Thyroid hormone-dependent metamorphosis in a direct developing frog.
The direct developing anuran, Eleutherodactylus coqui, lacks a tadpole, hatching as a tiny frog. We investigated the role of the metamorphic trigger, thyroid hormone (TH), in this unusual ontogeny. Expression patterns of the thyroid hormone receptors, TRalpha and TRbeta, were similar to those of indirect developers. TRbeta mRNA levels increased dramatically around the time of thyroid maturation, when remodeling events reminiscent of metamorphosis occur. Treatment with the goitrogen methimazole inhibited this remodeling, which was reinitiated on cotreatment with TH. Despite their radically altered ontogeny, direct developers still undergo a TH-dependent metamorphosis, which occurs before hatching. We propose a new model for the evolution of anuran direct development.
Callery
E M
EM
Department of Anatomy and Cell Biology and Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 3G5.
Elinson
R P
RP
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D013956:Antithyroid Agents / Q000494:pharmacology; D002025:Bufonidae / Q000196:embryology*; D003001:Cloning, Molecular; D004625:Embryo, Nonmammalian / Q000187:drug effects; D007150:Immunohistochemistry; D008675:Metamorphosis, Biological / Q000502:physiology*; D008713:Methimazole / Q000494:pharmacology; D008969:Molecular Sequence Data; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D013963:Thyroid Hormones / Q000502:physiology*; D013997:Time Factors
D013956:Antithyroid Agents; D011988:Receptors, Thyroid Hormone; D012269:Ribosomal Proteins; D013963:Thyroid Hormones; C075184:ribosomal protein L8, rat; D008713:Methimazole