Saturday, March 26, 2016

Penguin brain evolution lags behind loss of flight

Photo Credit: Connor Murphy | Daily Texan Staff
Until about 60 million years ago, penguins soared above the ocean. When they lost the ability to fly, their brains took a while to catch up.

UT geological sciences graduate student James Proffitt compared 3-D models of the inside of the earliest-known flightless penguin skull fossil to the brain shapes of modern penguins. This fossil is about 60 million years old — this penguin was probably alive soon after all penguins stopped flying.
He expected to find that flightlessness soon affected the ancient penguin’s brain structure, making it similar to modern penguins. However, this ancient penguin brain was significantly different from those of modern penguins, even though they were both flightless. These differences suggest modern penguin brains may not have evolved until relatively recently, according to Proffitt.

“It seems like ancient penguins have a lot more in common with other close diving relatives than they do with modern penguins,” Proffitt said. “When flightlessness evolved, the changes in the brain that you see in modern penguins don’t show up until much later.”

Even though it couldn’t fly, this 60-million-year-old penguin’s skull is more similar to those of present-day birds that can both dive and fly than to modern flightless penguins. Penguin
neurology took a long time to catch up to flightless behavior, according to Paul Scofield, the senior curator of natural history at the Canterbury Museum in New Zealand and co-author of the paper.

“I think this result clarifies that the evolution of penguins was rapid and that not all elements of the body suddenly became perfectly adapted to diving,” Scofield said. “Other studies have shown that the brain’s development lags behind the evolution of the body and this is certainly the case in this species.”

The evolution of bird brains is easier to study than other types of animals because bird skulls are closely fitted to the brain. Proffitt’s work used x-ray computed tomography, or CT scanning, to look inside the fossilized skull and observe the shape of the brain.

Chris Torres, an ecology, evolution and behavior graduate student currently in Antarctica studying bird evolution, also uses this CT scanning method to learn about other types of bird brains from fossils.

“Odd as it may sound, we don’t need brains to study brains anymore,” Torres said. “This has profound implications for what we can learn from fossil record, which preserves hard structures like skulls but not soft tissues like brains. CT has revolutionized the way we study how bird brains evolve.”

Proffit is interested in studying penguin evolution because, according to him, they came from a larger group of birds that both fly and swim, but have since evolved flightlessness.

“They make a really great group to examine this broader evolutionary idea of how animals respond to such a big change in ecology and what happens to the rest of their body,” he said.

There is still a lot of research that scientists need to do to understand the relationship between behavior and brain structure, according to Proffitt.

“I think it’s a complicated question to try and disentangle how locomotion effects neurology,” he said. “That’s more of a nuanced scientific story that isn’t as appealing as a firm answer.”


Friday, March 18, 2016

Wednesday, March 9, 2016

Penguin Feathers Inspire Ice-Proof Material

By mimicking the hierarchical microstructure of penguin feathers, researchers have developed an ice-proof insulating material.

Rebecca Tan | March 8, 2016

AsianScientist (Mar. 8, 2016) - Have you ever wondered how penguins stay warm and dry despite their sub-zero living environments? Now, researchers from Beihang University have identified microstructures on penguin feathers responsible for their anti-icing properties, and have even designed a feather-inspired nanofiber membrane that can be used as an ice-proof material. Their results have been published in The Journal of Physical Chemistry C.

Nature is a rich source of inspiration for scientists studying superhydrophobic, or water-repelling, materials. The rough texture of lotus leaves, for example, have served as the basis for the design of stain-resistant clothing. Similarly, the ability of penguins to survive in cold and wet environments is thought to be due to the superhydrophobic nature of their feathers which would cause water to slide off before ice has had a chance to form.

However, superhydrophobic surfaces are known to function poorly precisely under cold and wet conditions. When humidity is high, the rough structure of superhydrophobic materials encourages the condensation of water which quickly turns into a layer of ice, while the adhesion strength of ice increases at ultralow temperatures, making it harder for ice that has been formed to slide off.
To better understand the anti-icing properties of penguin feathers, a team of researchers at Beihang University used scanning electron microscopy to study the microstructure of feathers from Humboldt penguins (Spheniscus humboldti).

The feathers had a hierarchical structure, with tiny hooks arranged at regular intervals on larger barbules that were in turn arranged on even larger barbs. The hooks formed a wrinkled three-dimensional network that effectively prevented water from soaking through.
“We found that the air-infused microscale and nanoscale hierarchical rough structures endow the body feathers of S. humboldti penguins with icephobicity,” study corresponding author Dr. Wang Jingming told Asian Scientist Magazine.
Mimicking the structure of the feathers with polyimide nanofibers, the researchers developed a membrane where the fibers were spaced a few micrometers apart. The membrane was shown to be highly water-resistant, even to microdroplets that had been cooled to -5°C.
“Because of its excellent electrical insulation and icephobicity, the polyimide nanofiber membrane could be used in applications such as ice-proof coatings for electrical cables,” Wang explained.
The researchers plan to further improve the anti-icing properties of their artificial feathers by studying the packing style of natural penguin feathers, another decisive factor determining their anti-icing properties.

The article can be found at: Wang et al. (2016) Icephobicity of Penguins Spheniscus Humboldti and an Artificial Replica of Penguin Feather with Air-Infused Hierarchical Rough Structures.
Photo: f.c.franklin/Flickr/CC.


Friday, March 4, 2016

Sex-Based Differences in Adélie Penguin (Pygoscelis adeliae) Chick Growth Rates and Diet

  • Published: March 2, 2016
  • DOI: 10.1371/journal.pone.0149090


Sexually size-dimorphic species must show some difference between the sexes in growth rate and/or length of growing period. Such differences in growth parameters can cause the sexes to be impacted by environmental variability in different ways, and understanding these differences allows a better understanding of patterns in productivity between individuals and populations. We investigated differences in growth rate and diet between male and female Adélie Penguin (Pygoscelis adeliae) chicks during two breeding seasons at Cape Crozier, Ross Island, Antarctica. Adélie Penguins are a slightly dimorphic species, with adult males averaging larger than adult females in mass (~11%) as well as bill (~8%) and flipper length (~3%). We measured mass and length of flipper, bill, tibiotarsus, and foot at 5-day intervals for 45 male and 40 female individually-marked chicks. Chick sex was molecularly determined from feathers. We used linear mixed effects models to estimate daily growth rate as a function of chick sex, while controlling for hatching order, brood size, year, and potential variation in breeding quality between pairs of parents. Accounting for season and hatching order, male chicks gained mass an average of 15.6 g d-1 faster than females. Similarly, growth in bill length was faster for males, and the calculated bill size difference at fledging was similar to that observed in adults. There was no evidence for sex-based differences in growth of other morphological features. Adélie diet at Ross Island is composed almost entirely of two species—one krill (Euphausia crystallorophias) and one fish (Pleuragramma antarctica), with fish having a higher caloric value. Using isotopic analyses of feather samples, we also determined that male chicks were fed a higher proportion of fish than female chicks. The related differences in provisioning and growth rates of male and female offspring provides a greater understanding of the ways in which ecological factors may impact the two sexes differently.

Download the entire paper at this link

Wednesday, March 2, 2016

Penguin brains not changed by loss of flight

University of Texas at Austin
IMAGE: This is an ancient penguin skull and endocast. Scale bar is 2.5 cm and letters indicate parts of the brain: ce, cerebellum; el, endosseus labyrinth; fl, floccular lobe; ol, optic lobe; os, occipital sinus impression; pb, pituitary bulb; t, telencephalon; w, wulst.
Credit: Courtesy of James Proffitt
Losing the ability to fly gave ancient penguins their unique locomotion style. But leaving the sky behind didn't cause major changes in their brain structure, researchers from The University of Texas at Austin suggest after examining the skull of the oldest known penguin fossil.

The findings were published in the Journal of Anatomy in February.

"What this seems to indicate is that becoming larger, losing flight and becoming a wing-propelled diver does not necessarily change the [brain] anatomy quickly," said James Proffitt, a graduate student at the university's Jackson School of Geosciences who led the research. "The way the modern penguin brain looks doesn't show up until millions and millions of years later."

Proffitt conducted the research with Julia Clarke, a professor in the Jackson School's Department of Geological Sciences, and Paul Scofield, the senior curator of Natural History at the Canterbury Museum in Christchurch, New Zealand, where the skull fossil is from.

The skull is from a penguin that lived in New Zealand over 60 million years ago during the Paleocene epoch. According to Proffitt, it likely lived much like penguins today. But while today's penguins have been diving instead of flying for tens of millions of years, the change was relatively new for the ancient penguin.

"It's the oldest [penguin] following pretty closely after the loss of flight and the evolution of flightless wing-propelled diving that we know of," Proffitt said.

The shape of bird skulls is influenced by the structure of the brain. To learn about early penguin brain anatomy, Proffitt used X-ray CT-scanning to digitally capture fine features of the skull's anatomy, and then used computer modeling software to create a digital mold of the brain, called an endocast.

The researchers thought that loss of flight would impact brain structure--making the brains of ancient penguins and modern penguins similar in certain regions. However, after analyzing the endocast and comparing it to modern penguin brain anatomy, no such similarity was found, Proffitt said. The brain anatomy had more in common with skulls of modern relatives that both fly and dive such as petrels and loons, than modern penguins.

It's difficult to know why modern penguins' brains look different than their ancestors' brains, Proffitt said. It's possible that millions of years of flightless living created gradual changes in the brain structure. But the analysis shows that these changes are not directly related to initial loss of flight because they are not shared by the ancient penguin brain.

However, similarities in the brain shape between the ancient species and diving birds living today suggest that diving behavior may be associated with certain anatomical structures in the brain.

"The question now is do the old fossil penguins' brains look that way because that's the way their ancestors looked, or does it have something maybe to do with diving?" Proffitt said. "I think that's an open question right now."
The research was funded by a grant from the National Science Foundation.