[Leps-l] monarchs, reversal of orientation and overwintering temperatures
Chip Taylor
chip at ku.edu
Thu Feb 21 13:45:14 EST 2013
http://www.climatecentral.org/news/spring-chill-sends-monarchs-fluttering-north-15634
http://www.cell.com/current-biology/abstract/S0960-9822(13)00087-0
Coldness Triggers Northward Flight in Remigrant Monarch Butterflies
Current Biology, 21 February 2013
Copyright © 2013 Elsevier Ltd All rights reserved.
10.1016/j.cub.2013.01.052
Authors
Patrick A. Guerra
,
Steven M. Reppert
Summary
Each fall, eastern North American monarch
butterflies (Danaus plexippus) migrate from their
northern range to their overwintering grounds in
central Mexico [1,2,3]. Fall migrants are in
reproductive diapause, and they use a
time-compensated sun compass to navigate during
the long journey south [4,5,6]. Eye-sensed
directional cues from the daylight sky (e.g., the
horizontal or azimuthal position of the sun) are
integrated in the sun compass in the midbrain
central complex region [7,8]. Sun compass output
is time compensated by circadian clocks in the
antennae so that fall migrants can maintain a
fixed flight direction south [9,10]. In the
spring, the same migrants remigrate northward to
the southern United States to initiate the
northern leg of the migration cycle. Here we show
that spring remigrants also use an
antenna-dependent time-compensated sun compass to
direct their northward flight. Remarkably, fall
migrants prematurely exposed to
overwintering-like coldness reverse their flight
orientation to the north. The temperature
microenvironment at the overwintering site is
essential for successful completion of the
migration cycle, because without cold exposure,
aged migrants continue to orient south. Our
discovery that coldness triggers the northward
flight direction in spring remigrants solves one
of the long-standing mysteries of the monarch
migration.
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