Here is the problem: About 200 chydorids in a 1-L vessel aggregate either on the bottom when the room lights are on, or in the dark in a corner of the vessel. The question is: How to get these zooplankters out of the corners and into the center of the vessel? Our answer: use a blue laser beam as a strange attractor.


At the beginning the room lights are on. The animals swim very close to the bottom of the vessel. As soon as the lights are switched off they begin to swim upwards. Some of them swim into the laser beam and "glow" up, just like fire flies. Others can see the flashes and swim towards them. End of the story: most animals swim within or around the laser beam. By the way: as soon as the room lights are switched on, all the animals swim back down to the bottom. We actually could repeat the whole "come here - go there" over twenty times before the animals got tired of it. This experimental set-up was instrumental to observe mating in calanoid copepods. However, we used it first to investigate swarming parameters in copepods. Akira Okubo, Jeannette Yen and Rudi Strickler were the team.

in memory of Akira Okubo
© STRICKLER - UWM 1999-2003 back