Sensory perception, neurobiology, and behavioral adaptations for predator avoidance in planktonic copepods

Abstract

Copepods are important grazers on microplankton in marine food webs and are, in turn, preyed upon by a wide range of predators with diverse feeding adaptations. Although copepods have evolved numerous adaptations to help them avoid predation, their escape behavior sets them apart from many other planktonic organisms. Mechanoreception is widely used by copepods to detect hydrodynamic disturbances created by approaching predators. When these disturbances are detected, copepods respond quickly with escape jumps that can accelerate them from a stationary position to speeds of over 600 body lengths per second within a few milliseconds. Myelinated nerves may improve the escape behavior of some copepods through faster conduction of nerve impulses. The differences in response latencies between myelinate and amyelinate copepod species are greatest in larger copepod species, where nerve signals must be conducted over longer distances. Environmental variability such as turbulence may affect the ability of both prey to detect predators and predators to capture their planktonic prey. Small amounts of turbulence favor the predator, while too much turbulence reduces predation. Understanding the sensory physiology of copepods and their behavioral adaptations for avoiding predation will increase knowledge of the factors affecting the structure and function of marine pelagic food webs.