Meeting Abstract

P3.28  Monday, Jan. 6 15:30  The effect of thyroid hormone on skeletal development in Xenopus laevis FERREIRA, A.*; GILMORE, E.; DION, J.; DAVIS, A.M.; MAGLIA, A.M.; SHEARMAN, R.M.; Framingham State Univ, MA; Framingham State Univ, MA; Framingham State Univ, MA; Framingham State Univ, MA; National Science Foundation, Arlington, VA; Framingham State Univ, MA aferreira5@student.framingham.edu

Thyroid hormone plays a key role in growth and development, including the initiation of ossification. Tri-iodothyronine (T3) is the active form of thyroid hormone in vertebrates. In frogs, T3 is responsible for the initiation and regulation of the dramatic metamorphic changes involved in the transition from the tadpole to the adult frog. Exposure to exogenous T3 has been shown to cause accelerated metamorphic change in Xenopus laevis (African clawed frog) tadpoles, including precocious tail resorption and progression of cartilage development. In addition, Hanken and Hall (1988) indicated that thyroid hormone increased the rate of ossification of the parashpenoid, frontoparietal, and exoccipital bones in Bombina orientalis (Oriental fire-bellied toad). Herein, we exposed X. laevis tadpoles to two different concentrations of exogenous T3 for 48 hours during early pre-metamorphic development (Nieuwkoop and Faber Stage 50). Tadpoles were then reared without further T3 exposure, developmental series were collected, and specimens were cleared and double stained for cartilage and bone. Tadpoles in the T3 treated groups were relatively smaller (snout-vent length) and reached NF stages faster than those in the untreated group. Similar to Hanken and Hall’s (1988) findings, onset of ossification of the parasphenoid, frotoparietal, and exoccipital occurred earlier (relative days) in T3 treated tadpoles than in untreated tadpoles. In addition, some bones of the upper and lower jaw began ossification at earlier NF stages in T3 treated tadpoles. In light of our findings, we revisit Hanken and Hall’s (1988) hypothesis that interspecific differences in ossification sequence may be the result of variation in sensitivity of osteogenic centers to T3.