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Home arrow Library arrow Articles arrow Artemia: Decapsulation, Hatching, Feeding, On-Growing and Enrichment

Artemia: Decapsulation, Hatching, Feeding, On-Growing and Enrichment PDF Print

by , South Australian Seahorse Marine Services

Covers the techniques involved in decapsulating (increases the hatching rate), hatching, feeding, on growing and enrichment of artemia or brine shrimp.

Decapsulation

The external surface of the cyst shell is often contaminated with bacteria, fungi or organic impurities. Decapsulation is highly recommended as a disinfection procedure prior to hatching cysts. The outer shell called the Chorion, cannot be digested and is not easy to separate from the nauplii via rinsing. If ingested this can be a cause of fry deaths.

When you open your pack of cysts you will notice they are all concave. Cysts are stored and sold in a dehydrated state, firstly we need to hydrate the cyst. This is done by soaking the cysts for about 2-3 hours in fresh water (tap water is fine). Using a cut-off plastic drink bottle works fine (see diagram). A rubber stopper with a hole large enough for an airline can be pushed into the neck of the bottle. An other plastic drink bottle, this time with the neck cut off can be used as a stand to hold your container.

Inverted, cut off soft drink bottle

A cut-off plastic soft drink bottle inverted can be used for both hatching and decapsulation

Because most people use small amounts, the following explanations work on 10 grams of dehydrated cysts, which is approx. 3 level teaspoons. Pour about 800 ml of tap water into your container and add 10 grams of cysts and aerate for 1-2 hours or until your cysts look spherical in shape.

Sodium hypochloride with 12.5% w/v of active ingredient (I.e. 120 grams/litre) with the desired concentration of active chlorine at 22 grams/litre. General household bleach contains only 4% m/v (42 g/l) active ingredient and tends to foam, it would be my suggestion to obtain sodium hypochloride and store in a dark container in a cool dry place. The active concentration decreases by about 1% per month, so purchase in small amounts, and you will not have to make the calculations to compensate for this fact. So I would use 800 ml of tap water with 55 ml of sodium hypochloride. Gentle aeration is required, large bubbles will prevent cysts from being decaped.

So you have aerated your cysts in 800 ml of water for about 1-2 hours and they are all spherical, now you add 55 ml of sodium hypochloride. This bleach causes all your cysts to turn brown, then white after about 2 minutes. You need to watch carefully as your cysts will now begin to turn orange. Using a pipette take a small sample every minute and check the colour of your cysts--when you have approximately 95% turned orange it is time to rinse. This process should take about 5-7 minutes. I always have a timer on standby as a guide, remember don't judge your hatch by time, always use your eyes to determine the percentage of orange cysts. If available a microscope is a great aid. Remember the chlorine is still working, so drain you cysts into 105µm screen and rinse thoroughly with tap water until all the smell of chlorine has gone (5 -10 minutes is usually ample). Don't take your time with this one, move as quickly as possible.

Artmenia cysts, dry and hydrated

Dry cyst (top) and hydrated cyst (bottom)

These cysts can now be hatched immediately or stored in the fridge for use within a week. For longer storage cysts can be dehydrated with a saturated brine solution. Saturated brine can be made by using tap water and cooking salt. Add salt at the rate of 350 grams to 1 litre of water. Place decaped cysts in inverted cut-off soft drink bottle with 500 ml of saturated brine solution and aerate for about 2 hours, all dehydrated cysts should sink to bottom, drain off and store in fridge in a fresh batch of saturated brine solution, cysts can be stored like this for 3 months. When they are required for hatching simply remove required amount and rinse in tap water several times before placing in sea water to commence hatching.

Remember that the weight of your cysts has changed! Dehydrated cysts straight from tin contain 0% moisture, decapsulated cysts contain about 70% moisture and dehydrated, decapsulated cysts contain about 45% moisture. This is important because when you hatch your cysts at a rate of 3 grams per litre of water you have to make allowance for this moisture especially when weighing cysts for hatching. If you hatch 5 grams at a time, just split your decap in two. Spoon measurements don't change dramatically.

If you want to do larger decaps but can't work out the cyst/bleach/water ratios, .

Hatching

Using the same container in which the artemia was decapsulated in (washed of course) your cysts can now be hatched. Temperature should be around 25-30 °C (77-86°F), sea water at the rate of 35 ppt, oxygen levels above 2mg/l are recommended (watch for large bubbles or foam as these trap cysts--rinsing your cysts in freshwater or soaking for 5-10 minutes should prevent foaming).

Your cysts should take about 18-24 hours to hatch, although up to 48 hours may be required for poor quality cysts or inappropriate hatching conditions. Adequate lighting (60 watt globe) aids in hatching time. You will have to watch your first hatch and determine the time taken.

Turn off aeration and hold a torch to the side of the container and you should be able to observe the Instar I hatched Artemia. These can now be rinsed through 105µm screen. An easy way of ensuring there is no debris with your artemia is to darken off the upper part of your container, add a strong light near the side of bottle after about 5-10 minutes all the nauplii will be attracted to the light, while the debris and unhatched cysts fall to the bottom, drain off this debris carefully, then begin to drain nauplii until all are in screen, remembering to only drain off half the water. If you leave this sit for a further 5-10 minutes a second harvest can be made.

Newly hatched or Instar 1 Artemia still have yolk reserves and are yet to develop a digestive tract, they cannot be enriched at this stage. The nutritional value of Artemia changes as they grow. Pre-adult and adult are lower in fat and higher in protein, while nauplii are higher in fat and lower in protein. The nutritional profile of Artemia can be altered with the use of microalgae and specially formulated enrichments like DC Super Selco®.

Feeding and On-Growing

After hatching Artemia become Instar I; they still have a yolk sac but have not as yet developed a digestive tract, making they unsuitable for enrichment. At 2 days old the nauplii moult and become Instar II, they have no yolk reserves and have started to feed and develop their digestive tract. To increase the nutritional value they are enriched or gut loaded with essential components such as highly unsaturated fatty acids. Instar II and Instar III rapidly lose weight and nutritional value and must be fed. Starving nauplii have no nutritional value at all.

Artemia are non-selective filter feeders, they will ingest any particles of food of the correct size (< 50 - 60µm). Most microalgae is of a suitable size and can be fed to Artemia, good food sources are Isochrysis, Tetraselmis, Chaetoceros and Dunaliella varieties. Dried micro algae pastes and powders work best when added to sea water and placed in a blender for 3-5 minutes. Gut loading of Instar II Artemia takes about 12-18 hours, while gut loading adult Artemia can be achieved in 6-8 hours.

Inert foods such as yeast, wheat flour, rice flour and even egg yolk are sometimes used to on-grow Artemia, unfortunately these cause water quality problems and increase the amount of water changes necessary. When on-growing Artemia it is best to use a conical shaped container with a central airline (do not use air stones- large air bubbles are preferable). Oxygen levels should exceed 2 mg/litre, pH should be maintained between 8-9, levels below or above can be lethal. Keeping all parameters close to seawater levels aids growth. Artemia can tolerate quite high levels of ammonia, although this is not highly recommended. Water changes weekly can aid with water quality.

Artemia should be fed 2-3 times daily, small feeds often works better than one large feed daily. I feed at about 2 gm (1/4 spoon) of inert feed per litre of water per day. The easiest way to determine feed amounts is to watch water transparency, especially when using algae. When using inert foods or algae pastes or powders these should be mixed with sea water and blended for approximately 3-5 minutes.

Each day it is a good idea to turn the airline off and let the debris settle; either swirl and bottom drain conical containers or siphon flat bottom containers and Artemia swim near surface. This aids with water quality and ensures Artemia don't get caught in any floating debris. Artemia should reach adult size and begin mating within 3-4 weeks. A top up of clean water to replace water taken in cleaning also aids water quality.

Hygiene is very important and care should be taken, ensuring wash of all equipment on a regular basis in warm soapy water and then rinsing in tap water is critical. Scrubbing out of all grow-out containers before re-use is recommended.

Rinsing of artemia in tap water or fresh salt water prior to feeding ensures no transfer of unwanted bacteria or parasites. Ciliates commonly contaminate cultures and can be harmful to seahorses, rinsing with tap water minimises this risk.

Enrichment

DC Super Selco® from INVE Aquaculture is my preferred enrichment. Enrichment can be done in the cut-off inverted plastic bottles used for hatching at a rate of 1/8 teaspoon per litre of water. This should be blended for 3-5 minutes also. Enrichment takes approximately 6-8 hours for adult Artemia and 12-18 hours for Instar II nauplii, optimum temperature for enrichment is around 25°C (77°F).

Prior to feeding, Artemia should be placed in appropriate size screen and rinsed in tap water for several minutes. Enrichment products can deteriorate water quality in tanks so it should be rinsed off prior to feed. Although the DC in DC Super Selco® stands for disinfects continuously it is best to be cautious and rinse all foods prior to feeding to your seahorses, either in tap water or clean sea water. If there is any bacteria you dilute it to minimal proportions.

Hygiene is a priority, all containers used must be rinsed prior to use, wash with hot soapy water after use and rinse thoroughly. Bacteria grow and thrive in food containers. We recommend every food source is washed either in fresh tap water or fresh sea water to dilute bacteria or eliminate it.

 
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