Which one among the following animals does not undergo periodic moulting of their external body covering?

Moulting, or ecdysis, is the periodic shedding of an external body covering to allow for growth. This process is a defining characteristic of the superphylum Ecdysozoa, which includes arthropods and nematodes [3]. Cockroaches and dragonflies, being arthropods, must periodically shed their hard chitinous exoskeletons to increase in size. Similarly, reptiles like the cobra (squamates) undergo ecdysis to shed their skin. In contrast, the earthworm belongs to the phylum Annelida [1]. While annelids have a moist cuticle used for gas exchange [2], they do not possess a rigid exoskeleton that requires periodic moulting for growth [1]. Instead, their bodies are segmented and flexible, allowing for growth without the shedding of the entire external body covering seen in ecdysozoans or squamates.

Sources

1. [1] https://oertx.highered.texas.gov/courseware/lesson/1754/overview
2. [3] https://www.britannica.com/science/ecdysis
3. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 9: Life Processes in Animals > 9.2.2 Do other animals breathe the same way as humans do? > p. 133