Convergent evolution and intermediate status of the sonic mechanism in a perciform fish Glaucosoma buergeri (Glaucosomatidae).

Abstract

Little is known about evolution of swimbladder sound production in fishes. Typical fish sound production utilizes fast muscles that drive the swimbladder to produce sound as a forced but rapidly‐damping response; a muscle contraction rate of 200 times/s will generate a sound with a fundamental frequency of 200 Hz. Recently, slow muscles have been demonstrated in a carapid fish. These muscles slowly extend the anterior swimbladder by stretching a swimbladder fenestra until the bladder snaps back exciting sound production. Here we describe sounds produced by a similar but phylogenetically‐unrelated mechanism in a perciform fish. A pair of extrinsic sonic muscles originates on the pterotic bones and inserts on the anterodorsal swimbladder just forward of a stretchable swimbladder fenestra. A fan‐shaped tendon that ends in a smooth muscle attaches to the bladder just forward of the fenestra. The tendon‐smooth muscle pair will be stretched by contraction of the rostral sonic muscles. Strain energy stored in th...