Question

Which of the following are correct for axolotl larva?
(i) It shows neoteny and paedogenesis.
(ii) The absence of thyroxine affects metamorphosis.
(iii) It is the larva of hemichordata.

• A. (i), (ii) and (iii)
• B. (i) and (ii)
• C. (ii) and (iii)
• D. (iii)

Answer 1

The correct option is B (i) and (ii)

The axolotl also known as a Mexican salamander (Ambystoma mexicanum) or a Mexican walking fish, is a neotenic salamander, closely related to the tiger salamander. Although the axolotl is colloquially known as a walking fish, it is not a fish, but an amphibian. Axolotls exhibit neoteny, meaning they reach sexual maturity without undergoing metamorphosis.

In the axolotl, metamorphic failure is caused by a lack of thyroid stimulating hormone, which is used to induce the thyroid to produce thyroxine in transforming salamanders. The feature of the salamander, that attracts the most attention is its healing ability: the axolotl does not heal by scarring and is capable of the regeneration of entire lost appendages in a period of months (paedogenesis). In some cases, axolotls have been known to repair a damaged limb, as well as regenerating an additional one, ending up with an extra appendage.