Duke Research Blog

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

Category: Animals (Page 2 of 18)

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

Lemur Poop Could Pinpoint Poaching Hotspots

DNA detective work aims to map the illegal pet lemur trade in Madagascar

Local business owners in Madagascar sometimes use ring-tailed lemurs to sell photo ops to tourists. Tourists visiting the country can easily support the illegal pet lemur trade unknowingly by paying to touch or have their picture taken with a lemur. Photo courtesy of the Pet Lemur Survey project (www.petlemur.com)

Businesses in Madagascar sometimes use ring-tailed lemurs to sell photo ops to tourists. Tourists visiting the country can easily support the illegal pet lemur trade unknowingly by paying to touch or have their picture taken with a lemur. Photo courtesy of the Pet Lemur Survey project (www.petlemur.com)

When Tara Clarke went to Madagascar this summer, she packed what you might expect for a trip to the tropics: sunscreen, bug spray. But when she returned seven weeks later, her carry-on luggage contained an unusual item: ten pounds of lemur droppings.

“That’s a lot of poop,” Clarke said.

A visiting assistant professor of evolutionary anthropology at Duke, Clarke and colleagues are analyzing DNA from lemur feces to pinpoint poaching hotspots in Madagascar’s pet lemur trade.

Pet lemurs are illegal in Madagascar, the only place on Earth where lemurs — the world’s most endangered primates — live in the wild.

More than 28,000 lemurs were taken from the wild and kept as pets on the island between 2010 and 2013 alone, surveys suggest.

Many pet lemurs are captured as babies, separated from their mothers and sold for less than two dollars apiece to hotels and restaurants to lure tourists, who pay to touch the animals and have their photo taken with them.

Anyone caught removing lemurs from the forest, selling them, or keeping them without a government permit can be fined and sentenced to up to two years in jail. But the laws are difficult to enforce, especially in remote villages, where rural poverty is common and law enforcement personnel may be few.

Clarke (left) and LaFleur (right) co-direct a nonprofit called Lemur Love that aims to protect ring-tailed lemurs and their habitat in southern Madagascar. Follow them at https://www.facebook.com/lemurloveinc/.

Primatologists Tara Clarke (left) and Marni LaFleur (right) co-direct a nonprofit called Lemur Love that aims to protect ring-tailed lemurs and their habitat in southern Madagascar. Follow them at https://www.facebook.com/lemurloveinc/.

In 2011, Malagasy officials began confiscating pet ring-tailed lemurs, the most popular species in the pet lemur trade, and handing them over to a non-governmental organization in southwestern Madagascar called Renalia, home of the Lemur Rescue Center.

About two dozen ring-tailed lemurs are currently being rehabilitated there in the hopes that many of them will one day be reintroduced to the wild.

But rounding up all the lemurs held illegally in private hands and taking them in would be nearly impossible, Clarke said. “There just isn’t a facility big enough, or the funding or the manpower.”

If we can figure out where the animals are being taken from the forest, Clarke said, we might be able to target those poaching hotspots and try to prevent them from becoming pets in the first place through education and outreach initiatives.

Ring-tailed lemurs live in southern Madagascar, an island nation off the coast of Africa. Map by Alex Dunkel.

Ring-tailed lemurs live in southern Madagascar, an island nation off the coast of Africa. Map by Alex Dunkel.

This summer, Clarke and biological anthropologist Marni LaFleur of the University of California, San Diego began collecting baseline samples of ring-tailed lemur poop from national parks and protected areas around southern and southwestern Madagascar, where ring-tailed lemurs live in the wild. They also collected samples from 19 ex-pets at the Lemur Rescue Center.

The samples are being shipped to the Primate Molecular Ecology Laboratory at Hunter College in New York for analysis.

There, with help from lab director Andrea Baden, the team will use DNA extracted from the wild samples to build a map of variation in ring-tailed lemur genes across their range.

By analyzing the DNA of the ex-pets housed at the Lemur Rescue Center and comparing it with their map, the researchers hope to pinpoint or rule out where the animals were first taken from the wild.

In addition to collecting feces, Clarke and LaFleur also worked with local guides to count ring-tailed lemurs in their natural habitat and estimate how many are left.

The pet trade isn’t the only threat to lemur survival. Over the past 40 years, logging, slash-and-burn agriculture, and charcoal production have reduced forest cover in southwestern Madagascar by nearly half.

“Their habitat is disappearing,” said Clarke, who has conducted field research in Madagascar since 2004.

Their 2016 census suggests that fewer than 2000 ring-tailed lemurs remain in the wild — a significant decline compared with the last census in 2000, when ring-tailed lemurs were estimated based on satellite images to number more than 750,000.

In every town the researchers visited they also passed out hundreds of posters about the illegal pet lemur trade as part of a nationwide education campaign called “Madagascar’s Treasure: Keeping Lemurs Wild,” which aims to raise interest in protecting the few wild populations that remain.

Lemur protection programs such as theirs can also benefit other threatened wildlife that share the lemurs’ forest habitat, such as the giant-striped mongoose and the radiated tortoise.

Keeping lemurs as pets isn’t unique to Madagascar. “There are thousands of lemurs in private hands in the U.S. too,” said Andrea Katz, curator at the Duke Lemur Center. Every year, the Duke Lemur Center gets phone calls from people in the U.S. looking for answers to questions about their pet lemurs’ health or behavioral problems.

“In some states it’s legal to have a pet lemur,” Clarke said. “You can find them online. You can find them in pet stores. A lot of times what happens is they reach sexual maturity and they get aggressive, and that’s when people call a zoo or a sanctuary.”

“Because you can see ring-tailed lemurs in zoos and movies people don’t think that they need our help. They don’t believe that they’re endangered. We’re trying to change that view,” Clarke said.

This research was supported by grants from the Margot Marsh Biodiversity Foundation and Conservation International’s Primate Action Fund.

These crowned lemurs are among more than 30 of the roughly 100 known lemur species in Madagascar that are affected by the pet lemur trade. Explore interactive data visualizations of pet lemur sightings in Madagascar by species, date and location at http://www.petlemur.com/data-visualization.html. Photo courtesy of the Pet Lemur Survey project (www.petlemur.com)

These crowned lemurs are among more than 30 of the roughly 100 known lemur species in Madagascar that are affected by the pet lemur trade. Explore interactive data visualizations of pet lemur sightings in Madagascar by species, date and location at http://www.petlemur.com/data-visualization.html. Photo courtesy of the Pet Lemur Survey project (www.petlemur.com)

Robin Smith

 

Post by Robin A. Smith

In Sync

DiTalia2The dividing red spots in this time-lapse video belong to a busily developing fruit fly embryo. A fruit fly egg can divide into some 6,000 cells in just two hours —  faster division than cancer tumors. To watch them action, graduate student Victoria Deneke and assistant professor Stefano Di Talia tagged the nuclei with a protein that glows red. In a recent study, they show that the cells coordinate their rapid divisions via waves of protein activity that spread across the embryo. The waves help ensure that all the cells enter the next stage of development at the same time.

Duke graduate student Victoria Deneke has been awarded an international student research fellowship from the Howard Hughes Medical Institute.

Duke graduate student Victoria Deneke has been awarded an international student research fellowship from the Howard Hughes Medical Institute.

Starting September 2016, Deneke became one of 20 graduate students from 14 countries selected for an international student research fellowship from the Howard Hughes Medical Institute.

Three-year fellowship is designed to support outstanding international graduate students studying in the United States who are ineligible for fellowships or training grants through U.S. federal agencies.

Born in El Salvador, Deneke earned her undergraduate degree in chemical engineering from the University of Notre Dame before joining Stefano Di Talia’s at Duke in 2013.

Fellows must be nominated by their institution; participation is by invitation only. Deneke is only the second student at Duke to receive an HHMI International Student Research Fellowship since the program was established in 2011.

CITATION:  “Waves of Cdk1 Activity in S Phase Synchronize the Cell Cycle in Drosophila Embryos,” Victoria Deneke, Anna Melbinger, Massimo Vergassola and Stefano Di Talia. Developmental Cell, August 2016. http://dx.doi.org/10.1016/j.devcel.2016.07.023

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

3-D Movies of Life at Nanoscale Named Best Science Paper of the Year

If you’ve ever wanted to watch a killer T cell in action, or see human cancer make new cells up-close, now is your chance.

A collection of 3-D movies captured by Duke biology professor Dan Kiehart and colleagues has won the 2015 Newcomb Cleveland Prize for most outstanding paper in the journal Science.

The paper uses a new imaging technique called lattice light-sheet microscopy to make super high-resolution three-dimensional movies of living things ranging from single cells to developing worm and fly embryos.

Cutting-edge microscopes available on many campuses today allow researchers to take one or two images a second. But the lattice light-sheet microscope, co-developed by 2014 Nobel Prize winner Eric Betzig, lets researchers take more than 50 images a second, and in the specimen’s natural state, without smooshing it under a cover slip.

You can watch slender antennae called filopodia extend from the surface of a human cancer cell, or tiny rods called microtubules, several thousand times finer than a human hair, growing and shrinking inside a slide mold.

Daniel Kiehart and former Duke postdoctoral fellow Serdar Tulu made a video of the back side of a fruit fly embryo during a crucial step in its development into a larva.

Chosen from among nominations submitted by readers of Science, the paper has been viewed more than 20,000 times since it was first published on October 24, 2014.

The award was announced on February 12, 2016, at an award ceremony held during the annual meeting of the American Association for the Advancement of Science (AAAS) in Washington, D.C.

Winners received a commemorative plaque and $25,000, to be shared among the paper’s lead authors Eric Betzig, Bi-Chang Chen, Wesley Legant and Kai Wang of Janelia Farm Research Campus.

Read more: “Lattice light-sheet microscopy: Imaging molecules to embryos at high spatiotemporal resolution,” Chen, B.-C., et al. Science, October 2014. DOI:10.1126/science.1257998

 

Post by Robin A. Smith Robin Smith

 

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