Predators catalyze an increase in chloroviruses by foraging on the symbiotic hosts of zoochlorellae.
Virus population growth depends on contacts between viruses and their hosts. It is often unclear how sufficient contacts are made between viruses and their specific hosts to generate spikes in viral abundance. Here, we show that copepods, acting as predators, can bring aquatic viruses and their algal hosts into contact. Specifically, predation of the protist Paramecium bursaria by copepods resulted in a >100-fold increase in the number of chloroviruses in 1 d. Copepod predation can be seen as an ecological "catalyst" by increasing contacts between chloroviruses and their hosts, zoochlorellae (endosymbiotic algae that live within paramecia), thereby facilitating viral population growth. When feeding, copepods passed P. bursaria through their digestive tract only partially digested, releasing endosymbiotic algae that still supported viral reproduction and resulting in a virus population spike. A simple predator-prey model parameterized for copepods consuming protists generates cycle periods for viruses consistent with those observed in natural ponds. Food webs are replete with similar symbiotic organisms, and we suspect the predator catalyst mechanism is capable of generating blooms for other endosymbiont-targeting viruses.
School of Biological Sciences, University of Nebraska, Lincoln, NE 68588-0118; jpdelong@unl.edu jvanetten1@unl.edu ddunigan@unlnotes.unl.edu.
John P
JP
DeLong
School of Natural Resources, University of Nebraska, Lincoln, NE 68583-0961.
Zeina
Z
Al-Ameeli
Department of Biology, Nebraska Wesleyan University, Lincoln, NE 68504-2794.
Garry
G
Duncan
Department of Plant Pathology/Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900 jpdelong@unl.edu jvanetten1@unl.edu ddunigan@unlnotes.unl.edu.
James L
JL
Van Etten
Department of Plant Pathology/Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900 jpdelong@unl.edu jvanetten1@unl.edu ddunigan@unlnotes.unl.edu.
David D
DD
Dunigan
D000818:Animals; D059001:Aquatic Organisms / Q000235:genetics; D002708:Chlorella / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D033342:Copepoda / Q000821:virology; D020387:Food Chain; D054884:Host-Pathogen Interactions / Q000235:genetics*; D017862:Phycodnaviridae / Q000235:genetics* / Q000502:physiology; D011235:Predatory Behavior; D013559:Symbiosis / Q000235:genetics
Paramecium bursaria endosymbionts; chloroviruses; copepod foraging; predator–prey interactions; virus dynamics