A group of Canadian researchers suggest that a hormone that influences human reactions has a similar effect on fish, noting that this behavioral impact has carried through since ancient times.
The study, which examined the effects of isotocin, a "fish version" of oxytocin, on a species of fish found that they react in a similar fashion as humans, according to a press release issued by McMaster University.
Researchers say this is an important discovery because it helps give insight as to why some species develop complex social behaviors while others tend to live in solitude. The team believes that this may unlock some evolutionary questions and shed light on the types of behaviors that have endured over time.
The fish studied were cichlid fish Neolamprologus pulcher, a "highly social species" found in Lake Tanganyika in Africa.
LiveScience notes that oxytocin is a hormone that is linked to social bonding, love, risky behavior and cooperation in humans.
"We know how this hormone affects humans," explains Adam Reddon, lead researcher and a graduate student in the Department of Psychology, Neuroscience & Behaviour at McMaster University. "It is related to love, monogamy, even risky behaviour, but much less is known about its effects on fish."
Researchers explained that this type of fish normally create a hierarchical environment with a dominant breeding pair at the top. Scientists injected one group of fish with the isotocin to see how it affected their behavior while maintaining a control group injected with a saline solution.
The team found that the fish who received the hormone reacted more aggressively towards "large opponents" despite their own smaller size during territorial conflicts, but in their own social large group setting, the treated fish became more submissive to the dominant members.
"The hormone increases responsiveness to social information and may act as an important social glue," says Reddon. "It ensures the fish handle conflict well and remain a cohesive group because they will have shorter, less costly fights."
"We already knew that this class of neuropeptides are ancient and are found in nearly all vertebrate groups," said Sigal Balshine, a professor in the Department of Psychology, Neuroscience & Behaviour. "What is especially exciting about these findings, is that they bolster the idea that function of these hormones, as modulators of social behaviour, has also been conserved."
The full findings have been published in the journal Animal Behavior.