Clownfish, the orange-, black- and white-striped fish made famous in the movie "Finding Nemo," are a gossipy bunch, popping and clicking amid their anemone homes to defend and reinforce their social status, according to new research.
Unlike the 360 other species of territorial marine fish in the Pomacentridae family, clownfish don't make a peep when mating. Researchers wondering why clownfish would bother to make noise in other circumstances discovered that their chatter helps maintain the rank and file among group members.
"Sound could be an interesting strategy for preventing conflict between group members," lead study author Orphal Colleye, a postdoctoral fellow at the University of Liège, Belgium, told LiveScience. "In terms of cost energy, you don't have to interact with another individual to determine which is the dominant and which is the subordinate, you just need to make a sound."
Pops and clicks
Clownfish have an unusual home life: Up to six fish form a group around a single sea anemone. The largest of the group is a female, the second largest is a male, and the rest are immature fish that do not have a gender. (Once they do, they will be able to change their gender as mating pairs die out.)
The researchers found that the larger clownfish that dominate the social circles with aggressive moves, such as chasing and charging, make popping sounds distinct from the static-like sounds of the smaller, more submissive clownfish. [Spectacular Photos of Sea Creatures]
Both in the wild and in captivity, a single clownfish can make both sounds: a pop toward a smaller fish, a click toward a larger fish.
"In general, fish don't make sounds unless they have a specific need to, because sound production potentially invites predators. The question then is, Why do they need to make sounds during aggressive interactions? Why risk advertising to predators then?" said University of Massachusetts professor Rodney Rountree, a fish acoustics expert,who was not involved in the study.
Colleye said the sounds are unlikely to endanger clownfish since they live symbiotically with sea anemones, which would sting any invaders.
"This fish lives in groups in the sea anemone and they are protected by it," Colleye said.
Deciphering fish sounds
Researchers also hypothesize that individual clownfish make slightly different sounds from each other, both in frequency and duration, as a way to reinforce their individuality.
However, that interpretation is open to question, since the signals of the submissive clownfish sound very similar.
"It's unclear to me what aspect of the signal distinguishes two individuals of the same size (though I note that in natural groups there are rarely two individuals of similar size)," Paul Buston, a biology professor at Boston University who was not involved in the study, wrote in an email.
Colleye said the researchers next would separate a mating pair in different tanks and then test visual, chemical and acoustic factors in identifying individuals.
The researchers also plan to examine the factors that underlie a clownfish's ability to change gender. If the dominant female dies, the male becomes the alpha female and the next largest in size becomes the breeding male. What factors, chemical, visual or auditory, cause this to happen are currently unknown.
However, for mating, sound is not necessary. "The male doesn’t need to produce sounds to attract females; there is no competitor," Colleye said.
The research appeared today (Nov. 7) in the online journal PLoS ONE.
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