The idea that eating together can make people feel more connected is not only limited to humans. According to a new study that examined two species of fish, fish can also bond during mealtime.
For this study, the researchers headed by Tanja Kleinhappel of the University of Lincoln in the United Kingdom examined whether or not two free- swimming shoals of fish - the three-spined sticklebacks (Gasterosteus aculeatus) and the nine-spined sticklebacks (Pungitius pungitius) - could bond even though they were from different species. These species of fish tend to live by one another in their natural environment.
In the lab setting, the researchers manipulated the type of food the fish ate as well as the makeup of each group of fish. After observing how the fish reacted to one another, the researchers found that in the group of mixed-species fish that were fed the same diet, the three-spined sticklebacks showed no preferences toward fish of the same species. In the group of mixed-species fish that were fed different diets, the three-spined sticklebacks appeared to bond with fish who ate the same diet regardless of species.
"This behavior is most likely mediated by the general familiarity of diet-derived chemical cues as fish were previously housed in different tanks and were unfamiliar to one another," Kleinhappel said. "The results therefore suggest the general familiarity of shared chemical cues could be a way by which to induce shoaling behavior between fish of the same and different species."
The researchers explained that fish that ate the same diet might be picking up on the same free amino acids that may have formed a part of the chemical cues. Studies have found that free amino acids in the fish's skin mucus closely resemble the acids that are found in their food source. This suggests that free amino acids could be playing a role in how fish select who they want to shoal with.
"This study demonstrates the importance of chemical cues as a possible mechanism for establishing familiarity, and thereby mediating within-group structure even between individuals in mixed-species aggregations," the study authors wrote. "Understanding these underlying mechanisms has significant implications for our understanding of other social dynamics, including social learning and information transfer."
The study was published in the journal Behavioral Ecology and Sociobiology.
