Using videography to quantify copepod movement and behavior: Effects of temperature, viscosity, and diet

Despite their small sizes, zooplankton occupy specialized niches and are adapted to their unique environments. However, we do not yet understand which environmental parameters are most important in determining zooplankton movement, activity, and foraging. Temperature, viscosity, and diet are all important environmental parameters that may influence zooplankton movement and behavior, and organisms may have behavioral, physical and physiological reactions to these stimuli. Furthermore, responses to characteristic environmental conditions may be a proximate explanation to understand the distribution, metabolism, and characteristic swimming patterns of various copepod species. To understand how copepod responses to environmental conditions may be mediated through physical, physiological and/or behavioral pathways, we used videography to compare two species of marine copepods, Acartia hudsonica and Parvocalanus crassirostris, under different temperature, viscosity, and dietary conditions. We developed a novel method of tracking particles in Python that allowed for rapid data collection and processing. We show that some functions, such as appendage beating frequency, are under metabolic (physiological) control and are mediated by temperature only, while other functions, such as feeding flux of A. hudsonica, are under physical control and are mediated by viscosity only. We did not observe significant behavioral responses under the different conditions. The differing capacity of A. hudsonica and P. crassirostris to alter their physical, physiological and behavioral responses to temperature, viscosity, and diet may help us begin to understand the distribution and abundances of these important copepod species.