Watching a Butterfly Wing Get its Color: An Unexpected Discovery in MBL Embryology

Watching a Butterfly Wing Get its Color: An Unexpected Discovery in MBL Embryology
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By Jennifer Tsang and Diana Kenney

Butterflies have fascinated Nipam Patel since he was eight years old, when he started building what today is a large collection of colorful specimens from all over the world. But it wasn’t until a few years ago that Patel, a professor at University of California-Berkeley, brought his love for butterflies to the MBL Embryology course, where he has served as a faculty member or course co-director since 2001.

Two summers ago, a “happy accident” in the Embryology course led Julian Kimura, then a course assistant and undergraduate at Duke University, and Ryan Null, a graduate student from Patel’s lab, to discover what Patel calls “an incredibly useful technique” for “windowing” the pupae of butterflies and observing and imaging their embryonic development. Null describes their unexpected find in the video below by Aaron Pomerantz, now a graduate student in Patel’s lab.

(For a somewhat slowed down version of one of the windowed pupa movies, see below.)

After some tweaking, Kimura and Null were able to reproducibly window butterfly pupae and watch the development of the hindwing. “Now our goal is to really be able to watch the [wing] scales developing in detail. We are interested in a phenomenon called structural color,” Patel says.

While some butterfly wing colors are due to pigments, others — typically blues and greens — are generated from light interacting with nanostructures on the surface or inside of the wing scales.

“Our ultimate goal is to understand how a single [butterfly] cell can make this elaborate nanostructure,” says Patel. “If the geometry of the nanostructure is 10 nanometers off, you’d have a noticeably wrong color. How can a cell make patterns at such a small scale, so accurately?”

With Kimura and Null’s windowing technique, they can peer into live pupae and image the developing hindwing with a dissecting microscope – or even an iPhone. “The key now is to be able to have fluorescent molecules in there and to use a confocal or super-resolution microscope to see real detail,” Patel says.

Indeed, Anna Czarkwiani and Neelima Sharma, students in this summer’s Embryology Course, have made another breakthrough and developed an approach for fluorescent live imaging of the actin network within butterfly scales.

National Geographic recently ran a story about the new windowing technique that features Pomerantz’s video.

Top photo caption: Nipam Patel in the MBL Embryology course with a few butterflies from his collection, including two blue Morpho butterflies that were studied by this year’s students. Credit: Jennifer Tsang