U. MINNESOTA (US)—A toxic alga, once thought to be a helpless, sun-loving microbe, is really a vicious, venom-producing predator responsible for massive fish kills in the Chesapeake Bay and other waterways.
Jian Sheng, aerospace engineering and mechanics faculty member at the University of Minnesota, studied K. veneficum, a toxic algal cell known as a dinoflagellate, found in estuaries worldwide.
Each year millions of dollars are spent on measures to control dinoflagellates around the globe. The species releases a substance called karlotoxin, which is extremely damaging to the gills of fish.
Researchers suspected the ecological role for producing karlotoxin was for self-defense against natural predators to relieve grazing pressure.
However, in a series of experiments using 3-D digital holographic microscopy initially developed at Johns Hopkins University, Sheng and colleagues found that the release of these toxins also serves to stun prey before ingestion—shifting the role from protection to aggression.
Details of the study are reported in the current issue of the journal Proceedings of the National Academy of Sciences (PNAS).
“In the paper, we have answered why these complicated molecules are made in nature in the first place and identify a possible alternative mechanism causing massive bloom,” explains Sheng. “We further suggest a new venue of predicting and eventually mediating the bloom events.”
Using 3-D high-speed holographic microscopy, the researchers studied the relationship between K. veneficum and its prey, a common, single-celled algal cell called a cryptophyte.
They found that K. veneficum releases karlotoxins to slow down prey prior to ingestion assumedly to increase predation success rate and promote its own growth.
This significantly shifts the understanding about what permits blooms to initiate and form. Instead of mortality prevention, the organism’s actions relate more closely to growth promotion through ingestion of a pre-package food source, the cryptophyte cell.
Researchers at Johns Hopkins University; the University of Hawaii’s Department of Marine Science; and the University of Maryland Biotechnology Institute’s Center of Marine Biotechnology contributed to the study.
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