Meeting Abstract
21.1 Monday, Jan. 4 Novel Toadfish Swimbladder Morphology Creates Nonlinear Acoustic Complexities RICE, Aaron N.*; LAND, Bruce R.; BASS, Andrew H.; Cornell Univ.; Cornell Univ.; Cornell Univ. arice@cornell.edu
Repeated morphological specializations of vocal structures across vertebrates have independently facilitated increased complexity in acoustic signals by generating nonlinear features. Such nonlinear acoustic complexity has been observed in vertebrate lineages including amphibians, songbirds, and mammals, but fishes have remained a notable exception. Nonlinear calls are produced by coupled peripheral vocal structures. However, most fishes only have a single swimbladder used to amplify sounds produced by sonic muscles, which constrains the ability to produce calls with such features. The toadfish, Batrachomoeus trispinosus, is unique among fishes in that it has two separate swimbladders, which may allow for an increased complexity and diversity of its vocal repertoire compared to other fishes. Detailed analysis of conspecifically and experimentally elicited B. trispinosus calls reveals that both courtship and agonistic vocalizations exhibit several classes of nonlinearities, including deterministic chaos, biphonation, subharmonics, and frequency jumps. Nonlinear time series analysis reveals that the deterministic chaos in B. trispinosus calls is consistent with chaotic calls from other tetrapods. When one of B. trispinosus’ vocal motor nerves is transected, their calls lose these nonlinear features, and both frequency and amplitude properties of the sound are altered (compared to pre-operation and sham-operated animals). This experimental manipulation provides an in vivo behavioral and physiological demonstration that the dual swimbladder system is responsible for nonlinear features present in B. trispinosus calls. The convergent, bilateral nature of peripheral vocal structures suggests a strong selection force favoring complex acoustic communicatory signals among all vocal vertebrate groups, including fishes.
