Brine Shrimp in the Classroom
Objective:
To introduce young students to Artemia, fascinating creatures better known as brine shrimp (or "sea-monkeys").
This series of simple experiments is intended to encourage habits of observation and discovery. For additional information on hatching brine shrimp from cysts, see our Hatching page.
Table of Contents
- Overview
- Introduction to Brine Shrimp
- Classroom Instruction
- Hatching Brine Shrimp Eggs
- What Do Brine Shrimp Eat?
- Growing Brine Shrimp
- Experiments
Overview: Brine Shrimp in the Classroom
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A sea monkey's no monkey or chimp. — C. Drewes |
Brine shrimp are small crustaceans that are readily available (as eggs) and safe in the classroom environment. They are also inexpensive, interesting, and relatively easy to care for.
Brine shrimp eggs are available at pet stores, where they are sold as food for tropical fish. Tropical fish hobbyists and commercial growers use newly hatched brine shrimp as a first feed for their fish fry (baby fish).
Hatching brine shrimp is an easy process, and raising brine shrimp (or "Sea Monkeys") is fascinating in itself. By raising brine shrimp, observing their development, and performing simple experiments, your pupils will soon become acquainted with some of the problems confronted by living organisms.
Your students will learn many things about brine shrimp just through using their powers of observation. They will be amazed to find living things coming from what looks like "dirt." Inductive reasoning, combined with the ability to focus on detail, will be heightened, and they will have the opportunity to care for their own animals.
If you have not encountered or raised brine shrimp before, both you and the pupils can enjoy learning about this fascinating creature. If you are familiar with brine shrimp, this "brine shrimp primer" will become a valuable guide in managing the different activities. As always, it would be best if you could participate in the brine shrimp experiments along with the students.
Grade Level and Scheduling
Experiments using brine shrimp are used primarily in the first to fourth grades. With younger children, loose, exploratory activities are the most appropriate. Young children will learn a great deal simply from hatching the brine shrimp from eggs and watching them grow. Older students (third and fourth graders) may want to go on to challenging experiments with their animals.
At the beginning, you will need to dedicate at least 30 minutes per class, two to three times a week. The students will probably want to spend at least a few minutes each day observing the brine shrimp.
Be Patient!
Brine shrimp are not completely predictable animals. Occasionally, the method of raising them described here has not worked — the eggs have not hatched or the newly hatched brine shrimp have died within a few days.
Brine shrimp are "high maintenance" animals once they are born. As continuous filter feeders, they must be fed often; but at the same time, they are sensitive to poor water quality. You may have to do frequent water exchanges during the course of the experiments. Variations in the density in which you stock your grow-out containers will affect the results of your experiments.
Through trial and error, the students will quickly gain a sense of the delicacy and complexity of a living organism and the rather narrow range of conditions in which they can survive. Their eventual success, when it comes, will be even more rewarding.
Keep trying! The charm of brine shrimp and the enthusiasm of your students will make it well worth the effort.
Safety Note
If by chance one of the pupils eats some brine shrimp eggs, do not panic. The brine shrimp eggs will not hatch in the stomach of the child. Strong enzymes and an acid pH in the digestive tract will metabolize the brine shrimp eggs as any other food. If the egg gets into a pupil' s eyes, wash immediately with running water. The students should wash their hands after handling the brine shrimp eggs — especially before lunch!
Introduction to Brine Shrimp
Brine Shrimp (scientific name Artemia franciscana) are known practically all over the world. They are found widely in North America. They occur south of San Francisco in places where salt water evaporates naturally along the California coast: in Mono and Soda Lakes in California; and in the Great Salt Lake, Utah.
In addition, they are found in salt flats (places where salt water may be evaporated commercially to produce salt), and are an important food source to many wildlife species, such as flamingos.
Children often ask whether brine shrimp ever grow big enough to eat. Brine shrimp are only distantly related to the shrimp we eat. A trip to a fish store will demonstrate this.
At the fish store, there usually are found a few shrimp with their heads still attached. If no whole shrimp are available, even headless but unshelled ones will do.
Have the children compare these edible shrimp with their brine shrimp. How are they different? How are they similar? Some of the children may enjoy looking for pictures of shrimp in books. Among the closest relatives of brine shrimp are the fairy shrimp, which are common in freshwater ponds, particularly in the spring. Perhaps your students can find some.
Wherever salt water is evaporated on a large scale, or salt lakes develop, brine shrimp will eventually appear. How do they get there? Certain birds visit salt waters — shorebirds such as gulls and stilts, for example. Could they transport the adult brine shrimp or eggs? Could brine shrimp eggs travel by wind?
An interesting fact to remember is that although brine shrimp grow very well under artificial conditions, brine shrimp are not found in the open ocean. This is because the brine shrimp's only defense mechanism against predators (fish and other invertebrates) is hyper-saline bodies of water.
For this reason, brine shrimp have developed the most efficient osmo-regulatory system in the animal kingdom. Ask the pupils to provide an explanation of why brine shrimp are present only in salt ponds and soda lakes and not in the ocean.
Classroom Instruction
Materials List for Brine Shrimp Experiments
- 1 vial of brine shrimp eggs
- 27 ounces of rock salt (makes up to 5 gallons of salt water)
- 15 plastic containers
- 30 hand lenses
- 30 plastic teaspoons
- 30 medicine droppers
- 1 measuring cup
Depending on the interests of your students and the nature of their experiments, you may also need the following:
- crayons, paper, masking tape, and other classroom supplies
- package of powdered yeast or spirulina algae powder
- microscopes
- microscope slides
- food coloring
- large rectangular glass dish
- small can of black enamel paint
- thermometers
- black construction paper
- colored cellophane
- glass aquarium
- aquarium air pump
- aquarium heater
- incandescent light source
- brine shrimp net
- air stone and tubing
Finding Out What They Are
After the students have had a chance to investigate the "little brown things" with their hand-held lenses and to guess what they are, you may want to tell them they are eggs. On the other hand, you may want to pursue the mystery a little longer. If the children have suggested that the little brown things might be seeds, they could plant the "seeds." Do they grow? If you tell the class that they are eggs, there will still be many questions. What kind of eggs are they? How do we get them to hatch?
What Kind of Eggs?
Of course, you cannot expect the children to be able to guess what kind of animal the eggs come from, but they are often able to make very good guesses about the size of the animal. One class decided that the eggs might well be from ants.
In thinking about this question, the children may come to realize that the size of an egg is related to the size of the animal that laid it. An ostrich has a larger egg than a chicken has. A bird with an egg the size of the brown stuff would be a very small bird. Later, the students may ask how big their brine shrimp will grow. You can then bring up the size of the eggs again.
How Do We Get Them to Hatch?
Students often suggest putting the eggs in the sun or under a pillow to keep them warm. Do they hatch? At this point, you may want to pass out a container and tablespoon of rock or marine salt to each child.
"What is this white stuff?" Sugar. Soap. Flour. Snow.
"Taste a little — it won't hurt you," one teacher suggested. It's salt!
You may now want to explain to the students that the eggs will hatch if they are put in salt water. Since brine shrimp hatch in widely varying concentrations of salt water — from 1% to 6% — you will find that some eggs hatch in solutions made from different "recipes."
Each student should use about one tablespoon of salt per pint of water. This standard salinity will be a good starting point for further salinity-related experiments.
After the 24-hour incubation process, you will notice that the water level has dropped a few millimeters. You may want to take this opportunity to discuss the concept of evaporation with the class. "Does the salt go away with the water?" Some of the students may want to leave a dish of salt water near a radiator or in the sun. "What remains when all the water is gone?"
Rapid changes in the salt concentration of the water, caused by the addition of a large amount of fresh water at one time, may kill the baby brine shrimp. You may need to remind the students to replenish the evaporated water before it gets too low.
You may also need to caution the children against putting in too many eggs. Just a pinch per pint of water is best. For larger volumes, a quarter teaspoon of brine shrimp eggs per quart or liter of salt water is more than enough. Just sprinkle the eggs on top of the water.
Do they sink or float? Some teachers have encouraged experiments right away, letting the children sprinkle the eggs in salt water and also in fresh water to see if both hatch.
Hatching Brine Shrimp Eggs
Hatching is an exciting event. Make sure there is plenty of time during the next two days to make frequent observations on the eggs. Plastic spoons will be useful for sampling.
Remember that the newly hatched brine shrimp (called Instar I nauplii) will appear as tiny, orange moving specks and will be difficult to see initially.
It may help to hold the hatching vessel up to the light and look through one side. Hand lenses or magnifying glasses will help. If a microscope is available, the children may be able to see changes in the eggs and the emergence of the brine shrimp embryo (called the umbrella stage) at the early hatching stages. The "umbrella" stage will begin after around 16-18 hours at 83°F or at around 24 hours at slightly cooler water temperatures.
While observing the newly hatched brine shrimp nauplii, you may hear comments such as:
"They're tiny!" "Mine are red!" "Thousands and thousands of them!" "They swim like a frog doing a breast stroke!" "They have little arms that pull them along!" "They jerk along!"
Note: If no brine shrimp nauplii are found after 72 hours, the brine shrimp eggs were probably old and lost viability.
A Pictorial Brine Shrimp Bulletin Board
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This is a good time to set up a bulletin board for displaying questions, answers, and drawings from the class. If the students record their observations in drawings over time, they will have a pictorial record of the development of the brine shrimp.
Be sure to mark the date of stocking and hatching of each container. From their drawings, you will be able to follow the details that each child is observing. Often, the drawings resemble a conventional "fish," as this is what they may expect the tiny organisms to grow into. As the brine shrimp continues to develop, the students will begin to observe these subtle changes, and their drawings will begin to resemble a brine shrimp.
Questions that you may ask to stimulate the closer observation:
- Can you see legs?
- Do they swim or float?
- Do they stay together?
- Do they ever bump into each other?
- Do they like to stay on one side of the container?
- Do they stay near the bottom or the top of the container?
- Are the eggs all hatched?
- Can you tell the difference between the shell and an unhatched egg?
- If we leave the unhatched egg in the water longer, will they hatch?
The students will soon begin to ask their own questions:
- What do we feed them?
- Are they alive?
- Can they see?
- Will they grow bigger?
- Can we count them?
What Do Brine Shrimp Eat?
The students will soon become concerned about what the brine shrimp eat. "Don't we have to feed them?" Feeding is not necessary if tiny microscopic plants or algae start to grow in the containers.
Placing the containers in natural light will stimulate algae and bacteria growth, which is the natural food of the brine shrimp. The key to successful grow-out of brine shrimp is to control the grazing of the natural food by lowering the density of brine shrimp per volume of water.
If you wish to feed the brine shrimp, it is important to follow these guidelines.
Brine shrimp are non-selective filter feeders and will feed on anything that is the right particle size (between 5 and 50 microns). Powdered brewers yeast is the easiest and is readily available in supermarkets. A better feed is powdered Spirulina algae, found in health or pet stores. The best feed is a frozen concentrated microalgae found at aquarium specialty stores.
Whichever feed you use, it is important not to overfeed, as this would result in fouling of the water and a quick die-off of the brine shrimp. A general rule is to feed no more than disappears and leaves the water crystal clear in two days. Once or twice weekly feeding should be sufficient.
Overfeeding will probably be completely avoided only with experience. When the students see that the brine shrimp die in water that is milky-white with yeast, they may understand that they have fed their animals too much.
The brine shrimp's gut can be more cleanly seen if it is fed a colored feed. Yeast dyed with food coloring is ideal for this purpose. Mix a drop of food coloring with a few grains of yeast in a plastic spoon. Mix in a few drops of salt water from one of the brine shrimp containers. Then add a brine shrimp to the spoon. The students will be amazed at how quickly the color of the gut changes as the colored food is ingested.
Growing Brine Shrimp
Within a few days to one week, the students will notice that the brine shrimp have really grown. "They have more legs now!" They may also notice that the brine shrimp move differently as they grow and mature. "They don't jerk anymore, and they glide!"
As the brine shrimp grow, encourage the students to observe them more closely. You may want to discuss with the class how to tell the males from the females. The students will probably assume that the largest brine shrimp are males, medium sized ones are females, and the tiny ones are the babies. As the brine shrimp mature, they will likely notice that some of the shrimp are carrying pouches and assume that these are egg-bearing females (which is correct). The others may have large "arms" up by their heads. These are "claspers" that the male uses to hold on to the female while mating. If you look carefully, you can see these details with the naked eye.
Under ideal conditions, a brine shrimp will mature and begin to reproduce within 2-3 weeks. A mature female can develop up to 150 eggs in her brood sack every 3-4 days. Under ideal conditions, the eggs will hatch within the brood sack and be released into the water as live, swimming baby brine shrimp or nauplii (pronounced "nau-plee-ai"). Under stressful conditions, such as high salinity or low temperatures, the eggs in the female's brood sack will go into "diapause" and become dormant. This "survival mode" is necessary to insure the survival of the next generation of brine shrimp once the growing conditions improve. Under natural conditions, such as in the Great Salt Lake in Utah, brine shrimp companies harvest the floating eggs that are produced by the adult population before the onset of cold winter temperatures.
Experiments
While it is relatively easy to hatch brine shrimp, it is more difficult to grow them to maturity (about 2-3 weeks) and maintain a reproducing population. Understanding the environmental or biological limits which the brine shrimp can tolerate is the most difficult hurdle to overcome.
With first and second graders, you may want to limit activities to hatching and observation only. Third and fourth graders can go on to some simple experiments and to more detailed observations.
Whatever experiments your students do, the activities will be most exciting and most valuable if the children themselves raise the questions and decide on the procedures. They will need encouragement and guidance from you, but try to let them puzzle things out for themselves as much as you can.
For example, in one class one particular boy had undeniable success. He had many brine shrimp and they thrived. Eventually, he had some of the largest ones in the class. He had grown them in brown jars. He and a couple of others set about trying to prove this method to themselves and to the rest of the class.
They got some more brown jars and set up some more cultures. The eggs hatched, and the young brine shrimp grew — but not in all the brown jars. They tried again with the same result; some of the cultures were unusually healthy, but others did not do as well, although they were using the same kind of jars. The boys decided that their previous success was due not only to the color of the jar but to other parameter(s) as well.
Another teacher began experimentation with the class by discussing the salt solution, which they had used for hatching the brine shrimp. She raised questions like these:
"Who do you suppose made up the 'recipe' we used?"
"How did they know how much salt to use?"
Some of the children thought the people who shipped the eggs had just read the recipe. "But how did the recipe get into a book?" the teacher asked. "Suppose the recipe is wrong. Maybe we could hatch the brine shrimp eggs better with more salt, or with less than they told us?"
The children were not natural doubters, but this teacher felt it worthwhile to get the children wondering. Those children who were interested in the question set up experiments.
It is unlikely that everyone in a class can become concerned about the same problem. At the beginning, it is often easier to start everyone off on the same experiment; but if you listen and watch, some of the children will almost immediately find new avenues to follow. If you are lucky, you will probably end up with several different experiments going on all at once.
Mistakes
Do not be surprised if your children make many, many mistakes. They will undoubtedly forget to label their jars, keep the water level up, or to keep conditions the same in jars that they are comparing.
Such mistakes can be constructive, if you help each child to see, as he or she goes along, why they need to keep records or keep conditions constant. This is much more fruitful than trying to prevent all mistakes by closely supervising or by requiring the children to keep records, whether or not they see a purpose for them.
Some Ideas for Experiments
The following are some questions you may raise or which may grow out of ideas the children have.
- In how much or how little salt can brine shrimp be hatched?
Here are some things that children have done:- Set up single containers of water and add amount of salt differing from the recommended amount (2 tablespoons of rock salt per quart or liter of water).
- Set up two containers of water and add 1 tablespoon of rock salt to one and 8 tablespoons of rock salt to the other.
- Set up two containers of water and add 1 tablespoon of rock salt.
- Set up 10 containers of water and add 1 tablespoon of salt to one, 2 to the next, and so on up to 10 tablespoons of rock salt. (The class arrived at this procedure only after the children had tried some variations of the above three.)
- Will brine shrimp eggs hatch in fresh water?
- Will brine shrimp babies grow in fresh water?
- Will brine shrimp grow in salt water made with table salt (iodized)?
- Does iodized table salt prevent brine shrimp eggs from hatching?
- Can you feed brine shrimp too much? If so, how much is too much? How much is enough?
- Who can keep brine shrimp alive the longest?
- Can you speed up the hatching of brine shrimp?
This will immediately involve the children in finding out exactly how long hatching does take. Their reports will not all be the same. What are the reasons for variations? Errors in observation, inability to watch the eggs every moment, temperature, light, aeration, shape of container — these are all reasons the children may suggest. A whole series of new experiments may come up if the children are interested.
- Do brine shrimp grow better if they are crowded or if they have lots of room?
- Where do brine shrimp spend most of the time? Do they prefer light or dark?
If you ask the children directly if they can find out whether the brine shrimp prefer light or darkness, it will be interesting to see what methods they think of to answer the question. Let them try as many methods as possible. Here are some that have been used:
- Shine a small penlight on a jar of brine shrimp babies placed in a dark corner or closet.
- A more systematic and long-term observation can be made in a rectangular glass baking dish. Paint half of the baking dish black. Cover the top with black construction paper.
Since the brine shrimp will respond to varying degrees of light intensity during their life cycle, do not be surprised if several children get different results. Suggest that they compare the ages and sizes of their brine shrimp, temperature and salinity of the water, and density or size of the containers. If the children are persistent and repeat the same experiments, they may observe that the young brine shrimp are strongly phototactic, or attracted to light; while the on-grown brine shrimp are not as phototactic. Can the children think of any reason why this is advantageous to the different age groups?
- Can brine shrimp or their eggs survive extreme temperatures (freezing or heating)?
Children will think of ways to find out the extremes of temperature that the brine shrimp can withstand. How do they think brine shrimp living in Canadian salt lakes survive the winter?
Growing a Single Brine Shrimp
Some children will probably want to keep a single brine shrimp in a jar by itself. You may want to suggest it to children whose questions can be answered in this way. Remember that the salt concentration of the water or salinity can affect the behavior of the brine shrimp. When transferring them from jar to jar, try to keep the salt concentration constant. Here are some experimental questions that children have answered with solitary brine shrimp:
- How many times does a brine shrimp shed or molts its shell?
The children may observe for the first time the fact that the brine shrimp shed or molt their outer shell, or exoskeleton, as they grow. Molted exoskeletons are often interpreted by the children as dead or "shrunk up" bodies. Brine shrimp, like all other arthropods, have rigid exoskeletons made of chitin, and they must molt the outer shell in order to grow. The new exoskeleton growing underneath is still soft and will expand to the size of the brine shrimp.
- Do brine shrimp keep on molting their exoskeleton indefinitely or do they eventually stay one size?
- How many eggs does a female brine shrimp lay? Does she lay them all at once or does she lay eggs many times?
- If you remove some of the eggs, dry them, and then put them into salt water, will they hatch?
- If you leave the eggs floating in salt water, will they eventually hatch?
- How do the children think brine shrimp are able to survive a drought or harsh winter?
- Are brine shrimp active at all times of the day? Do they ever sleep?
- How fast does a brine shrimp swim?
This is a very difficult question to answer. A few children may be patient enough to work out some techniques for seeing how rapidly brine shrimp can swim. Restricting the brine shrimp to shallow water will help in measuring distance. The brine shrimp can be put in a large glass dish (8" x 12") with a half-inch of salt water in the bottom. Place a dish or a sheet of glass or plastic over the top of the tray. The child can follow the path of the brine shrimp using a colored marking pen. Another child can record the time in minutes. Actual distances are measured by placing a string over the marker tracings and then stretching it out along side a ruler.
Two boys who tried this finally abandoned trying to determine how fast a brine shrimp could swim, but they came up with some interesting patterns of brine shrimp motion. Do you think the brine shrimp would swim straight for long distances (relatively) or swim in a random, zigzag fashion?
- Does a brine shrimp swim faster if it is moving out of darkness in to light rather than vice versa?
- How long will individual brine shrimp live?
(Experts say that brine shrimp can survive up to 6 months).
A Final Suggestion
If a local pet store sells live adult brine shrimp, it would be much easier to purchase a teaspoon or fluid ounce of live adult brine shrimp to conduct some of the above experiments.