Bioluminescence helps us to better understand life in the mesopelagic and deep sea. The mesopelagic zone is the open water environment that ranges from a depth of 100-200 meters to 1,000 meters. This zone, also called the midwater zone, does not support phytoplankton or other plants because light is very dim. This means that photosynthesis cannot take place here. Krill, copepods, and ostracods are small crustaceans common to the environment. Arrow worms, squid, and many small fish, including bristlemouths and lanternfishes are also found in this environment. Animals that live in the mesopleagic possess photophores, which are specialized organs that produce light.

The bioluminescent photophores of mesopelagic animals produce light that helps the animal blend in with the background. This is called counterillumination, which is similar to countershading. Most mesopelagic bioluminescence is blue-green. Many of the animals can control their bioluminescence, making it bright for bright backgrounds and dim for dim ones. This can be very important for avoiding predation, for attracting prey, and for communication and courtship. Some animals use photophores to produce bioluminescence, while others use specialized tissues, and others have symbiotic bacteria that live in specialized cells and produce the light.

Bioluminescence is as common to the deep sea as it is to the mesopelagic. However, deep-sea organisms do not use bioluminescence for counterillumination. It is too dark in the deep sea for this to be effective. Instead, it is used for attracting prey, communication, and for courtship. Deep-sea animals mostly include fishes with the following characteristics: small size, small eyes, large mouths, expandable stomachs, and poorly developed swim bladders. Bristlemouths and anglerfishes are the most common to this area.

• Construction paper,
• Popsicle sticks,
• crayons and/or markers,
• scissors, glow in the dark paint,
• glow in the dark glue (both are available at Walgreens).
• One to two packages of glow sticks (depending on class size), which are also available at WalgreenÕs or Party City.
• Pictures of mesopelagic and deep-sea animals, such as bristlemouth fish, lanternfish, anglerfish, squid, and krill (A good book to use is Ocean by Miranda MacQuitty, which can be found at Barnes and Noble Bookstores).
• Pictures should be enlarged and placed on posterboard.
• A video on the topic of bioluminescence is also needed. The video shows animals emitting their bioluminescence. It also gives an in depth look at what bioluminescence is and how it works. The video can be found at the University of Arizona Library, or can be ordered from the Discovery Channel.

The activity is for the whole class (approximately 25 students).

1) Start by giving the students a brief introduction: Define bioluminescence, discuss how it works, and discuss what kinds of environments it would be found in.
2) Ask the students what kinds of animals they think would have bioluminescence. This will help engage the students in the lesson. Then show them pictures of bioluminescent organisms.
3) Put the video in for them to watch. The video shouldnÕt last longer than 15 minutes. This will help them see first hand what bioluminescence is and how it works.
4) Prepare the students for the glow stick activity. The classroom should be arranged so that there are not any obstacles in the center of the room.
5) Give each student a glow stick. It is necessary to bend them so that the chemical reaction is activated and the stick begins to glow.
6) Choose a couple of students who will get to be the predators the number of predators will depend on the size of the class. For a class of 25, there should be about 3-4 predators.
7) Divide the other students into groups. Each group represents a different species of bioluminescent organisms.
8) The students can come up with secret flashes on their stick so that they know their group from another group. The goal is to not get eaten by the predator.
9) Send the predators into the hall.
10) The groups should be broken up. The groups should try and find each other so that they can reproduce. The students should try and find the other members of their group based on their secret flashing code.
11) Turn all the light off and let the predators into the room. The predators are going to tag anyone they can. If a student gets tagged, then they must they are out and must wait until the next game starts.
12) If two members of the same group find each other, then they can go release another member of their group that has been tagged.
13) The game will end if the predator tags everybody.
14) This can be done a number of different times and the different people can play the predators.
15) After this is complete and everyone has settled down, pass out the necessary materials for the students to design their own bioluminescent organism. Glow in the dark paint and glue is available. After the pictures are drawn and cut out, glue (or tape) a Popsicle stick on the end so that they can be held like a lollipop.
16) Show and tell each studentÕs animal.
17) End the lesson with a worksheet on bioluminescence, or a small quiz to check and see what they have learned.