Following the people and events that make up the research community at Duke

Tag: biology

Two Ways to Weird: How Whale Noses Moved to the Top of Their Head

Sticky post
A blue whale skeleton suspended in London’s Natural History Museum

Odd skulls are nothing new to V. Louise Roth, a professor in the Department of Biology. Much of her research centers on how animals’ shapes and sizes evolve and develop, so weirdly shaped bones are at the core of her work. But when Ph.D. student Rachel Roston drew her attention to the peculiarities of whale skulls, even Roth was astounded.

“There are some pretty weird mammal skulls out there,” Roth said. “I have studied morphological development in elephants, which are also kind of a crazy choice, but in terms of which bone goes where I think cetaceans are the weirdest ones.”

Cetaceans are the group that includes baleen whales – such as humpback whales – and toothed whales – such as dolphins and killer whales. Unlike almost all other vertebrate animals, cetaceans don’t breathe out of their mouths or from a nose placed in front of their face, but from a blowhole located on top of their head.

How did it get up there?

Rachel Roston, a graduate student in the Duke Biology department, recently published a paper with Professor Louise Roth, about some of the ways dolphin, whale and porpoise skulls break the rules of anatomy.

A new study published in the Journal of Anatomy by Roth and Roston, now a postdoctoral researcher at the University of Washington, reveals how whale and dolphin skulls undergo a complete transformation through their embryonic and fetal development, resulting in a re-orientation of their nasal passages.

What’s more, there’s not just one way to do it: baleen whales and toothed whales move their nostrils to the tops of their heads in two very different ways.

“It’s not just that they are developing the same thing in different ways,” said Roston, who led this work as part of her Ph.D. in Biology at Duke. “Looking from the outside of the body all you see is that both of them have their nose on the top of their head, but when you look inside their skulls, they are actually totally different blowholes.”

A toothed whale clears its blowhole. Photo by Friedrich Frühling

To figure out which bone went where and in which way, Roston looked at CT scans of baleen and toothed whales’ embryos in different stages of development and drew a dotted timeline of anatomical changes through the animals’ development.

Early-stage embryos look very much alike in most vertebrate animals: small, with a disproportionally large head, big eyes and oral and nasal cavities in the front of their face. As the embryos develop, they take different paths and become more and more similar to their own species.

Most of them keep their noses and their mouths in front of their face, but dolphins and whales transform their whole heads to change the direction of their nasal passage while keeping the snout facing forward.

“We think of the nostrils as something you find at the tip of the snout,” Roth said. “But whales go through some key changes in bone orientation that decouple one from the other.”

“It’s like looking at a cubist Picasso painting,” Roston said. “The eyes, nose and mouth are all there, but their relationships to each other are completely distorted.”

Whale embryos at different developmental stages. The white arrow shows how the nasal cavity shifts position through embryonic development.

This internal shuffling requires that the parts forming the roof of the embryo’s mouth move away from those that form its nasal passage. Initially parallel in small young embryos, they end up at an angle of about 45 degrees in baleen whales. In toothed whales this final angle is even wider, closer to 90 degrees.

In baleen whales, a key rotation happens at the back of the skull, where it meets the spine. Rather than being perpendicular to the ground, as in the head of a dog, the back of the skull is tilted forward towards the snout.

In toothed whales, the point of inflexion for this rotation is in the middle of the head. A bone in the center of the skull changes shape, curving upwards as the nasal passage ends facing up.

Roston and Roth both say that museum collections and non-destructive scanning techniques, such as CT scans, were key for this project because whale embryo specimens are difficult to come by. When a gravid female dies, small embryos often go unnoticed in their mother’s massive carcass. But older fetuses are larger than your typical sedan, making them difficult to preserve intact and store in museums. The few specimens found in museums must therefore be studied with the proverbial velvet gloves, or, in this case, CT scans.

“In science you always question ‘how come no one’s done this before?’” Roston said. “Here, it was because specimens are precious, so you don’t want to cut them up and destroy them.”

“Sometimes we’re looking at museum specimens that are 100 years old. This was an opportunity to describe them in a way that I hope will still be useful 100 years from now.”

Read more about weird whale skulls.

The research was funded by Duke University. Roston has also been supported by the National Institutes of Health.

CITATION: “Different Transformations Underlie Blowhole and Nasal Passage Development in a Toothed Whale (Odontoceti: Stenella attenuata) and a Baleen Whale (Mysticeti: Balaenoptera physalus),” Rachel A. RostonV. Louise Roth, Journal of Anatomy. DOI: 10.1111/joa.13492

Post by Marie Claire Chelini PhD, Duke Biology

Tracking Tiny Moving Targets

This squiggly line shows the path taken by a snippet of DNA as it might move around within the soupy interior of a cell. Duke’s Kevin Welsher and colleagues have developed a technique that turns a microscope into a ‘flight tracker’ for molecules, making it possible to follow the paths of viruses and other particles thousands of times smaller than the period at the end of this sentence. Until now, such techniques have required particles to be tethered to make sure they stay within the field of view. But the Welsher lab has developed a way to lock on to freely moving targets and track them for minutes at a time.

Researchers created a tiny circuit through a single water molecule, and here’s what they found

Graphic by Limin Xiang, Arizona State University

Many university labs may have gone quiet amid coronavirus shutdowns, but faculty continue to analyze data, publish papers and write grants. In this guest post from Duke chemistry professor David Beratan and colleagues, the researchers describe a new study showing how water’s ability to shepherd electrons can change with subtle shifts in a water molecule’s 3-D structure:

Water, the humble combination of hydrogen and oxygen, is essential for life. Despite its central place in nature, relatively little is known about the role that single water molecules play in biology.

Researchers at Duke University, in collaboration with Arizona State University, Pennsylvania State University and University of California-Davis have studied how electrons flow though water molecules, a process crucial for the energy-generating machinery of living systems. The team discovered that the way that water molecules cluster on solid surfaces enables the molecules to be either strong or weak mediators of electron transfer, depending on their orientation. The team’s experiments show that water is able to adopt a higher- or a lower-conducting form, much like the electrical switch on your wall. They were able to shift between the two structures using large electric fields.

In a previous paper published fifteen years ago in the journal Science, Duke chemistry professor David Beratan predicted that water’s mediation properties in living systems would depend on how the water molecules are oriented.

Water assemblies and chains occur throughout biological systems. “If you know the conducting properties of the two forms for a single water molecule, then you can predict the conducting properties of a water chain,” said Limin Xiang, a postdoctoral scholar at University of California, Berkeley, and the first author of the paper.

“Just like the piling up of Lego bricks, you could also pile up a water chain with the two forms of water as the building blocks,” Xiang said.

In addition to discovering the two forms of water, the authors also found that water can change its structure at high voltages. Indeed, when the voltage is large, water switches from a high- to a low-conductive form. In fact, it is may be possible that this switching could gate the flow of electron charge in living systems.

This study marks an important first step in establishing water synthetic structures that could assist in making electrical contact between biomolecules and electrodes. In addition, the research may help reveal nature’s strategies for maintaining appropriate electron transport through water molecules and could shed light on diseases linked to oxidative damage processes.

The researchers dedicate this study to the memory of Prof. Nongjian (NJ) Tao.

CITATION: “Conductance and Configuration of Molecular Gold-Water-Gold Junctions Under Electric Fields,” Limin Xiang, Peng Zhang, Chaoren Liu, Xin He, Haipeng B. Li, Yueqi Li, Zixiao Wang, Joshua Hihath, Seong H. Kim, David N. Beratan and Nongjian Tao. Matter, April 20, 2020. DOI: 10.1016/j.matt.2020.03.023

Guest post by David Beratan and Limin Xiang

Combining Up-Close Views of Science, Nature With the Magic of Light

Zinnia stamen by Thomas Barlow, Duke University

Thomas Barlow ’21 finds inspiration in small everyday things most people overlook: a craggy lichen growing on a tree, a dead insect, the light reflected by a pane of glass. Where we might see a flower, Barlow looks past the showy pink petals to the intricate parts tucked within.

The 20-year-old is a Duke student majoring in biology. By day, he takes classes and does research in a lab. But in his spare time, he likes to take up-close photographs using objects he finds outside or around the lab: peach pits, fireflies. But also pipettes, pencils.

A handheld laser pointer and flitting fireflies become streaks of light in this long-exposure image in Duke Forest. By Thomas Barlow.

Barlow got interested in photography in middle school, while playing around with his dad’s camera. His dad, a landscape architect, encouraged the hobby by enlisting him to take photos of public parks, gardens and playgrounds, which have been featured on various architects’ websites and in national publications such as Architecture Magazine. But “I always wanted to get closer, to see more,” Barlow said.

In high school he started taking pictures of still lifes. But he didn’t just throw flowers and fruit onto a backdrop and call it art. His compositions were a mishmash of insects and plants arranged with research gadgets: glass tubes, plastic rulers, syringes, or silicon wafers like those used for computer chips.

“I like pairing objects you would never find together normally,” Barlow said. “Removing them from their context and generating images with interesting textures and light.”

Sometimes his mother sends him treasures from her garden in Connecticut to photograph, like the pale green wings of a luna moth. But mostly he finds his subjects just steps from his dorm room door. It might be as easy as taking a walk through Duke Gardens or going for one of his regular runs in Duke Forest.

Having found, say, a flower bud or bumblebee, he then uses bits of glass, metal, mirrors and other shiny surfaces — “all objects that interact with light in some interesting way” – to highlight the interaction of light and color.

“I used to be really obsessed with dichroic mirrors,” pieces of glass that appear to change colors when viewed from different angles, Barlow said. “I thought they were beautiful objects. You can get so many colors and reflections out of it, just by looking at it in different ways.”

In one pair of images, the white, five-petaled flowers of a meadow anemone are juxtaposed against panels of frosted glass, a pipette, a mechanical pencil.

Another image pair shows moth wings. One is zoomed in to capture the fine details of the wing scales. The other zooms out to show them scattered willy-nilly around a shimmering pink circle of glass, like the remnants of a bat’s dinner plate.

Luna moth wings and wing scales with dichroic mirror, Thomas Barlow

For extreme close-ups, Barlow uses his Canon DSLR with a microscope objective mounted onto the front of a tube lens. Shooting this close to something so small isn’t just a matter of putting a bug or flower in front of the camera and taking a shot. To get every detail in focus, he takes multiple images of the same subject, moving the focal point each time. When he’s done he’s taken hundreds of pictures, each with a different part of the object in focus. Then he merges them all together.

At high magnification, Barlow’s flower close-ups reveal the curly yellow stamens of a zinnia flower, and the deep red pollen-producing parts of a tiger lily.

“I love that you can see the spikey pollen globules,” Barlow said.

Stomata and pollen on the underside of a tiger lily stamen, by Thomas Barlow

When he first got to Duke he was taking photos using a DIY setup in his dorm room. Then he asked some of the researchers and faculty he knew if there was anything photography-related he could do for their labs.

“I knew I was interested in nature photography and I wanted to practice it,” Barlow said.

One thing led to another, and before long he moved his setup to the Biological Sciences building on Science Drive, where he’s been photographing lichens for Daniele Armaleo and Jolanta Miadlikowska, both lichenologists.

“A lichen photo might not seem like anything special to an average person,” Barlow said. “But I think they’re really stunning.”

Powered by WordPress & Theme by Anders Norén