Cheating to score a free ride is a well-documented behavior by many animals, even plants. But microscopically small, single-celled algae? Yes, they do it too.
“There are cheaters out there that we didn’t know of,” said William Driscoll, lead author of a research report on the topic who studied an environmentally devastating toxic alga that is invading U.S. waters as part of his doctoral research in the lab of Jeremiah Hackett, an assistant professor of ecology and evolutionary biology.
Driscoll isolated several strains of the species Prymnesium parvum–the “golden algae” that has devastated a number of Texas freshwater fisheries in past years–and noticed that some grew more quickly and do not produce any of the toxins that protect the algae against competition from other species of algae.
“When those ‘cheaters’ are cultured with their toxic counterparts, they can still benefit from the toxins produced by their cooperative neighbors – they are true ‘free riders’,” Driscoll explained.
The study, published in the journal Evolution, adds to the emerging view that microbes often have active social lives. Future research into the social side of toxic algae could open up new approaches to control or counteract toxic algal blooms, which can pose serious threats to human health and wipe out local fisheries, for example.
Prymnesium belong to a group of algae known as golden algae, so named for their accessory pigments, which give the cells a golden sheen. This toxic species lives mostly in oceans and only recently has invaded freshwater environments. Its distant relatives include the equally microscopic diatoms, which make up a large part of phytoplankton, and giant kelp.
The algae produce toxins that are deadly to fish but so far have not been shown to threaten the health of humans or cattle. Many scientists believe the toxin arose as a chemical weapon to wipe out other algae and other organisms competing for the same nutrients and sunlight on which the algae depend. The discovery of cheaters that don’t bother to produce toxin, however, throws a wrench into this scenario.