Borboletas Monarcas revelam nova maneira na qual os animais 'sentem' o campo magnético da Terra

Monarch Butterflies Reveal a Novel Way in Which Animals Sense Earth's Magnetic Field

ScienceDaily (Jan. 27, 2010) — Building on prior investigation into the biological mechanisms through which monarch butterflies are able to migrate up to 2,000 miles from eastern North America to a particular forest in Mexico each year, neurobiologists at the University of Massachusetts Medical School (UMMS) have linked two related photoreceptor proteins found in butterflies to animal navigation using the Earth's magnetic field.

Monarch butterflies resting in a tree. (Credit: iStockphoto/Paul Tessier)

The work by Steven Reppert, MD, professor and chair of neurobiology at UMMS; Robert Gegear, PhD, research assistant professor of neurobiology; Lauren Foley, BS; and Amy Casselman, PhD, was recently described in the journal Nature.

The research team used fruit flies engineered to lack their own Cryptochrome (Cry1) molecule, a UV/blue-light photoreceptor already known to be involved in the insects' light-dependent magnetic sense. By inserting into those deficient flies butterfly Cry1, a homolog of the fly protein, or the related butterfly protein Cry2, the researchers found that either form can restore the flies' magnetic sense in a light-dependent manner, illustrating a role for both Cry types in magnetoreception. "Because the butterfly Cry2 protein is closely related to the one in vertebrates, like that found in birds which use the Earth's magnetic field to aid migration," states Dr. Reppert, "the finding provides the first genetic evidence that a vertebrate-like Cry can function as a magnetoreceptor."

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Nature advance online publication 24 January 2010 | doi:10.1038/nature08719; Received 12 August 2009; Accepted 1 December 2009; Published online 24 January 2010

Animal cryptochromes mediate magnetoreception by an unconventional photochemical mechanism

Robert J. Gegear1, Lauren E. Foley1, Amy Casselman1 & Steven M. Reppert1

Department of Neurobiology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, Massachusetts 01605, USA

Correspondence to: Robert J. Gegear1Steven M. Reppert1Correspondence and requests for materials should be addressed to S.M.R. (Email: steven.reppert@umassmed.edu) or R.J.G. (Email: robert.gegear@umassmed.edu).

Understanding the biophysical basis of animal magnetoreception has been one of the greatest challenges in sensory biology. Recently it was discovered that the light-dependent magnetic sense of Drosophila melanogaster is mediated by the ultraviolet (UV)-A/blue light photoreceptor cryptochrome (Cry)1. Here we show, using a transgenic approach, that the photoreceptive, Drosophila-like type 1 Cry and the transcriptionally repressive, vertebrate-like type 2 Cry of the monarch butterfly (Danaus plexippus) can both function in the magnetoreception system of Drosophila and require UV-A/blue light (wavelength below 420 nm) to do so. The lack of magnetic responses for both Cry types at wavelengths above 420 nm does not fit the widely held view that tryptophan triad-generated radical pairs mediate the ability of Cry to sense a magnetic field. We bolster this assessment by using a mutant form of Drosophilaand monarch type 1 Cry and confirm that the tryptophan triad pathway is not crucial in magnetic transduction. Together, these results suggest that animal Crys mediate light-dependent magnetoreception through an unconventional photochemical mechanism. This work emphasizes the utility of Drosophilatransgenesis for elucidating the precise mechanisms of Cry-mediated magnetosensitivity in insects and also in vertebrates such as migrating birds.

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