Vol. 53, 2014

The auditory roles of the gas bladder and suprabranchial chamber in walking catfish (Clarias batrachus)

Yi Ta Shao^1,2, I-Shiung Chen² and Hong Young Yan^1,3*

¹Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, 23-10, Dawen Road, Jiaoshi 26242, Taiwan
²Institute of Marine Biology, National Taiwan Ocean University, Keelung 20224, Taiwan
³Hanse-Wissenschaftskolleg Institute for Advanced Study, Lehmkuhlenbusch 4, Delmenhorst 27753, Germany

Abstract
Background: The enhanced auditory abilities of certain fish are dependent on specialized hearing structures. Several gas-holding structures, including the suprabranchial chamber, otic gas bladder, and Weberian apparatus-linked gas bladder, have been demonstrated to improve the hearing ability of fish. The walking catfish (Clarias batrachus), a benthic species, is unique in that it has both a suprabranchial chamber (SC) and a Weberian apparatus-linked, encapsulated gas bladder (WGB). This study aimed to investigate the respective roles of these two structures in contributing to the overall hearing ability of walking catfish.
Results: The auditory evoked potentials method was used to measure hearing thresholds in intact fish and fish with a deflated WGB and/or SC. Gas removal from the WGB increased auditory thresholds at all frequencies tested (0.4 to 5.0 kHz), whereas injection of water into the SC shifted the threshold only at frequencies below 3.0 kHz. However, such a correlation was not observed for the SC at 4.0 and 5.0 kHz.
Conclusions: The findings indicated that both the encapsulated WGB and the SC had an accessory auditory role. However, WGB enhanced hearing abilities in the whole frequency range, whereas SC did not.

Key words: Hearing ability; AEP; Catfish; Weberian apparatus; Suprabranchial chamber.

*Correspondence: E-mail: hyyan@gate.sinica.edu.tw