One of the most impressive demonstrations of bioluminescence is also the easiest. Dinoflagellates, the most common sources of bioluminescence at the sea surface, are readily maintained and grown almost anywhere. They produce bright bioluminescence when agitated. The following instructions describe how to give a most impressive demonstration!
Suggested Demonstrations and Simple Experiments with Dinoflagellates
If you don’t live by the ocean, where you can see dinoflagellate bioluminescence in its natural setting, the next best thing is to obtain your own culture of dinoflagellates. Refer to the dinoflagellate culturing web page for instructions on how to obtain and grow your own luminescent dinoflagellates.
The best demonstration is the old shake-em-up technique. Take your flask of cells and swirl it! Just make sure it is during the dark phase of their day/night cycle. If you take dinoflagellates out of their day phase and place them in the dark, nothing will happen. The bioluminescence system is controlled by a biological rhythm; bioluminescence is turned off during the day.
It is challenging to measure levels of bioluminescence unless you have an instrument such as a luminometer. An alternative is to take photos using a sensitive digital camera. Depending on the brightness of the bioluminescence, an ISO of 10,000 or higher is needed to image the light emission. You can quantify digital images using the free software Fiji and analyzing pixel intensity.
- At any time: View cells under microscope.
- To be performed in a darkened room during the night phase of the dinoflagellates.
- Mechanical stimulation: rap with knuckles, swirl around, or bubble air in flask containing culture.
- Chemical stimulation: add some drops of 10% acetic acid (or vinegar) to a test tube containing part of your culture. The increased acidity of the solution activates the luminescent chemistry within the cells.
- Pour cells gently into small dish and place under microscope. Add a few drops of 10% acetic acid (or vinegar) while observing/measuring luminescence.
- The effect of light and dark cycle on dinoflagellate bioluminescence.
- Grow some dinoflagellates on a normal day/night cycle, while others are grown on a reverse cycle so that they have their nighttime during our day.
- Stimulate (shake) the two batches and observe/measure which produces brighter bioluminescence.
- Hint: In most dinoflagellates, bioluminescence is minimal during their day.
- The effect of light inhibition on dinoflagellate bioluminescence.
- Take dinoflagellates during their night cycle and expose half to room lights while the others are kept in the dark.
- After 30 minutes in each condition, stimulate (shake) the two batches and observe/measure which produces brighter bioluminescence.
- Hint: Nighttime dinoflagellate bioluminescence is inhibited by light exposure.
- The effect of illumination on the brightness of dinoflagellate bioluminescence.
- Grow batches of dinoflagellates at different light levels during the day. This is done by varying the distance of the batches from a light source. For example, double the distance means one quarter the light intensity.
- During the dark phase, stimulate (shake) the batches and observe/measure the brightness of bioluminescence.
- Hint: Less illumination can mean less energy for the dinoflagellates.
- The effect of stimulus strength on the brightness of dinoflagellate bioluminescence.
- Place batches in dinoflagellates in vertical columns, e.g., graduated cylinders.
- Use an aquarium air pump with a control valve that is adjusted to have different air streams, as tested in a dish/tank using tap water. Use tubing and air stones so they reach into the graduated cylinder.
- During the dark phase, turn on the air pump and observe/measure the brightness of bioluminescence as a function of the amount of bubbling from the air stone. Bubbles really stimulate dinoflagellate bioluminescence!
- Hint: Also observe how the rate of bubbling affects how long the bioluminescence lasts before it is exhausted.