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Full-Text Articles in Biotechnology
A Magnetic Compass Aids Monarch Butterfly Migration, Robert Gegear, Patrick Guerra, Steven Reppert
A Magnetic Compass Aids Monarch Butterfly Migration, Robert Gegear, Patrick Guerra, Steven Reppert
Robert J. Gegear
Convincing evidence that migrant monarch butterflies (Danaus plexippus) use a magnetic compass to aid their fall migration has been lacking from the spectacular navigational capabilities of this species. Here we use flight simulator studies to show that migrants indeed possess an inclination magnetic compass to help direct their flight equatorward in the fall. The use of this inclination compass is light-dependent utilizing ultraviolet-A/blue light between 380 and 420 nm. Notably, the significance of light <420 nm for inclination compass function was not considered in previous monarch studies. The antennae are important for the inclination compass because they appear to contain light-sensitive magnetosensors. For migratory monarchs, the inclination compass may serve as an important orientation mechanism when directional daylight cues are unavailable and may also augment time-compensated sun compass orientation for appropriate directionality throughout the migration.
Discordant Timing Between Antennae Disrupts Sun Compass Orientation In Migratory Monarch Butterflies, Robert Gegear, Patrick Guerra, Christine Merlin, Steven Reppert
Discordant Timing Between Antennae Disrupts Sun Compass Orientation In Migratory Monarch Butterflies, Robert Gegear, Patrick Guerra, Christine Merlin, Steven Reppert
Robert J. Gegear
To navigate during their long-distance migration, monarch butterflies (Danaus plexippus) use a time-compensated sun compass. The sun compass timing elements reside in light-entrained circadian clocks in the antennae. Here we show that either antenna is sufficient for proper time compensation. However, migrants with either antenna painted black (to block light entrainment) and the other painted clear (to permit light entrainment) display disoriented group flight. Remarkably, when the black-painted antenna is removed, re-flown migrants with a single, clear-painted antenna exhibit proper orientation behaviour. Molecular correlates of clock function reveal that period and timeless expression is highly rhythmic in brains and clear-painted …
Human Cryptochrome Exhibits Light-Dependent Magnetosensitivity, Robert Gegear, Lauren Foley, Steven Reppert
Human Cryptochrome Exhibits Light-Dependent Magnetosensitivity, Robert Gegear, Lauren Foley, Steven Reppert
Robert J. Gegear
Humans are not believed to have a magnetic sense, even though many animals use the Earth's magnetic field for orientation and navigation. One model of magnetosensing in animals proposes that geomagnetic fields are perceived by light-sensitive chemical reactions involving the flavoprotein cryptochrome (CRY). Here we show using a transgenic approach that human CRY2, which is heavily expressed in the retina, can function as a magnetosensor in the magnetoreception system of Drosophila and that it does so in a light-dependent manner. The results show that human CRY2 has the molecular capability to function as a light-sensitive magnetosensor and reopen an area …
Defining Behavioral And Molecular Differences Between Summer And Migratory Monarch Butterflies, Robert Gegear, Haisun Zhu, Amy Casselman, Sriramana Kanginakudru, Steven Reppert
Defining Behavioral And Molecular Differences Between Summer And Migratory Monarch Butterflies, Robert Gegear, Haisun Zhu, Amy Casselman, Sriramana Kanginakudru, Steven Reppert
Robert J. Gegear
Background: In the fall, Eastern North American monarch butterflies (Danaus plexippus) undergo a magnificent long-range migration. In contrast to spring and summer butterflies, fall migrants are juvenile hormone deficient, which leads to reproductive arrest and increased longevity. Migrants also use a time-compensated sun compass to help them navigate in the south/southwesterly direction en route for Mexico. Central issues in this area are defining the relationship between juvenile hormone status and oriented flight, critical features that differentiate summer monarchs from fall migrants, and identifying molecular correlates of behavioral state. Results: Here we show that increasing juvenile hormone activity to induce summer-like …
Behavioural Assessment Of Visual Acuity In Bumblebees (Bombus Impatiens), Robert Gegear, Todd Macuda, Terence Laverty, Brian Timney
Behavioural Assessment Of Visual Acuity In Bumblebees (Bombus Impatiens), Robert Gegear, Todd Macuda, Terence Laverty, Brian Timney
Robert J. Gegear
measure resolution acuity in bumblebees (Bombus impatiens). Bees were required to discriminate between horizontal and vertical gratings in a Y-maze apparatus. The gratings had a mean luminance of 9 cd m−2 and a Michelson contrast of 84 %. For different bees, either the horizontal or vertical grating was rewarded. Rewarded gratings were associated with a sucrose and water solution (30 % sucrose by volume) and unrewarded gratings with plain water. Acuity estimates were established at several different viewing distances over several sessions using a method of constant stimuli. Visual acuity functions were generated from the performance data, and acuity thresholds …