Multiple exaptations leading to fish sound production

Abstract

The term exaptation introduced by Stephen J. Gould and Elizabeth Vrba has been used infrequently. The high diversity of sound‐producing mechanisms in fishes highlights a recurrent use of this process in unrelated taxa. We propose that sonic evolution typically involves exaptations: in many fish taxa, sound production was acquired by the independent modification of existing structures with other functions. These structures were modified into complex effectors for courtship and agonistic sound production without major changes to their gnathostome Bauplan. Existing anatomical structures (teeth, bones, etc.) were likely first used in non‐voluntary sound production, which incidentally provided advantages and could then be selected specifically for signal production leading to the refinement of more sophisticated sonic organs. We postulate that in many if not most cases, sound‐production specializations originated in fish taxa that took advantage of incidental non‐voluntary sounds. We use different case‐studies to show that exaptation may be a key, albeit largely unrecognized, agent of major morphological and behavioural changes.

Disturbance calls of five migratory Characiformes species and advertisement choruses in Amazon spawning sites

“…There is a wide diversity of independently‐derived sonic muscles in teleosts (Fine & Parmentier, ) and these have arisen as exaptations of structures used in other contexts such as buoyancy, swimming and feeding (Parmentier et al ., ). Sonic muscles may be intrinsic, attaching exclusively to the swimbladder, or extrinsic with a variably‐distant origin and attaching directly to the swimbladder or indirectly to a bone or tendon that moves the swimbladder (Ali et al ., ; Fine et al ., ; Fine & Parmentier, ).…”

Sound production in femaleTrichopsis schalleri(Labyrinth fishes): comparison to males and evolutionary considerations

“…A process in which an existing structure is modified and takes over a second function is termed exaptation by Parmentier et al (2017). Those authors argue that sonic mechanisms in fishes (and perhaps other vertebrates) are often the result of exaptation.…”

Sound production mechanism in triggerfish (Balistidae): a synapomorphy

“…Therefore, we can reasonably argue that the detailed sonic mechanism using pectoral fins, scutes and the swim bladder could be a strong Balistidae feature. It could have evolved from locomotory movement and be a new example of exaptation (Parmentier et al, 2017a). Despite large similarities, sounds of B. undulatus are different from the sounds of R. aculeatus and R. rectangulus in terms of total duration and dominant frequency.…”