Symbionts take the wheel… Host manipulation and magnetic sensing

The ecology and evolution of directional behavior and animal magnetic sensing

Primary collaborators; Lukas Landler (Research Institute of Molecular Pathology, Vienna), John Phillips (Virginia Tech)

Symbionts can have unexpected and bizarre influences over their hosts. In this project we use experimentally manipulated magnetic fields and behavioral test arenas to demonstrate that 1) crayfish have a biological compass and can sense Earth’s magnetic fields, 2) that crayfish, like many vertebrate organisms, orient their bodies to Earth’s magnetic fields, and most amazingly,  3) crayfish worms alter their hosts’ response to magnetic cues (Landler et. al in revision)!! This is the first evidence that symbionts can alter magnetically structured behavior of their hosts.


How we test crayfish magnetic sensing and behavioral responses: a) Crayfish are tested in visual symmetrical chambers, each one covered with a diffuser. Beneath each chamber a plastic mash reflects the light and prevents the animals from seeing the camera. b) The crayfish are tested in a randomly chosen magnetic field (out of four possible magnetic field directions, towards topographic N, E, S, W), then the magnetic field are rotated. Two example crayfish (grey and black) and there mean vectors of axial body alignment for two magnetic field settings are shown. c) The individual mean vectors of all test fields are combined and the obtained mean direction is used as the axial alignment of an individual.



Are crayfish worms manipulating the spatial behavior of their hosts? Crayfish show a spontaneous magnetic alignment behavior (SMA) by orienting their bodies along experimentally manipulated North/South magnetic axis (top). However, the response is much stronger when crayfish have few symbiotic worms (bottom left), and disappears when crayfish have more than 5 symbiotic worms (bottom right).