Predicting pressure sensitivity through ontogeny in larval red drum (Sciaenops ocellatus)

Abstract

Detecting acoustic pressure allows larval fishes to hear lower amplitude sounds at a broader frequency range compared to detection of particle motion alone, improving settlement success and survival for fishes that use acoustic cues. Rapid development alters bladder dimensions and otolith-bladder distances, factors influencing pressure sensitivity, suggesting ontogenetic change in this sensory capability. Micro-computed tomography of lab-reared red drum (Sciaenops ocellatus) was used in a finite-element model to predict pressure sensitivity in larvae 8.5 to 18 mm in standard length. In the model, swim bladder and otolith geometry were exposed to a plane wave at frequencies within the typical audible frequency range. The acceleration at points on the sagitta, asteriscus, and lapillus when the bladder was air-filled was compared to results from models using a water-filled bladder. The air-filled bladder amplified otolith motion by a factor of 57 to 3773 times that of a water-filled bladder at 2000 Hz, with a small decrease in amplification with excitation frequencies farther from bladder resonance. Otolith-bladder distances increased with standard length, which decreased amplification, but a rapid increase in bladder volume with fish size partially compensated. Larval fishes are predicted to detect acoustic pressure but experience changes in pressure sensitivity during early development.Detecting acoustic pressure allows larval fishes to hear lower amplitude sounds at a broader frequency range compared to detection of particle motion alone, improving settlement success and survival for fishes that use acoustic cues. Rapid development alters bladder dimensions and otolith-bladder distances, factors influencing pressure sensitivity, suggesting ontogenetic change in this sensory capability. Micro-computed tomography of lab-reared red drum (Sciaenops ocellatus) was used in a finite-element model to predict pressure sensitivity in larvae 8.5 to 18 mm in standard length. In the model, swim bladder and otolith geometry were exposed to a plane wave at frequencies within the typical audible frequency range. The acceleration at points on the sagitta, asteriscus, and lapillus when the bladder was air-filled was compared to results from models using a water-filled bladder. The air-filled bladder amplified otolith motion by a factor of 57 to 3773 times that of a water-filled bladder at 2000 Hz, with ...