A New Look Inside the Butterfly Chrysalis - Evolution News & Views

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A New Look Inside the Butterfly Chrysalis

One of many highlights in the Illustra Media documentary Metamorphosis: The Beauty and Design of Butterflies is the MRI sequence where Dr. Richard Stringer used MRI to "slice" a chrysalis into 200 parts to watch the transformation going on inside (see our article "Peering Into the Chrysalis"). 3-D animations made from the slices allowed viewers to glide through a chrysalis over time to see the organs and structures of an adult butterfly taking shape.

Now, two British teams have made new high-resolution sequences using CT scanners. One team imaged Morpho butterflies during its initial metamorphosis to monitor the changes to the respiratory apparatus. Another team at the University of Manchester monitored the whole 16-day metamorphosis of the Painted Lady butterfly. Their results were published in an open-access paper in the Journal of the Royal Society Interface (for Supplementary Material with videos, see here.) Remarkably, the insects didn't suffer from daily doses of X-radiation. Most hatched and flew away just fine.

Live Science posted a gallery of some of the resulting images, colorized for clarity, from various angles. The accompanying news article on Live Science focuses on the technology, not the amazing transformation going on inside. An article at PhysOrg includes a short video clip showing the images from various angles.

The Royal Society paper gives no credit to Stringer's work, but it also says nothing about the evolution of metamorphosis. The only mention comes in the context of how CT scanning "provides an excellent opportunity for relatively easy comparison between life stages for developmental studies and evolutionary comparisons between various taxonomic groups." (Emphasis added.)

The PhysOrg article tries to minimize the miraculous transformation, from one body plan to another, very different one:

Interestingly, the videos show that the breathing system for the insects doesn't change much from beginning to end -- unlike the gut which shrinks dramatically. They also show that the changes that go on are part of a deconstruction and reconstruction process rather than a massive breakdown of everything into small bits which then reform as new parts.

It's understandable that the breathing system must function the whole time the insect is in the chrysalis, but the statement ignores the major changes required in the legs, the heart, the eyes, and virtually every system as a crawling creature that munches on leaves prepares to become a flying insect that feeds on nectar, with many new structures such as compound eyes, sex organs, a proboscis, antennae, jointed appendages, and, of course, wings. A Monarch caterpillar is confined to a milkweed plant; a Monarch butterfly is capable of traveling 3,000 miles in the air. As the film Metamorphosis illustrates, that's like breaking down a Model T and rebuilding the parts into a helicopter.

Speaking of migration (and of Painted Lady butterflies), another wonderful migration story came to light recently. The BBC News reported last October that the case of the "disappearing" Painted Lady butterflies was solved. Radar imaging revealed an "astonishing" migration of 9,000 miles between tropical Africa and the Arctic Circle. The migration had not been witnessed before because the butterflies fly so high -- up to 1,000 meters. Scientists figure it takes six generations to complete the migratory cycle, compared to four for the Monarch.

Richard Fox, co-author of a paper on this in Ecography, gets emotional about this feat:

"The migration of the monarch in North America is kind of world famous as this of wonder of nature and yet this annual migratory movement that painted ladies are undertaking is even greater," said Mr Fox.

"So we've kind of got this amazing creature right under our noses without really realising," he said.

"This tiny creature weighing less than a gram, with a brain the size of a pin head, and no opportunity to learn from older, experienced individuals, undertake an epic intercontinental migration."

With some twenty thousand butterfly species around the world (to say nothing of other amazing animals), advocates of intelligent design have no shortage of living things to draw on and showcase. Isn't that better than the current bad habit of simply assuming Darwinian evolution, as the authors of the Ecography paper do when they say, "Our results reveal the highly successful strategy that has evolved in these insects"? These findings suggest that on the subject of butterflies, science has barely scratched the surface.