Inside the Monkey Brain

By Ashley Mooney

Both in the lab and on a tropical island, primate behaviors can shed light on social-decision making.

To fully understand the biology of social-decision making, Michael Platt, director of the Duke Institute for Brain Science, conducts lab work at Duke and field research an island off the coast of Puerto Rico called Cayo Santiago. His research focuses on understanding both the physiological and social aspects of decision making.

“Our brains are exquisitely tuned to making [social] decisions and acquiring the information to inform them,” Platt said. “When these processes go awry, as occurs in disorders like autism, schizophrenia or anxiety disorders, the consequences can be devastating.”

Courtesy of Lauren Brent.

Courtesy of Lauren Brent.

Platt’s group uses rhesus macaques as model animals because of their strong behavioral, physiological and neurobiological similarity to humans. But understanding how the monkey brain—and thus the human brain—works requires both laboratory-based biological information and social studies in a natural environment.

Researchers can combine the knowledge they gain from lab and field studies to create a holistic picture of the biological basis of behavior, said Lauren Brent, associate research fellow at the University of Exeter who did her post-doc with Platt at Duke.

Lab studies are best suited for quantitative, repeatable studies in which variables can be precisely controlled, Platt said. On the other hand, field studies emphasize external validity and an animal’s response in its natural conditions, but are not suitable for determining precise measurements of internal processes.

In the lab, Platt’s group studies the neural mechanisms that mediate prosocial and antisocial decisions, Platt said. They can also study the ways in which humans can enhance prosocial decisions using pharmacological or behavioral interventions.

On Cayo, the researchers are exploring the genetic factors that shape individual differences in social behavior and decision-making in free-living monkeys. They use observations, behavioral experiments and blood and fecal samples to study the monkeys non-invasively.

“The project on Cayo and the work that goes on the lab are complementary in the best sense because we can do things on Cayo that we can’t do in the lab,” Brent said. “For example, we have hundreds of monkeys, of known pedigree, interacting with each other in a purely spontaneous and naturalistic fashion. You can’t get that in a lab.”

Lauren Brent conducting behavioral observations on Cayo. Courtesy of Lauren Brent.

Lauren Brent conducting behavioral observations on Cayo. Courtesy of Lauren Brent.

Although working with free-ranging monkeys can produce more naturalistic results, Brent noted that there are drawbacks to working in the field.

“Working with monkeys in the field is painstaking,” Brent said. “You need to be physically fit, but moreover it is a mentally demanding thing to do because you need to pay close attention to everything that is going on in the group at all times so that the data are as finely detailed and accurate as possible.”

Brent found that a monkey’s position in its social network is heritable and can impact the survival of its infants. She determined a monkey’s social connections using grooming and spatial proximity, or how long one monkey spends sitting next to other monkeys.

“Regardless of how big your family is, monkeys who are better connected in the grooming network have greater reproductive success,” Brent said. “Together, these results suggest that social interactions have adaptive benefits and are something on which selection has acted.”

Student Melissa Chieffe: Budding Conservation Biologist

By Nonie Arora

Melissa Chieffe, a Junior Biology major, grew up outside Cleveland, Ohio and arrived at Duke enthusiastic about following a pre-vet path. As a freshman, she began volunteering at the Duke Lemur Center as a technician assistant. Through her work, she became interested in conservation in Madagascar and decided to apply to OTS – South Africa.

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A map of Chieffe’s travels. Credit: Melissa Chieffe using Google Maps. (click on map to learn more)

Through OTS – South Africa, she had the opportunity to travel all around the region and work on three group research projects, focusing mainly on ecology and conservation in the Kruger National Park.

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Melissa Chieffe. Credit: Liza Morse

In the first, she collected data for the Kruger long-term research initiative on vegetation changes caused by elephants. Specifically, she honed in on damage done to AppleLeaf trees (Philenoptera violacea) and assessed damage done to 175 trees of that species in the Kruger National Park. The study looked at bark stripping and toppling of trees caused by elephants. Bark stripping happens when elephants rub their tusks on trees; if the elephants remove too much mark the trees are more likely to die, according to Chieffe.

From their study, her team observed a bottleneck in tree size: the elephants generally knocked trees over before they could reach their mature height. Their preliminary data indicated that higher elephant population densities - combined with frequent burnings in the savannah - made it harder for trees to reach the mature stage.

In their independent research project, Chieffe and her group had the opportunity to work with a population of captive elephants. The elephant population in the Kruger National Park has been growing exponentially since the termination of culling operations in the 1990s, which is causing problems for the vegetation and the nearby rural farms, according to Chieffe. The elephants are known to destroy crops, fences, and storage facilities. The students looked into using bee hives as a deterrent for elephants. Chieffe explained that beehive fences could have great applications for conservation through community based conservation initiatives.

They used the sound of bees buzzing & the scent of honey to stand in as surrogates for bee hives. Wild elephants exhibited defensive retreating behaviors when exposed to the bee sounds and scents.

Camera traps

Chieffe learns to use camera traps (above) and photo of lion cubs taken by a camera trap (below). Credit: Melissa Chieffe

Chieffe learned to use camera traps (above) and made a photo of lion cubs with a camera trap (below). Credit: Melissa Chieffe

In her faculty field project, Chieffe worked with Professor Jeremy Bolton, an expert in the field, and Professor Tali Hoffman from the University of Cape Town to study camera traps. Chieffe’s team set up four camera traps at five different watering holes, which are known to act as ”nodes of activity” for wildlife, to compare efficacy of two types of camera traps: field scan and motion sensor. Camera traps can be used to to record endangered animals and to survey biodiversity of an area.

“I enjoyed living in nature reserves, the national park, constantly surrounded by amazing researchers and scientists and others who are involved in conservation management. It was inspiring to live near them. We also got to present our findings to park management, which was awesome,” Chieffe said.

The program has helped her further her ambitions in conservation biology.

“I thought it was a dream [to become a conservation biologist]. But meeting people who are actually doing what I now want to do has made it seem realistic,” Chieffe said. She hopes to continue with  her research in South Africa on elephants and vegetation this summer.

Volunteer Network Shouldn’t be Stranded and Dying

measurements on a dead dolphin (Photo: Susan Farley)

During a lab necroscopy, Dr. Vicky Thayer (left) takes measurements on a dead dolphin as student Samantha Emmert records the data. (Photo: Susan Farley)

Guest Post by Samantha Emmert, a Biology and Evolutionary Anthropology undergraduate at the Duke Marine Lab

The rolling sand dunes and gentle waves of Emerald Isle are so picturesque that I almost forget why I am there: to conduct a necropsy (autopsy on a non-human) on a stranded bottlenose dolphin. Vicky and I have been searching for the animal for about an hour now, driving up and down the beach. Suddenly, I catch a whiff of rotting flesh. Great! We’ve found it!

During my year at the Duke Marine Lab, I am volunteering for the North Carolina Central Coast Marine Mammal Stranding Network. This is no normal year for the network and others like it on the east coast. In the last seven months, 1081 bottlenose dolphins have stranded between New York and Florida. This magnitude of strandings is almost ten times the average, and has therefore been declared an “Unusual Mortality Event” by the National Oceanic and Atmospheric Administration. The cause of these deaths? Morbillivirus, the disease family that includes human measles.

For Independent Study credit I have been collecting data about the stranded dolphins and comparing them to data from 1987-88, the last and only other time there was a morbillivirus Unusual Mortality Event affecting bottlenose dolphins. I have found that this event is following the patterns of 87-88 almost exactly, particularly in terms of the sex and age of dolphins, and when and where they are stranding. These patterns may be a strong indicator for the path of future events.

Dolphin strandings in the area are reported to Dr. Vicky Thayer, the network’s coordinator and a Duke alumna (M.E.M. 1982, Ph.D. 2008). Vicky then calls her volunteers, such as myself, to assist in a response. Today, the dolphin was freshly dead and in good shape for a full necropsy. As Vicky assesses the dolphin for signs of human interaction, I sharpen knives and prepare vials to hold tissue samples. I put on my boots, coveralls, and gloves (things are about to get bloody). Together, Vicky and I peel back blubber and slice through flesh in order to reach the organs that are most impacted by morbillivirus: the lungs, associated lymph nodes, and spinal cord.

This Unusual Mortality Event is not the only problem that the network has been facing this year. Their federal funding for the upcoming year was not renewed.

Many marine mammal rescue networks, such as this one, rely on the John H. Prescott Marine Mammal Rescue Assistance Grant Program, established under amendments to the Marine Mammal Protection Act. However, the number of networks that received awards declined from 39 in 2012 to 12 in 2013. Only two of those 2013 recipients are in the geographic range affected by the dolphin mortality, compared to 13 in 2012. Particularly during a time when they are busiest, the loss of funding has been a huge stress for the networks.

Samantha climbs out of a freshly dug beach grave for yet another dead dolphin.

Samantha and Vicky got to this dolphin just before town workers buried it on the beach and were able to get their tissue samples.

Throughout the necropsy, several fishermen stop by to ask what we are doing. They’ve been fishing on this beach for decades and are aware of the increased occurrence of strandings in the area. It is vital to us that they understand the importance of reporting stranded animals.

“As top predators in coastal waters, these animals are sentinels of ocean health. When they wash ashore in unprecedented numbers, we should direct our attention and funding to learn as much as we can about the cause,” Vicky explains while taking apart the carcass.

We reach the lungs and, sure enough, they are discolored and covered in lesions. We cut chunks from the lung, lung lymph node, and spinal cord and I squish them into small vials. They will be sent to a lab in California to be tested for morbillivirus. The data we record and samples we take will be useful for the many researchers interested in this event across the nation.

It is hard to say what will become of the NC Central Coast Marine Mammal Stranding Network and others like it. Without renewed funding in the 2014 year, Vicky will be unable to continue the network and stranding response will stop in this area. Valuable data for long-term research on stranded animals will be lost. Live-stranded animals will die on beaches unaided. In order to protect and conserve these beloved species, the Prescott Grant and other funding sources must be made more readily available.

Turtle Sexes are Temperamental

Guest post by Lauren Burianek, doctoral candidate in cell biology

A pair of one-week-old red-eared sliders. The one on the right looks a little cranky. (Tadpole667 via Wikimedia Commons)

A pair of one-week-old red-eared sliders. (Tadpole667 via Wikimedia Commons)

When humans are developing, they snuggle in a warm environment and everything is provided by the mother. The sex of this developing fetus is determined by its individual genetic makeup, particularly the presence of the X and Y chromosomes.

But laid as an egg in a hole on a riverbank, the sex of a red-eared slider turtle is determined by the temperature at which the egg is developed.

At temperatures above 84.6°F, the hatchling will develop into a female, but at lower temperatures, the hatchling will develop into a male. However, at exactly this temperature (called the pivotal temperature), half of the hatchlings will be female and the other half will be male.

Scientists have no idea how temperature affects the sex of the turtle hatchlings, but researchers in Blanche Capel’s lab at Duke are trying to find out.

Red-eared sliders breed in late spring near riverbanks in Louisiana. Researchers carefully collect the eggs from common nesting spots and send the eggs to Duke University. In the Capel lab, graduate student Mike Czerwinski then buries the eggs in sand and places them into incubators at different temperatures. From here, he will analyze the gonads, or sexual organs, of the turtle embryos incubated at the different temperatures.

Grad student Mike Czerwinski in the Capel lab.

Grad student Mike Czerwinski in the Capel lab.

Czerwinski and his colleague Lindsey Mork discovered that when the turtle embryos were incubated at the pivotal temperature, both gonads developed into either testes or ovaries, but rarely did the two gonads develop into one of each.

Then, they incubated the turtle embryos at the pivotal temperature, dissected the two gonads and incubated each of them at different temperatures, either male-developing or female-developing temperatures. Surprisingly, the separated pairs of gonads still attempted to develop into the same sex regardless of the incubation temperature.

Tyrannosaurus Rex may have had temperature-sensitive eggs too. (tlcoles via Wikimedia Commons)

Tyrannosaurus Rex may have had temperature-sensitive eggs too. (tlcoles via Wikimedia Commons)

For example, if one of the gonads incubated in the male-developing temperature readily turned into a testis, the other gonad of the embryo, even though it was incubated in female-developing temperatures, is slower to develop into an ovary than expected, suggesting that it was genetically predisposed to be a testis.

“The results are exciting because it shows that there is a global mechanism beyond temperature dependence that allows for sex determination,” said Czerwinski. “All we’ve known up until now is that temperature is important for these turtles, but now we know that there also has to be a genetic component. Sex determination is so varied between different species, but this might give us insight into how we’re all connected.”

Climate change could definitely be a factor in the survival of these turtles and other temperature-dependent species. After all, the dinosaurs are thought to have exhibited temperature-dependent sex determination.

With increasing temperatures, a higher proportion of hatchlings will be females. Snapping turtles, however, have found a way to combat this – by moving north. The same species of snapping turtles exhibit different pivotal temperatures at different latitudes.

Evolution truly is an amazing process.

Stem Cells Might Tell Us Why Chimps Can’t Blush

Guest post by graduate student Sheena Faherty

Clint the Chimpanzee

Clint the chimpanzee was the first member of Pan troglodytes to have his DNA sequenced. Thanks, dude. (Photo from Yerkes National Primate Research Center.)

Clint the chimpanzee is at it again.

The first chimpanzee to have his genome sequenced in 2005 has now made another mammoth contribution to science, this time with his stem cells.

Using these stem cells, Greg Wray, professor in Biology and Evolutionary Anthropology and his former Ph.D. student, Lisa Pfefferle, recently published an article detailing an exciting new genomic tool that provides a sneak peek into how fundamental differences at the genetic level can lead to drastic differences we see at the outward level between humans and chimpanzees.

This fascinating new approach is based on a specific type of adult stem cells, known as adipose derived stromal cells (ASC). The beauty of ASCs is that they can be manipulated to morph into different types of mature cells. These cells can then be poked, prodded, and scrutinized under the microscope as a means to delve into fundamental questions regarding the molecular basis of human origins.

This work adds a powerful new tool to the field of comparative primate genomics. The goal is to discover the source of traits that set humans apart from other animals, like spoken language or the sole ability to blush when embarrassed.

By comparing humans with our closest genetic cousin, the chimpanzee, we can begin to uncover qualities unique to both humans and chimpanzees. These discoveries might lie within the genome.

Lisa Pfefferle developed a new technique, based on Clint's stem cells, to get at human-chimp differences. (Photo courtesy of Lisa Pfefferle.)

Lisa Pfefferle developed a new technique, based on Clint’s stem cells, to get at human-chimp differences. (Photo courtesy of Lisa Pfefferle.)

In a beautifully designed experiment, Wray and Pfefferle obtained a precious stock of Clint’s frozen ASCs, manipulated them into fat cells, known as adipocytes, and then compared his adipocytes with three different populations of human ASCs. (Clint, a resident of the Yerkes National Primate Research Center in Georgia, died at age 24 a few months before his genome was published.)

Using next-generation sequencing approaches, the researchers were then able to compare over 10,000 genes between human and chimpanzee. The results of this comparison show central differences within the set of genes that may be contributing to the obvious dissimilarities between humans and chimpanzees.

For example, genes controlling the development and function of the immune system were significantly higher in chimpanzees than in humans. It is well documented that chimpanzees are able to heal wounds faster than humans. This may be why.

In contrast, genes involved in the cell cycle and DNA processing, important for passing on genetic information and repairing DNA damage within cells, were expressed at a higher level in humans.

This novel approach of using ASCs in a controlled laboratory setting will undoubtedly be a valuable complement to existing studies on comparative primate genomics.

CITATION: Pfefferle, LW and Wray GA. Insights From a Chimpanzee Adipose Stromal Cell Population: Opportunities for Adult Stem Cells to Expand Primate Functional Genomics. October 2013: 1–18, doi:10.1093/gbe/evt148

Mining Appalachia has permanent effects on its landscape

A satellite comparison of the Hobet-21 Mine in 1987 and 2002 (Courtesy of NASA).

A satellite comparison of the Hobet-21 Mine in 1987 (below) and 2002 (Courtesy of NASA).

By Ashley Mooney

While mining the Appalachian mountains provides fuel to many areas of the East coast, Mariah Arnold, Fulbright scholar and Duke doctoral candidate, found that current mining practices may release toxic substances that devastate local ecosystems.

Arnold said about 450 mountains across the country have been destroyed by mountaintop mining. She focuses her research on the Hobet-21 mine in southeastern West Virginia—the largest surface mine in the state.

“The problem with mountaintop mining is that the impacts are so long term,” said Richard Di Giulio, professor of environmental toxicology and Arnold’s advisor. “We’ve blown away mountains and they will never come back.”

Most mountaintop mining in West Virginia occurs in remote, sparsely populated areas, Di Giulio said. Although one can drive relatively close to the sites themselves, the true effects are hard to see from the ground.

During mountaintop mining, miners extract coal by removing the land above the coal seams, then use a process called valley filling to repurpose the excess land, Arnold said. The process releases selenium, a sometimes toxic naturally occurring element found in the earth.

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Arnold and Research Analyst Ty Lindberg collecting samples in the Mud River. Courtesy of Mariah Arnold and Ty Lindberg.

“Selenium is released into the environment when you blast off that mountain and you have all that excess rock, which has been in that mountain for a very long time,” Arnold said. “When you expose it to the air and rain and weathering events, that rock is broken down, and in that rock is selenium. Selenium is then washed down into aquatic habitats.”

Not all forms of selenium are toxic, and some are actually required in human diets to survive. According to the U.S. Environmental Protection Agency website, there is a limit on “the highest concentration of [selenium] in surface water to which an aquatic community can be exposed indefinitely without resulting in an unacceptable effect.”

Arnold found that samples taken from the Mud River, which flows through the mining site, contain significantly more selenium than the legal limit. The excess selenium has killed off several fish species and caused reproductive failure and jaw deformities in the remaining fish, she said. Species from a fork of the river that does not flow through the mining site do not exhibit the same problems.

A key to Arnold’s findings is biofilm, which refers to a group of microorganisms that stick to each other on surfaces in the river. The biofilm in the Mud River converts the selenium released from mining from an inorganic, harmless form to a dangerous organic form of the compound. Some animals, including fish and insects, eat the biofilm and therefore ingest the now-harmful substance.

“A third of [the selenium in the river] was in green algae,” Arnold said. “The first thing these fish eat is that green algae, so that’s really the dose the fish are getting…. These biofilms are controlling the movement of selenium.”

The long-term impact of selenium exposure in many species, including humans, is still unknown, said Di Giulio. Future studies will include selenium’s effect on human health and further understanding the role of biofilm.

While some species can evolve and adapt to the rising selenium concentrations, Di Giulio said the mountains themselves could never recover, because they require hundreds of years to adapt to the changing ecology.

“You have forever essentially destroyed this landscape,” Di Giulio said. “You go there, its like, ‘oh we need flat space here for shopping centers and hospitals and schools,’ but yet the population density really is [low]. Do you need this much?”