This is Jim Fiorendino, your host for On the Ocean.
Did you know that some phytoplankton are thieves? Phytoplankton are microscopic marine organisms that make their own food through photosynthesis. Photosynthesis is a chemical reaction that requires light, carbon dioxide, and water. Photosynthesis occurs in special structures within phytoplankton cells known as plastids. Without plastids, phytoplankton cannot photosynthesize.
There are some phytoplankton that lack plastids of their own, yet still depend on photosynthesis for survival. They accomplish this by eating other phytoplankton and stealing their plastids. Typically, these predatory phytoplankton will digest their prey, but preserve their prey’s plastids. In some cases, the entire prey cell may be maintained for a short time. This behavior is known as kleptoplastidy. Phytoplankton that engage in kleptoplastidy are mixotrophic, since they both photosynthesize and feed on other phytoplankton.
Once acquired, the plastids that mixotrophic phytoplankton steal from their prey continue photosynthesizing and producing food. The plastids will last for several days or weeks, but must eventually be replaced. Some species of phytoplankton can replicate captured plastids, extending their lifespan. Interestingly, plastids that have already been stolen can be passed to another mixotrophic plankter. The toxic bloom-forming alga Dinophysis ovum obtains its plastids from the marine ciliate Mesodinium rubrum. Mesodinium rubrum does not create its own plastids, instead stealing them from a tiny strictly photosynthetic phytoplankter.
This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean.