The Complete Guide to Artemia (Brine Shrimp): Biology, Cysts, and Hatching
, by David Lo, 11 min reading time
Artemia, commonly known as brine shrimp, are one of the most important live foods used in aquaculture and aquarium breeding. Their unique cysts can survive extreme conditions and hatch into nutrient-rich nauplii that are ideal for feeding fish and crustacean larvae. This comprehensive guide explains the biology of Artemia, the structure of brine shrimp cysts, and the environmental factors that control successful hatching. You will learn how Artemia embryos remain dormant, what happens during the hatching process, and how temperature, salinity, light, and pH influence hatch rates. Whether you are an aquarist, breeder, or aquaculture professional, understanding Artemia biology can help you improve hatch success and raise healthier fish fry.
The Complete Guide to Artemia (Brine Shrimp): Biology, Cysts, and Hatching
Brine shrimp (Artemia) are among the most important live foods used in aquaculture and aquarium breeding. For decades they have been the primary food source for larval fish and crustaceans because of their nutritional value, ease of storage, and predictable hatching characteristics.
Today, billions of Artemia nauplii are hatched every day around the world to feed fish larvae, shrimp, and other aquatic organisms. Understanding the biology of Artemia, the structure of their cysts, and the environmental factors that control hatching can significantly improve hatch success and larval survival.
This guide provides a comprehensive overview of Artemia biology, cyst structure, and the science behind successful hatching.
What Is Artemia?
Artemia are small crustaceans belonging to the order Anostraca, commonly referred to as brine shrimp. They inhabit hypersaline environments such as salt lakes, salt pans, and solar salterns where most other aquatic organisms cannot survive.
Their classification is as follows:
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Phylum: Arthropoda
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Class: Crustacea
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Subclass: Branchiopoda
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Order: Anostraca
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Family: Artemiidae
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Genus: Artemia
Several species of Artemia are known, including:
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Artemia franciscana
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Artemia persimilis
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Artemia tunisiana
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Artemia urmiana
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Artemia monica
In addition to these sexually reproducing species, there are several parthenogenetic strains consisting entirely of females capable of reproducing without fertilization.
Artemia are uniquely adapted to extreme environments and can tolerate salinity levels far higher than those tolerated by most aquatic organisms.
Natural Habitat of Artemia
Artemia occur in hypersaline lakes and coastal saltworks around the world. These habitats often have salinity levels exceeding 70 parts per thousand, which excludes most predators such as fish.
Their ability to regulate salt balance makes them one of the most efficient osmoregulators among crustaceans. This adaptation allows Artemia populations to thrive in environments that would be lethal to most aquatic animals.
Natural Artemia populations have been recorded in:
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North and South America
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Europe
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Africa
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Asia
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Australia
Their global distribution is believed to be aided by migratory birds, which transport cysts between salt lakes.
The Artemia Life Cycle
The Artemia life cycle consists of several distinct stages:
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Dormant cyst
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Embryo development
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Nauplius larva
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Juvenile stage
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Adult shrimp
Under favorable conditions, Artemia can complete their life cycle in as little as 8–10 days.
Adult Artemia can grow up to 10 mm in length and produce hundreds of offspring during their lifespan.
Artemia Cysts (Brine Shrimp Eggs)
The dormant eggs of Artemia are called cysts. These cysts are remarkable biological structures capable of surviving extreme environmental conditions.
They can remain viable for years in a dry state and begin development only when exposed to water and favorable environmental conditions.
Cysts typically measure 200–300 micrometers in diameter and appear as small brown spherical particles.
Their ability to remain dormant makes them ideal for long-term storage and commercial distribution.
Structure of an Artemia Cyst
The Artemia cyst shell consists of three main layers:
Chorion
The outermost layer is called the chorion. It is a rigid shell composed primarily of lipoproteins and chitin.
The chorion provides protection against:
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mechanical damage
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ultraviolet radiation
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environmental stress
In aquaculture, the chorion can be removed through a process called decapsulation using hypochlorite.
Outer Cuticular Membrane
The second layer is the outer cuticular membrane, which acts as a selective permeability barrier.
This membrane prevents large molecules from entering the embryo while still allowing gases such as carbon dioxide to diffuse through.
Embryonic Cuticle
The innermost layer is the embryonic cuticle, a transparent elastic membrane that eventually becomes the hatching membrane during incubation.
Inside this membrane lies the dormant Artemia embryo.
Dormancy and Cryptobiosis
Dry Artemia cysts exist in a state known as cryptobiosis, where metabolic activity is virtually halted.
This allows the embryos to survive extreme environmental conditions including:
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desiccation
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radiation
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extreme temperatures
When the cyst absorbs water and becomes hydrated, metabolism resumes and embryonic development begins.
The Artemia Hatching Process
Hatching occurs in several stages.
Hydration
When cysts are placed in seawater, they absorb water and become spherical within one to two hours.
During this phase the embryo begins reactivating metabolic processes.
Breaking Stage (E-1)
After approximately 15–20 hours, the cyst shell ruptures. This stage is known as breaking.
The embryo remains enclosed within the hatching membrane.
Emergence Stage (E-2)
The embryo emerges completely from the shell but remains attached beneath it.
During this stage the nauplius begins developing its appendages.
Nauplius Release
The hatching membrane eventually ruptures, releasing the free-swimming Artemia nauplius.
This larval stage is commonly used as live food in aquaculture and aquarium breeding.
Artemia Nauplii
The newly hatched larva is known as the Instar I nauplius.
Characteristics include:
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size of approximately 400–500 micrometers
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orange coloration due to yolk reserves
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three pairs of appendages
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a single median eye (nauplius eye)
At this stage the digestive tract is not yet functional and the nauplius relies entirely on internal yolk reserves.
After approximately 12 hours the nauplius molts into Instar II, where feeding begins.
Metabolism During Hatching
The metabolism of Artemia cysts is driven primarily by the conversion of trehalose into glycerol and glycogen.
This biochemical process plays a key role in regulating osmotic pressure inside the cyst.
As glycerol accumulates, water continues to enter the embryo, increasing internal pressure until the cyst shell bursts.
This mechanism allows Artemia embryos to regulate osmotic balance during the early stages of development.
Environmental Factors Affecting Hatching
Successful Artemia hatching depends on several environmental parameters.
Temperature
Optimal hatching temperatures range between 25°C and 30°C.
Metabolism slows at lower temperatures and may cease entirely below approximately 4°C.
Hydrated cysts exposed to temperatures above 40°C can suffer irreversible damage.
Salinity
Artemia cysts can hatch in a wide range of salinities, but optimal results are typically obtained around 25–35 ppt.
Higher salinity levels increase the osmotic pressure difference required for shell rupture, delaying hatching.
pH
The optimal pH range for hatching is 8.0–9.0.
Enzymatic processes involved in breaking the hatching membrane are sensitive to pH changes.
Light
Light acts as an important trigger for metabolic activation in Artemia cysts.
Low light intensity may delay hatching or reduce hatch rates.
Measuring Artemia Hatch Quality
Several metrics are used to evaluate cyst quality.
Hatching Percentage (H%)
Hatching percentage represents the proportion of cysts that produce nauplii.
Hatching Efficiency (HE)
Hatching efficiency measures the number of nauplii produced per gram of cysts under standardized conditions.
Hatching Rate
Hatching rate describes how quickly nauplii emerge during incubation.
Three time points are typically measured:
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T0 – first appearance of nauplii
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T10 – 10% hatch
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T90 – 90% hatch
The difference between T90 and T10 indicates hatching synchrony.
Hatching Output
Hatching output measures the biomass of nauplii produced per gram of cysts.
This is particularly important for commercial hatcheries.
Why Artemia Are So Important in Aquaculture
Artemia remain the most widely used live feed organism in aquaculture because they offer several advantages:
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long-term cyst storage
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predictable hatching
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suitable size for larval fish
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high nutritional value
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easy enrichment with nutrients
Despite advances in artificial diets, Artemia nauplii are still considered the most reliable starter feed for fish and crustacean larvae.
Conclusion
Artemia are remarkable organisms whose unique biology has made them indispensable in aquaculture and aquarium breeding.
Their cysts represent one of nature’s most resilient reproductive strategies, capable of surviving extreme environmental conditions for extended periods.
By understanding the biology of Artemia cysts and the environmental factors controlling hatching, aquaculturists and hobbyists can greatly improve hatch success and larval survival.
As research continues, Artemia will likely remain a cornerstone of larval nutrition in both commercial aquaculture and home aquariums.
References
Abreu-Grobois, F.A., & Beardmore, J.A. (1980). Genetic differentiation and speciation in the brine shrimp Artemia.
Barigozzi, C. (1974). Artemia: a survey of its significance in genetic studies.
Bowen, S.T., Fogarino, E.A., Hitchner, K.N., Dana, G.L., & Chow, V.H. (1978). Ecological isolation in Artemia.
Clegg, J.S., & Conte, F.P. (1980). A review of Artemia cyst biology.
Croghan, P.C. (1958). The osmotic and ionic regulation of the brine shrimp Artemia.
Persoone, G., Sorgeloos, P., Roels, O., & Jaspers, E. (1980). The Brine Shrimp Artemia: Ecology, Culturing, Use in Aquaculture.
Sato, T. (1967). Influence of pH on Artemia hatching enzyme activity.
Vanhaecke, P., & Sorgeloos, P. (1982). International study on Artemia cyst quality and hatching characteristics.