Question

Axolotl larva possesses
a. External gills
b. Laterally compressed tail
c. Caudal fin
d. All of the above

Answer 1

Hint: Larva are the immature stages of an organism which in normal course matures into a fully fertile adult organism. In amphibia, the larva are aquatic and contain gills for respiration and fins. However, they lose all these features upon reaching adulthood.

Complete answer:
Axolotl is an amphibian and is the larva of tigrinum or tiger salamander. They are very similar to the salamander larvae as they possess external gills and a caudal fin which extends from behind the head and up to the vent. The axolotls reach adulthood without undergoing metamorphosis and exhibit neoteny. This can be described as a process in which instead of developing lungs and moving onto the terrestrial habitats, the adults remain aquatic and possess gills.

The axolotl larva possesses three pairs of external gill stalks or rami. The gill stalk arises behind their heads and is employed in the movement of oxygenated water. In order to increase surface area of the external gill rami, they are lined with filaments which are used for gas exchange. Gill filaments are also known as fimbriae. Underneath the external gills, four gills are found and the gill slits are lined with gill rakers. The main purpose of the external gills is respiration. In addition to this, buccal pumping or the process of gulping air from the surface may be used in order to receive oxygen.

In Axolotl larva legs and feet are rather smaller in structure while the tail is long. The tail present is laterally compressed. The caudal fin extends from the back of the head to the tip of the tail. A fin extends to the tip of the tail from between the hind legs.

Axolotls are the larva which retain the different larval characteristics of amphibians such as gills, caudal fin, laterally compressed tail but reach sexual maturity without undergoing metamorphosis. Thus, Axolotl larva exhibit the structural features similar to the typical salamander larvae.

Hence, the correct answer is option (D).

Note: The Axolotl larva are the larva of the salamander Ambystoma spp. These larvae retain their larval characteristics such as external gills, caudal fin and a laterally compressed tail. The larva matures into adulthood but still bear all the structural peculiarities of the larval stage. Hence, the axolotl larva bear pairs of external gills, caudal fin as well as laterally compressed tail.