Thyroid hormone in skeletal development of cyprinids: effects and morphological consequences

Abstract

The effects of thyroid hormone (TH) level changes on skeletal development were studied in cyprinids Labeobarbus intermedius (Barbinae) and Danio rerio (Danioninae). TH was revealed to influence development of a skull, axial skeleton, paired fins and girdles, and squamation. Usually, high TH-level promotes the premature onset and acceleration of ontogenetic processes, whereas TH-deficiency delays and retards them. However, skeletal elements differ in TH-responsiveness. Alterations of TH level induce developmental changes in some structures but do not cause any changes in others. As a result, the normal sequence of ontogenetic events and the temporal interrelations between ontogenetic processes undergo changes resulting in changes in adult morphology.