Journal of Fish Biology (2010) 77, 1406–1423 doi:10.1111/j.1095-8649.2010.02765.x, available online at wileyonlinelibrary.com The ears of butterflyfishes (Chaetodontidae): ‘hearing generalists’ on noisy coral reefs? J. F. Webb*†‡, J. L. Herman‡, C. F. Woods‡ and D. R. Ketten§ *Department of Biological Sciences, University of Rhode Island, Kingston, RI 02881, U.S.A., ‡Department of Biology, Villanova University, Villanova, PA 19085, U.S.A. and §Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, U.S.A. (Received 17 January 2009, Accepted 23 July 2010) Analysis of the morphology of all three otolithic organs (sacculus, lagena and utriculus), including macula shape, hair cell morphology, density, orientation pattern, otolith morphology and the spatial relationships of the swimbladder and ear, reveals that butterflyfishes in the genera Chaetodon (which has anterior swimbladder horns) and Forcipiger (which lacks anterior swimbladder horns) both demonstrate the ear morphology typical of teleosts that lack otophysic connections, fishes that have traditionally been considered to be ‘hearing generalists’. © 2010 The Authors Journal compilation © 2010 The Fisheries Society of the British Isles Key words: CT; hair cells; laterophysic connection; otolith; swimbladder. INTRODUCTION Coral reefs are characterized by high sound levels originating from both abiotic and biotic sources (Au, 2002). A major source of sounds on reefs are those produced by coral reef fishes (Moulton, 1958; McCauley & Cato, 1998, 2000, 2001, 2002), which communicate acoustically despite high background noise levels. Thus, hearing specializations might be expected among coral reef fishes that communicate acous- tically. For instance, members of the holocentrid subfamily Myripristinae (e.g. the soldierfishes Myripristis spp.) are sound-producing, crepuscular reef fishes (Salmon, 1967; Horch & Salmon, 1973) that possess a well-developed otophysic connection (large, robust anterior swimbladder horns in contact with the thinned wall of the otic capsule) and have enhanced hearing capabilities (lower thresholds and broader frequency range; Coombs & Popper, 1979). Their ears are characterized by very large, dense otoliths (Nelson, 1955; pers. obs.) and highly modified morphology of the sensory macula (hair cell epithelium) in the sacculus, the largest of the three otolithic organs (Popper, 1977). Interestingly, other holocentrids [e.g. squirrelfishes, Sargocentron Fowler (=Adioryx )] lack an otophysic connection (Nelson, 1955), have generalized saccular morphology (Popper, 1977) and unremarkable hearing capa- bilities (e.g. lower sensitivity and narrow range of frequency detection; Coombs †Author to whom correspondence should be addressed. Tel.: +1 401 874 2609; fax: +1 401 874 2065; email: jacqueline webb@mail.uri.edu 1406 © 2010 The Authors Journal compilation © 2010 The Fisheries Society of the British Isles