Question

In which among the following animals, retrogressive metamorphosis is found?
A) Vertebrata
B) Urochordata
C) Invertebrates
D) Chordates

Answer 1

Hint:Metamorphosis refers to transformation of larva into adult. In this process the juvenile larva goes through many different stages before transforming into an adult.

Complete Answer:
Firstly, we will understand what exactly is retrogressive metamorphosis.
Retrogressive metamorphosis means degenerative changes wherein an active larva metamorphoses into a sedentary adult. In Urochordata, the notochord is present only in the larval tail. Tail and nervous system are reduced in adults because the adult is sedentary.

Retrogressive metamorphosis is the characteristics of Ascidians (Urochordates or tunicata). When an organism changes from a very advanced form to its primitive form then it is called retrogressive metamorphosis. In Ascidians, a progressive and active larva metamorphoses into a primitive sedentary adult.
Now, we will look at the organisms having this type of metamorphosis-
>Examples of Urochordata are Ascidia, Salpa, Doliolum.
>Branchiostoma is a Cephalochordate and Balanoglossus is a hemichordate animal.

Additional information: In most species of animals, embryonic development leads to a larval stage with characteristics very different from those of the adult organism. Very often, larval forms are specialized for some function, such as growth or dispersal.
🡺The pluteus larva of the sea urchin, for instance, can travel on ocean currents, whereas the adult urchin leads a sedentary existence.
🡺The caterpillar larvae of butterflies and moths are specialized for feeding, whereas their adult forms are specialized for flight and reproduction, often lacking the mouthparts necessary for eating. The division of functions between larva and adult is often remarkably distinct.

Hence, the correct answer is option B (Urochordata).

Note:Animals that perform metamorphosis are said to have indirect development. In earthworm development is direct which means no larval stage and hence no metamorphosis.