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Magnetite-based Magnetoreception and Magnetic
Sensory Transduction in Chinook Salmon
Presentation to OHRC, September 20, 2010
M. Renee Bellinger & Michael BanksMarine Fisheries Genetics Laboratory
Hatfield Marine Science CenterOregon State University
Newport, Oregon200 nm
Overview• Magnetoreception is well-documented• Earth’s magnetic field and types of information provides
to organisms for orientation• Evidence for functionally different magnetoreceptors
– Inclination / polar compasses– Light-dependent / -independent processes
• The magnetic sensory organelle in fish, reptiles and amphibians has not been conclusively located
• Current limitations to understanding magnetic sensory transduction
• Research goals and objectives
Earth diagram from Freake et al. 2006
Magnetic FieldsMagnetic North Pole
Magnitude of Intensity
Angle of Magnetic Field Lines(inclination)
90°
90°
Magnetic South Pole
Polar and Inclination Compasses are
Functionally Different
(Ritz et al. 2000)
S T
Figure from T .Ritz website, UC Irvine
200 nmPhoto from Mann et al. (1988)
NS
Shüler (2008)
Fleissner et al. 2007
Radical Pairs Iron-Mineral
Earth diagram from Freake et al. 2006
Magnetoreception
http://www.mlahanas.de
https://91middleschoolscience.wikispaces.com
http://www.statesymbolsusa.org/images/South_Carolina
http://www.wildpacificsalmon.com
Weitkamp 2010 Figure 2
Magnetic Remanence & Sensory Pathways: Salmon
Moore et al. 1990
Olfactory Rosette
Dii Backtracing of ros-V Innervating Olfactory Rosette (Walker et al. 1997)
olfactory rosette (Kudo et al. 2009); drawing Baier et al. (1994)
Magnetite Reflectance In Basal Lamina
Walker et al. 1997
X 190 mag.
Chains SDM 1 μM
Locate candidate magnetoreceptors in situ and demonstrate their role in magnetic
sensory transduction
1. Identify genes unique to magnetosomes or other iron-mineral particles
2. Use these genes to develop probes that can be used to locate magnetosomes in situ
3. Link iron-minerals to sensory transduction
Cells containing magnetite can be separated from non-magnetic cells
Tissue homogenate
Non-magnetic cells sinkto bottom of tube
Magnetic cells collect at pole of magnet
Leading Hypothesis
Gene expression in magnetite- and non-magnetite containing tissue homogenates
will be similarReject null hypothesis: genes uniquely expressed or more abundantly expressed in magnetite-containing tissues, relative to non-magnetic tissues are considered “candidate genes”
Dependent Hypotheses –assuming leading Ho is rejected
1. Probes developed from candidate genes will hybridize to (a) extracts of mRNA from magnetite containing tissue and extracts of tissue that contain magnetite, but not to non-magnetic tissue/mRNA extracts, and (b) candidate magneto-receptor cells in situ
Pfister P, Rodriguez I PNAS 2005;102:5489-5494
Use genes uniquely associated with magnetosomes to locate candidate
magnetoreceptors in situExpression of V1r-like Transcripts in Zebrafish
Intact magnetosome(Walker 1997)
Contributions to Research• Understand mechanisms that underpin salmon’s ability
to navigate and home, and salmon ocean migratory patterns
• Findings generalized to other studies of orientation• Apply similar techniques to other vertebrates to better-
understand magnetoreception• Foundation for studies of magnetic field effects on
circadian rhythms and other neural processes• Understand impacts of electromagnetism on ocean (and
land) dwelling organisms