Hatching instruction for the Copepod Eggs from Acartia tonsa
Copepods of the species Acartia tonsa are the superfood for breeding fish, crab, shrimp and jellyfish larvae. Due to their particularly high nutrient content, they are a sought-after live food. Thanks to blue biotechnology, it is now possible to breed the marine plankton species Acartia tonsa in a controlled land-based way and to buy the copepod eggs in a saline solution. We are very enthusiastic about the successes in breeding and have therefore created a step-by-step guide.
Similar to the incubation of Artemia eggs, we propose the following procedure:
1. Prepare sea water
Incubate copepods cysts in freshly prepared sea water. The water should be sterilized beforehand and contain 30 to 35 g/l salt. It is best to prepare the salt water solution with boiled tap water or osmosis water. It is best to use aquaristic sea salt from a specialist.
2. Container and Aeration
As incubator we recommend the design as it is also used in the incubation of Artemia eggs. This means a cylindrical container that tapers downwards (e.g. inverted PET bottle with open bottom). An aeration pipe is placed at the bottom end of the container to ensure homogeneous mixing. The aeration tube should have a diameter of 6 to 8 mm. The aeration should be relatively coarse and less intense (about 3-5 bubbles/sec.). It is important that the copepod eggs remain evenly mixed and cannot sediment anywhere. Otherwise the hatching rate will be reduced. The oxygen concentration should be above 6 mg/l. If, on the other hand, you set too fine bubbles with a wood ejector, this can skim the eggs and on the other hand discharge the freshly hatched nauplii.
3. Dosage of the Eggs
Shake the bottle vigorously before dosing. Use 20,000 copepod eggs per litre of sea water. 20,000 eggs correspond to 2 ml of mixed solution (dosing spoon is included with algova products). For experienced breeders, the dosage can be increased to 40,000 copepods of eggs per litre. The hatching rate may vary depending on storage conditions, egg age and incubation methods, but is usually between 70-90 % in the first two months after purchase (after which the hatching rate decreases slightly).
The optimal incubation temperature for the copepod species Acartia tonsa is between 20 and 25°C. The temperature of 25°C should not be exceeded.
5. pH Value
The optimum pH value should be between 8.0 and 8.3. Freshly prepared sea water normally has a pH value of 8.2 at 30 g/l. The pH value can be readjusted or stabilised by adding sodium hydrogen carbonate (also known as sodium bicarbonate). However, a dosage of 1 g/l should not be exceeded.
The breeding area should be best illuminated indirectly with natural daylight. Avoid direct sunlight, otherwise the container will heat up excessively. Alternatively, artificial lighting is also possible, but this should be set with a timer according to the daily cycle (12 h on/12 h off).
7. Hatching and observation
Hatching occurs in the time range from 48 h to 72 h after incubation has started. Most nauplii hatch in this time range. The time it takes for the first nauplii to hatch depends on the lighting and the temperature. The copepods of Acartia tonsa hatch with a size of 70-110 µm. They are visible to the eye in a glass vessel in front of a strong light source. Alternatively, they can be observed very well under the binocular.
The freshly hatched nauplii should be fed as quickly as possible or kept at a cool temperature of 10°C. After 24 hours, the nauplii have already lost a large part of their nutritional value at 25°C. The nauplii should be fed as quickly as possible. Carefully filter the brood solution through a zooplankton sieve with a mesh size of 50 µm and then immediately use the nauplii to feed the larvae or rinse off the gauze with water from the larval container or aquarium.
9. Growing Copepods
If the nauplii are to grow into copepods, they must be fed with high-quality microalgae. We recommend Rhodomonas or Isochrysis. These are the only microalgae that stimulate female copepods to produce and lay eggs. The alga Isochrysis is for example contained in the product RotiBomb from algova, which is also suitable for the further breeding of copepods. Add a little bit algae/powder to the sea water every day, so that the water is just slightly yellowish/greenish. Typical development of Acartia tonsa nauplii:
Day 1-2: Nauplii 70-110 µm
Day 10-14: Adult animals 650-800 µm
Day 14-80: Adult animals grow to a maximum of 1200 µm
For the further growth of the culture we recommend to increase the amount of breeding water by about 50% daily from the 3rd until the 10th day. Example: If you start with 10.000 eggs in 500 ml sea water, the amount of sea water should be 2,5 litres on 6th day and 13 litres on 10th day.
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