Meeting Abstract
Thyroid hormone (TH) is critically important to numerous aspects of vertebrate development, and can affect coordinated suites of traits. The hormone affects ossification and craniofacial morphogenesis, but the specific sensitivities of different craniofacial elements, and the integration with functional feeding behavior remained poorly understood. We show that in zebrafish, normal levels of TH are required for proper craniofacial development, and for normal kinematic integration of adult feeding behavior. Hypothyroidism results in incomplete ossification of numerous bones and altered craniofacial proportions. We show that TH is required for properly integrated suction feeding behavior, and that a lack of TH disrupts feeding kinematics in several respects, including changes to jaw protrusion, cranial elevation and hyoid depression. Moreover, we find that the hormone coordinates the onset of adult feeding behavior, and that the feeding kinematics of hypothyroid adults resemble those of larvae in certain aspects. Given the coordinated changes induced by modulating TH, evolutionary changes in TH production and metabolism are hypothesized to play an important role in craniofacial adaptation and diversification. To place the craniofacial skeletogenesis and feeding behaviors influenced by TH into a broader phylogenetic context, we examined the feeding kinematics of seven other Danionin species, including the paedomorphic genus Danionella. We show that disrupted TH metabolism in zebrafish causes some aspects of craniofacial morphometrics and feeding kinematics to more closely resemble those of other species, suggesting that changes in TH may indeed play a role in craniofacial diversification.
