DISSERTATION RESEARCH: Feast or Flee: How do Microzooplankton Detect and Avoid Predators?

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Animals sense a multitude of tactile, olfactory, visual, and aural sensory cues from predators and prey, integrate these cues, and respond with appropriate behaviors; avoidance or prey capture, respectively. Understanding how animals integrate these multiple signals to evoke complex behaviors is one of the central challenges in the biology of behavior. Single celled eukaryotes have many of the same sensory characteristics, at the cellular level, as multicellular animals and therefore provide excellent conceptual and functional analogues of sensory and behavioral traits in higher organisms. The researcher will use a marine microzooplankton ciliate, Favella sp., as a model organism to investigate sensory mechanisms that allow them to perceive and integrate cues from predators and prey in order to successfully capture prey while avoiding predation. Because these single celled organisms represent an early evolving group of eukaryotes, characterization of their sensory capabilities will provide insights into the evolution of integrated cell signaling and emergent behavioral traits in multicellular organisms. Moreover, understanding the predator-prey interactions of these microzooplankton, a group of organisms responsible for consuming ~60 % of marine primary productivity, will enable a better understanding of the role they play in supporting marine food webs and in fluxes of nutrients in surface oceans. Both of these larger ecosystem scale processes have implications for marine ecosystem services (e.g. fisheries) and for biogeochemical cycles that impact our climate. In addition to these important science questions, the proposed research will foster cross-disciplinary collaboration of the graduate student with experts in microzooplankton ecology. Professional training, science communication and career development of the researcher will be promoted with support to attend high profile scientific meetings. The award will also allow the researcher to further develop and implement teaching programs for high school students that will help attract them to science and technology subjects at college level, and motivate them to become involved in research as undergraduates. Microzooplankton alveolates (ciliates and dinoflagellates) transfer substantial amounts of energy from primary production to larger metazoan consumers. Underlying these predator-prey interactions are complex behaviors that allow them to efficiently capture preferred prey and evade predation by sensing and integrating a variety of stimuli from each. Despite the ecological importance of these behavioral interactions, no previous research has examined how microzooplankton are able to differentiate between predators and prey despite receiving similar types of sensory information from both. This proposal builds upon dissertation research investigating the sensory mechanisms that marine microzooplankton possess to sense and respond to signals from their prey. The first objective is to determine the behavioral responses of Favella sp. to dinoflagellate and copepod predators, and the effectiveness of these behavioral responses. High-speed videomicroscopy (250 fps) and particle tracking techniques will quantify the behavioral responses of Favella sp. to chemical, mechanical (contact) and hydrodynamic stimuli from predators and prey. The second objective will determine the mechanistic basis of behavioral responses to predators identified in objective 1. This will be accomplished using a combination of high-speed video microscopy, electrophysiology, and fluorescent ion-sensitive dyes to determine how ionotropic and metabotropic mechanisms mediate signal transduction and predator evasion behaviors. Particle image velocimetry will also be utilized to determine how the flow field surrounding Favella sp. may be modified during predator evasion behaviors to decrease its hydrodynamic signature and therefore the likelihood that it will be ingested. In summary, the proposed experiments will extend current research on ciliate-prey behavioral interactions to address the question of how this single celled organism can integrate microscale environmental cues to detect and consume appropriate prey, and evade ingestion by predators.