The inner ear proteome of fish

The mechanisms that underpin the formation, growth and composition of otoliths, the biomineralized stones in the inner ear of fish, are largely unknown, as only a few fish inner ear proteins have been reported. Using a partial transcriptome for the inner ear of black bream (Acanthopagrus butcheri), in conjunction with proteomic data, we discovered hundreds of previously unknown proteins in the otolith. This allowed us to develop hypotheses to explain the mechanisms of inorganic material supply and daily growth band formation. We further identified a likely protein mediator of crystal nucleation and an explanation for the apparent metabolic inertness of the otolith. Otoliths are routinely employed as natural chronometers, being used for age and growth estimation, global fisheries stock assessments, and the reconstructions of habitat use, movement, diet histories, and the impacts of climate change. Our findings provide an unprecedented view of otolith molecular machinery, aiding in interpretation of these essential archived data.