A few ocean creatures -- including some dinoflagellates -- use chemical energy to produce light in a process called bioluminescence. Although many bioluminescent animals live in the deep light-free ocean, others live at or near the surface. One example is the small class of crustaceans known as ostracods. Luminescent ostracods create two chemicals which they release into the water. When these chemicals mix, one product of the reaction is a blue-green light. Also, stirring up water in where ostracods live can produce a green glow, often visible at night in the wake of ships or in the crashing surf.
Raphael Dubois, who studied bioluminescence in clams in 1887, coined the names luciferin and luciferase for two components of bioluminescent systems. Luciferin is a species-specific pigment. Luciferase is an enzyme that catalyzes the oxidation of luciferin. Luciferin and luciferase occur in the salivary gland found below the sea firefly's lower jaw. Luciferin and luciferase are released into the sea water as granules. If the water is disturbed, the granules dissolve and blue light is emitted. Luciferin acts directly as a substrate in the generation of light. Luminescence occurs with the addition of oxygen in the presence of luciferase and salts.
Energy comes from many different sources in the ocean. Bioluminescence is a common biological energy source. In this activity, students crush dried ostracods on a slide with a little water and observe bioluminescence.
  • Bioluminescence is formed from a chemical reaction within an organism
  • This form of energy production is very common among sea organisms
  • These energy bursts are utilized in a number of ways
Dried luminescent ostracods (can be mail ordered, see below), Glass slide with slide cover, Water with eye dropper, "Glow dough" or other glow-in-the-dark material, Glow stick (optional), Fluorescent minerals and "black" light (optional)
Dried luminescent ostracods can be obtained from biological supply companies, for example Carolina Biological Supply who refers to them "sea fireflies" (www.carolina.com; use search term "sea firefly"). Ordering one gram of sea fireflies (about $50) will be sufficient for one class of students. Half a gram (about $30) will work if students are broken into larger groups. The fluorescent mineral demonstration is optional. The glow-in-the-dark materials and glow stick demonstrations are simple and engaging, and so are highly recommended. Glow sticks can often be purchased at camping or automotive supply stores, where they are sold as emergency light sources, or from SCUBA diving supply stores which sell them for night diving. Split the class into pairs or small groups for activity. Each group will need their own ostracod(s), glass slide and cover, eye dropper, and water. For best effect, darken room before groups attempt to observe bioluminescence.
Discuss briefly the different types of luminescence. Fluorescence is where atoms in a crystal are excited by ultraviolet light. They then release that energy as visible light. (Fluorescent rocks glow when exposed to ultraviolet light, when you take the light away, then the glow disappears immediately.) Phosphorescence is similar to fluorescence except the material continues to glow after the light source has been removed. This is because the excited atoms do not drop down to ground state right away, but slowly over time. (Hold "glow dough" or other glow-in-the- dark objects -- e.g., some watches, some T-shirt decorations, etc. -- up to the light for some time, remove from light and then darken room. These phosphorescent materials will produce light for awhile.) Chemoluminescence occurs when two chemicals mix, react, and one of the by-products of the reaction is light. (This can be demonstrated by cracking the middle of the glow stick and shaking the two chemicals together to create light.) Luminescent ostracods produce light, but since it comes from an organism, it is called bioluminescence.
Luminescent ostracods are known to the Japanese as umi botaru (sea fireflies). These small crustaceans live on the sea bottom during the day and venture out and up in the water column to feed at night. Measuring only 0.5 to 5 mm in length, the body of the sea firefly is enclosed within hinged bivalve shells. If available, demonstrate different examples of fluorescence (e.g., fluorescent rocks), phosphorescence (e.g., "glow dough") and chemoluminescence (e.g., glow stick). Alternatively, give the students the materials (i.e., fluorescent rocks, glow dough, and glow stick) and let them experiment to discover for themselves under which conditions each type of material will glow. This will prepare them for the demonstration on bioluminescence.
  1. In a darkened room, place one or two dried ostracods on a slide.
  2. Place one drop of water on the ostracod.
  3. Cover and crush the ostracod with the slide cover.
  4. Write down what you observe. Can you see bioluminescence? What color is it?
  • Animals and plants bioluminesce for a variety of reasons.
    • Any ideas on why organisms might evolve the ability to glow?
    • For example, luminescent ostracods in the ocean produce a bright cloud much larger than the ostracod itself... how might this be beneficial?
  • Have students do library research project, each one on a different bioluminescent animal or plant.
Adapted from Orange County Marine Institute and San Juan Institute activity series AND "Visit to an Ocean Planet" CD-ROM, Copyright 1998, California Institute of Technology and its licenses.