Meeting Abstract
Weberian apparatus (WA), known to enhance hearing in otophysan fishes, conduct sound vibrations through coupling of the gas bladder and inner ear. WA of the zebrafish are well developed with four pair of ossicles, and present diverse morphotypes in laboratory settings, and thus provide a great platform to understand the conductive hearing system of vertebrates. A key question is whether an isometric growth model (IM) can explain observed hearing capability of zebrafish through ontogeny. Here we present the first study to model isometric WA growth in zebrafish. We scanned an adult zebrafish using uCT (4.67 um/voxel) and reconstructed the WA digitally at its original size (OM, length of the ossicular chain (Lwoc) 2.6 mm). We then generated an IM series allowing size to vary from 1 to 10 mm in Lwoc. To evaluate their biomechanical performance, we performed harmonic analyses using Finite Element Analysis. The results show that the OM of WA predicts the expected amplitude and phase of the vibration. Second, analyses of the IM series result in proportional increase of bone displacement in each ossicle and a constant amplitude factor (ratio of amplitude of the first and last ossicles) with increasing size. Results from the OM suggest that the WA acts as a spring-transmitter at audible frequencies, permitting a coupling of gas bladder motion to the saccule. Furthermore, the IM could explain observed audiogram in actual zebrafish ontogenetic sequences. These findings suggest that the functionality of WA could be weakly influenced by allometric changes in ossicles chain morphology through zebrafish ontogeny. This model has potential to further elucidate whether the WA in different otophysan species of varied WA morphologies and sizes are comparable in terms of biomechanical performance.
