Today’s factismal: Some dinoflagellates use bioluminescence to attract big fish that eat the little fish that eat dinoflagellates.
Obi-wan said it best: “There’s always a bigger fish”. And he probably learned that from dinoflagellates. These tiny little critters have a whip at one end that they use for propulsion, a shell made out of cellulose, and a variety of lifestyles that ranges the gamut from photosynthesis to hunter. Then again, with more than 2,200 species of dinoflagellate, there is plenty of room for just about any oddity. But perhaps the oddest thing that any dinoflagellate species does is flash blue lights when startled or jostled.
Interestingly, it was that blue flash that first attracted people to them; the very first paper written about dinoflagellates was called “Animalcules which cause the Sparkling Light in Sea Water” and it hit the popular press way back in 1753. Today, quite a bit is known about how and why they flash. The reaction is similar to that of the firefly (and uses some of the same chemicals) but it happens for much different reasons. Like the firefly, they flash only at night. However, the firefly flashes in order to attract his lady-love and the dinoflagellate flashes to attract big fish (partly because dinoflagellates don’t have lady-loves. Poor dinoflagellate.). The rapid motion of small fish causes a pressure wave which triggers the flash; this is why they often flash in the wake of boats at sea. And the light that they generate attracts big fish that come to dine on the little fish that are feasting on the dinoflagellate.
And the most interesting thing about the dinoflagellate flash is that it only happens within a specific pH range; if the water is too basic or too acidic, the poor dinoflagellate can’t flash. As a result, some ecologists in San Diego Bay are using the flash as a way of checking the water quality: flashing dinoflagellates means that everybody’s happy (except the big fish that thought it was a call to dinner). If you’d like to join the ecologists as they research more about dinoflagellates and the health of the bay, then head over to: