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Bringing Past Articles Current to 2020: Butterflies, Hummingbirds, More

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Butterflies

Here are items reported in 2019 that have made news in 2020: more on butterflies, hummingbirds, and the Cambrian explosion.

Structural Color in Butterflies

Past articles at Evolution News have discussed the phenomenon of structural color, in which colors are intensified not by pigments but by optics. In a variety of animals, light interference from microscopic ridges and other structures can intensify and diminish particular wavelengths. Butterflies are particularly good at this.

A new study published in PNAS extends the trick with light into the infrared, giving butterflies an additional advantage: warmth!

The optical properties of microstructures on butterfly wings are well studied in the visible spectrum, providing an understanding of the origins of structural coloration. Meanwhile, there is a need for evaluating their midinfrared optical properties, due to the critical role these properties play in thermoregulation. While a high visible absorptivity offers heating by absorption of solar radiation, a high midinfrared emissivity offers heat loss via thermal emission. Here we evaluate the midinfrared optical properties of 4 butterfly species from different habitats and analyze the effect of this emissivity on wing temperature. With the wing temperatures attaining similar values irrespective of their habitats of origin, our findings demonstrate the potential influence of butterfly wing microstructures on midinfrared optical properties and thermoregulation.

Hummingbird Pancakes

Some birds are also masters of structural color. Hummingbirds, featured in Illustra Media’s Flight: The Genius of Birds, are champions at it. Researchers at the Chicago Field Museum of Natural History looked at the microstructures in the iridescent throat feathers of male hummingbirds and found shapes that looked like pancakes: “hummingbirds’ melanosomes are pancake-shaped and contain lots of tiny air bubbles,” the researchers found.

Hummingbirds are some of the most brightly-colored things in the entire world. Their feathers are iridescent — light bounces off them like a soap bubble, resulting in shimmering hues that shift as you look at them from different angles. While other birds like ducks can have bright feathers, nothing seems to come close to hummingbirds, and scientists weren’t sure why. But a new study in Evolution shows that while hummingbird feathers have the same basic makeup as other birds’, the special shape of their pigment-containing structures enables them to reflect a rainbow of light.

The rows of pancake-shaped structures creates “a more complex set of surfaces,” the scientists found, that can produce an iridescent rainbow of colors. Darwinism was not particularly helpful in the research.

“The big question that keeps me up at night is, why are some groups of birds more colorful than others?”says Chad Eliason, the paper’s first author and a postdoctoral researcher at the Field Museum in Chicago. “You can look out your window and see drab brown birds, and then you have this glittering gem flutter to your hummingbird feeder. Why are hummingbirds so colorful?  Is it the environment, is it sexual selection? Or is it something about the internal mechanisms, the physics and the way colors are produced?”

If they keep asking that last question with an open mind, ID theory can offer some possibilities. Otherwise Darwinians have to suppose that “melanosome shape and the thickness of the feather lining are traits that evolved separately” and came together just right, by chance.

Humans and Fruit Flies Related, But How?

Here’s news from Columbia University’s Zuckerman Institute. Did you know fruit flies see in color? And that their color vision principles resemble that of humans?

Columbia scientists have identified a brain circuit that drives fruit flies’ ability to see in color — and found that it bears a striking resemblance to the circuitry behind our own capacity for color vision. These findings shed light on the fundamental, yet mysterious, process by which information about light waves is transmitted from the eye to the brain. This research will not only fuel new investigations into how color vision works in flies and humans, but could also spur efforts to develop algorithms that help computers see in color.

If intelligent designers develop algorithms and circuits, it seems logical to assume that color vision algorithms and circuits in both flies and humans had an intelligent source. Then scientists can logically conclude that humans and fruit flies are related by design — not by blind, unguided evolution.

Cloudina Still Cloudy

Günter Bechly asked here the other day, “Did Cloudinids Have the Guts to Be Worms?” Dr. Bechly knows well that his fellow paleontologists are desperately looking for dots to connect the Ediacaran fauna with the Cambrian animals. As he notes, a valiant attempt was made at Missouri State University to show that Cloudina (see past coverage from Evolution News, here, here, and here) was actually a wannabee annelid worm. Lead researcher Jim Schiffbauer makes a “gutsy proposition” that fossils of Cloudina found in Nevada contain preserved soft tissue impressions of a gut. The team looks really excited about the possibility.

“Not only are these structures the oldest guts yet discovered, but they also help to resolve the long-debated evolutionary positioning of this important fossil group,” said Schiffbauer, an associate professor of geological sciences in the MU College of Arts and Science and director of the X-ray Microanalysis Core facility. “These fossils fit within a very recognizable group of organisms — the cloudinids — that scientists use to identify the last 10 to 15 million years of the Ediacaran Period, or the period of time just before the Cambrian Explosion.We can now say that their anatomical structure appears much more worm-like than coral-like.” [Emphasis added.]

But are the dark impressions found in cross sections of the fossils really remains of a digestive tract? The paper in Nature Communications tries to sound hopeful, but issues caveats to avoid charges of wishful thinking.

There are several caveats that should be considered, however. First and foremost, some of these features are not uniformly representative across all of the cloudinomorphs — which should serve as a caution toward future attempts to resolve relationships within this morphotypic group. Moreover, at least some of these alleged diagnostic features (or lack thereof) may be taphonomic noise rather than primary biological signal.

Later,

To our knowledge, the structures reported herein are not only the first recognizable soft tissues in cloudinomorphs, but also the oldest guts yet described in the fossil record. As such, the Wood Canyon tubular fossil assemblage has provided a unique view into early animal anatomy. Nonetheless, for at least the cautions listed throughout the discussion above, we choose to refrain from shoehorning the cloudinomorphs into any explicit polychaete family. However, it is the sum of their parts — including the external tube structure, internal soft tissues, and presumed behavioral considerations — that may best denote placement amongst the Annelida as the most plausible.

It seems fair to reserve judgment on the wishful claim and take the caveats instead. Bechly: “The conundrum of the Cambrian explosion thus remains with us and poses a major problem for Darwinian evolution.”

Photo: Heliconius sara, by Pro2 [CC BY-SA].