Duke Research Blog

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

Category: Lemurs (Page 1 of 4)

Aging Gracefully, and Cheaply, in a Small Space

The old joke is, “We’ve cured cancer several times — in mice!”

But the trouble with our favorite lab animal is that they aren’t nearly as close to humans as we had hoped.

Researchers who are working on human longevity obviously need a model organism — they can’t keep their funding going for 100 years to see how a person dies. And other primates aren’t ideal, either; they’re also pretty long-lived and expensive to house, besides.

microcebus mouse lemurs

Mouse lemurs at a lab outside Paris eagerly lap up their calories. Sometimes it’s great being in the control group. (CNRS photo)

So what if you had a primate that was relatively short-lived, say 13 years tops, and quite small, say 100 grams, a bit bigger than a mouse? Behold the Mouse Lemur, Microcebus, the smallest member of the primate family.

In a pair of presentations Friday during the Duke Lemur Center’s 50th Anniversary scientific symposium, gerontologists Fabien Pifferi of the French national lab CNRS, and Steven Austad, chair of biology at the University of Alabama-Birmingham (UAB), made their arguments for how well “le microcèbe” might work in studying aging in humans.

Pifferi works at one of two mouse lemur breeding colonies in France, which is housed in an elegant old chateau in Brunoy, a suburb southeast of Paris. There, a 450-member breeding colony of grey mouse lemurs produces about 100 pups a year, and the scientists have devised many clever, non-invasive ways to test their physical and mental abilities as they age.

“It seems like their normal aging is very similar to humans,” Pifferi said. But about 20 percent of the tiny lemurs follow a different trajectory, marked by the formation of brain plaques, atrophy of the brain and cognitive declines. It’s not exactly Alzheimer’s disease, he said, but it may be a useful scientific model of human aging.

Aging, UAB’s Austad began, is already the number one health challenge on the planet and will remain so for the foreseeable future. We need a good research model to understand not just how to achieve longevity, but how to live healthy longer, he said.

Filbert, a grey mouse lemur, was born at the Duke Lemur Center in June 2013, weighing less than two cubes of sugar. He should still be around in 2023 at least.

Filbert, a grey mouse lemur, was born at the Duke Lemur Center in June 2013, weighing less than two cubes of sugar.

Citing some early studies on using calorie restriction and rapamycin to increase longevity, Austad said mouse lemurs may be “a mid-way model between mice and humans.”

The CNRS colony at Brunoy tried to replicate a study on calorie restriction and longevity that had yielded mixed results in other animals. The mouse lemurs in the experimental condition thrived.

“I saw this colony last year,” Lemur Center Director Anne Yoder said. “The one remaining control animal was old and feeble and sort of pathetic. The four calorie-restricted animals were bouncing around, they were glossy.” Though suffering age-related blindness at that point, they were very much alive and frisky, Pifferi added.

“I think the mouse lemur is a great intermediate to do these sorts of studies,”  Austad said.

But, as you may imagine, some members of the lemur community who have dedicated their lives to preserving rare and critically endangered lemurs might struggle with the idea of  breeding up mouse lemurs to use as lab animals, even if the tests are non-invasive. Nobody asked hostile questions, but the discussion is sure to continue.

Karl Leif BatesPost by Karl Leif Bates

How to Get a Lemur to Notice You

Duke evolutionary anthropology professor Brian Hare studies what goes on in the minds of animals.

Duke evolutionary anthropology professor Brian Hare studies what goes on in the minds of animals.

Duke professor Brian Hare remembers his first flopped experiment. While an undergraduate at Emory in the late 1990s, he spent a week at the Duke Lemur Center waving bananas at lemurs. He was trying to see if they, like other primates, possess an important social skill. If a lemur spots a piece of food, or a predator, can other lemurs follow his gaze to spot it too?

First he needed the lemurs to notice him. If he could get one lemur to look at him, he could figure out if other lemurs then turn around and look too. In similar experiments with monkeys and chimps, oranges had done the trick.

“But I couldn’t get their attention,” Hare said. “It failed miserably.”

Hare was among more than 200 people from 25 states and multiple countries who converged in Durham this week for the 50th anniversary celebration of the Duke Lemur Center, Sept. 21-23, 2016.

Humans look to subtle movements in faces and eyes for clues to what others are thinking, Hare told a crowd assembled at a two-day research symposium held in conjunction with the event.

If someone quickly glances down at your name tag, for example, you can guess just from that eye movement that they can’t recall your name.

We develop this skill as infants. Most kids start to follow the gaze of others by the age of two. A lack of interest in gaze-following is considered an early sign of autism.

Arizona State University graduate student Joel Bray got hooked on lemurs while working as an undergraduate research assistant in the Hare lab.

Arizona State University graduate student Joel Bray got hooked on lemurs while working as an undergraduate research assistant in the Hare lab.

“Gaze-following suggests that kids are starting to think about the thoughts of others,” Hare said. “And using where others look to try to understand what they want or what they know.”

In 1998 Hare and researchers Michael Tomasello and Josep Call published a study showing that chimpanzees and multiple species of monkeys are able to look where others are looking. But at the time not much was known about cognition in lemurs.

“When you study dogs you just say, ‘sit, stay,’ and they’re happy to play along,” Hare said. Working at the Duke Lemur Center, eventually his students discovered the secret to making these tree-dwelling animals feel at home: “Lemurs like to be off the ground,” Hare said. “We figured out that if we just let them solve problems on tables, they’re happy to participate.”

Studies have since shown that multiple lemur species are able to follow the gaze of other lemurs. “Lemurs have gone from ignored to adored in cognitive research,” Hare said.

 

Ring-tailed lemurs are among several species of lemurs known to follow the gaze of other lemurs. The ability to look where others are looking is considered a key step towards understanding what others see, know, or might do. Photo by David Haring, Duke Lemur Center.

Ring-tailed lemurs are among several lemur species known to follow the gaze of other lemurs. The ability to look where others are looking is considered a key step towards understanding what others see, know, or might do. Photo by David Haring, Duke Lemur Center.

Robin SmithPost by Robin A. Smith

Why Testing Lemur Color Vision is Harder Than it Looks

Elphaba the aye-aye is not an early riser. A nocturnal primate with oversized ears, bulging eyes and long, bony fingers, she looks like the bushy-tailed love child of a bat and an opossum.

She would much rather sleep in than participate in Duke alum Joe Sullivan’s early morning vision tests.

“I can’t blame her,” said Sullivan, who graduated from Duke in 2015.

Elphaba is one of 14 aye-ayes at the Duke Lemur Center in Durham, North Carolina, where researchers like Sullivan have been trying to figure out if these rare lemurs can tell certain colors apart, particularly at night when aye-ayes are most active. But as their experiments show, testing an aye-aye’s eyesight is easier said than done.

Elphaba the aye-aye takes a vision test at the Duke Lemur Center in Durham, North Carolina. She’s getting encouragement from student researcher Joe Sullivan and technician Jennifer Templeton. Photo by David Haring.

Elphaba the aye-aye takes a vision test at the Duke Lemur Center in Durham, North Carolina. She’s getting encouragement from student researcher Joe Sullivan and technician Jennifer Templeton. Photo by David Haring.

Aye-ayes don’t see colors as well as humans do. While we have genes for three types of color-sensing proteins in our eyes, aye-ayes and most other mammals have two, one tuned to blue-violet light and another that responds to green.

In all animals, the eyes’ color-detecting machinery depends on medium to bright light. In a version of “use it or lose it,” the genes responsible for color vision in some nocturnal species have decayed over time, such that they see the world in black and white.

But in aye-ayes, research shows, the genes for seeing colors remain intact, and scientists at Duke and elsewhere are trying to understand why.

One possibility is the aye-aye’s color vision genes are mere leftovers, relics passed down from daylight-loving ancestors and no longer useful to aye-ayes today.

Or, the genes may have been preserved because color vision gives aye-ayes an edge. Wild aye-ayes live by eating fruit, nuts, nectar and grubs in the rainforests of Madagascar. Wouldn’t an animal that could distinguish the blue fruits of a favorite snack like the Traveler’s palm from the green of the surrounding foliage have an advantage?

Understanding what aye-ayes can see is no easy feat. One of the most common tests for colorblindness, the Ishihara, requires the subject to recognize and identify numbers hidden within a patch of colored dots of different sizes and brightness.

Aye-ayes don’t read numbers, so Sullivan tests for color vision using food and colored cards.

The first tests were simple enough. In a dimly lit enclosure, a trainer held up two cards: a white card and a black one.

Each time the aye-ayes chose the white card over the black one by reaching out and touching it with their hand, the animal got a peanut.

Even animals with no color vision can tell white from black, so Sullivan was confident they’d ace the test. But aye-ayes aren’t programmed to please. Just getting them to sit still, instead of running around their enclosure, was a challenge.

One aye-aye, 29-year-old Ozma who was born in the wild in Madagascar, never got the hang of even the most basic task, a warmup involving a single white card.

“That’s when I realized that aye-ayes don’t always play by my rules,” said Sullivan, who started working at the Duke Lemur Center as an undergraduate research intern in 2012.

After four months and 200 trials, all five of the aye-ayes in Sullivan’s study started picking the white card more often than not, with Merlin, Elphaba and Grendel passing the test at least 70 percent of the time.

Norman and Ardrey tended to reach for the card on their left, no matter what the color.

Sullivan isn’t giving up. Still working at the Duke Lemur Center post-graduation, now he’s trying to see if aye-ayes can distinguish a purplish card from a green one, in brighter light more similar to dawn or dusk.

So far, Merlin and Grendel are getting it right just over half the time, leaving Sullivan still unsure if the aye-ayes are choosing the cards by their colors or by some other cue.

“I came in thinking that the aye-ayes were going to play nice and do everything I wanted. That was so wrong,” Sullivan said. “Still, they’ve been very good sports.”

How do you give a lemur a vision test? Photo by David Haring, Duke Lemur Center.

How do you give a lemur a vision test? Photo by David Haring, Duke Lemur Center.

Post by Robin A. Smith Robin Smith

2016 Going on 2030: The Madagascar Winter Forum

For two and a half cold days in January, 91 Duke students and I had the opportunity to immerse ourselves in Malagasy culture—without the warmth of its sub-tropical climate.

We were participants in Duke’s 2016 Winter Forum:  ‘Madagascar 2030: Sustainable Development Innovation Challenge’. The goal was to design solutions to help the country meet its Sustainable Development goals by the year 2030.

Winning team Mamboly

Winning team Mamboly

After being divided into teams of four or five, we were all given a task to solve through the creation of a social venture. The forum was steeped in the spirit of entrepreneurship, with lessons and guidance being given by Duke faculty members, notably Deb Johnson and Matthew Nash from the I&E Center, and social entrepreneurs in Madagascar.

The forum began with a trip to the Duke Lemur Center, followed by lectures about Madagascar at Fuqua School of Business from faculty and guest speakers.

After spending a day learning about the island nation’s wonderful history and biodiversity, as well as its challenges, we were ready to work on our pitch. Each team was given about 36 hours to help solve one of the country’s most pressing problems: poverty, food insecurity, environment, and health.

Team YOgLO presenting their pitch for locust harvesting as fare for food-insecure regions.

Team YOgLO presenting their pitch for locust harvesting as fare for food-insecure regions.

So my team and I had a day and a half to help solve hunger in Madagascar.

Some hours and many headaches later, we created a model of a scalable non-profit social venture using innovative aquaponic farming technology. And, after overcoming a disaster featuring spilled orange juice, a laptop, and unsaved changes, we were ready to pitch.

I was blown away by the wide range of creative solutions that were offered by my peers. From an agricultural research framework, to a locust-farming business, each team made an effective argument for how they could help mitigate food insecurity in Madagascar.

Team Mamboly, won with a pitch for a scholarship program in sustainable agricultur. Team Medex, was the people’s choice for their proposal to use drones to deliver much-needed medicines to isolated communities.

One of my favorite takeaways from the forum.

One of my favorite takeaways from the forum.

The forum taught me the importance of research in entrepreneurship, social and otherwise (and I’m not just saying that because I happen to write for the Duke Research Blog). Most of the time we spent on our pitch was gathering information about food insecurity in southwest Madagascar and how our idea can be designed with the local area in mind.

I also learned that well-meaning ventures often fail because the do-gooder didn’t use human-centered design in their product or service, or didn’t do enough research into the current competition, the culture of the area, or how they might scale their product.

My teammate Elena Lie “learned to never leave drinks close to my laptop, to always save presentations on the cloud, and to always keep calm when the unexpected things happen.” And William Ding “learned a lot about Madagascar and the issues it faces from experts on the field, both in-person and over Skype.”

Until next year.

2015-09-03 17.36.37 Post by Devin Nieusma, Duke 2019

A Gutsy Approach to Lemur Science

By Sheena Faherty, biology Ph.D. candidate

Can the microorganisms living in a baby lemur’s gut help it grow up to be a vegetarian or an omnivore?

A new study appearing May 13 in Plos One shows that baby lemurs’ gut bacteria have different, diet-dependent strategies for reaching adult mixtures of microbes.  This, in turn, might contribute to why some lemurs are strictly leaf-eaters, while some nosh on just about everything.

lemur eating flowers

A black and white ruffed lemur (Varecia variegata) finds North Carolina’s vegetation as delicious as it is beautiful. (Duke Lemur Center, David Haring)

Erin McKenney, lead author on the study and a Ph.D. candidate in the Biology department, is looking at the patterns of how the bacteria colonize the gut of their lemur host and why this is essential for helping the adult lemurs navigate their environment — and their diets.

“This study is important because all mammals are born with basically sterile guts,” McKenney said. “But by the time we’re adult mammals, there are 20 trillion bacteria living in the gut. (The bugs are an) adaptive super organ that has co-evolved with the host and dictated the host’s evolution. We want to know more about how that happens.”

This “microbiome” of the gut is a jack-of-all-trades, performing jobs like protecting the host’s body from pathogens and helping it digest food. When the gut’s microbes digest foods that are high in fiber — like plant matter — some of the digestion by-products are absorbed by the intestine, which provides nutrition for the body. Humans get up to 10 percent of our daily nutritional requirements from fiber breakdown by bacteria.

Erin McKenney

Erin McKenney scooping lemur poop for SCIENCE!

“Mammals don’t secrete the enzymes that are necessary, so no mammal can digest fiber on its own,” McKenney said. “These microbes are performing an incredibly important life process for us.”

At the Duke Lemur Center, McKenney collected fecal samples from three different species of lemur that evolved to eat different foods—a strict leaf-eater, and two omnivores. Using DNA sequencing, she determined the communities of bacteria that are living in their guts at different life stages from birth to adulthood.

Watching microbiomes through time may enable her to answer the question of how the microbiome of each species becomes teeming with 20 trillion bacteria, and if the patterns differ based on diet.

lemur eating pokeweed

Vegetarian lemurs can eat a surprising variety of stuff we’d find nasty, like pokeweed and even poison ivy. (Duke Lemur Center, David Haring)

The results suggest that all species of baby lemurs, when they are born and nursing from their mothers have similar microbiome profiles that are much less complex than adult profiles. But leaf-eaters that eat the most fiber show adult microbiome profiles as soon as solid foods are introduced, which is in contrast to the other two species that take longer to reach adult microbiome profiles. Additionally, leaf-eaters have more complex microbial communities, which allows them to digest fiber-rich foods.

“So when you start to think about the really big picture, beyond everything the gut microbes do for the hosts they live inside of, we find the microbes have done an incredible service to mammalian speciation. The only way that we have leaf-eaters is because of these gut microbes,” McKenney said.

Underwater Cave is a Lemur Treasure Trove

Guest post by Gregg Gunnell, Division of Fossil Primates

(A version of this column originally appeared in the Duke Lemur Center newsletter)

Lagerstätten – that word sends a shiver of excitement up and down the spine of every paleontologist.

In German the word means ‘storage place’ or ‘deposits,’ but in paleontology it has come to mean a very rich fossil deposit that contains complete or nearly complete specimens that sample a wide variety of the creatures living at a certain time.

cave diver

A cave diver and subfossil specimen in Aven Cave, Madagascar. The plastic triangle is a scale for photographs of the specimen in situ. (Image by Phillip Lehman and Pietro Donaggio-Bitner)

As you might imagine, Lagerstätten are quite rare. Some of the more famous examples are the Burgess Shale in Canada which preserves soft body outlines of ancient (530 million years ago) Cambrian animals; the Jurassic (150 Ma) Solenhofen limestones in Germany where the famous Archaeopteryx is found; and the middle Eocene (45 Ma) Messel Oil Shale in Germany which preserves whole skeletons of many birds, mammals, reptiles, amphibians, and insects.

I have had the good fortune to be in on the discovery of two Lagerstätten in addition to studying specimens from two others. The first one our team discovered was in 1998 in Pakistan, a place we named Gandhera Quarry. It preserves a remarkable wealth of early Eocene (52 Ma) mammals from Balochistan Province – an assemblage that has yet to completely studied.

But the latest and most exciting to me as Director of the Division of Fossil Primates in the Duke Lemur Center happened late last year in Southwest Madagascar.

The discovery of subfossils at a place called Aven Cave was known to local people, but not reported to the scientific community until an Australian cave diver named Ryan Dart saw it. The cave and its specimens are underwater. The specimens are called subfossils, because they aren’t old enough to have completed (or in some cases even started) the fossilization process.

A joint team from the University of Antananarivo, Duke University, University of Massachusetts, Brooklyn College and Midwestern University led an expedition to this cave site in October 2014. Cave divers Phillip Lehman  and the Dominican Republic Speleological Society dive team helped us find a treasure trove of subfossils.

lemur skulls

Lemur skulls, as they were found in the cave, with a scale marker. (Photo courtesy of Phillip Lehman and Pietro Donaggio-Bitner)

Only a preliminary survey has been made of Aven Cave to date, but it is clear already that it is one of the richest subfossil sites ever discovered in Madagascar. The initial list of animal specimens found in the cave includes three genera of extinct lemurs (Pachylemur, Mesopropithecus, and Megaladapis) as well as one species of a living form, Lemur catta, the familiar ring-tailed lemur. In addition to the primates there are abundant specimens of bats (Hipposideros), carnivores (the extinct fossa Cryptoprocta spelea as well as a smaller, still living species, C. ferox), two species of rodents, an extinct pygmy hippopotamus, crocodiles, turtles, and two bird species including the extinct elephant bird Mullerornis.

Not only is there a diverse assembly of species coming from Aven Cave, the sample is also abundant, with many species represented by multiple specimens. Many specimens appear to be complete or nearly complete skeletons.

The expedition was aided by Mr. Lovasoa Dresy, the director of Tsimanampetsotsa National Park, and was generously supported by the National Science Foundation and the National Geographic Society.

We anticipate many more and surprising discoveries in the future. Stay tuned for updates from Aven Cave!

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