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From ants to algorithms

April 16, 2020

ASU researchers study ant colonies to better understand complex organic systems

A lot of people know that ants live in the ground, build ant hills and lay down invisible chemical trails. Temnothorax rugatulus does none of that. Instead, these ants live in free-form crevices, and their communication and division of labor are there for all to see, including scientists.

Which is why Stephen Pratt and Gabriele Valentini are so interested in these tiny ants. In a new study, the Arizona State University researchers explored how each member of a T. rugatulus colony, a complex functional organization with no central control, manages to effectively communicate among themselves and to make decisions that allow them to thrive.

Understanding how each member of the colony communicates and how labor is divided can help researchers design algorithms for complex artificial systems or better understand complex organic systems, like the brain, said Valentini, a postdoctoral research associate whose background is in computer science and complex systems.

“Modeling heterogeneity informs engineering,” said Valentini, who is also the lead author of the study.

For example, modeling heterogeneity could help design algorithms for robot swarms and, if humans were to decide to colonize another planet, such swarms could be dispatched from Earth and tasked with deciding where to build structures that humans would inhabit.

Given their relatively small colony size of about 200 members, their longevity and their overt physical contact with one another, T. rugatulus serve as a near-ideal model for exploring complex systems.

“They’re very nice for getting this fine-scale detailed description of individual behavior and at the same time observing this interesting collective behavior,” said Pratt, a professor of life sciences and the study’s principal investigator. Of note, each ant lives two to three years, long enough to have the same ant participate in multiple studies.

Pratt, who studies insects’ complex social lives, explains that ant colonies acts as a kind of collective intelligence.

He and other researchers have known for a long time that ants divide labor among specialists. But previous research on collective intelligence has often assumed that all ants behave the same and follow the same rules. Not so, say Pratt and Valentini. Different ants undertake very different roles.

To find out what those roles looked like, Pratt, Valentini and their colleagues looked at how a colony of T. rugatulus behaved when they were compelled to find a new nest. Moving to new quarters means the ants have to find new crevices, reach a consensus on which one is best, and finally, move into their new home. All that activity requires clear communication and a division of labor.

“And they have to do that without anyone seeing the big picture,” Pratt said. “It’s not like there’s any one ant that gets informed about all the possible nests and figures out which one is best, and then tells everyone where to go. There’s no ant who knows everything.”

That’s why the researchers tracked and observed each ant's movements. They paint-marked each ant with a unique color code and then observed their emigration process.

painted ant colony on right side with diagram of movements on left

Colony of Temnothorax rugatulus ants composed of a queen, larvae and paint-marked workers with an illustration of the recruitment network generated by the interaction of primary, secondary, passive and wandering ants. Image courtesy of Gabriele Valentini/ASU

What the researchers came up with was this: a huge data set, to which Valentini put order using statistical analysis. Valentini’s analysis showed a mash-up of active ants and passive ants on a continuum of behavior.

“It’s easier to model these systems if you treat all the ants as identical, but we know that’s not true,” Valentini said.

Active ants include primary workers, which make up about one-third of the colony. Primary ants play a major role in choosing a new nest site. These ants leave the nest, explore possible new nest sites and then bring each other to candidate nest sites using tandem runs.

Tandem runs are a way of recruiting other members of the colony to a new nest and sharing information about its location. In a tandem run, one ant finds a nest that she thinks is a suitable new home and leads another ant to the candidate nest to assess it.

In addition to primary ants, about one-fifth of the colony consists of secondary ants that are carried to a candidate nest by a primary ant. Eventually, these secondary ants begin to carry other nest-mates from the old nest to the new nest. Of note, secondary ants aren’t the colony’s decision-makers, but, instead, they help implement the move to the colony’s new nest.

Video courtesy Gabriele Valentini.

Once the colony achieves a quorum, the workers ramp it up: They quickly carry the remaining members, known as passive ants, to the new nest. Passive ants make up about 40% of the colony.

Intriguingly, the researchers found another segment of the colony that did not behave like the other ants. Pratt and Valentini dubbed these ants “wanderers.” The wanderers made up about 10% of the colony and did not appear to be decision-makers or implementers. However, they made several visits to the candidate nest.

Pratt and Valentini speculate that the wanderers are foraging for food or perhaps they are primary ants that are dissatisfied with their new home and are still looking for better alternatives. “Perhaps they are very picky, and never find a nest that’s good enough,” Valentini said.

No matter, the researchers now have a better idea of what these ants are about.

“As biologists, we gathered this data, but it sat around for a long time, and we weren’t sure how to handle it,” Pratt explained. “It was when we started working with engineers, like Gabri and Ted Pavlic, and physicists like Sara Walker, they just brought a whole new perspective to it.”

The study, “Division of labour promotes the spread of information in colony emigrations by the ant Temnothorax rugatulus,” was published online in the “Proceedings of the Royal Society B” on April 1. In addition to Valentini and Pratt, the paper’s authors include Naoki Masuda, Zachary Shaffer, Jake Hanson, Takao Sasaki, Sara Imari Walker and Theodore Pavlic.

Top illustration: Temnothorax rugatulus ants have a stereotypical posture that they use to carry nestmates. Credit: Alex Cabrera/ASU

Science writer , Media Relations and Strategic Communications

Health care heroes by day, homework warriors by night

ASU nursing students help with COVID-19 pandemic, while balancing studies


April 16, 2020

It is not unusual for graduate students to work while pursuing their degrees. Such is the case for a majority of Doctor of Nursing Practice students in Arizona State University's Edson College of Nursing and Health Innovation. 

But while other graduate students might help pay their way through school by teaching, or driving for Uber, these DNP students are working in health care. So when a health crisis arises like the current global pandemic, all 259 of them are in a unique position to make an impact now — before earning their diplomas. A health care worker wears a mask and other protective equipment. Edson College graduate students are in a unique position, caring for patients now as RNs, while also finishing up their advanced practice degrees. Download Full Image

“While they’re working toward their advanced nursing practice degrees, they’re contributing as nurses to meet the demand of our community by performing COVID-19 testing and caring for patients in need,” said Daniel Crawford, clinical assistant professor and director of Edson College’s DNP program.  

Yuna Sakoma and Megan Nichols are two of those students. Both are set to graduate next month and both are currently working as registered nurses on the front lines in Phoenix but in different capacities. 

Sakoma works in a Valley hospital, where her pulmonary floor was recently converted to a dedicated COVID-19 floor. She says they’re still trying to adjust to the changes and the ever-evolving guidelines they need to comply with. 

“It’s definitely added more anxiety and discomfort just dealing with the unknown. I think it’s very stressful for nurses. But just because we feel fear doesn’t mean that we’re going to bend our responsibility and run away; this is our calling,” Sakoma said.

Nichols is another testament to that. 

She left her full-time job at Phoenix Children’s Hospital to focus on school but when this crisis hit she knew she had to help. So now, she sets off every morning to her new pandemic position, screening essential workers for signs of COVID-19. 

“It was hard watching fellow nurses, physicians and respiratory therapists and techs on the front lines just getting hammered. I have a skill set that can help and I have an even more developed skill set now in terms of policy and procedures that I’ve learned in the DNP program. So sitting here and doing nothing, I just couldn’t continue that,” said Nichols. 

That advanced skill set is coming in handy as complex questions arise around constantly changing guidelines and best practices for adapting policies and procedures in response to the pandemic.

While neither Nichols nor Sakoma oversteps their current license as registered nurses, their colleagues are aware of their education and how close they are to graduation. As a result, they are often sought out for that additional expertise by their co-workers.

“It is interesting to be working as an RN but to have that knowledge base, so I’m trying to use it more in helping to look at certain protocols for what we do with symptomatic employees vs. asymptomatic employees or somebody who was possibly exposed vs. somebody who definitely was exposed. I’m trying to help more in that area than with the diagnostic-type questions that are coming my way even if I think I can answer them,” Nichols said.

Similarly, Sakoma also focuses on nonclinical areas where she can apply the advanced practice skills that keep her, her colleagues and patients safe. 

Both nurses acknowledged the risks involved for themselves and all health care workers who are working day in and day out to save lives around the world. They also shared the unease they feel these days.

“It's just like a pit in our stomach just to get ready for work because we’re going to be exposed to it, we’re going to need to isolate ourselves from our loved ones. You know we can’t go see family. Some nurses are renting places away from the family so they won’t spread this infection from work,” Sakoma said.

And they’re lucky. Right now they’re in facilities with proper personal protective equipment or, PPE, to help shield them from infection.

Even so, Nichols is one of those nurses who has prepared for the possibility that she’ll be exposed. When she heads off to work she brings a go-bag with her, packed with extra clothes, toiletries and essentials in case she can’t go home for fear of spreading the virus to her fiance.

“It’s still a risk if you work in health care of any type that you can be exposed. I have a whole plan where I can go to a friend's place, who isn’t living there right now and I can quarantine there if I need to,” she said.

Between those stressful shifts, they turn back into students, working on finishing up their final coursework and their doctoral projects — for another few weeks at least. 

Sakoma is earning a Family Nurse Practitioner, DNP, and Nichols a Pediatric Nurse Practitioner, DNP. 

Edson’s nationally-ranked DNP program prepares students at the highest level of nursing education; it is three years long and requires hundreds of clinical hours on top of projects and other assignments. 

“The education that these students are getting provides them a lot of value in understanding, diagnosing and treating disease processes," Crawford said. "Our students and graduates will be in an excellent position to ensure the highest quality health outcomes and to contribute to quality improvement measures immediately.” 

For students like Sakoma and Nichols who are set to graduate in May, the bulk of those in-person clinical requirements were completed before the coronavirus required physical distancing measures and a shift to remote learning for the remainder of the semester.

Still, in light of all that is going on and because of the extraordinary position many of these students are in, Edson College is responding accordingly.

“As a program, we’ve really tried to convey the message to students that it’s going to be OK and we’re here to work through this with you,” Crawford said.

With graduation so close, there’s a mix of excitement including plans to watch the virtual ceremonies and anxiety about what comes next in life and in their careers, which are so tightly intertwined.  

“Finally I’m at the end of three years of hard work, of schoolwork and working at the same time but it's just so chaotic at this moment that it just feels so unreal. I mean I’m excited to be done but at the same time I’m not sure what kind of a job I’m going to get as an NP in this pandemic,” Sakoma said.

Her hope is to find a position in an outpatient primary care clinic to start and then eventually move into dermatology. 

For Nichols, the dream job revolves around serving pediatric patients in vulnerable communities, providing care and education while working toward building resilience. 

More immediately though her focus is on the pandemic. She says this is not just going to go away and the health care community needs help in the form of widespread testing to get the upper hand.

“I hope we can ramp up testing and I know that will freak people out with the number of cases that go up but maybe then we can truly get a handle on this and see what it’s doing in the community. Because until we really understand what it’s doing, exactly how it's spreading and who is most at risk, we’re just chasing our tail.”

The one thing that is certain is that someday soon they, along with more than 70 of their graduating DNP classmates, will become nurse practitioners, filling a huge need within the health care system. 

Amanda Goodman

Media relations officer, Edson College of Nursing and Health Innovation

602-496-0983