Q.What are parapodia? Name the animal in which they occur as locomotor structures.

[!TLDR] Parapodia are paddle-like lateral extensions used for locomotion in polychaetes such as Nereis. …

[!ANSWER] Parapodia are the characteristic locomotor appendages of class Polychaeta.

Each body segment of a polychaete bears a pair of fleshy, paddle-like lateral projections called parapodia, each armed with numerous chitinous bristles (setae). By rhythmically moving these parapodia against the surrounding water or substrate, polychaetes such as Nereis (the ragworm) generate the thrust needed for both crawling over a surface and active swimming, making parapodia the primary locomotor structures of the class. Parapodia are absent in the other two annelid classes, Oligochaeta and Hirudinea — Oligochaetes (like Pheretima) instead bear only a few simple setae directly from the body wall, without any pa …

• Confusing parapodia with the simple setae of Oligochaeta — parapodia are a much larger, paddle-like structure unique to Polychaeta. …