Summary
Thyroid hormones trigger the tadpole to frog change, including tail loss and limb growth.
In depth
Thyroid hormone drives resorption of the tail, growth of limbs, gill loss and remodelling of the gut. Tail cells undergo apoptosis. Without thyroid hormone, tadpoles grow but do not metamorphose.
Different tissues respond differently to the same hormone: tail cells die, limb cells grow. Thyroid hormone receptors and deiodinase enzymes control tissue-specific response. Environmental pollutants can disrupt this.
Remember: it is a classic example of hormone-triggered development.
In frogs, the aquatic herbivorous tadpole transforms into a land-living carnivorous adult. Rising thyroid hormone (thyroxine and triiodothyronine) from the thyroid triggers it, and tissues respond differently: limbs grow, the tail is resorbed by apoptosis, gills are replaced by lungs, the gut shortens and eyes reposition.
Prolactin opposes metamorphosis, and timing is influenced by temperature and food. Removing the thyroid keeps tadpoles larval, while adding thyroid hormone speeds the change. Some salamanders such as axolotls stay larval (neoteny) unless treated with thyroid hormone.
Example: tail cells die because of lysosomal enzymes.
Key idea: one hormone causes opposite fates in different tissues.
Frequently asked questions
What is Metamorphosis in Amphibians?
Thyroid hormones trigger the tadpole to frog change, including tail loss and limb growth.
Which area of biology covers Metamorphosis in Amphibians, and how advanced is it?
Metamorphosis in Amphibians is one of the 54 topics in Developmental Biology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Sex Determination, Induction, Apoptosis in Development.
Can you give an example of Metamorphosis in Amphibians?
Axolotls retain larval features (neoteny) unless given thyroid hormone.
What should I learn before Metamorphosis in Amphibians?
Metamorphosis in Amphibians is a Beginner topic, so no earlier topic is required. Other Beginner topics in Developmental Biology that pair well with it include Fertilisation, Zygote, Embryo.
What topics are related to Metamorphosis in Amphibians?
The closest topics to Metamorphosis in Amphibians are Sex Determination, Induction, Apoptosis in Development, Developmental Timing. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Metamorphosis in Amphibians?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Metamorphosis in Amphibians. To practise the whole of Developmental Biology, use the Developmental Biology quiz.
How is Metamorphosis in Amphibians different from Sex Determination?
Metamorphosis in Amphibians: Thyroid hormones trigger the tadpole to frog change, including tail loss and limb growth. Sex Determination: The SRY gene on the Y chromosome triggers male development in mammals. Read both side by side and note what each one explains.
How should I study Metamorphosis in Amphibians step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Sex Determination and explain the difference aloud. Finally, take the Developmental Biology quiz and come back to this page for any question you miss.