Monarchs in captivity do not migrate (Introduction)

by David Turell , Wednesday, June 26, 2019, 00:00 (1977 days ago) @ David Turell

If monarch eggs are incyb ated and raised in captivity, they lose the drive to migrate:

https://www.sciencedaily.com/releases/2019/06/190624161141.htm

" Monarch butterflies purchased from a commercial breeder did not fly in a southward direction, even in offspring raised outdoors, in a new study conducted by scientists at the University of Chicago. Wild-caught monarchs bred indoors under simulated outdoor conditions also did not orient south, suggesting that captive breeding disrupts the monarch's famous annual migratory behavior.

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"Monarchs breed during the summer and autumn, the autumn generation being the one that migrates. Tenger-Trolander collected eggs from the commercially purchased adults after they mated and raised them to adult butterflies. That summer generation then became the parents of the autumn generation.

"Tenger-Trolander then tested this autumn generation in a "flight simulator" to see the predominant direction they fly. The simulator is an open-ended, metal cylinder, like a pipe standing on one end. The butterfly is connected to a rod near the top opening of the cylinder by a metal pin, or tether, attached to its abdomen. This makes the butterflies fly in place inside the cylinder, but they are free to rotate 360 degrees. The rotating dial records the direction of the butterfly every two milliseconds and saves the data to a computer.

"Butterflies that exhibit migratory behavior should fly predominantly toward the south inside this flight simulator. The locally-captured monarchs raised in the same gardens did just that. However, Tenger-Trolander saw that the generation of butterflies bred from the commercial monarchs didn't fly in a dominant direction.

" Tenger-Trolander also performed a second set of experiments starting with only wild-caught monarchs and rearing the offspring completely inside. She tried to mimic outdoor conditions by adjusting temperature and the hours of daylight, but as a group, these butterflies did not show signs of migratory flight either. Some individuals did fly pointing south, but as a group they did not collectively fly predominantly in a southward direction. In fact, taking a chrysalis that had been developing outdoors and bringing it inside just as it was about to emerge also "broke" the migratory behavior in the group as a whole.

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"'We can't point to a single genetic change that did it because there are lots of them," he said. "But we think somewhere buried in the genome are changes that have broken it.'"

Comment: Despite not findings genetic changes, this suggests that there are epigenetic influences of some sort, and that normally living monarchs contain instructions they must follow.