METHOD FOR PRODUCING FREE SWIMMING ARTEMIA NAUPLII AND PACKAGED CYSTS FOR USE IN THAT METHOD

摘要

1. A method for producing free swimming Artemia nauplii starting from a quantity of Artemia cysts, including diapauzing cysts, by incubating the cysts in a hatching medium, in a density which comprises maximally about 5 g cyst dry matter per litre hatching medium, for a predetermined incubation period and under conditions allowing at least a portion of the cysts to hatch and to release free swimming nauplii within this predetermined incubation period, in which method the cysts are brought in contact with hydrogen peroxide to break diapause in at least a number of said diapauzing cysts in order to enable them to produce free swimming nauplii within said predetermined incubation period, characterised in that said hydrogen peroxide is introduced in the hatching medium in an amount selected within the range between 0.5 and 30mg/l hatching medium. 2. A method according to claim 1, characterised in that the selected amount of hydrogen peroxide is lower than 20mg/l and more particularly lower than 15mg/I and is higher than 1mg/l, in particular higher than 2mg/l and more particularly higher than 3mg/l. 3. A method according to claim 1 or 2, characterised in that the cysts are hatched in said hatching medium in a density of less than 4 g cyst dry matter per litre, in particular in a density of less than 3 g cyst dry matter per litre and preferably in a density of about 2 g or less cyst dry matter per litre. 4. A method according to any one of the claims 1 to 3, characterised in that said cysts comprise such an amount of diapauzing cysts that by introducing an optimal amount of hydrogen peroxide in the hatching medium, the hatching percentage can be increased from X % to a maximum hatching percentage of M % and said amount of hydrogen peroxide is selected within said range to increase the hatching percentage from X % to a hatching percentage which is at least equal to X % + 0.4* (M-X) %, and preferably to a hatching percentage which is at least equal to X % + 0.6* (M-X) %. 5. A method according to claim 4, characterised in that said maximum hatching percentage is determined by taking a number of samples of the cysts, by hatching these samples in hatching media differing from one another by a different amount of hydrogen peroxide introduced per volume unit therein and situated within said range, by determining the hatching percentages for the different hydrogen peroxide amounts, and by selecting the highest hatching percentage amongst the determined hatching percentages. 6. A method according to any one of the claims 1 to 3, characterised in that for selecting said amount of hydrogen peroxide, a number of samples of the cysts are taken, these samples are hatched in hatching media differing from one another by a different amount of hydrogen peroxide introduced per volume unit therein and situated within said range, the hatching percentages are determined for the different hydrogen peroxide amounts and the maximum percentage M % amongst these hatching percentages, and a hydrogen peroxide amount is selected which increases the hatching percentage from X % to a value higher than X %, in particular a hydrogen peroxide amount which gives either the maximum hatching percentage of M % or a hatching percentage which is at least equal to X % +0.4* (M-X) % and preferably at least equal to X % + 0.6* (M-X) %, a hydrogen peroxide amount corresponding substantially to said hydrogen peroxide amount which gives said maximum hatching percentage of M % being most preferably selected. 7. A method according to any one of the claims 1 to 6, characterised in that said hydrogen peroxide is introduced in the hatching medium by adding hydrogen peroxide and/or at least one compound to this medium which produces hydrogen peroxide in the hatching medium, the hydrogen peroxide being preferably introduced in the hatching medium by adding at least one hydrogen peroxide producing compound which contains a peroxide link and which is selected more particularly from the group comprising peroxides, perborates, persulfates, peracetates or combinations thereof to the hatching medium, the hydrogen peroxide producing compound being preferably a solid compound and comprises most preferably calcium and/or magnesium peroxide. 8. A method according to any one of the claims 1 to 7, characterised in that said hydrogen peroxide is introduced in the hatching medium less than 10 hours, preferably less than 8 hours, more preferably less than 6 hours and most preferably less than 5 hours after having started to incubate the cysts therein. 9. A method according to claim 8, characterised in that said hydrogen peroxide is introduced substantially simultaneously with the cysts in the hatching medium, in particular by being mixed with the cysts and/or by being adhered or coated thereon. 10. A method according to any one of the claims 1 to 9, characterised in that said predetermined incubation period is a period of about 24 hours or less and at least 90 % of the cysts which hatch within an incubation period of 48 hours are hatched within this predetermined incubation period. 11. Artemia cysts destined to be incubated in a hatching medium to produce free swimming nauplii, which cyst show a hatching percentage of X% of the total number of full cysts when they are hatched in the hatching medium in the absence of hydrogen peroxide, characterised in that the Artemia cysts are combined with a quantity of hydrogen peroxide and/or of at least one compound which produces hydrogen peroxide when added to the hatching medium, which quantity is sufficient to introduce an amount of hydrogen peroxide in the hatching medium which increases the hatching percentage of the cysts from X% to a hatching percentage higher than X% when this amount of hydrogen peroxide is introduced in the hatching medium. 12. Artemia cysts according to claim 11, characterised in that said quantity of said hydrogen peroxide and/or of said hydrogen peroxide producing compound is determined in such a manner that when adding this quantity to the hatching medium wherein the cysts are to be incubated, the hatching percentage of the cysts is increased from X% to said hatching percentage higher than X%. 13. Artemia cysts according to claim 11 or 12, characterised in that said quantity of said hydrogen peroxide and/or of said hydrogen peroxide producing compound is determined in such a manner that when adding this quantity to the hatching medium wherein the cysts are to be incubated, an amount of hydrogen peroxide comprised between 0.5 and 30mg/l is introduced therein. 14. Artemia cysts according to any one of the claims 11 to 13, characterised in that they are destined to be incubated in the hatching medium in a predetermined density of about 5 g or less cyst dry matter per litre. 15. Artemia cysts according to any one of the claims 11 to 14, characterised in that said cysts comprise such an amount of diapauzing cysts that by introducing an optimal amount of hydrogen peroxide in the hatching medium, the hatching percentage can be increased from X % to a maximum hatching percentage of M % and said amount of hydrogen peroxide is such that when the cysts are hatched in the presence thereof the hatching percentage is at least equal to X % + 0.4* (M-X) %, and preferably at least equal to X % + 0.6* (M-X) %. 16. Artemia cysts according to any one of the claims 11 to 15, characterised in that the Artemia cysts are combined with a quantity of at least one compound which produces hydrogen peroxide when added to the hatching medium, which hydrogen peroxide producing compound containing preferably a peroxide link and is more particularly selected from the group comprising peroxides, perborates, persulfates, peracetates or combinations thereof, the hydrogen peroxide producing compound being preferably a solid compound and comprises most preferably calcium and/or magnesium peroxide. 17. Artemia cysts according to any one of the claims 11 to 16, characterised in that said quantity of said hydrogen peroxide and/or of said compound comprises and/or produces less than about 15 mg and more than about 0.5 mg, preferably more than about 1 mg and most preferably more than about 1.5 mg hydrogen peroxide per gram cyst dry matter, which quantity is preferably mixed with the cysts and/or adhered or coated thereon. 18. Artemia cysts according to claim 17, characterised in that said quantity of said hydrogen peroxide and/or of said compound comprises and/or produces less than about10 mg and preferably less than about 7.5 mg hydrogen peroxide per gram cyst dry matter. 19. Artemia cysts according to any one of the claims 11 to 18, characterised in that the cysts are jointly packaged with said quantity of hydrogen peroxide and/or of at least one compound which produces hydrogen peroxide when added to the hatching medium. 20. Artemia cysts according to claim 19, characterised in that said quantity of said hydrogen peroxide and/or of said hydrogen peroxide producing compound is contained in a further packaging separating this hydrogen peroxide and/or this compound from the cysts. 21. Artemia cysts according to claim 19 or 20, characterised in that said quantity of said hydrogen peroxide and/or of said compound is contained in the same packaging as the cysts and is in particular mixed with the cysts and/or adhered or coated thereto.