Thyroxine is the hormone responsible for metamorphosis in frogs.

Metamorphosis is the process by which a frog undergoes transformation from its larval stage (tadpole) to its adult stage. During this process, various changes occur in the frog's body structure, physiology, and behavior.

Thyroxine is a hormone produced by the thyroid gland in the frog's body. It plays a crucial role in regulating the metabolic rate and influencing the growth and development of various organs and tissues.

During the tadpole stage, the frog primarily relies on gills for respiration and has a long tail for swimming. However, as the tadpole grows, it needs to undergo metamorphosis to adapt to a terrestrial lifestyle. Thyroxine plays a key role in orchestrating these changes.

Here is how thyroxine affects different aspects of metamorphosis in frogs:

1. Tail resorption: Thyroxine induces the gradual absorption of the tadpole's tail, which is no longer needed for swimming in the adult frog. This process involves the breakdown of tail tissues and their reabsorption by the body.

2. Gill development: Thyroxine stimulates the development of lungs in the frog while suppressing the growth of gills. As a result, the frog transitions from aquatic respiration to breathing air.

3. Limb development: Thyroxine promotes the growth and differentiation of limb buds, leading to the development of legs. The hind legs appear first, followed by the front legs.

4. Skin changes: Thyroxine influences the pigmentation and texture of the frog's skin. It causes the tadpole's smooth, slimy skin to transform into the rough, dry skin of an adult frog.

Overall, thyroxine acts as a master regulator during frog metamorphosis, coordinating the timing and sequence of developmental changes. It controls the transition from aquatic to terrestrial life by initiating morphological, physiological, and behavioral modifications.

In conclusion, thyroxine is the hormone responsible for metamorphosis in frogs. It plays a vital role in the transformation from tadpole to adult frog, regulating the development of various organs and tissues.