Mechanism of Mating and Migration
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See the migration in action!! (2)
Over 3000 Miles!
4 Generations!
1 Destination!
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Monarchs can be tracked through labels!
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Migration Resources Are Seasonal
-Hover over the image carousel to view all of arizona's milkweed-
Migration timing relies on resource availability. When the flowers die, it's time to leave (3)!
Milkweed seasons vary depending on the species...
Arizona Native Milkweed species bloom between early April- late August (20).
Milkweed Carousel Image Credit
Monarch Mating Mechanism!
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Watch a video about the mating process (3)
Learn about mating at the overwintering site during the 4th generation! The gift of a large spermatophore increases the female's chance of survival during her migration back north. The male dies one week later after copulation.
Males: sperm is formed in the Ejaculatory duct(19).
Females: can store sperm in the spermatophore without fertilizing the eggs for up to several months(19).
Monarchs are a polygamous species with the females mating with multiple males(8)
How?
The male chases down the female until he catches her(10).
Rather than utilizing chemical courtship similar to other Danaid butterflies, the monarch butterfly uses a coercive mating system (10).
Once inserted, the female ceases her struggle and with wings closed, allows the male to fly her to cover.
The couple remains connected for up to 16 hours.
During this time, the male loses near 10% of his body mass in the donation of a large spermatophore. This nutritious gift increases the females chance at migration and a successful reproduction (13).
Once completed, the females store the sperm during their northward migration until a suitable host plant is located(19).
Watch this short clip to view mating in action (1)
Note: the "video unavailable" symbol is false.
To access the link, click the "watch on YouTube"
Mating In action!
Juvenile Hormone (19)
Produced in the corpora allata gland.
A hormone that ushers in sexual maturation of the reproductive system.
During reproductive diapause, this hormone is not produced. The individual is sexually immature.
The 4th generation does not produce Juvenile hormone until after the overwintering period.
Reproductive Diapause:
"A period of physiologically enforced dormancy between periods of activity."
-Merriam Webster's Dictionary(21)
The Monarchs in this video are preparing to leave their winter home in Mexico (5)! They are no longer under reproductive diapause and are preparing to head north to lay their eggs. The males will not make this journey, but will mate and die in Mexico.
The Importance of Antennae
Chemoreception:
The ability to sense chemicals through receptors (8).
Female Monarchs utilize chemoreception to find their milkweed host plant (1)!
Microscopic image of a Monarch Antenna!
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Photoreception:
The ability to sense light through receptors (8).
Antennae aid in migration as they allow the Monarch to sense the direction of the sun (8)!
Time Compensated Sun Compass
Circadian Clock :
" Being, having, characterized by, or occurring in approximately 24-hour periods or cycles (as of biological activity or function)."
Webster's Dictionary (16)
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How does it work?
As the sun Moves throughout the day, monarchs are able to orient south based on the their position in relation to the sun. This mechanism is known as a time compensated sun compass (4).
During the fall, monarchs migrating south should keep the sun 90 degrees to their left as they fly as sunrise. This is because the sun would be directly east of them (8). However, as the day progresses, the Monarchs should adjust their orientation to compensate for the movement of the sun (4).
This orientation is accomplished through the photoreceptors in their antennae as shown above (8).