The differential requirement for Cib2 and Cib3 in specific hair cell subtypes in the zebrafish inner ear and lateral line is closely linked to the distinct mechanotransduction properties of these hair cells. In the primary posterior lateral line (pLL), hair cells that respond to posterior flow rely on Tmc2b, while those that respond to anterior flow can utilize both Tmc2b and Tmc2a. The study indicates that Cib2 is essential for mechanosensitive function in hair cells that express Tmc2a, which are oriented to detect anterior flow. Conversely, Cib3 appears to compensate for Cib2 in hair cells that primarily express Tmc2b and are oriented for posterior flow. This suggests that Cib2 and Cib3 may have evolved to fulfill specific roles in the mechanotransduction process, with Cib2 being crucial for the function of hair cells that require a broader range of Tmc proteins for mechanosensitivity. The ability of Cib3 to partially substitute for Cib2 in certain contexts highlights the functional redundancy and evolutionary conservation of these proteins, which may be critical for maintaining the integrity of the mechanotransduction apparatus across different hair cell types.