How The Butterflies Got Their Spots

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How two butterfly species have evolved exactly the same striking wing colour and pattern has intrigued biologists since Darwin’s day. Now, scientists at Cambridge have found “hotspots” in the butterflies’ genes that they believe will explain one of the most extraordinary examples of mimicry in the natural world.Heliconius, or passion-vine butterflies, live in the Americas — from the southern United States to southern South America. Although they cannot interbreed, H. melpomene and H. erato have evolved to mimic one another perfectly.

These delicate butterflies have splashes of red and yellow on their black wings, signaling to birds that they contain toxins and are extremely unpalatable. They mimic one another’s colour and pattern to reinforce these warning signals.Scientists have studied these butterflies since the 1860s as a classic case of evolution in action, but only now is modern sequencing technology unlocking the underlying genetics.The Cambridge-led team of researchers from UK and US universities, which has been breeding the butterflies in Panama for the past decade, has been searching for the genes responsible for the butterflies’ wing patterns and the answer to the question of whether the same genes in two different species are responsible for the mimicry.
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Long-Distance Migration Shapes Butterfly Wings

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A University of Georgia study has found that monarch butterflies that migrate long distances have evolved significantly larger and more elongated wings than their stationary cousins, differences that are consistent with traits known to enhance flight ability in other migratory species.
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Monarch Butterflies Reveal A Novel Way In Which Animals Sense Earth’s Magnetic Field

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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.

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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Butterflies Use Penis To Gauge Sex Competition

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BUTTERFLY sex is not as elegant an affair as you might think. It seems that male monarch butterflies conduct an all-out sperm war based on a crude measure of how much sperm is stored inside a female from a previous mating.
During sex the males physically restrain the females for an entire day while injecting them with a fluid which contains fertile sperm as well as seemingly functionless cells without nuclei.

Michelle Solensky of The College of Wooster in Ohio paired male monarch butterflies with a selection of females that had had different numbers of partners.

She found that males could selectively increase or decrease the amount of fertile sperm in their deposits. For example, they deposited slightly more into a female for each of her previous mates (Animal Behaviour, DOI: 10.1016/j.anbehav.2008.10.026). “This may explain earlier observations that the last male to mate has a reproductive advantage,” says Solenksy.
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