Impedance transformation by the middle ear of terrestrial vertebrates is considered to be a function of the ossicular lever apparatus, which increases force and decreases velocity at the stapes footplate relative to the tympanic membrane, and the ratio of tympanic membrane area to stapes footplate area (the area ratio), which increases pressure at the stapes. A recent vibrometric study has found that the velocity ratio between tympanic membrane and stapes footplate is higher in male bullfrogs (Rana catesbeiana) than in females. Although the tympanic membrane area is known to be larger in male bullfrogs, the area ratio has apparently never been compared between the sexes. The hypothesis that a lower area ratio in males helps to compensate for the higher velocity ratio was investigated by comparing tympanic membrane, stapes footplate and operculum areas in frogs of both sexes. Contrary to expectation, the difference in stapes footplate area between males and females is very small, and area ratios are considerably higher in males. Area ratios increase with increasing body size in both sexes. Operculum area does not differ between the sexes. The apparent difference in impedance transformation between male and female frogs might be necessary due to different inner ear impedances, or might reflect serious inadequacies in the conventional models of middle ear function.

Keywords:
Middle ear, Bullfrog, Sexual dimorphism, Area ratio, Tympanic membrane
1.
Anson, M., A.C. Pinder, M.J. Keating, and S.H. Chung (1985) Acoustic vibration of the amphibian eardrum studied by white noise analysis and holographic interferometry. J. Acoust. Soc. Am., 78: 916–923.
2.
Boatright-Horowitz, S.S., and A. Megela Simmons (1995) Postmetamorphic changes in auditory sensitivity of the bullfrog midbrain. J. Comp. Physiol. A, 177: 577–590.
3.
Bolt, J.R., and R.E. Lombard (1985) Evolution of the amphibian tympanic ear and the origin of frogs. Biol. J. Linn. Soc., 24: 83–99.
4.
Capranica, R.R. (1966) Vocal response of the bullfrog to natural and synthetic mating calls. J. Acoust. Soc. Am., 40: 1131–1139.
5.
Capranica, R.R. (1976) Morphology and physiology of the auditory system. In Frog Neurobiology (ed. by R. Llinas and W. Precht), Springer Verlag, Berlin, pp 551–557.
6.
Dallos, P. (1973) The Auditory Periphery: Biophysics and Physiology. Academic Press, New York.
7.
Duellman, W.E., and L. Trueb (1986) Biology of Amphibians. The Johns Hopkins University Press, Baltimore, MD.
8.
Fox, J.H. (1995) Morphological correlates of auditory sensitivity in anuran amphibians. Brain Behav. Evol., 45: 327–338.
9.
Frishkopf, L.S., R.R. Capranica, and M.H. Goldstein (1968) Neural coding in the bullfrog’s auditory system – a teleological approach. Proc. IEEE, 56: 969–980.
10.
Gummer, A.W., J.W.T. Smolders, and R. Klinke (1989) Mechanics of a single-ossicle ear: I. The extra-stapedius of the pigeon. Hear. Res., 39: 1–13.
11.
Hetherington, T.E. (1992a) The effects of body size on the evolution of the amphibian middle ear. In The Evolutionary Biology of Hearing (ed. by D.B. Webster, R.R. Fay and A.N. Popper), Springer-Verlag, New York, pp 421–437.
12.
Hetherington, T.E. (1992b) The effects of body size on functional properties of middle ear systems of anuran amphibians. Brain Behav. Evol., 39: 133–142.
13.
Hetherington, T.E. (1994) Sexual differences in the tympanic frequency responses of the American bullfrog (Rana catesbeiana). J. Acoust. Soc. Am., 96: 1186–1188.
14.
Jaslow, A.P., T.E. Hetherington, and R.E. Lombard (1988) Structure and function of the amphibian middle ear. In The Evolution of the Amphibian Auditory System (ed. by B. Fritzsch, M.J. Ryan, W. Wilczynski, T.E. Hetherington and W. Walkowiak), John Wiley and Sons, New York, pp 69–91.
15.
Jørgensen, M.B., and M. Kanneworff (1998) Middle ear transmission in the grass frog, Rana temporaria. J. Comp. Physiol. A, 182: 59–64.
16.
Khanna, S.M., and J. Tonndorf (1972) Tympanic membrane vibrations in cats studied by time-averaged holography. J. Acoust. Soc. Am., 51: 1904–1920.
17.
Manley, G.A. (1972) The middle ear of the Tokay gecko. J. Comp. Physiol., 81: 239–250.
18.
Mason, M.J., and P.M. Narins (2002a) Vibrometric studies of the middle ear of the bullfrog (Rana catesbeiana) I: The extrastapes. J. Exp. Biol., 205:3153–3165.
19.
Mason, M.J., and P.M. Narins (2002b) Vibrometric studies of the middle ear of the bullfrog (Rana catesbeiana) II: The operculum. J. Exp. Biol., 205: 3167–3176.
20.
Moffat, A.J.M., and R.R. Capranica (1978) Middle ear sensitivity in anurans and reptiles measured by light scattering spectroscopy. J. Comp. Physiol. A, 127: 97–107.
21.
Narins, P.M., E.R. Lewis, A.P. Purgue, P.J. Bishop, L.R. Minter, and D.P. Lawson (2001) Functional consequences of a novel middle ear adaptation in the central African frog Petropedetes parkeri (Ranidae). J. Exp. Biol., 204: 1223–1232.
22.
Noble, G.K. (1931) The Biology of the Amphibia. McGraw-Hill Book Company, Inc., New York.
23.
Pinder, A.C., and A.R. Palmer (1983) Mechanical properties of the frog ear: vibration measurements under free- and closed-field acoustic conditions. Proc. R. Soc. Lond. B, 219: 371–396.
24.
Puria, S., W.T. Peake, and J.J. Rosowski (1997) Sound-pressure measurements in the cochlear vestibule of human-cadaver ears. J. Acoust. Soc. Am. 101: 2754–2770.
25.
Purgue, A.P. (1997) Tympanic sound radiation in the bullfrog Rana catesbeiana. J. Comp. Physiol. A, 181: 438–445.
26.
Relkin, E.M. (1988) Introduction to the analysis of middle-ear function. In Physiology of the Ear (ed. by A.F. Jahn and J. Santos-Sacchi), Raven Press, New York, pp 103–123.
27.
Rosowski, J.J., L.H. Carney, T.J. Lynch, and W.T. Peake (1986) The effectiveness of external and middle ears in coupling acoustic power into the cochlea. In Lecture Notes in Biomathematics, Vol. 64: Peripheral Auditory Mechanisms (ed. by J.B. Allen, J.L. Hall, A. Hubbard, S.T. Neely and A. Tubis), Springer-Verlag, New York, pp. 3–12.
28.
Rosowski, J.J., W.T. Peake, T.J. Lynch, R. Leong, and T.F. Weiss (1985) A model for signal transmission in an ear having hair cells with free-standing stereocilia. II. Macromechanical stage. Hear. Res., 20: 139–155.
29.
Saunders, J.C., R.K. Duncan, D.E. Doan, and Y.L. Werner (2000) The middle ear of reptiles and birds. In Comparative Hearing: Birds and Reptiles (ed. by R.J. Dooling, R.R. Fay and A.N. Popper), Springer, New York, pp 13–69.
30.
Shofner, W.P., and A.S. Feng (1981) Post-metamorphic development of the frequency selectivities and sensitivities of the peripheral auditory system of the bullfrog, Rana catesbeiana. J. Exp. Biol., 93: 181–196.
31.
Snedecor, G.W., and W.G. Cochran (1967) Statistical Methods (6th ed.). The Iowa State University Press, Ames, IA.
32.
Sokal, R.R., and F.J. Rohlf (1995) Biometry (3rd ed.). W.H. Freeman and Co., New York.
33.
von Békésy, G. (1960) Experiments in Hearing (transl. and ed. by E.G. Wever). McGraw Hill Book Company Inc., New York.
34.
Werner, Y.L., and P.G. Igić (2002) The middle ear of gekkonoid lizards: interspecific variation of structure in relation to body size and to auditory sensitivity. Hear. Res., 167: 33–45.
35.
Werner, Y.L., L.G. Montgomery, S.D. Safford, P.G. Igić, and J.C. Saunders (1998) How body size affects middle-ear structure and function and auditory sensitivity in gekkonoid lizards. J. Exp. Biol., 201: 487–502.
36.
Wever, E.G., and Y.L. Werner (1970) The function of the middle ear in lizards: Crotaphytus collaris (Iguanidae). J. Exp. Zool., 175: 327–342.
37.
Wright, A.H., and A.A. Wright (1949) Handbook of Frogs and Toads of the United States and Canada (3rd ed.). Comstock Publishing Co., Ltd., Ithaca, NY.
38.
Zar, J.H. (1999) Biostatistical Analysis (4th ed.). Prentice-Hall, Upper Saddle River, NJ.
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2003
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