Duke Research Blog

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

Category: Animals (Page 1 of 12)

How A Zebrafish’s Squiggly Cartilage Transforms into a Strong Spine

A column of green cartilage cells divides into an alternating pattern of green cartilage and red vertebra

Our spines begin as a flexible column called the notochord. Over time, cells on the notochord surface divide into alternating segments that go on to form cartilage and vertebrae.

In the womb, our strong spines start as nothing more than a rope of rubbery tissue. As our bodies develop, this flexible cord, called the notochord, morphs into a column of bone and cartilage sturdy enough to hold up our heavy upper bodies.

Graduate student Susan Wopat and her colleagues in Michel Bagnat’s lab at Duke are studying the notochords of the humble zebrafish to learn how this cartilage-like rope grows into a mature spine.

In a new paper, they detail the cellular messaging that directs this transformation.

It all comes down to Notch receptors on the notochord surface, they found. Notch receptors are a special type of protein that sits astride cell membranes. When two cells touch, these Notch receptors link up, forming channels that allow messages to rapidly travel between large groups of cells.

Notch receptors divide the outer notochord cells into two alternating groups – one group is told to grow into bone, while the other is told to grow into cartilage. Over time, bone starts to form on the surface of the notochord and works its way inward, eventually forming mature vertebrae.

X-ray images of four zebrafish spines

Meddling with cellular signaling on the notochord surface caused zebrafish spines to develop deformities. The first and third image show healthy spines, and the second and fourth image show deformed spines.

When the team tinkered with the Notch signaling on the surface cells, they found that the spinal vertebrae came out deformed – too big, too small, or the wrong shape.

“These results demonstrate that the notochord plays a critical role in guiding spine development,” Wopat said. “Further investigation into these findings may help us better understand the origin of spinal defects in humans.”

Spine patterning is guided by segmentation of the notochord sheath,” Susan Wopat, Jennifer Bagwell, Kaelyn D. Sumigray, Amy L. Dickson, Leonie F. Huitema, Kenneth D. Poss, Stefan Schulte-Merker, Michel Bagnat. Cell, February 20, 2018. DOI: 10.1016/j.celrep.2018.01.084

Post by Kara Manke

Student Ingenuity vs. Environmental Issues (like Cow Farts)

Lots of creative and potentially life changing ideas filled the Fitzpatrick CIEMAS atrium last weekend. From devices meant to address critical environmental issues such as global warming and lion fish invasiveness, to apps that help you become more sustainable, Duke’s Blueprint tech ideation conference showcased some awesome, good ol’ student-led ingenuity.

These bright students from around Durham (mostly from Duke) competed in teams to create something that would positively impact the environment. The projects were judged for applicability, daringness, and feasibility, among other things. During the Project Expo, all teams briefly presented to viewers like a school science fair.

One of the projects I liked a lot was called Entropy—a website with your own personal plant (I named mine “Pete”) that grows or dies depending on your sustainable actions throughout the day. The user answers simple yes or no questions, such as, “did you turn off the lights today?”

You can also complete daily goals to get accessories like a hat or mustache for your plant. The website connects to Facebook, so you can track your friends’ progress and see how green they’re living. Ultimately it’s just a good, fun way to keep your sustainability in check. Pete was looking super-cute after I spammed the yes button.

Another interesting innovation posed a solution to the difficulty of catching lion fish. Humans are a lion fish’s only predator, and we hunt them by spear fishing. Since lion fish are highly invasive, catching them en-masse could seriously benefit the biodiversity of the ocean (plus, they taste delicious). So one team came up with a canopy like contraption that attracts lion fish to hang out underneath it, and then snatches them all up at once like a net. Pretty neat idea, and if it was implemented on a large scale could be a huge benefit to the Earth’s oceans (and restaurants)!

After the expo, the top seven teams were selected and given three minutes to present to the judges and audience as a whole.

Every project was astounding. “Collide-o-scope” came up with a simple Arduino-based device to transmit elephant seismic activity to train drivers nearby in order to reduce the number of train-elephant collisions in India and Sri Lanka — currently a huge problem, for both us as humans and the elephant population.

Another team, “Manatee Marker,” proposed a system of solar powered buoys to detect manatees, with the hope of reducing frequent manatee-boat accidents. Considering that manatees are quiet, basically camouflaged, and thermally invisible, this was quite an ingenious task.

Perhaps my favorite project, “Algenie” stole the show. Methane gas is a huge factor to global warming — around twenty-five times more potent as a heat-trapping gas than Carbon Dioxide — and a lot of it comes from cow farts. However, we’ve recently discovered that putting seaweed in cow feed actually lowers methane emissions almost entirely! So this team came up with a vertical, three-dimensional way to grow algae — opposed to “two-dimensionally” growing across a pond — that would maximize production. Global warming is obviously a massive issue right now and Algenie is looking to change that. They ended up getting first place, and winning a prize of $1,000 along with GoPros for every team member.

Algenie’s prototype

At the end of the day, it wasn’t about the prize money. The competition was meant to generate creative and practical ideas, while promoting making a difference. After  attending the expo I felt more aware of all the environmental issues and influenced to help out. Even if you don’t feel like spending the time drafting up a crazy buoy manatee-detecting system, you can still do your part by living sustainably day to day.

Blueprint has done an awesome job of spurring young, enthusiastic students towards helping this planet — one cow fart at a time.

Post by Will Sheehan; Will SheehanPictures from Duke Conservation Tech

How A Bat’s Brain Navigates

Most of what we know about how the hippocampus, a region of the brain associated with memory formation and spatial representations, comes from research done on rodents. Rat brains have taught us a lot, but researchers in Israel have found an interesting alternative model to understanding how the hippocampus helps mammals navigate: Bats.

The Egyptian fruit bat proved the perfect subject for studies of mammalian navigation.

Weizmann Institute neurophysiologist Nachum Ulanovsky, PhD, and his team have looked to bats to understand the nuances of navigation through space. While previous research has identified specific cells in the hippocampus, called place cells, that are active when an animal is located in a specific place, there is not much literature describing how animals actually navigate from point A to point B.

Nachum Ulanovsky

Ulanovsky believes that bats are an ingenious model to study mammalian navigation. While bats have the same types of hippocampal neurons found in rats, the patterns of bats’ neurons’ firings more closely match that of humans than rats do.

Ulanovsky sought to test how bats know where they are going. Using GPS tracking equipment, his team found that wild bats that lived in a cave would travel up to 20 kilometers to forage fruit from specific trees. Night after night, these bats followed similar routes past perfectly viable food sources to the same tree over and over again.

The understanding of hippocampal place cells firing at specific locations doesn’t explain the apparent guided travel of the bat night after night, and other explanations like olfactory input do not explain why the bats fly over good food sources to their preferred tree.

The researchers designed an experiment to test how bats encode the 3D information necessary for this navigation. By letting the bats fly around and recording brain activity, Ulanovsky and team found that their 3D models are actually spherical in shape. They also found another type of hippocampal cells that encode the orientation the bat is facing. These head direction cells operate in a coordinate system that allows for a continuity of awareness of its orientation as the animal moves through space.

http://www.cell.com/cms/attachment/2091916945/2076305003/gr1_lrg.jpg

Ulanovsky found bats relied on memory to navigate toward the goal.

To understand how the bats navigate toward a specific goal, the researchers devised another experiment. They constructed a goal with a landing place and a food incentive. The bat would learn where the goal was and find it. In order to test whether the bats’ ability to find the goal was memory-based, or utilized the hippocampus, the researchers then conducted trials where the goal was hidden from the bats’ view.

To test whether the bats’ relied on memory, the Ulvanosky team measured the goal direction angle, or the angle between the bat’s head orientation and the goal. After being familiarized with the location of the goal, the bats tended toward a goal-direction angle of zero, meaning they oriented themselves toward the goal even when the goal was out of sight.

Continued research identified cells that encode information about the distance the bat is from the goal, the final piece allowing bats to navigate to a goal successfully. These hippocampal cells selectively fire when the bat is within specific distances of the goal, allowing for an awareness of location over distance.

While Ulanovsky and his team have met incredible success in identifying new types of cells as well as new functions of known cells in the hippocampus, further research in a more natural setting is required.

“If we study only under these very controlled and sterile environments, we may miss the very thing we are trying to understand, which is behavior,” Ulanovsky concluded.

By Sarah Haurin

Researchers Get Superman’s X-ray Vision

X-ray vision just got cooler. A technique developed in recent years boosts researchers’ ability to see through the body and capture high-resolution images of animals inside and out.

This special type of 3-D scanning reveals not only bones, teeth and other hard tissues, but also muscles, blood vessels and other soft structures that are difficult to see using conventional X-ray techniques.

Researchers have been using the method, called diceCT, to visualize the internal anatomy of dozens of different species at Duke’s Shared Materials Instrumentation Facility (SMIF).

There, the specimens are stained with an iodine solution that helps soft tissues absorb X-rays, then placed in a micro-CT scanner, which takes thousands of X-ray images from different angles while the specimen spins around. A computer then stitches the scans into digital cross sections and stacks them, like slices of bread, to create a virtual 3-D model that can be rotated, dissected and measured as if by hand.

Here’s a look at some of the images they’ve taken:

See-through shrimp

If you get flushed after a workout, you’re not alone — the Caribbean anemone shrimp does too.

Recent Duke Ph.D. Laura Bagge was scuba diving off the coast of Belize when she noticed the transparent shrimp Ancylomenes pedersoni turn from clear to cloudy after rapidly flipping its tail.

To find out why exercise changes the shrimp’s complexion, Bagge and Duke professor Sönke Johnsen and colleagues compared their internal anatomy before and after physical exertion using diceCT.

In the shrimp cross sections in this video, blood vessels are colored blue-green, and muscle is orange-red. The researchers found that more blood flowed to the tail after exercise, presumably to deliver more oxygen-rich blood to working muscles. The increased blood flow between muscle fibers causes light to scatter or bounce in different directions, which is why the normally see-through shrimp lose their transparency.

Peer inside the leg of a mouse

Duke cardiologist Christopher Kontos, M.D., and MD/PhD student Hasan Abbas have been using the technique to visualize the inside of a mouse’s leg.

The researchers hope the images will shed light on changes in blood vessels in people, particularly those with peripheral artery disease, in which plaque buildup in the arteries reduces blood flow to the extremities such as the legs and feet.

The micro-CT scanner at Duke’s Shared Materials Instrumentation Facility made it possible for Abbas and Kontos to see structures as small as 13 microns, or a fraction of the width of a human hair, including muscle fibers and even small arteries and veins in 3-D.

Take a tour through a tree shrew

DiceCT imaging allows Heather Kristjanson at the Johns Hopkins School of Medicine to digitally dissect the chewing muscles of animals such as this tree shrew, a small mammal from Southeast Asia that looks like a cross between a mouse and a squirrel. By virtually zooming in and measuring muscle volume and the length of muscle fibers, she hopes to see how strong they were. Studying such clues in modern mammals helps Kristjanson and colleagues reconstruct similar features in the earliest primates that lived millions of years ago.

Try it for yourself

Students and instructors who are interested in trying the technique in their research are eligible to apply for vouchers to cover SMIF fees. People at Duke University and elsewhere are encouraged to apply. For more information visit https://smif.pratt.duke.edu/Funding_Opportunities, or contact Dr. Mark Walters, Director of SMIF, via email at mark.walters@duke.edu.

Located on Duke’s West Campus in the Fitzpatrick Building, the SMIF is a shared use facility available to Duke researchers and educators as well as external users from other universities, government laboratories or industry through a partnership called the Research Triangle Nanotechnology Network. For more info visit http://smif.pratt.duke.edu/.

Post by Robin Smith, News and Communications

Post by Robin Smith, News and Communications

Meet Africa’s Bird Master of Vocal Imitation

The red-capped robin-chat (Cossypha natalensis) can mimic the songs and calls of dozens of other bird species – even their duets, says Duke researcher Tom Struhsaker.

The red-capped robin-chat (Cossypha natalensis) can mimic the songs and calls of dozens of other bird species – even their duets, says Duke researcher Tom Struhsaker.

Singing a duet in a foreign language isn’t just for opera stars — red-capped robin-chats do it too. These orange-brown birds with grey wings can imitate the sounds of 40 other bird species, even other species’ high-speed duets.

The latter finding comes from Tom Struhsaker, adjunct professor of evolutionary anthropology at Duke. Struhsaker didn’t set out to study robin-chats. His interest in their vocal abilities developed while studying monkeys in Kibale Forest in Uganda, where he lived for nearly two decades from 1970 to 1988.

Their typical song “sounds like a long, rambling human-like whistle,” Struhsaker said. But during the 18 years he spent studying and living in Kibale, Struhsaker also heard these birds impersonate the tambourine-like courtship call of the crested guineafowl, the crow of a rooster, and the “puweepuweepuwee” of a crowned eagle, among others.

“The robin-chat’s ability to imitate is so good that many a bird watcher has looked skyward vainly searching for a crowned eagle performing its aerial display, when in fact the source of the eagle’s undulating whistle was a robin-chat in the nearby understory,” Struhsaker said.

He also noticed that if he whistled, eavesdropping robin-chats would approach and call back, and if he tweaked the pitch and sequence of notes in his whistle, the birds sometimes changed their reply.

This suggests red-capped robin-chats may be lifelong learners, unlike many other bird species that only learn songs during critical time windows, Struhsaker said.

But the robin-chat doesn’t stop at mimicking others’ solo performances. Notably, Struhsaker also heard them imitate the duet of the black-faced rufous warbler.

Black-faced rufous warblers sing a rapid-fire “seee-oooo-ee” duet with their mates. The two birds take turns such that the male sings the “seee,” the female chimes in with the “oooo” and the male fires back with the final “ee,” with no pauses between the three notes. The partners sing back and forth so seamlessly that they are often mistaken for a single bird.

“In order to do this, birds have an incredibly rapid reaction time, much greater than that of humans,” Struhsaker said.

On two occasions he heard single robin-chats sing both the male and female parts of the warbler duet by themselves. On another occasion he heard two robin-chats make music together as the warblers do, with one singing the male warbler’s part and the other singing the female part.

“This suggests these birds have an unusually high level of auditory perception and reaction time and cognitive ability,” Struhsaker said.

CITATION:  “Two Red-Capped Robin-Chats Cossypha Natalensis Imitate Antiphonal Duet of Black-Faced Rufous Warblers Bathmocercus rufus,” Thomas Struhsaker. Journal of East African Natural History, Dec. 2017. https://doi.org/10.2982/028.106.0201.

 

Some Lemurs are Loners, Others Crave Connection

DURHAM, N.C. — If lemurs were on Facebook, Fern would have oodles of friends, liking and commenting on their posts. Captain Lee, on the other hand, would rarely send a friend request.

Best buddies Fern and Alena at the Duke Lemur Center in Durham, North Carolina. Photo by Ipek Kulahci.

Best buddies Fern and Alena at the Duke Lemur Center in Durham, North Carolina. Photo by Ipek Kulahci.

These are just two of the distinct personalities discovered in a recent study of group dynamics in ring-tailed lemurs, primate cousins that live in groups of up to two dozen on the island of Madagascar.

First author Ipek Kulahci spent several years studying ring-tailed lemurs housed at the Duke Lemur Center in North Carolina and the St. Catherines Island Lemur Program in Georgia. Along the way, she noticed a lot of variation in social behavior from one lemur the next. She observed socialite Fern, loner Captain Lee, best buddies Limerick and Herodotus and other lemur characters.

Some individuals seemed more outgoing than others. To try to quantify that, she followed four groups of ring-tailed lemurs over two consecutive years and recorded their behavior a minimum of four times a week for at least two months.

A social network of lemurs. Each circle represents an individual lemur, and lemurs who respond to each other’s calls are connected by arrows. Thicker arrows indicate lemurs who respond more frequently and have a stronger social bond.

A social network of lemurs. Each circle represents an individual lemur, and lemurs who respond to each other’s calls are connected by arrows. Thicker arrows indicate lemurs who respond more frequently and have a stronger social bond.

Using a method called social network analysis, she was able to measure how many connections each lemur had, with whom, and how strong those connections were. She was also able to figure out which lemurs were most influential in each group — either because they connected others, or because they had well-connected friends.

Kulahci and colleagues found that lemurs behaved consistently no matter what their age, sex or social situation. Some lemurs like Fern tended to seek connection; reinforcing social bonds by frequently picking through their friends’ fur and responding to other lemurs’ calls and scent marks.

Their interactions weren’t always amicable — the more socially active lemurs were also more likely to chase others or pick fights with individuals with whom they weren’t on friendly terms. “But they have a drive to interact with others, rather than be a loner,” said Kulahci, now a postdoctoral researcher at University College Cork in Ireland.

The researchers also found that lemurs, like us, don’t bond with just anyone. Whether they were extroverted or shy, all lemurs had an inner circle of groupmates they tended to groom, call back, or otherwise keep in touch with more than others.

Ipek Kulahci, postdoctoral researcher at University College Cork in Ireland.

Ipek Kulahci, postdoctoral researcher at University College Cork in Ireland.

“They essentially have buddies,” Kulahci said.

“This is important because social connectedness influences health, immunity, survival,” Kulahci said. “This is true for animals as well as humans.”

The results appeared online Dec. 9, 2017, in the journal Animal Behaviour.

Other authors on this study include Asif Ghazanfar and Daniel Rubenstein of Princeton University. This study was funded by grants from the Animal Behavior Society, American Society of Mammalogists, American Society of Primatologists and Princeton University.

CITATION:  “Consistent Individual Variation Across Interaction Networks Indicates Social Personalities in Lemurs,” Ipek Kulahci, Asif Ghazanfar and Daniel Rubenstein. Animal Behaviour, Dec. 9, 2017.  https://doi.org/10.1016/j.anbehav.2017.11.012

by Robin Smith

by Robin Smith

Captive Lemurs Get a Genetic Health Checkup

DURHAM, N.C. — Careful matchmaking can restore genetic diversity for endangered lemurs in captivity, researchers report.

Ring-tailed lemurs born at the Duke Lemur Center have seen a recent infusion of new genetic material at key genes involved in the immune response, finds a new study.

Thanks to a long-term collaborative breeding program that transfers animals between institutions to preserve genetic diversity, genetic variation at one region was restored to levels seen in the wild.

The findings, published in the journal Ecology and Evolution, are important for the ability of future generations to fight disease.

Baby lemur twins Nemesis and Narcissa were the product of a breeding program developed by the American Association of Zoos and Aquariums to preserve the future genetic health of North America’s captive ring-tailed lemurs. Their mother Sophia was among 62 ring-tailed lemurs recommended for breeding across 20 institutions nationwide in 2016. Photo by David Haring, Duke Lemur Center.

Baby lemur twins Nemesis and Narcissa were the product of a breeding program developed by the American Association of Zoos and Aquariums to preserve the future genetic health of North America’s captive ring-tailed lemurs. Their mother Sophia was among 62 ring-tailed lemurs recommended for breeding across 20 institutions nationwide in 2016. Photo by David Haring, Duke Lemur Center.

Distant primate cousins with long black-and-white striped tails, ring-tailed lemurs live on the African island of Madagascar and nowhere else except in zoos and other captive facilities.

Some studies suggest that as few as 2,500 ring-tailed lemurs live in the wild today. Habit loss, hunting and the illegal pet trade have reduced their numbers by at least 50 percent in recent decades.

An additional estimated 2,500 ring-tailed lemurs live in zoos around the world, where experts work to maintain their genetic health in captivity.

The researchers studied DNA sequence variation at a region of the major histocompatibility complex, or MHC, a part of the genome that helps the immune system identify disease-causing bacteria, viruses and parasites.

Because different MHC gene variants recognize different types of pathogens, greater MHC diversity means animals are able to fend off a wider array of invaders.

The researchers estimated the number of MHC variants in 121 captive individuals born at the Duke Lemur Center and the Indianapolis and Cincinnati Zoos between 1980 and 2010.

They also compared them with 180 wild individuals from southwestern Madadgascar at the Bezà Mahafaly Special Reserve, where the animals regularly interbreed with lemurs from nearby forests.

Not surprisingly, MHC diversity was lower in captivity than in the wild.

Today’s captive ringtails came from a small group of ancestors that carried only a small fraction of the total genetic variation found in the larger wild population. Since their establishment, gene flow between captive populations and wild lemurs has been restricted.

Overall, the researchers found 20 unique MHC variants in the captive population, fewer than half the number in their wild counterparts.

However, efforts to identify good genetic matches across dozens of institutions have helped to preserve and even improve upon the diversity that is left.

For infants born at the Duke Lemur Center, MHC gene diversity remained low but stable for three decades from 1980 to 2010, then increased significantly from 2010 to 2013, researchers found.

Genetic contributions from several transplants contributed to the comeback.

An arranged marriage between ring-tailed lemurs at the Duke Lemur Center in North Carolina produced healthy twins Griselda and Hedwig in 2016. The infants are among 40 to 60 ring-tailed lemur infants born in North American zoos and other facilities each year. Photo by David Haring, Duke Lemur Center.

An arranged marriage between ring-tailed lemurs at the Duke Lemur Center in North Carolina produced healthy twins Griselda and Hedwig in 2016. The infants are among 40 to 60 ring-tailed lemur infants born in North American zoos and other facilities each year. Photo by David Haring, Duke Lemur Center.

The American Association of Zoos and Aquariums (AZA) tries to maintain a genetically healthy population by moving animals between institutions as potential mates. A team of experts uses computer software to help pick the best pairs for breeding.

Between 1980 and 2013, more than 1,160 ring-tailed lemurs were transferred between 217 institutions in North America alone.

In 2009, a male named Randy was transferred from the Saint Louis Zoo to the Duke Lemur Center for pairing with Sprite, a resident female. Experts also brought a mother-daughter pair, Schroeder and Leisl from the Zoo at Chehaw in Georgia, as potential mates for a resident male named Aracus.

“They saw an immediate improvement in the diversity of the offspring that were born,” said lead author Kathleen Grogan, who conducted the study while working on a doctorate with co-author Christine Drea at Duke University.

Grogan and colleagues are now examining whether MHC gene diversity helps the animals live longer or produce more offspring, as has been shown for other species.

“Not only do these lemurs serve as an assurance against extinction of their Malagasy counterparts, but maintaining as many variations of genes is important for keeping the individual lemurs, as well as the population healthy for any future challenges it may face,” said AZA Species Survival Plan Coordinator Gina Ferrie, a population biologist at Disney’s Animal Kingdom.

Conserving genetic diversity in captive populations over multiple generations is challenging due to their small size and relative isolation, but careful breeding can stem the loss, said Grogan, now a postdoctoral fellow at Pennsylvania State University.

Other authors include Michelle Sauther of the University of Colorado-Boulder and Frank Cuozzo at LaJuma Research Centre in South Africa.

This research was supported by Duke University, the International Primatological Society, Primate Conservation Inc., the University of Colorado-Boulder, the University of North Dakota, the National Science Foundation (BCS 0922465, BCS-1232570, IOS-071900), the Margot Marsh Biodiversity Foundation, the St. Louis Zoo and the American Society of Primatologists.

CITATION:  “Genetic Wealth, Population Health: Major Histocompatibility Complex Variation in Captive and Wild Ring-Tailed Lemurs (Lemur Catta),” Kathleen Grogan, Michelle Sauther, Frank Cuozzo and Christine Drea. Ecology and Evolution, Date. DOI: 10.1002/ece3.3317

Science on the Trail

Duke launches free two-week girls science camp in Pisgah National Forest.

Duke launches free two-week girls science camp in Pisgah National Forest.

DURHAM, N.C. — To listen to Destoni Carter from Raleigh’s Garner High School, you’d never know she had a phobia of snails. At least until her first backpacking trip, when a friend convinced her to let one glide over her outstretched palm.

Destoni Carter

Destoni Carter from Raleigh’s Garner High School was among eight high schoolers in a new two-week camp that combines science and backpacking.

Soon she started picking them up along the trail. She would collect a couple of snails, put them on a bed of rocks or soil or leaves, and watch to see whether they were speedier on one surface versus another, or at night versus the day.

The experiment was part of a not-so-typical science class.

From June 11-23, 2017, eight high school girls from across North Carolina and four Duke Ph.D. students left hot showers and clean sheets behind, strapped on their boots and packs, and ventured into Pisgah National Forest.

For the high schoolers, it was their first overnight hike. They experienced a lot of things you might expect on such a trip: Hefty packs. Sore muscles. Greasy hair. Crusty socks. But they also did research.

The girls, ages 15-17, were part of a new free summer science program, called Girls on outdoor Adventure for Leadership and Science, or GALS. Over the course of 13 days, they learned ecology, earth science and chemistry while backpacking with Duke scientists.

Duke ecology Ph.D. student Jacqueline Gerson came up with the idea for the program. “Backpacking is a great way to get people out of their comfort zones, and work on leadership development and teambuilding,” said Gerson, who also teamed up with co-instructors Emily Ury, Alice Carter and Emily Levy, all Ph.D. students in ecology or biology at Duke.

Marwa Hassan of Riverside High School in Durham studying stream ecology as part of a two-week summer science program in Pisgah National Forest. Photo by Savannah Midgette.

Marwa Hassan of Riverside High School in Durham studying stream ecology as part of a two-week summer science program in Pisgah National Forest. Photo by Savannah Midgette.

The students hauled 30- to 40-pound loads on their backs for up to five miles a day, through all types of weather. For the first week and a half they covered different themes each day: evolution, geology, soil formation, aquatic chemistry, contaminants. Then on the final leg they chose an independent project. Armed with hand lenses, water chemistry test strips, measuring tapes and other gear, each girl came up with a research question, and had two days to collect and analyze the data.

Briyete Garcia-Diaz of Kings Mountain High School surveyed rhododendrons and other trees at different distances from streambanks to see which species prefer wet soils.

Marwa Hassan of Riverside High School in Durham waded into creeks to net mayfly nymphs and caddisfly larvae to diagnose the health of the watershed.

Savannah Midgette of Manteo High School counted mosses and lichens on the sides of trees, but she also learned something about the secret of slug slime.

“If you lick a slug it makes your tongue go numb. It’s because of the protective coating they have,” Midgette said.

High schoolers head to the backcountry to learn the secret of slug slime and other discoveries of science and self in new girls camp

High schoolers head to the backcountry to learn the secret of slug slime and other discoveries of science and self in new girls camp

The hiking wasn’t always easy. On their second day they were still hours from camp when a thunderstorm rolled in. “We were still sore from the previous day. It started pouring. We were soaking wet and freezing. We did workouts to keep warm,” Midgette said.

At camp they took turns cooking. They stir fried chicken and vegetables and cooked pasta for dinner, and somebody even baked brownies for breakfast. Samantha Cardenas of Charlotte Country Day School discovered that meals that seem so-so at home taste heavenly in the backcountry.

“She would be like, ugh, chicken in a can? And then eat it and say: ‘That’s the most amazing thing I’ve ever had,’” said co-instructor Emily Ury.

Savannah Midgette and Briyete Garcia-Diaz drawing interactions within terrestrial systems as part of a new free summer science program called Girls on outdoor Adventure for Leadership and Science, or GALS. Learn more at https://sites.duke.edu/gals/.

Savannah Midgette and Briyete Garcia-Diaz drawing interactions within terrestrial systems as part of a new free summer science program called Girls on outdoor Adventure for Leadership and Science, or GALS. Learn more at https://sites.duke.edu/gals/.

The students were chosen from a pool of over 90 applicants, said co-instructor Emily Levy. There was no fee to participate in the program. Thanks to donations from Duke Outdoor Adventures, Project WILD and others, the girls were able to borrow all the necessary camping gear, including raincoats, rain pants, backpacks, tents, sleeping bags, sleeping pads and stoves.

The students presented their projects on Friday, June 23 in Environment Hall on Duke’s West Campus. Standing in front of her poster in a crisp summer dress, Destoni Carter said going up and down steep hills was hard on her knees. But she’s proud to have made it to the summit of Shining Rock Mountain to see the stunning vistas from the white quartz outcrop near the top.

“I even have a little bit of calf muscle now,” Carter said.

Funding and support for GALS was provided by Duke’s Nicholas School of the Environment, Duke ecologist Nicolette Cagle, the Duke Graduate School and private donors via GoFundMe.

2017 GALS participants (left to right): Emily Levy of Duke, Destoni Carter of Garner High School, Zyrehia Polk of East Mecklenburg High School, Rose DeConto of Durham School of the Arts, Briyete Garcia-Diaz of Kings Mountain High School, Marwa Hassan of Riverside High School, Jackie Gerson of Duke, Daiana Mendoza of Harnett Central High School, Savannah Midgette of Manteo High School, Samantha Cardenas of Charlotte Country Day School and Alice Carter of Duke.

2017 GALS participants (left to right): Emily Levy of Duke, Destoni Carter of Garner High School, Zyrehia Polk of East Mecklenburg High School, Rose DeConto of Durham School of the Arts, Briyete Garcia-Diaz of Kings Mountain High School, Marwa Hassan of Riverside High School, Jackie Gerson of Duke, Daiana Mendoza of Harnett Central High School, Savannah Midgette of Manteo High School, Samantha Cardenas of Charlotte Country Day School and Alice Carter of Duke.

 

Marine Parasites — Little Guys That Make a Big Difference

If you’re anything like me, the first images that come to mind when you hear the words “marine biology” are singing whales, dolphins racing each other, sharks flying out of the water, maybe a swordfish brawl or two — all the big, flashy stuff.

Of all the things “marine biology” invokes, parasites are probably at the very bottom of my list.

Not so for Joe Morton, a PhD student at the Nicholas School of the Environment and self-taught expert on the parasites that inhabit marine organisms. In fact, Morton posits that parasites play one of the most important roles in all of ecology, by modifying the behavior of ecologically influential host species. And he’s got the research to back it up.

Once back at the lab, Morton takes his place behind the microscope to study his research subjects: marine parasites. Courtesy: Joe Morton.

Morton’s academic quest into the world of marine parasites began about six years ago when he was a master’s student at UNC’s Institute of Marine Sciences — just down the road from Duke’s own Marine Lab, where he’s now stationed. Having just read Carl Zimmer’s pop-science book Parasite Rex, Morton wondered whether the marsh periwinkle snails (Littoraria irrorata) he was studying could be infected.

“In my spare time, I would go into the lab at night with a hammer and crack open a bunch of snails to see what I would find,” Morton said. “I didn’t find anything in the literature at the time about Littoraria harboring parasites, which I thought was really unusual because they’re really well-known, important marsh gastropod.”

Morton began to systematically collect Littoraria from local salt marshes, determine their infection status, then examine how the parasites affected the behavior of infected individuals and, in turn, how these behavioral changes affected the ecological health of the salt marsh. This way, Morton figured out that Littoraria infected with digenean trematodes (a class of parasite) climbed and grazed on marsh grass less often than uninfected Littoraria. He also noticed that infected Littoraria congregated at salt marsh “die-off borders,” the edges where marsh grasses stop growing sparsely and start growing in healthy amounts.

A microsopic view of digenean trematodes, the parasites that infect marsh periwinkle snails. Courtesy: Joe Morton.

Based on these observations, Morton designed an experiment to test whether the prevalence of infection among Littoraria correlated with marsh grass health.

“I found that, even under drought stress conditions, parasites could effectively slow the rate at which the marsh died off and help maintain marsh ecosystem structure,” Morton said. “More structure means more nursery habitat for fish. It means more nursery habitat for fiddler crabs. Increased filtration rate of water into the sediment because of crab burrows. The point is, parasites help to increase ecosystem resistance to drought stress.”

Joe Morton traipses through the salt marsh on a windy day. Courtesy: Joe Morton.

Morton was the first to demonstrate this relationship between parasites and marsh health in a behavioral experiment. It’s been a major focus of his research ever since.

“Parasites constitute more than half the life on the planet, but until very recently, parasites were somewhat ignored by ecologists,” Morton said.

Indeed, Morton’s former advisor once told him “never study anything smaller than your thumb.” According to Morton, this was a very widely-held view in ecology up until the last few decades.

“That was very much the idea at the time: these are small things; they probably mean a lot to individual organisms, but they’re may not be important to ecosystems. And now we know that’s just not the case,” Morton said. “Almost everywhere we look, parasites are there; they’re ubiquitous. And they have an important role to play.”

Though parasites are a hot topic in ecology nowadays, Morton, a self-declared “lifelong contrarian,” has a very distinct memory of a childhood moment foreshadowing his current research focus.

“I remember sitting in a barber shop and reading Popular Science magazine, which has an annual list of the ten worst jobs in science. I remember right at the top of the list was ‘parasitic worm biologist.’ And something in my head was just like ‘yeah, I’ll do that,’” Morton said.

Post by Maya Iskandarani

Lemur Research Gets a Gut Check

Baby Coquerel’s sifaka

Clinging to her mom, this baby Coquerel’s sifaka represents the only lemur species at the Duke Lemur Center known to fall prey to cryptosporidium, a microscopic parasite that causes diarrhea that can last for a week or more. The illness wipes out much of the animals’ gut microbiome, researchers report, but fecal transplants can help them recover. Photo by David Haring, Duke Lemur Center.

DURHAM, N.C. — “Stool sample collector” is not a glamorous way to introduce oneself at a party. But in the course of their research, gut microbiologists Erin McKenney and Lydia Greene have spent a lot of time waiting for animals to relieve themselves.

They estimate they have hundreds of vials of the stuff, from a dozen primate species including lemurs, baboons and gorillas, sitting in freezers on the Duke University campus.

The researchers aren’t interested in the poop per se, but in the trillions of bacteria inhabiting the gastrointestinal tract, where the bugs help break down food, produce vitamins and prevent infection.

A few years ago, McKenney and Greene started collecting stool samples at the Duke Lemur Center to see how the microbial makeup of lemurs’ guts varies from birth to weaning, and as their diets change over the seasons. And what happens when they get sick?

Illustration of Cryptosporidium, a widespread intestinal parasite that causes diarrhea in people, pets, livestock and wildlife worldwide. Courtesy of the U.S. Centers for Disease Control.

Illustration of Cryptosporidium, a widespread intestinal parasite that causes diarrhea in people, pets, livestock and wildlife worldwide. Courtesy of the U.S. Centers for Disease Control.

Between 2013 and 2016, ten of the lemurs they were studying contracted cryptosporidium, or “crypto” for short, a waterborne parasite that causes diarrhea in people, pets, livestock and wildlife worldwide.

All of the infected animals were Coquerel’s sifakas — the only lemur species out of roughly 20 at the Duke Lemur Center known to fall prey to the parasite — and most of them were under five years old when they fell ill.

Animals that tested positive were moved into separate holding areas away from other animals and visitors. Keepers wore protective suits, gloves, face masks and booties while working in the animals’ enclosures to prevent infection.

All of the animals eventually recovered. Along the way, six of the affected animals were treated with antibiotics, and three were also fed a slurry of saline and feces from a healthy relative.

McKenney and Greene collected stool samples before, during and after infection for up to two months. They used a technique called 16S ribosomal RNA sequencing to identify the types of bacteria in the samples based on their genes, and compared the results with those of 35 unaffected individuals.

In a healthy gut microbiome, “good” bacteria in the gut compete with “bad” microbes for space and nutrients, and secrete substances that inhibit their growth.

The guts of sick and recovering sifakas are host to a very different assortment of microbes than those of unaffected animals, the researchers found.

Not surprisingly, both crypto infection, and antibiotic treatment, wiped out much of the animals’ gut flora — particularly the bacterial groups Bifidobacterium, Akkermansia, Succinivibrio and Lachnospiraceae.

Even after the infections cleared, most animals took another several weeks to stabilize and return to normal levels of gut biodiversity, with younger animals taking longer to recover.

The only animals that made a full comeback within the study period were those that received a fecal transplant, suggesting that the treatment can help restore gut bacterial diversity and speed recovery.

The patterns of gut recolonization following crypto infection mirrored those seen from birth to weaning, said McKenney, now a postdoctoral researcher at North Carolina State University.

The researchers hope their findings will help control and prevent crypto outbreaks in captive primates. Because lemurs are more closely related to humans than lab mice are, the research could also help scientists understand how the gut microbiome protects humans from similar infections and facilitates recovery.

“Thanks to bioinformatics and advances in sequencing, the microbiome gives us a window into the health of these animals that we’ve never had before,” said Greene, a graduate student in ecology at Duke.

They published their findings June 15, 2017, in the journal Microbial Ecology in Health and Disease.

Duke evolutionary anthropology professors Christine Drea and Anne Yoder were senior authors on this study. This research was supported by the National Science Foundation (1455848) and the Duke Lemur Center Directors Fund.

CITATION:  “Down for the Count: Cryptosporidium Infection Depletes Gut Microbiota in Coquerel’s Sifakas,” Erin McKenney, Lydia Greene, Christine Drea and Anne Yoder. Microbial Ecology in Health and Disease, June 15, 2017. http://dx.doi.org/10.1080/16512235.2017.1335165

Post by Robin Smith, science writer, Office of News & Communications

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