Artemia salina, commonly known as brine shrimp, are small aquatic crustaceans found globally in highly salty environments such as salt lakes and salt ponds. Though not true shrimp, they are more closely related to cladocerans and triops. Their widespread presence in these extreme habitats makes them a subject for scientific study and commercial applications.
Understanding Brine Shrimp Biology
Artemia salina typically grows to about 8-10 mm, though some can reach up to 15 mm in length. Their elongated bodies are divided into at least 20 segments, and they possess 11 pairs of flat, leaf-like appendages called phyllopodia that beat rhythmically. These appendages also serve a respiratory function, as brine shrimp breathe through their feet. They have three eyes: one naupliar eye in their larval stage, with two more complex compound eyes developing as they mature.
Brine shrimp are filter feeders, consuming microscopic algae, bacteria, and detritus ranging from 1 to 50 micrometers in size. Their life cycle begins with dormant cysts, which are eggs encased in a hard shell. When submerged in saltwater, these cysts hydrate, and the embryo within resumes development. After approximately 20 hours, the outer membrane of the cyst cracks, and a free-swimming larva, known as a nauplius, emerges.
Nauplii grow and differentiate through about 15 molts, developing into adults within 18 to 21 days. Adult brine shrimp can reproduce in two ways: sexually, where a male fertilizes a female’s eggs, or asexually through parthenogenesis, where unfertilized eggs develop into female offspring. Females can switch between producing live nauplii (ovoviviparous reproduction) or dormant cysts (oviparous reproduction), depending on environmental conditions. The color of adult Artemia can vary from pale white to pink, green, or transparent, often influenced by the salt concentration of their environment.
Surviving Extreme Environments
Artemia salina exhibits physiological adaptations that enable it to thrive in hypersaline conditions. Their survival is attributed to an efficient osmoregulatory system, which allows them to manage high salt concentrations in their bodies. This system helps prevent excessive water loss or salt absorption, maintaining their internal balance in a wide range of salinities. They are rarely found in open oceans due to predators, which cannot tolerate the high salinity Artemia inhabits.
Brine shrimp also demonstrate a notable tolerance to anoxia, or very low oxygen levels, which often occur in their dense, saline habitats. They can synthesize efficient respiratory pigments, such as hemoglobin, to cope with these conditions. This adaptation allows them to extract oxygen more effectively from their environment, even when it is scarce.
A key adaptation of Artemia is cryptobiosis, specifically anhydrobiosis, a state of suspended animation their cysts can enter. When environmental conditions become unfavorable, such as extreme desiccation, temperature fluctuations, or oxygen deprivation, the embryos within the cysts halt their metabolism and become surrounded by a thick, protective shell. These dormant cysts can remain viable for extended periods, even years, surviving extreme temperatures, radiation, and complete dehydration. Upon rehydration in suitable conditions, these cysts can re-enter active metabolism and hatch.
Diverse Uses of Artemia
Artemia salina is used in various applications, primarily due to their ease of hatching and nutritional profile. They are extensively used as a primary live feed source in aquaculture for the larval stages of fish and crustaceans. Freshly hatched Artemia nauplii are rich in protein, making up to 40% of their dry weight, and contain essential fatty acids and vitamins. The ability to store their cysts dry for years allows for on-demand hatching, providing a convenient and labor-efficient food source for hatcheries worldwide.
Beyond aquaculture, Artemia serves as a valuable model organism in scientific research. Their resilience and relatively simple biology make them suitable for studies in toxicology, genetics, and environmental science. For instance, their cysts were even taken on Apollo 16 and 17 missions to the moon to investigate the effects of radiation on development. They are also used to study host-microbiome interactions due to their unique ability to maintain a distinct bacterial microbiome.
Their ability to hatch from dormant eggs has also made them popular in the pet trade. Marketed commercially as “Sea-Monkeys,” these kits allow individuals to easily hatch and observe brine shrimp. This application highlights their appeal for educational purposes and as an accessible introduction to aquatic life.
Hatching and Cultivating Artemia
Hatching Artemia salina cysts involves specific environmental conditions. A salinity range of 12-36 parts per thousand (ppt) is generally suitable for hatching, though some studies suggest lower salinities like 15 ppt can yield good results. The water temperature plays a significant role, with optimal hatching occurring at 26-28°C (80-82°F) within 24 hours. Temperatures below this range will prolong hatching time, while exceeding 30°C (86°F) can potentially harm the developing nauplii.
Constant light is beneficial for successful hatching, and aeration, typically provided by a coarse-bubbling air stone, is important for circulation and oxygen supply. Dechlorinated tap water or spring water is recommended, with non-iodized salt dissolved to achieve the desired salinity. Some sources suggest adding an aquarium water conditioner to neutralize heavy metals, which can hinder hatching.
For basic care and cultivation beyond hatching, maintaining water quality is essential. A preferred salinity range for culturing adult brine shrimp is 35-40 ppt, using aquarium-grade marine salt. Regular monitoring and adjustment of pH, ideally between 7.5 and 8.5, supports their well-being. Feeding can involve Spirulina algae powder, yeast, or powdered fish food, but overfeeding should be avoided to prevent water quality issues. Weekly water changes of approximately one-quarter of the culture volume, replaced with new saltwater, help maintain a healthy environment.