Tag: metamorphosis in frogs

Gudernatsch discovered that metamorphosis in frog's tadpole begins only when adequate amount of thyroxine is secreted by the thyroid of the tadpole. It was also found that hyposecretion of thyroxine retards and hypersecretion enhances the rate of metamorphosis. In the hilly tracts of North America from whose soil all iodine has been washed away by rainwater, the tadpoles of Ambystoma probably never metamorphose. Therefore, these tadpoles grow to a large size and attain sexual maturity,i.e., these become paedogenetic larvae. This phenomenon is called paedogenesis. The paedogenetic larvae of Ambystoma are called Axolotl larvae. Addition of thyroxine or iodine in pond water naturally induces and enhances metamorphosis in the tadpoles.

Metamorphosis is the process of transformation from an immature form to an adult form in two or more distinct stages. metamorphosis generally takes place in insects or amphibians and some molluscs, crustaceans, cnidarians, echinoderms and tunicates.
Metamorphosis is seen in frogs which are developed form of the larval stage called the tadpoles. Also, metamorphosis is seen in insects where the adult forms develop from the larva and which also includes the pupal or resting stages as in silkworms.
So, the correct answer is option D.

A tadpole (also called a pollywog) is the larval stage in the life cycle of an amphibian, particularly that of a frog or toad. They are usually wholly aquatic, though some species have tadpoles that are terrestrial. When first hatched from the egg they have a more or less globular body, a laterally compressed tail and internal or external gills. As they grow they undergo metamorphosis, during which process they grow limbs, develop lungs and reabsorb the tail. Most tadpoles are herbivorous. 

Metamorphosis is the sequential developmental stages which are characterized by the process of cell division, differentiation, and maturation. It includes morphological and genetical changes.

Both amphibians and insects have larval forms. They also undergo a process called metamorphosis to come out of the larval stage. In addition to that both use DNA, RNA, ATP, the basic metabolic processes are the same. They are  multicellular organisms. they have a bilateral symmetry, they are both eukaryotes. They have  specializations of cells in regard to sensory, reproductive and metabolic systems. 

Insects shed their exoskeleton in order to grow which is known as moulting. Moulting allows the body of insects to expand under protected conditions. An instar is a developmental stage of insects, between each moult until sexual maturity is reached.

• Molting hormone or Ecdysone is produced by the prothoracic glands which regulates metamorphosis.
  
• It's principle function is to stimulate a series of physiological events (collectively known as apolysis) that lead to synthesis of a new exoskeleton.
• During this process, the new exoskeleton forms as a soft, wrinkled layer underneath the hard parts (exocuticle plus epicuticle) of the old exoskeleton.