Learning intention: Learn about the biology of Artemia and why they are important.
Plan and carry out their own experiment to learn about the movement of Artemia.
Vocabulary: algae, aquaculture, artemia, crustacean, cyst, dormant, larvae, mortality, moult, nauplius, phototaxic, sustainable
Small fish may eat a wide range of foods, including bacteria, plankton, worms, crustaceans and algae. Artemia is a small crustacean that is used around the world as fish food for aquaculture (fish farming) and aquarium feeds.
Artemia are also known as brine shrimp. They are commercially advertised as sea monkeys and sold as pets. They look similar to shrimp, however have 11 pairs of legs and a long tail.
Sea monkeys are not found in the sea as there are too many predators- their only defence is surviving in extreme salinity where few other organisms can grow.
Artemia live in salt lakes and dried up salt flats around the world- including the salt lakes at Rottnest Island. They feed on microscopic algae and tiny bacteria that live in these hyper-saline environments. They are filter feeders, meaning they sift the water for tiny particles of food.
Artemia can reproduce either by having nauplii ( freshly hatched artemia), or to survive in a harsh, salty environment, they produce 'cycsts'- an egg surrounded by a hard shell. The cysts can lay dormant or inactive for several years if salt lakes dry up. The tough cysts can also survive temperatures that are below freezing and oxygen-free environments.
Cysts that are placed in water start to hatch in a few hours. Artemia nauplii have only one eye but develop two more when they mature. The nauplii are positively phototaxic, meaning they are attracted to light. Adult Artemia are negatively phototaxic, so swim away from light.
Artemia 'moult' (shed their external skeleton) around 15 times before they become mature. They grow to about one centimetre long. Males have two large antennae on their heads, while females have small antennae and a large egg sack.
Artemia don't sleep- they need to be constantly on the move to eat and breathe. They breathe through their feet.
These tiny crustaceans and their cysts are often used to feed fish larvae, as they are just the right size to be eaten by small fish.
Artemia can be enriched by feeding them nutrient-rich diets such as microalgae and highly unsaturated fatty acids. In aquaculture, the enriched Artemia are fed to fish larvae to ensure they are getting the right diet for maximum health and growth.