Saturday Journal Club

MIGRATION: ‘SEEING’ THE COMPASS


Animals make use of the Earth’s magnetic field for various different functions, including compass and map orientation in true navigation or as a time cue and trigger for developmental and physiological programs. Birds are among the most thoroughly investigated model systems for the analysis of the impact of magnetic fields on behavior and physiology. The hypothesis that migrating birds utilize the geomagnetic field for orientation had been proposed as early as 1859. However, the neurobiological mechanisms and the magnetophysical principles of the underlying sensory processes that lead to this ability are largely unknown. 

Two biophysical mechanisms currently dominate the scientific discussion: 
The iron-mineral-based hypothesis suggests that magnetic information is detected by magnetoreceptors in the upper beak and transmitted through the ophthalmic branch of the trigeminal nerve to the brain. 
The light-dependent hypothesis suggests that magnetic field direction is sensed by radical pair-forming photopigments in the eyes and that this visual signal is processed in cluster N, a specialized, night-time active, light-processing forebrain region. 

This week I shall be presenting a recent work which seems to suggest that a vision-mediated mechanism underlies the magnetic compass in migratory songbirds, and that the putative iron-mineral-based receptors in the upper beak connected to the brain by the trigeminal nerve are neither necessary nor sufficient for magnetic compass orientation in European robins (Erithacus rubecula).

Samudra

Date: 28th November, Saturday
Time: 11 a.m.
B333


Reference:

Visual but not trigeminal mediation of magnetic compass information in a migratory bird

Manuela Zapka, Dominik Heyers, Christine M. Hein, Svenja Engels, Nils-Lasse Schneider, Jo¨rg Hans, Simon Weiler, David Dreyer, Dmitry Kishkinev, J. Martin Wild & Henrik Mouritsen

NATURE| Vol 461|29 October 2009