Diving into dual functionality: Swim bladder muscles in lionfish for buoyancy and sonic capabilities.

Area of Science:

• Ichthyology
• Bioacoustics
• Functional Morphology

Background:

• The swim bladder primarily aids buoyancy but can be involved in hearing and sound production.
• The use of swim bladder muscles for sound may be an exaptation, with limited models demonstrating dual function in movement and sound.
• Investigating the functional roles of swim bladder-associated muscles in Pteroinae (lionfish) is crucial for understanding their bioacoustics and locomotion.

Purpose of the Study:

• To investigate the functions of swim bladder-associated muscles in lionfish species.
• To determine if these muscles are involved in sound production and/or locomotion.
• To explore the potential exaptive use of these muscles for sound generation.

Main Methods:

• Electromyography and histology to analyze sonic muscles.
• Cineradiography to observe muscle function during movement and sound production.
• Analysis of sonic features, morphology, and sound production in Pterois volitans, P. radiata, and Dendrochirus zebra.

Main Results:

• Pterois volitans, P. radiata, and Dendrochirus zebra produce low-frequency hums and knocks when disturbed.
• Sound production is linked to muscles originating from the neurocranium and inserting on the swim bladder.
• Cineradiography shows these muscles alter swim bladder shape and body pitch, aiding locomotion.

Conclusions:

• Swim bladder-associated muscles in lionfish are likely responsible for sound production (hums and knocks) and locomotion.
• Fast muscle contractions correlate with sound production, while sustained contractions modify swim bladder shape and body pitch.
• This study provides evidence for the dual role of these muscles, supporting the exaptation hypothesis for sound production.