Upon studying the genetic code of an octopus and then subjecting it to the ‘party drug’ MDMA, researchers have uncovered a genetic link between the social behaviour of humans and octopuses, despite being separated by evolution for 500 million years.
During the 2010 World Cup, the world’s best football players displayed their skills to millions while another celebrity stole headlines across the globe. Paul, the octopus, was heralded with human-like brain complexity as he managed to predict 12 out of 14 games correctly. In reality, octopuses are more closely related to snails and other marine mollusks than humans, separated by 500 million years of evolution. A preliminary study, however, published in Current Biology by Eric Edsinger and Gül Dölen at the Johns Hopkins University School of Medicine in Baltimore may have uncovered a genetic link between the social behavior of humans and octopuses.
Edsinger and Dölen have mapped out the genome of the Californian two-spot octopus (Octopus bimaculoides), taking a closer look at genes which control the transport of neurotransmitters; the molecules which allow our neurons to communicate. The neurotransmitter serotonin is associated with social behavior and is best known for controlling our moods by contributing to feelings of well-being and happiness. The study found that the transporter which attaches serotonin to the membrane of neurons in both humans and octopuses were almost genetically identical.
This serotonin transporter binding site is also the location at which the ‘party drug’ MDMA attaches to brain cells and affects our mood. The researchers set out to see whether Octopus bimaculoides would display the same behavioral traits that humans do when exposed to the drug.
Male and female octopuses were observed in experimental chambers with increased social behaviors after being exposed to liquified MDMA, compared to control conditions where the animals displayed solitary behaviors. According to the researchers, the octopuses displayed similar prosocial behavioral responses found in humans.
While social behavior is commonplace across the animal kingdom, octopuses are often anti-social and solitary beings, only breaking this behavior when natural circumstances such as reproduction arise. The results from this preliminary study suggest that the neural mechanisms controlling social behavior in the octopus do exist and that the role of serotonin transmission in regulating this behavior has remained, even after 500 million years of evolution. While the results are preliminary and repeat experiments are needed, it is thought that the octopus may be able to be used as a model for brain research in the future.
"If a gene sequence is conserved for 500 million years, it must be very important," Edsinger says. "A human is a massively complex system and if you just look within that system, it is hard to know what is relatively important. But if you compare it to the genomes of other animals, you can find the critical elements that evolution just hasn't been able to change over millions of years. From a pharmacological or medical standpoint, these are the elements -- such as this serotonin transporter -- that may be really important to make sure are functioning correctly."
By Ellis Moloney
FUNDING INFO: This work was supported by grants from the Kinship Foundation, Hartwell Foundation, and Klingenstein-Simons Foundation (G.D.) and the Vetlesen Foundation (E.E.)
REF: Edsinger, E. and Dölen, G. (2018). A Conserved Role for Serotonergic Neurotransmission in Mediating Social Behavior in Octopus. Current Biology. DOI: 10.1016/j.cub.2018.07.061
