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First published online December 1, 2006
Journal of Experimental Biology 209, 4994-5004 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02609

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Acoustic communication in territorial butterflyfish: test of the sound production hypothesis

Timothy C. Tricas^*, Stephen M. Kajiura and Randall K. Kosaki

Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii at Manoa, Honolulu, HI 96822, USA

View larger version (22K): [in this window] [in a new window]   Fig. 1. Schematic diagram of the laterophysic system in butterflyfishes of the genus Chaetodon. This unique anatomical feature is a putative acoustico-lateralis hearing mechanism located at the junction of the trunk lateral line (TLL) and head lateral line (HLL) canal systems. The laterophysic connection is formed by gas-filled horns (H) that extend from the anterior swim bladder (SB) and a small tympanum (dark circle and X) on the medial edge of the canal in the supracleithrum bone (S). The swim bladder horns also project towards the otic capsule. Figure modified with permission from Webb and Smith (2000).

View larger version (8K): [in this window] [in a new window]   Fig. 2. Model bottle method used in field experiments to evoke and record motor and acoustic behaviors produced by Chaetodon multicinctus. One or two fish (one shown) were collected by divers, placed in a glass jar and introduced into the territory of a conspecific pair. A hydrophone (H) placed near the bottle detected sounds that were recorded on the audio channel of an underwater video camera (VC). The resident pair quickly discovered the intruders and initiated agonistic acoustic behaviors.

View larger version (17K): [in this window] [in a new window]   Fig. 3. Behaviors associated with sound production in the multibanded butterflyfish, Chaetodon multicinctus. (A) The tail slap behavior occurs after escalated displays and aggression by territorial residents towards bottled intruders and is performed within a distance of one body length from the bottle. The tail slap produces both a low frequency hydrodynamic pulse and a brief broadband acoustic click. (B) The jump behavior is displayed by resident fish and involves several movement patterns: the approach and face (1) and rapid turn (2) are followed by a short swimming ascent (3) and intense lateral display (4). The rapid turn produces a low frequency hydrodynamic pulse that is followed by several rapid acoustic pulses. (C) The pelvic fin flick behavior is produced by both residents and bottled intruders (illustrated), involves the extension of the pelvic fins and a single acoustic pulse. (D) The grunt train sound was produced only by bottled fish when approached by territory residents and may be an alert call to the mate. No body movements were observed during the production of this sound. Broken lines indicate sound production.

View larger version (42K): [in this window] [in a new window]   Fig. 4. Motor patterns and sounds produced by multiband butterflyfish, Chaetodon multicinctus during agonistic interactions with bottled conspecifics. (A) The tail slap starts with a lateral display followed by tail slap and turn motor patterns (lower panel) that produce acoustic stimuli (waveform on lower trace). A strong hydrodynamic pulse with signals at 20-60 Hz results from the lateral motion of the body towards the intruder (lower spectrogram). The tail slap occurs at the end of the turn that produces a broadband click (upper spectrogram). In this instance the tail slap was immediately followed by a second lateral display. (B) Jump behavior starts with a frontal motor display towards the bottled intruders, a rapid turn of the body, and swimming ascent that is followed by an intense lateral display (lower panel). The turn and ascend behaviors produce acoustic stimuli that include a low frequency component made during the turn followed by a pulse train during the ascent (waveform on lower trace). Note that spectrum of sounds made during both the turn and ascent are from <100-700 Hz, with lower frequencies due to the hydrodynamic pulse made during the turn (spectrogram).

View larger version (11K): [in this window] [in a new window]   Fig. 5. Relative frequency of sounds produced during aggressive social interactions in the multiband butterflyfish, Chaetodon multicinctus. The tail slap, grunt and dorsal-anal fin (DA) erect acoustic behaviors were produced exclusively by territory residents and directed towards bottled conspecifics. Grunt trains were recorded only from bottled fish (most frequently when in pairs) when territory holders came into view and may be an alert or distress signal to the mate. The fin flick acoustic pulse was produced by both resident and bottled fish during confrontations. N values are given beneath each behavior.

View larger version (50K): [in this window] [in a new window]   Fig. 6. Sound production by multiband butterflyfish, Chaetodon multicinctus, intruders during encounters with conspecific territory holders. (A) The pelvic flick behavior by an intruder involves the extension of the pelvic fins that produces an acoustic stimulus during this motion (waveform on lower trace). This sound has a frequency spectrum just below 200 Hz and is also produced during displays by resident fish towards bottled intruders. Arrows show start and end of pelvic fin extension. (B) The grunt train sound is produced by bottled intruder pairs when confronted by territory residents. Unlike all other acoustic signals observed, the grunt train was not associated with any visible body movements, thus most likely is caused by internal muscle movements. This sound included a series of regular spaced pulses (waveform on lower trace) that have a strong frequency component at 400-500 Hz (spectrogram). Note the harmonics associated with each pulse that indicate that this internally generated sound may result in part from resonance of the swim bladder.