Some species of clownfish have absolutely no personality, a study by Australian researchers has found.
Research by the University of Wollongong and Southern Cross University analysed the behavioural patterns of two species of subtropical clownfish, or anemonefish: Amphiprion mccullochi, which is endemic to a shallow lagoon on Lord Howe island, off the coast of New South Wales; and Amphiprion latezonatus, which has a much wider distribution along Australia’s east coast.
The resulting paper, Some anemonefish lack personality, was published in the December issue of Coral Reefs journal.
It found that A.mccullochi displayed distinct, individual personalities – mainly through varying degrees of bold or aggressive behaviour – while A.latezonatus showed no discernible individual personality traits but appeared to act as a group.
Tropical clownfish, such as Amphiprion ocellaris, the species made popular by Pixar movie Finding Nemo in 2003, also showed distinct individual personalities, making A.latezonatus the bland one in the group.
Lead researcher Dr Marion Wong, from the University of Wollongong, said observing different personality traits in clownfish was no different from observing different personality traits in dogs. Humans accept the idea of different personalities in dogs because we spend so much time with them.
“We don’t normally spend time and hang out with clownfish,” she said. “But if we did do that and hang out with them like we hang out with our dogs, we would see that yes, they do have individual personalities.”
Wong said the conclusion about A.latezonatus was drawn not because they did not exhibit any interesting behavioural traits, but because all specimens observed during the study period displayed identical behaviours.
“There wasn’t much between-individual variation; individuals were quite consistent, but they were all on the same level of boldness and shyness,” she said.
An individual personality is taken to be individual behaviours in response to the same conditions.
“One individual might have an over-inflated reaction to a stressful situation or a certain occurrence, whereas another one might have a really chilled-out reaction to it,” Wong said. “So you tend to associate one with being anxious and one as being more relaxed.”
About 60 individuals from both species were filmed in their natural environment using underwater cameras. Researchers recorded 15 minutes of footage at the same time each day, then analysed the footage to see how often individual fish displayed three distinct types of behaviour: boldness, aggression, and sociability.
Each behaviour was scored out of 10. Boldness was measured on how much time the fish spent out of contact with its anemone; sociability by the number of non-aggressive acts they performed with other clownfish, which the study said included “meetings, soft touches of fins and submissive body shakes”; and aggressiveness was measured by the number of aggressive acts towards other clownfish, including biting and chasing.
The study hypothesises that the A.latezonatus does not display individual personalities because it lives in a more dangerous, turbulent environment than the sheltered lagoon of A.mccullochi.
There is limited scientific research pointing to other personality-devoid fish, which could paradoxically make A.latezonatus’s groupthink unique.
Or it could be that researchers find evidence of personality-less fish too dull to publish.
“We don’t really know if that’s just a feature of the fact that if researchers don’t find a personality they don’t publish the paper, or if it’s quite unusual for a fish not to have an apparent personality,” Wong said.