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

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.