Efficient mate finding in planktonic copepods swimming in turbulence.

François-Gaël Michalec,Sami Souissi,Markus Holzner,Itzhak Fouxon

doi:10.7554/elife.62014

Abstract

Zooplankton live in dynamic environments where turbulence may challenge their limited swimming abilities. How this interferes with fundamental behavioral processes remains elusive. We reconstruct simultaneously the trajectories of flow tracers and calanoid copepods and we quantify their ability to find mates when ambient flow imposes physical constrains on their motion and impairs their olfactory orientation. We show that copepods achieve high encounter rates in turbulence due to the contribution of advection and vigorous swimming. Males further convert encounters within the perception radius to contacts and then to mating via directed motion toward nearby organisms within the short time frame of the encounter. Inertial effects do not result in preferential concentration, reducing the geometric collision kernel to the clearance rate, which we model accurately by superposing turbulent velocity and organism motion. This behavioral and physical coupling mechanism may account for the ability of copepods to reproduce in turbulent environments.

Highlights

Zooplankton play pivotal roles in aquatic ecosystems
We measure simultaneously the motion of the calanoid copepod Eurytemora affinis and neutrally buoyant flow tracers in a device generating homogeneous isotropic turbulence via two panels of counter-rotating disks located on its lateral sides (Fig. 1A)
Our results identify the physical and behavioral mechanisms that enable calanoid copepods, tiny crustaceans that dominate the zooplankton biomass and represent the most abundant metazoans in the ocean and estuaries, to maintain efficient mate finding when ambient flow challenges their limited swimming abilities and impairs motion strategies and olfactory orientation

Summary

Introduction

Zooplankton play pivotal roles in aquatic ecosystems They channel nutrients and energy from the primary producers to higher trophic levels (Cushing, 1975), support the development of larger organisms including commercially important fishes (Beaugrand et al, 2003), and form an important component of the biological carbon pump (Steinberg and Landry, 2017). Motility in the zooplankton mediates and governs processes that determine much of their individual fitness (Kiørboe, 2008, 2011) and that influence the biological dynamics of the ecosystem at multiple scales. This has direct ramifications for global processes such as food web productivity and the cycling and export of carbon in the ocean

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Results

Conclusion