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Do leaf-cutter ants Atta colombica obtain their magnetic sensors from soil?

Permanent URL:
http://handle.nal.usda.gov/10113/58326
Abstract:
How animals sense, process and use magnetic information has remained largely elusive. In insects, ferromagnetic particles are candidates for a magnetic sensor. Recent studies suggest that ferromagnetic minerals from soil can be incorporated into the antennae of the migratory ant Pachycondola marginata (Oliveira et al. 2010). We used Neotropical leaf-cutter ants Atta colombica to test whether soil contact is necessary for the acquisition and use of a magnetic compass. Atta colombica typically relies on pheromonal trails, but is the only invertebrate known to use a magnetic compass to update a calculated path integrated home vector (Riveros and Srygley 2008). Here we show that contact with soil is necessary for A. colombica to incorporate magnetic particles that can be used as a magnetic compass, and yet we also show that ants can biosynthesize magnetic particles. Workers from a soil-free colony ignored a 90° shift in the horizontal component of the magnetic field, yet significantly oriented homeward despite the experimental occlusion of any geocentric cues. In contrast, workers from a soil-exposed colony oriented homeward, shifted with the magnetic field or oriented in an intermediate direction. Homeward orientations under shifted magnetic fields suggest that leaf-cutter ants are able to determine a path integrated home vector in conditions where only proprioceptive information is available. Strikingly, ants from the soil-free colony also had ferromagnetic particles, yet, as observed by Ferromagnetic Resonance (FMR), these particles differed from those in soil-exposed ants and evidently were not associated with a magnetic compass sensitive to the horizontal shift in the magnetic field.
Author(s):
Robert B Srygley
Subject(s):
Atta colombica , Pachycondyla , insects , invertebrates , soil
Source:
Behavioral Ecology and Sociobiology 2014 v.68
Language:
English
Year:
2014
Collection:
Journal Articles, USDA Authors, Peer-Reviewed
File:
Download [PDF File]
Rights:
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.