Observing Brine Shrimp Author: Jolene Routson

Overview: Students observe brine shrimp eggs, create an appropriate environment for their survival, and observe their growth.

Lesson Concepts:

• Scientists work through careful observations and recording of those observations.

Grade Span: 3–5

Materials:

• Vial of brine shrimp eggs (available at most pet stores or online)
• Aquarium salt (or sea salt)
• Fish bowl
• One jar for each group
• One hand lens for each student
• Measuring cup and tablespoon
• Brewer’s yeast
• Science journal for each student

Advance Preparation:

— Vials of brine shrimp and aquarium salt should be purchased from a pet supply store.

Time: 50–60 minutes (for initial observation and environmental setup); continued observations will be less time consuming.

Grouping: Pairs or threes

Teacher Background:

Brine shrimp (Artemia franciscana) are found widely in North America. They can be found in the salt ponds south of San Francisco and in places where salt water evaporates naturally along the California coast and in the Great Salt Lake, Utah. Brine shrimp can also be found in salt flats and are an important food source for many wildlife species such as flamingos.

Brine shrimp are only distantly related to the shrimp we eat. Among the closest relatives to the brine shrimp are the fairy shrimp, which are common in fresh water ponds. Although brine shrimp grow very well under artificial conditions and in inland salt lakes, they are not found in the open ocean. This is because the brine shrimp’s only defense mechanism against predators is its habit of living in hyper-saline bodies of water. Brine shrimp are said to have evolved the most efficient osmoregulatory system in the animal kingdom.

Brine shrimp are non-selective filter feeders. They will feed on anything that is the right particle size (between 5–50 microns). Feeding is not necessary if tiny microscopic plants or algae start to grow in the containers. If containers are placed in natural light (not direct sunlight), bacteria and algae growth will be stimulated. However, powdered brewers yeast is also an option and is readily available in grocery stores. A general rule for feeding is to administer no more than will disappear and leave the water crystal-clear in two days. Feeding once or twice a week should be sufficient (it is not necessary to feed shrimp until they are hatched).

As the brine shrimp mature, you may want to discuss how to tell males from females. The female brine shrimp is larger than the male. Female brine shrimp carry pouches for eggs. A mature female shrimp can develop up to 150 eggs in her brood sack every 3–4 days. The males seem to have larger “arms” up by their heads. These are “claspers” that the male uses to hold onto the female while mating. Under ideal conditions, brine shrimp will mature and begin to reproduce within 2–3 weeks.

Note: it is important that students understand evaporation. The jars should only be refilled with fresh water because salt does not evaporate. Also, rapid changes in the salt concentration may kill the brine shrimp.

Teacher Resources: Photographs of brine shrimp and interesting information can be found at: www.monolake.org/naturalhistory/shrimp.htm.

Explore this link for additional information on the topics covered in this lesson:

• Development

Teaching Tips:

— Brine shrimp tend to be fairly resilient to varying conditions, however it is important to keep shrimp in a fairly warm location. (Note: Room temperature is acceptable, however, warmer temperature may promote faster growth.)
— It is not recommended to use pickle jars for raising brine shrimp. Even after thorough washing, shrimp tend not to hatch and grow in such an environment.
— Discuss evaporation, as it will be necessary to refill jars regularly. Remember, water evaporates and salt does not.
— The gut of a brine shrimp can be more easily observed if it is fed colored food. Yeast dyed with food coloring is ideal. Mix a drop of food coloring with a few grains of yeast in a plastic spoon. Mix a few drops of salt water from one of the shrimp containers and add brine shrimp to the spoon.

Vocabulary: observation, evaporation, life cycle, and environment

Procedure:

1. For each group of students, sprinkle a few eggs onto white paper. Have students make an illustration and record observations: size, color, shape, etc.
2. Students should brainstorm what the “brown stuff” could be.
3. Allow students to look at the aquarium/sea salt and discuss what they notice.
4. Tell the students that the groups are going to put some things together and see what happens over the next few days.
5. Begin setting up hatcheries. About one tablespoon of salt to one cup of water works well. (However, check the egg/aquarium salt directions as contents vary with each.)
6. Have students use a marker to mark the water level on the side of the jar, so it can be refilled to the same level after evaporation. Have students sprinkle a pinch of eggs onto the top of the salt water. Observe and record changes. Eggs will initially float and then sink.
7. Watch carefully; in 3–5 days students should observe small shrimp swimming. They will be difficult to see, but will soon grow.
8. Have the students record their observations by drawing and writing each day in their journals until the brine shrimp are grown. As the brine shrimp begin to develop, students will observe subtle changes and their drawings should begin to resemble a brine shrimp.
9. Questions that may be asked to facilitate closer observation: Can you see legs? Do they swim or float?
10. As a wrap-up, have students draw the life cycle of a brine shrimp, from egg to adult. This will reinforce their understanding and serve as an assessment tool.

Extensions:

Have students compare the affect of differences in salinity (the environment) on the hatching rate and survival of brine shrimp. See Environmental Differences.