Friday, July 15, 2005
A new study by an international research
team shows for the first time that clownfish populations found in
different regions of the Indian Ocean demonstrate diverse calls --
either “chirps” or “pops” -- when defending their territory.
These findings may
help researchers better understand the role of sounds in fish behavior
and how changes in behavior may lead to the formation of new and
Michael L. Fine,
Ph.D., a Virginia Commonwealth University Life Sciences biologist
studying fish sound production, together with researchers at the
University of Liege in Belgium and the
Research Center on the Marine and Freshwater Ecosystem in France, are
the first to report geographic variation in sounds of a coral-reef fish
species. Their findings were published online Friday in
The Proceedings of The Royal Society B –
coral-reef fish can be fairly similar in populations of a species living
thousands of miles apart because their eggs can be dispersed widely by
strong ocean currents,” said Fine, a professor in the Department of
Biology at VCU who helped analyze the recorded fish sounds using
computer software. “However, we found that there were differences in the
sounds produced in the same species living in the reefs of Madagascar
They found a
differentiation of agonistic calls produced by the clownfish,
Amphiprion akallopisos, from populations in Madagascar and Indonesia
– a distance of approximately 4,000 miles.
The research team identified three different sound types in the
Madagascar fish and two in the Indonesian group. Results from the sound
analyses showed that the Madagascar fish produced “chirps,” and both
groups produced two types of pops — “short pops” and “long pops.”
provide evidence of differentiation of local populations,” he said.
According to Fine, sounds are important in maintaining separation
between species, and they tend to change in related animals undergoing
speciation. Generally, the pattern generators and anatomy that control
sound production are believed to result from genetic instructions.
“In this case, the
different sounds that are produced may
reflect genetic changes that have occurred because the two fish
populations have probably been separated for long periods,” he said.
Fishes make sounds
for different reasons, but the two most common types of sounds are made
for courtship and agonistic behaviors, said Fine. The differences
observed in the agonistic callings of these populations is a complexity
not previously recorded in fish acoustic communication.
The team collected
fish from the two geographic locations and observed them in a community
tank. A sea anemone and clownfish pair were placed in the center of the
tank, and after 15 minutes, a second pair of clownfish was introduced to
the tank. Sounds were recorded when the fish defended its sea anemone.
The sea anemone, which is a home to these fish, possesses stinging cells
that protect the clownfish, but can kill other fishes.
recorded using a device called a hydrophone. They measured the
differences in the number of pulses, pulse duration and dominant
frequency in the sounds produced.
“Typically an animal needs to have a territory in order to mate. The sea
anemone is a valuable resource to the fish. If another pair wants to
invade it, the existing pair does not want to share,” Fine said.
“Therefore, sounds were produced by the pair of clownfish when other
fishes entered the sea anemone.”
with Eric Parmentier, Ph.D, assistant professor, and Pierre Vandewalle,
Ph.D., professor, both at the University of Liege in Belgium; and
Jean-Paul Lagardère, Ph.D., a researcher with the Research Center on the
Marine and Freshwater Ecosystem in L’Houmeau, France.
About VCU and VCU Medical Center
Virginia Commonwealth University is a major, urban public research university with national and international rankings in sponsored research. Located in downtown Richmond, VCU enrolls more than 31,000 students in 226 degree and certificate programs in the arts, sciences and humanities. Sixty-seven of the programs are unique in Virginia, many of them crossing the disciplines of VCU’s 13 schools and one college. MCV Hospitals and the health sciences schools of Virginia Commonwealth University comprise VCU Medical Center, one of the nation’s leading academic medical centers. For more, see www.vcu.edu.