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Brain imaging reveals that not all monogamous mammals are ‘wired for love’ in the same way

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Brain imaging reveals that not all monogamous mammals are ‘wired for love’ in the same way

Humans aren’t the only mammals that form long-term bonds with a single, special mate — some bats, wolves, beavers, foxes and other animals do, too. But new research suggests the brain circuitry that makes love last in some species may not be the same in others.

The study, appearing Feb. 12 in the journal Scientific Reports, compares monogamous and promiscuous species within a closely related group of lemurs, distant primate cousins of humans from the island Madagascar.

Red-bellied lemurs and mongoose lemurs are among the few species in the lemur family tree in which male-female partners stick together year after year, working together to raise their young and defend their territory.

Once bonded, pairs spend much of their waking hours grooming each other or huddled side by side, often with their tails wrapped around each other’s bodies. Males and females of these species spend a third of a lifetime with the same mate. The same cannot be said of their closest relatives, who change partners often.

To biologists, monogamy is somewhat a mystery. That’s in part because in many animal groups it’s rare. While around 90% of bird species practice some form of fidelity to one partner, only 3% to 5% of mammals do. The vast majority of the roughly 6,500 known species of mammals have open relationships, so to speak.

“It’s an uncommon arrangement,” said lead author Nicholas Grebe, a postdoctoral associate in professor Christine Drea’s lab at Duke University.


Which raises a question: what makes some species biologically inclined to pair up for the long haul while others play the field?

Studies over the last 30 years in rodents point to two hormones released during mating, oxytocin and vasopressin, suggesting that the key to lasting love may lie in differences in how they act on the brain.

Some of the first clues came from influential research on prairie voles, small mouse-like mammals that, unlike most rodents, mate for life. When researchers compared the brains of monogamous prairie voles with their promiscuous counterparts, montane voles and meadow voles, they found that prairie voles had more “docking sites” for these hormones, particularly in parts of the brain’s reward system.

Since these “cuddle chemicals” were found to enhance male-female bonds in voles, researchers have long wondered if they might work the same way in humans.

That’s why the Duke-led team turned to lemurs. Despite being our most distant primate relatives, lemurs are a closer genetic match to humans than voles are.


The researchers used an imaging technique called autoradiography to map binding sites for oxytocin and vasopressin in the brains of 12 lemurs that had died of natural causes at the Duke Lemur Center.

The animals represented seven species: monogamous red-bellied and mongoose lemurs along with five promiscuous species in the same genus.

“They’re really the only comparable natural experiment to look for biological signatures of monogamy in primates,” Grebe said.

Comparing the brain imaging results in lemurs with previous results in voles and monkeys revealed some noticeable differences in the density and distribution of hormone receptors. In other words, oxytocin and vasopressin appear to act on different parts of the brain in lemurs — which means they may also have different effects, depending on their target cell’s location.

But within lemurs, the researchers were surprised to find few consistent differences between monogamous species and promiscuous ones.

“We don’t see evidence of a pair-bond circuit” akin to that found in rodent brains, Grebe said.

As a next step, the team is looking at how lemur couples behave toward each other if the actions of oxytocin are blocked, by feeding them an antagonist that temporarily prevents oxytocin from binding to its receptors in the brain.

So what can lemurs teach us about love? The authors say their findings caution against drawing simple conclusions based on rodent experiments about how human social behaviors came to be.

Oxytocin may be the “potion of devotion” for voles, but it may be the combined actions and interactions of multiple brain chemicals, along with ecological factors, that create long-lasting bonds in lemurs and other primates, including humans, Grebe said.

“”There are probably a number of different ways through which monogamy is instantiated within the brain, and it depends on what animals we’re looking at,” Grebe said. “There’s more going on than we originally thought.”

Other authors were: Annika Sharma at Duke, Sara Freeman at Utah State University, Michelle Palumbo at the California National Primate Research Center, Heather Patisaul at North Carolina State University, and Karen Bales at the University of California, Davis.

This work was supported by grants from the National Science Foundation (SBE-1808803), the National Institute of Mental Health (NIMH R21MH115680), the Josiah Charles Trent Memorial Foundation Endowment Fund, the Charles Lafitte Foundation for Research, and Duke University.

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Warming of Antarctic deep-sea waters contribute to sea level rise in North Atlantic, study finds

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Brain imaging reveals that not all monogamous mammals are ‘wired for love’ in the same way


Analysis of mooring observations and hydrographic data suggest the Atlantic Meridional Overturning Circulation deep water limb in the North Atlantic has weakened. Two decades of continual observations provide a greater understanding of the Earth’s climate regulating system.

A new study published in the journal Nature Geoscience led by scientists at University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, and the National Oceanic and Atmospheric Administration’s Atlantic Oceanographic and Meteorological Laboratory, found that human-induced environmental changes around Antarctica are contributing to sea level rise in the North Atlantic.

The research team analyzed two decades of deep sea oceanographic data collected by observational mooring programs to show that a critical piece of Earth’s global system of ocean currents in the North Atlantic has weakened by about 12 percent over the past two decades.

“Although these regions are tens of thousands of miles away from each other and abyssal areas are a few miles below the ocean surface, our results reinforce the notion that even the most remote areas of the world’s oceans are not untouched by human activity,” said the study’s lead author Tiago Biló, an assistant scientist at the Rosenstiel School’s NOAA Cooperative Institute for Marine and Atmospheric Studies.

As part of the NOAA-funded project DeepT (Innovative analysis of deep and abyssal temperatures from bottom-moored instrument), the scientists analyzed data from several observational programs to study changes over time in a cold, dense, and deep water mass located at depths greater than 4,000 meters (2.5 miles) below the ocean surface that flow from the Southern Ocean northward and eventually upwells to shallower depths in other parts of the global ocean such as the North Atlantic.

This shrinking deep-ocean branch — that scientists call the abyssal limb — is part of the Atlantic Meridional Overturning Circulation (AMOC), a three-dimensional system of ocean currents that act as a “conveyer belt” to distribute heat, nutrients, and carbon dioxide across the world’s oceans.

This near-bottom branch is comprised of Antarctic bottom water, which forms from the cooling of seawater in the Southern Ocean around Antarctica during winter months. Among the different formation mechanisms of this bottom water, perhaps the most important is the so-called brine rejection, a process that occurs when salty water freezes. As sea ice forms, it releases salt into the surrounding water, increasing its density. This dense water sinks to the ocean floor, creating a cold, dense water layer that spreads northward to fill all three ocean basins — the Indian, Pacific, and Atlantic oceans. During the 21st century, the researchers observed that the flow of this Antarctic layer across 16°N latitude in the Atlantic had slowed down, reducing the inflow of cold waters to higher latitudes, and leading to warming of waters in the deep ocean.

“The areas affected by this warming spans thousands of miles in the north-south and east-west directions between 4,000- and 6,000-meters of depth,” said William Johns, a co-author and professor of ocean sciences at the Rosenstiel School. “As a result, there is a significant increase in the abyssal ocean heat content, contributing to local sea level rise due to the thermal expansion of the water.”

“Our observational analysis matches what the numerical models have predicted — human activity could potentially impose circulation changes on the entire ocean,” said Biló. “This analysis was only possible because of the decades of collective planning and efforts by multiple oceanographic institutions worldwide.”



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Octopus inspires new suction mechanism for robots

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Brain imaging reveals that not all monogamous mammals are ‘wired for love’ in the same way


A new robotic suction cup which can grasp rough, curved and heavy stone, has been developed by scientists at the University of Bristol.

The team, based at Bristol Robotics Laboratory, studied the structures of octopus biological suckers, which have superb adaptive suction abilities enabling them to anchor to rock.

In their findings, published in the journal PNAS today, the researchers show how they were able create a multi-layer soft structure and an artificial fluidic system to mimic the musculature and mucus structures of biological suckers.

Suction is a highly evolved biological adhesion strategy for soft-body organisms to achieve strong grasping on various objects. Biological suckers can adaptively attach to dry complex surfaces such as rocks and shells, which are extremely challenging for current artificial suction cups. Although the adaptive suction of biological suckers is believed to be the result of their soft body’s mechanical deformation, some studies imply that in-sucker mucus secretion may be another critical factor in helping attach to complex surfaces, thanks to its high viscosity.

Lead author Tianqi Yue explained: “The most important development is that we successfully demonstrated the effectiveness of the combination of mechanical conformation — the use of soft materials to conform to surface shape, and liquid seal — the spread of water onto the contacting surface for improving the suction adaptability on complex surfaces. This may also be the secret behind biological organisms ability to achieve adaptive suction.”

Their multi-scale suction mechanism is an organic combination of mechanical conformation and regulated water seal. Multi-layer soft materials first generate a rough mechanical conformation to the substrate, reducing leaking apertures to just micrometres. The remaining micron-sized apertures are then sealed by regulated water secretion from an artificial fluidic system based on the physical model, thereby the suction cup achieves long suction longevity on diverse surfaces but with minimal overflow.

Tianqi added: “We believe the presented multi-scale adaptive suction mechanism is a powerful new adaptive suction strategy which may be instrumental in the development of versatile soft adhesion.

“Current industrial solutions use always-on air pumps to actively generate the suction however, these are noisy and waste energy.

“With no need for a pump, it is well known that many natural organisms with suckers, including octopuses, some fishes such as suckerfish and remoras, leeches, gastropods and echinoderms, can maintain their superb adaptive suction on complex surfaces by exploiting their soft body structures.”

The findings have great potential for industrial applications, such as providing a next-generation robotic gripper for grasping a variety of irregular objects.

The team now plan to build a more intelligent suction cup, by embedding sensors into the suction cup to regulate suction cup’s behaviour.



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One third of China’s urban population at risk of city sinking, new satellite data shows

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Brain imaging reveals that not all monogamous mammals are ‘wired for love’ in the same way


Land subsidence is overlooked as a hazard in cities, according to scientists from the University of East Anglia (UEA) and Virginia Tech.

Writing in the journal Science, Prof Robert Nicholls of the Tyndall Centre for Climate Change Research at UEA and Prof Manoochehr Shirzaei of Virginia Tech and United Nations University for Water, Environment and Health, Ontario, highlight the importance of a new research paper analysing satellite data that accurately and consistently maps land movement across China.

While they say in their comment article that consistently measuring subsidence is a great achievement, they argue it is only the start of finding solutions. Predicting future subsidence requires models that consider all drivers, including human activities and climate change, and how they might change with time.

The research paper, published in the same issue, considers 82 cities with a collective population of nearly 700 million people. The results show that 45% of the urban areas that were analysed are sinking, with 16% falling at a rate of 10mm a year or more.

Nationally, roughly 270 million urban residents are estimated to be affected, with nearly 70 million experiencing rapid subsidence of 10mm a year or more. Hotspots include Beijing and Tianjin.

Coastal cities such as Tianjin are especially affected as sinking land reinforces climate change and sea-level rise. The sinking of sea defences is one reason why Hurricane Katrina’s flooding brought such devastation and death-toll to New Orleans in 2005.

Shanghai — China’s biggest city — has subsided up to 3m over the past century and continues to subside today. When subsidence is combined with sea-level rise, the urban area in China below sea level could triple in size by 2120, affecting 55 to 128 million residents. This could be catastrophic without a strong societal response.

“Subsidence jeopardises the structural integrity of buildings and critical infrastructure and exacerbates the impacts of climate change in terms of flooding, particularly in coastal cities where it reinforces sea-level rise,” said Prof Nicholls, who was not involved in the study, but whose research focusses on sea-level rise, coastal erosion and flooding, and how communities can adapt to these changes.

The subsidence is mainly caused by human action in the cities. Groundwater withdrawal, that lowers the water table is considered the most important driver of subsidence, combined with geology and weight of buildings.

In Osaka and Tokyo, groundwater withdrawal was stopped in the 1970s and city subsidence has ceased or greatly reduced showing this is an effective mitigation strategy. Traffic vibration and tunnelling is potentially also a local contributing factor — Beijing has sinking of 45mm a year near subways and highways. Natural upward or downward land movement also occurs but is generally much smaller than human induced changes.

While human-induced subsidence was known in China before this study, Profs Nicholls and Shirzaei say these new results reinforce the need for a national response. This problem happens in susceptible cities outside China and is a widespread problem across the world.

They call for the research community to move from measurement to understanding implications and supporting responses. The new satellite measurements are delivering new detailed subsidence data but the methods to use this information to work with city planners to address these problems needs much more development. Affected coastal cities in China and more widely need particular attention.

“Many cities and areas worldwide are developing strategies for managing the risks of climate change and sea-level rise,” said Prof Nicholls. “We need to learn from this experience to also address the threat of subsidence which is more common than currently recognised.”



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