Oyster shells acting as amplifiers   

The most plausible hypothesis to explain this power of diffusion is also the most amusing.  The oysters may not only be a source of shelter; they may also serve as an amplifier, thus amplifying the sounds emitted by Onuxodon, and therefore increasing their chances of being heard by their fellow pearlfish. "It’s a tentative idea", Loïc Kéver adds carefully. "Because, once again, we don’t know if they only emit sound from inside the oyster or also outside their host. We also don’t know if they use the bivalves as amplifiers, and if this behaviour has a decisive role in terms of calling or reproducing. In any case, we sent shells to Marco Lugli, an Italian researcher and co-author of the publication. He kept the shells in a half-open position which is close to the natural position. He placed a diffuser in them that emitted a white noise, whereby all the frequencies are at the same intensity, and a microphone. He noticed that the sound emitted was amplified by the oysters, particularly regarding the frequencies close to those that we found mainly in the sounds collected in Onuxudon."

 
These are encouraging initial results, that nevertheless require more in-depth research. The oyster can indeed amplify the sound emitted by Onuxodon. But is this particularity useful to these fish, or is it superfluous, calculated, or are they unaware of it? Another question whose answer shall depend on more in-depth behavioural studies. Even if the fact that the oyster shells can facilitate the propagation of sound in an environment as noisy as the coral reefs appears to be particularly useful. This ingenious discovery, whether accidental or not, has helped this branch of species to evolve. However, these initial experiments on oysters were carried out in an aquarium. And the propagation of sound is still a tricky phenomenon to understand and study, since it varies greatly depending on the environment. Nothing allows the researchers to confirm that these properties are just as efficient in the depths of the lagoons. Thanks to the studies in the aquarium, it was possible to elaborate plausible and appealing hypotheses. Nevertheless, the nocturnal activity of these fish and the time they spend hidden in their oysters make it difficult to study them and requires new experiments to be carried out in the field.