Development of neuroendocrine components of the thyroid axis in the direct-developing frog Eleutherodactylus coqui: formation of the median eminence and onset of pituitary TSH production.
Direct-developing frogs lack, wholly or in part, a wide range of larval features found in metamorphosing species and form adult-specific features precociously, during embryogenesis. Most information on thyroid regulation of direct development relies on hormone manipulations; the ontogeny of many thyroid axis components has not been fully described. This analysis examines differentiation of the median eminence of the hypothalamus and production of thyroid-stimulating hormone (TSH) by the pituitary of the direct-developing frog Eleutherodactylus coqui. The median eminence is established two-thirds of the way through embryogenesis. Cells immunoreactive to human TSHβ antibodies are first detected during embryogenesis and quantitative changes in TSHβ-IR cells resemble those in metamorphosing amphibians. Formation of the median eminence of the hypothalamus and TSHβ production by the pituitary precede or coincide with morphological changes during embryogenesis that occur during metamorphosis in biphasic anurans. Thus, while the onset of neuroendocrine regulation has changed during the evolution of direct development, it is likely that these thyroid axis components still mediate the formation of adult features.
Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, CO 80309, United States; Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States. Electronic address: dajenni@siue.edu.
David H
DH
Jennings
Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States.
Bryce
B
Evans
Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, CO 80309, United States.
James
J
Hanken
D000818:Animals; D001001:Anura / Q000196:embryology* / Q000378:metabolism; D001927:Brain Diseases / Q000378:metabolism / Q000473:pathology*; D002454:Cell Differentiation; D005260:Female; D007124:Immunoenzyme Techniques; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D008297:Male; D008473:Median Eminence / Q000378:metabolism / Q000473:pathology*; D008675:Metamorphosis, Biological / Q000502:physiology*; D010902:Pituitary Gland / Q000196:embryology* / Q000378:metabolism; D013961:Thyroid Gland / Q000196:embryology* / Q000378:metabolism; D013972:Thyrotropin / Q000378:metabolism*
D013972:Thyrotropin
Direct development; Median eminence; Metamorphosis; Thyroid axis; Thyroid-stimulating hormone