Connecting the navigational clock to sun compass input in monarch butterfly brain
Department of Neurobiology
Medical Subject Headings
Animal Migration; Animals; Brain; Butterflies; CLOCK Proteins; Circadian Rhythm; Gene Expression; Immunohistochemistry; In Situ Hybridization; Neural Pathways; Photoreceptor Cells, Invertebrate; Phylogeny; Polymerase Chain Reaction; Retina; Rod Opsins; Sunlight; Trans-Activators; Ultraviolet Rays
Life Sciences | Medicine and Health Sciences | Neuroscience and Neurobiology
Migratory monarch butterflies (Danaus plexippus) use a time-compensated sun compass to navigate to their overwintering grounds in Mexico. Although polarized light is one of the celestial cues used for orientation, the spectral content (color) of that light has not been fully explored. We cloned the cDNAs of three visual pigment-encoding opsins (ultraviolet [UV], blue, and long wavelength) and found that all three are expressed uniformly in main retina. The photoreceptors of the polarization-specialized dorsal rim area, on the other hand, are monochromatic for the UV opsin. Behavioral studies support the importance of polarized UV light for flight orientation. Next, we used clock protein expression patterns to identify the location of a circadian clock in the dorsolateral protocerebrum of butterfly brain. To provide a link between the clock and the sun compass, we identified a CRYPTOCHROME-staining neural pathway that likely connects the circadian clock to polarized light input entering brain.
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Citation: Neuron. 2005 May 5;46(3):457-67. Link to article on publisher's site