What is the functional role of the hundreds of rows of tiny teeth in the whale shark's mouth?

They are vestigial structures playing no active role in mastication

Despite possessing hundreds of rows of teeth within their massive mouths, these structures are functionally insignificant concerning the shark's primary feeding method. The teeth are minute and are explicitly characterized as vestigial structures, meaning they are remnants of ancestral features that no longer serve an active purpose in the mechanical process of chewing or tearing food. Since the whale shark is a filter feeder that ingests water and filters out organisms larger than 2 to 3 millimeters, it does not bite or masticate its food. Therefore, the presence of these teeth does not contribute to the intake or processing of their diet, which relies entirely on the specialized internal filtering apparatus located at the gill slits.