Mussels are dioecious, the reproductive gland is located around the dorsal intestines of the foot, in the form of a grape-like gland, the reproductive season is usually in summer, the spermatozoa are fertilized in the gill cavity of the external gills until the formation of the hooked larvae. Fertilized eggs will not be washed out by the flow of water due to the adhesion of the mother's role, and stay in the gill cavity development, so the gill cavity of the external valve gills is also known as the nursery sac, here we take a look at the mussel reproduction techniques!

Parental mussel selection and cultivation

1, parental mussel selection

① parental mussel shell color should be bright, greenish-blue, shell intact without mutilation, the "abdomen" bulge round, mussel body robust and plump, strong closed-shell force, the mussel age of 6 to 8 winter age is good, the female mussel is best to be the mother mussel.

② sex of pearl mussels from the appearance of difficult to distinguish, must be based on the internal gill filament sparsity and the number of roots, in order to accurately determine. Generally female mussels are slightly larger, wider growth whorls, shells are also slightly wider, slightly thicker. Open mussels, female mussels gill filaments are arranged closely, after sexual maturity, the number of gill filaments of the outer gill flap up to 100 to 120, male mussels gill filaments are arranged sparsely, after sexual maturity, the number of gill filaments of the outer gill flap is only 60 to 80.

2, pro mussel cultivation: pro mussel cultivation pool area of the best in 2000 square meters or more, the water depth of 1.5 meters, the bottom of the pool silt thickness is moderate. Breeding water oxygen content of 4.0 to 8.0 mg / liter, pH 6.5 to 8.0, bait biomass of 10 to 20 mg / liter. The water quality should not be over-fertilized, so as to avoid stunting or sexual reversal of female reproductive cells due to lack of oxygen. If a small area of water is used to cultivate parent mussels, it must have slow-flow conditions.

3, put the ratio: general male and female by 2:1 ratio (that is, 2 male clip 1 female for 1 combination), and tail to tail hanging in the water layer for sex ratio combination breeding. Parent mussel cultivation work should start in the fall, to regular injection and discharge of pool water, timely reproduction of bait organisms, to promote the development of pro mussel gonads, maturity.

Fertilization and embryonic development

1. Fertilization season: take delta sail mussels as an example. Generally, the sail mussel has the ability to reproduce at the age of three. Sexual maturity begins in May each year. Sexual maturity, the appearance of the gonads of the female sail mussel is orange, and the male sail mussel's gonads are white. The spawning season is from May to July. Mature eggs are round and spherical, and mature spermatozoa are able to swing their tails and swim when examined microscopically. When the majority of eggs in the reproductive nest is mature, the female mussels will be ovulated and fertilized. Sailfish mussels spawn 5 to 8 times a year, egg production of 400,000 to 500,000 grains.

2, fertilization methods: mussels fertilization methods are natural fertilization and induced fertilization of two kinds.

① natural fertilization: in the breeding season of mussels, female mussels mature eggs through the reproductive pore discharged to the body of the outer coat cavity, male mussels mature spermatozoa discharged by the vas deferens through the reproductive pore to the gill cavity, and then discharged through the outlet pipe to the outside of the body of water. The spermatozoa follow the water into the female mussel's outer coat cavity to combine with the eggs to be fertilized and complete fertilization. Fertilized eggs in the mother mussels on the left and right sides of the external gill flaps for embryonic development.

② induced fertilization: male mussel germ cells usually mature before female mussels. Female mussels can be part of the egg maturity, artificially remove the male mussel semen, diluted with reproductive saline injected into the outer coat membrane of the female mussels, and the female mussels are placed in advance of the water temperature is higher than the original pool water temperature of 3 to 5 ℃ in the fertilization basin, induced fertilization. The semen injected for the first time only plays the role of inducing female mussels to ovulate, and it is necessary to use the same method to inject the second diluted semen, and this time the sperms in the semen happen to be fertilized with the mature eggs that are induced. By inducing fertilization, mussels can be brought forward into the breeding season.

3, embryonic development: fertilized eggs since the egg cleavage, through the fertilized egg? Mulberry stage? Blastocyst stage? protozoal stage? The embryonic development process of the hooked larva, the formation of hooked larva. The entire embryonic development process generally takes 35 to 50 days.

Harvesting hooked larvae

After the development of hooked larvae on the external gill flap of the mother mussel, with peduncles and hooks, able to parasitize the fish body, but also must be parasitized on the body of the fish to complete the metamorphosis process, becoming a juvenile mussel. Therefore, in the hooked larva is about to come out of the membrane, we should use the fish as a "seedling collector", the hooked larva collected on the fish body.

1, picking fish selection: bighead carp, silver carp, grass carp, carp can be picked up hooked larvae, but the temperament of bighead carp and grass carp species is good. Each mussel each picking needs 9.9 cm specification fish species 300 to 500 tails. It is necessary to choose good fish species with healthy physique in order to tolerate more parasites of hook mesoparasites.

2, maturity identification: immature hooked larvae do not have the ability to parasitize, the maturity of hooked larvae must be identified. Identification method is to take out a few cultivated female mussels, first of all, open the mussels with a shell opener, plus plug fixed to a certain extent, and then use a probe in the middle of the mussels gill flap to pick out a few hooked larvae, if the hooked larvae can be picked out of each other to adhere to form a chain, it is a mature hooked larva.

3, seedling collection methods

① indoor seedling collection: in the basin filled with 10 ~ 15 cm deep clean water, the mother mussels after sampling placed flat on the bottom of the basin, and then put into the seedling fish, and through the water pipe so that the water becomes running water, a few hours after the mother mussels to stimulate the discharge of glochidia larvae.

② outdoor seedling collection: in the fresh water of the river, lake, available fish box seedling collection. The number of seedlings is large, suitable for mass production. Seedling collection should be replaced in a timely manner, to about 200 tails of hooked larvae parasitized per fish is appropriate, the number of too large will cause the death of the fish fry collection. One day before the harvesting of seedlings, the fish should be harvested to pull the net to exercise, enhance its physical condition, and discharge feces, in order to avoid the harvesting of seedlings contaminated with hooked larvae.

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