In a step towards better understanding drug abuse and modeling epidemics such as the opioid crisis that has swept over America, researchers have induced a morphine “addiction” in Camponotus floridanus, a species of ant. This is the first study to present ants as an invertebrate model that can self-administer drugs without a natural food reward such as sugar. Although drug addictions in rats have previously been studied, the social organization of ants makes them a better model for how social interactions can affect the spread of addiction.
Ant investigating a crytalline substance. Photo taken by L. Shyamal. https://commons.wikimedia.org/wiki/File:Myrmicaria_brunnea.jpg
First, to see if the ants could actually form addictions to drugs, the researchers performed a sucrose-fading paradigm and morphine exposure where a group of experienced forager ants received a bowl of sucrose and morphine dissolved in water, and the concentration of the sucrose was lowered while the concentration of morphine was increased. Meanwhile, the control group’s bowl contained only sucrose and underwent the same procedure of concentration reduction. On day five, there was no sucrose left in the bowls, and only the group that had been exposed to morphine returned to drink at the bowls. This demonstrated a pattern of addiction where ants desired morphine even without sucrose, their natural energy source.
To test the ants’ preference for morphine, researchers then performed a two-dish choice test where ants chose between a bowl of sucrose and a bowl of morphine. Like addicts, sixty-five percent of ants in the morphine exposure group chose morphine, while most of the ants in the control group and ants that had been previously unexposed to the lab chose a food reward, sucrose. This shows that ants are not predisposed to choosing morphine and will usually choose sucrose when exhibiting their natural behavior. Researchers’ analysis of the morphine exposure group’s brains showed that they had significantly higher levels of dopamine, a chemical that induces pleasure and is strongly associated with addiction in humans, than the control group.
Although these results are promising, other scientists have argued that the study has not demonstrated that the ants exhibit true substance dependence which involves symptoms such as withdrawal and tolerance, so it’s possible that the ants cannot fully model human addict behavior. Hopefully, researchers will address these concerns by conducting future studies that test for these symptoms.
I also question how well ant social interactions can model a human society. According to Dr. Mark Moffett, an entomologist at the Smithsonian Institution, humans may be more similar to ants than primates society-wise, because like humans, ants can have huge populations that number in the millions. The evolution of large colonies has lead to widespread construction of infrastructure and pathways of communication, decreased autonomy, more teamwork, a greater division of labor, and even some trade. He has also stated that information and actions taken tend to accelerate in bigger colonies, much like in human societies. Since ant colonies mirror human cities in so many ways, the spread of addiction in a human society can likely be modeled through ant social networks. Much like how friends and family might influence each other into trying recreational drugs, ants would likely pass on information about drugs like they do tasks and food sources. The speed of the spread of addiction could also be compared between smaller colonies and larger colonies as a model for the expansion of the opioid epidemic in the suburbs and the large cities. Dr. Marc Seid, one of the lead researchers on this project, has also stated that he has already begun creating mathematical models of ant social networks to better understand the larger effects of addiction. While mathematical models may be useful, it is important to conduct experimental research on the ants to confirm the models’ predictions and present the most convincing results.
Hopefully, the results of this and future studies can influence public policy and initiatives on controlling and preventing the spread of addiction. In the end, these ench-ant-ing, f-ant-astic ants may well be our most import-ant model of addiction.