Increasingly scientists are discovering unusual mechanisms by which fish make and hear secret whispers, grunts and thumps to attract mates and ward off the enemy.
In just one bizarre instance, seahorses create clicks by tossing their heads. They snap the rear edge of their skulls against their star-shaped bony crests.
This and other discoveries made in recent years come as the focus on the sounds that fish make is growing beyond ‘really loud sounds that last a long time,’ fish behaviorist Timothy Tricas** at the University of Hawaii at Manoa told LiveScience. ‘Seahorse clicks are brief, only about five to 20 milliseconds,’ he said.
…Tricas and his colleagues studied butterflyfishes, a family that includes 126 species with bright colors and striking patterns found on just about every coral reef in the world. One group within the butterflyfish family, comprising more than 80 species, are the only fish known so far to couple their swim bladders, which are organs that improve hearing, with their body’s lateral lines, organs running down their sides that help detect motion in the surrounding water. This might be akin to a person hearing sounds by wiring their ears together with the little hairs on his or her skin.
This setup in butterflyfish seemed like a possible new hearing system, “but no one had ever heard butterflyfish make a sound. We discovered they do,” Tricas said.
Using underwater cameras and sound recorders known as hydrophones on Hawaiian coral reefs, Tricas and his colleagues discovered butterflyfish emitted several types of sounds only 10 to 150 milliseconds long using tail slaps, fin flicks, fin spine extensions, grunts and jumps.
“If you’re up close to them with a hydrophone, you can hear the sounds, but the total power in a single sound is miniscule compared to the loud and long sounds the toadfish and [fish known as] midshipman can make, which can last for seconds or minutes and can be heard 10 to 20 feet away,” Tricas said.
Tricas presented research on these and other fish sounds at a meeting of the Acoustical Society of America in Hawaii last month*.
…Studying fish sounds could help shed light on the evolution of communication and hearing, as well as related behaviors, such as finding of mates or defending of territory, Tricas said. For instance, the fact that butterflyfish can effectively only whisper “may help explain the evolution of their pairing behavior, why the fish appear so social, and why almost all butterflyfish affiliate with one another so often.”
Currently the purposes of some fish sounds remain complete mysteries.
Full article at “Talking Fish: Wide Variety of Sounds Discovered” [Auditory, System]
——-
*Timothy Tricas co-contributed 3 papers on Wednesday, 29th November 2006:
2:40pm Sound production and hearing ability in the Hawaiian sergeant fish.
3:25pm Sound communication by the forceps fish, Forcipiger
flavissimus (Chaetodontidae)
3:40pm Acoustico-lateralis communication in coral reef butterflyfishes
——-
**Info from Timothy Tricas’ homepage:
“Our research is focused on the evolution of sensory systems in relation to the natural behavior and ecology of coral reef fishes. The coral reefs of Hawaii and other Pacific regions afford excellent opportunities to study the sensory biology and behavior of marine fishes. One important group is the butterflyfishes (family Chaetodontidae), which occur on nearly all coral reef systems. Some of our current projects include the evolution of a specialized hearing mechanism in butterflyfishes (the laterophysic connection), sound production, neuropeptides as modulators of hearing and lateral line sensory systems, and the evolution of social behavior.”
——-
A recently published paper:
Acoustic communication in territorial butterflyfish: test of the sound production hypothesis
Timothy C. Tricas, Stephen M. Kajiura and Randall K. Kosaki
The Journal of Experimental Biology 209, 4994-5004
Published by The Company of Biologists 2006
doi:10.1242/jeb.02609
Butterflyfishes are conspicuous members of coral reefs and well known for their visual displays during social interactions. Members of the genus Chaetodon have a unique peripheral arrangement of the anterior swim bladder that connects with the lateral line (the laterophysic connection) and in many species projects towards the inner ear. This morphology has lead to the proposal that the laterophysic connection and swim bladder system may be a specialized structure for the detection of sound. However, the relevant stimuli, receiver mechanisms and functions for these putative hearing structures were unknown because butterflyfishes were previously not recognized to produce sounds during natural behavior. We performed field experiments to test the hypothesis that Chaetodon produces sounds in natural social contexts. Acoustic and motor behaviors of the monogamous multiband butterflyfish, C. multicinctus, were evoked and recorded by placement of bottled fish into feeding territories of conspecific pairs. We demonstrate that territory defense includes the production of agonistic sounds and hydrodynamic stimuli that are associated with tail slap, jump, pelvic fin flick and dorsal-anal fin erection behaviors. In addition, grunt pulse trains were produced by bottled intruders and are tentatively interpreted to function as an alert call among pair mates. Acoustic behaviors include low frequency hydrodynamic pulses: less than 100 Hz, sounds with peak energy from 100 Hz to 500 Hz, and a broadband high frequency click (peak frequency=3.6 kHz), which is produced only during the tail slap behavior. These results provide a biological framework for future studies to interpret the proximate function of the acoustico-lateralis sensory system, the evolution of the laterophysic mechanism and their relevance to butterflyfish social behavior.
John Latter / Jorolat
Evolution Research:
http://evomech1.blogspot.com/
Technorati: hydrophone, sound, hearing, ability
