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Morphological integration in the cranium during anuran metamorphosis.
J Hanken1, C H Summers, B K Hall
1Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder 80309-0334.
Experientia
|September 15, 1989
Summary
Thyroid hormone (T3) drives cranial cartilage and bone development during anuran metamorphosis. However, T3 acts independently on each tissue, revealing separate developmental timing rather than tight coupling.
Area of Science:
- Developmental biology
- Endocrinology
- Comparative anatomy
Background:
- Anuran metamorphosis involves significant cranial remodeling.
- Thyroid hormone is a key regulator of amphibian metamorphosis.
- Cranial cartilage and bone must integrate during this process.
Purpose of the Study:
- To investigate the role of thyroid hormone in integrating cranial cartilage and bone during anuran metamorphosis.
- To determine if thyroid hormone synchronizes developmental events between cranial cartilage and bone.
Main Methods:
- Premetamorphic tadpoles (Bombina orientalis) received intracranial implants of plastic micropellets delivering exogenous triiodothyronine (T3).
- Morphological changes in cranial cartilage and bone were assessed following T3 treatment.
- The relative timing of developmental events in both tissues was compared.
Main Results:
- Exogenous T3 precociously induced metamorphic changes in both cranial cartilage and bone.
- T3 treatment dissociated the relative timing of developmental events between cartilage and bone.
- Cranial tissues respond independently to endocrine factors.
Conclusions:
- Morphological integration of cranial cartilage and bone during metamorphosis is partly mediated by independent tissue responses to endocrine factors.
- Developmental coupling between cranial cartilage and bone is not tightly regulated by thyroid hormone.
- Thyroid hormone influences cranial development but does not strictly synchronize cartilage and bone maturation.