Question

Neoteny is shown by the members of
(a)Urodela
(b)Anura
(c)Apoda
(d)Lacertilia

Answer 1

Hint: Juvenilization is another name for neoteny and is the delaying or slowing of the physiological (or somatic) development of an organism and is mainly in some amphibian species.

Complete answer:
Neoteny can be defined as the failure or delay of the larva to metamorphose while becoming sexually mature. It is the character of some animals, mainly amphibians. One of the best examples is the axolotl larva of Amblystoma. This aquatic animal has gills, develops gonads, lays eggs, and attains a large size. Amblystoma on the other hand is also terrestrial and without gills. It was considered that the axolotl should be a separate genus in the beginning. But with the administration of thyroxine, axolotl lost its gills and developed lungs. It metamorphosed into the adult. By reducing the water level, the metamorphosis of axolotl can be induced.
Proteus and Necturus are permanently neotenous forms. They retain their larval features and reproduce sexually like a mature animal.

Additional information:
Kollmann classified neoteny into two categories:
-Partial neoteny: The most simple postponement of metamorphosis beyond the normal period is included in this type. Retardation of metamorphosis can occur due to temporary changes in ecological conditions or due to sudden physiological abnormality.
-Total neoteny: The animals under this category become sexually mature at the larval stage but retain larval characters, like (i) external gills, (ii) tail-fin, (iii) ill-developed eyes, (iv) ill-developed fin on the back and (v) very weak limbs. Total neotenic animals are paedogenic.
Additionally, paedogenesis involves the capability of reproduction at the larval stage. In the case of total neoteny, the sexually functional larvae cease to metamorphosis. In extreme cases of total neoteny as seen in Necturus and Proteus the larvae attain sexual maturity and they remain in that stage without undergoing metamorphosis.

So, the correct answer is ‘Urodela’.

Notes: It was considered that formerly full neotenic forms with external gills should be placed in the group of most primitive amphibians. But, today it is believed that it can be the result of secondary adaptive modifications in their larval stage.