlimited in length (depending on the number of bdelloids). The area of the breeding platform is prepared according to 1.5 kg of leeches per square meter.

(2) build cocoons with leeches

The oviposition cocoon bed should be a relatively soft soil with a soil moisture content of 30% to 40% (it can be crumpled by hand and can be dispersed by gently shaking). After the parent leeches are put into the cocoon bed, they will naturally drill slowly into the soil, and then drill an oblique or vertical hole upward, with a width of about 1 cm, a depth of 5 cm and a depth of 5 cm and 4 forks. The front end of the leech rests upward in the acupoint, in which the single-celled gland secretes a thin mucus, which mixes with air to form a soap foam, and then secretes another mucus to form an egg cocoon wall, which is wrapped around the band to form an egg cocoon.

(3) Leech oviposition

The cocooning and spawning of leeches are completed continuously, and it takes about 30 minutes from cocooning and spawning to exit. A leech can produce 2 cocoons and 3 cocoons, and a few can produce 4 cocoons. The size of the cocoon varies greatly, the first one is the largest, and the last egg cocoon is the smallest. Most of the cocoons are oval or oval, spongy or honeycomb, with an average short diameter of 26.5 mm and a long diameter of 18.7 mm. The average weight of each egg cocoon is 1.68 grams. There are about 595 cocoons per kilogram.

(4) artificial hatching of leech egg cocoon

Incubator: there are plastic buckets, plastic foam boxes and so on.

Operation: the loose sand and loose loam are mixed together as hatching soil and placed at the bottom of the container with a thickness of 1cm to 2cm. Then the pointed end of the egg cocoon is placed neatly on the hatching soil and covered with several layers of gauze or cotton cloth to maintain a certain degree of humidity. In order to prevent the young leeches from escaping, the hatching container was covered with a layer of 60-mesh nylon sieve, and finally wrapped tightly with plastic sheeting to prevent the evaporation of water in the incubator. The indoor temperature is controlled between 20 ℃ and 28 ℃, and the best one is 25 ℃. The humidity of the incubated soil is between 30% and 40%.

Under the above conditions, young leeches can be hatched after about 25 days. In order to prevent the hatched leeches from escaping, a larger water tank or other water container can be set up under the incubator, which contains an appropriate amount of water to accept the hatched leeches and put some bamboo slices or sticks on the water surface for the young leeches to climb up and perch on it. There are 1520 young leeches in most of the cocoons, more than 30 at most and 12 at least in each cocoon. After all the egg cocoons are hatched, they can be taken out and put into the bamboo basket, a plastic foam board can be put into the breeding pond, and the basket containing egg cocoons can be placed on the foam board, and the hatched leeches can go directly into the temporary culture pond. In order to facilitate observation, the foam board is fixed in one place to prevent drift.

The standard of high-quality leech seedlings: the body color of high-quality leech seedlings should be dark purplish red and dynamic. Putting the leech seedlings in the washbasin and touching it with chopsticks can make a rapid response, the vermiculite body shrinks into a ball, and sometimes its tail tip can be seen flapping, with high phototaxis sensitivity. The young leeches were temporarily reared in water for more than 15 hours, and the survival rate reached more than 95%, indicating that the quality of young leeches was good. The newly hatched young leeches show cork color, and the body color gradually changes to that of adult leeches with the growth of the larvae. During the temporary recuperation period, the main management work is baiting and changing water. Because it is a young leech, the management workload is not large.

III. Plastic foam box culture

⒈ box selection

The plastic foam box had better be refitted with a new one, such as the old one, as long as it does not leak, and the opening around it is intact, and the one with a lid can also be used. Open a rectangular opening of 20cm × 25cm in the center of the box cover for observation, feeding, changing water, etc. In order to prevent leeches from escaping from the opening of the lid, a special funnel-shaped anti-escape net must be installed at the opening of the lid. The production method of the anti-escape net is as follows: the net is conical, take the steel bar with a diameter of 4 mm to make a box slightly larger than the opening of the lid, sew it into a conical bag with man-made fiber cloth, and sew the mouth of the bag on the steel frame.

two。 Use water

Aquaculture water can be used with pollution-free river water, well water or reservoir water.

3. Release seedlings

When releasing seedlings, the amount of water in the box should not be too much, generally reaching the height of 1, 3, 3, 1 and 2 of the box wall. Box raising leech seedlings can release young leeches or medium leeches, generally young leeches in late May, leeches in mid-late June. It is difficult to raise young leech seedlings, and beginners can choose to raise middle leeches. When the author tried to breed, the artificial seedlings were self-propagated, and 200 young leeches were released in each box. The seedling amount of middle leeches (young leeches) is 80 million.

4. Daily management work

(1) bait

The main baits are water fleas, water earthworms, snails, field snails, longevity snails, clams, clam meat and scraps of livestock and poultry. At the beginning of the culture, 12% of the leech weight was fed with 15% of the daily feed, and 20 days later, 10% of the leech weight was fed with 12% of the feed. Feed leeches less than 6 centimeters long, snails must be mashed, and must be washed clean before mashing, otherwise it is easy to bring germs, 500 grams of leeches need to be fed snail 4kg 5kg.

(2) changing water

The amount of water exchange is small when the water temperature in the box is below 18 ℃, generally once every two days, the total amount of water exchange is 1 ℃, 1 ℃ and 2; when the water temperature is above 18 ℃, the water exchange volume should be gradually increased with the increase of water temperature, that is, from 1 ℃ 2 to 3 ℃ 4. In addition, the water should be changed every 10 days, and the temperature difference is within ±4 ℃.

(3) removal of residual bait

3-4 hours after each feeding, the residual bait should be removed, especially in the high temperature season in summer to prevent the breeding of residual bait fermentation pathogenic microorganisms.

(4) separate cultivation

With the growth of leeches, the same specifications will be kept in different boxes for easy management.

5. Harvest

Box-raised leeches grow very fast and can be harvested when they grow to an average of 40 leeches per 500 grams in early October.