Q.What are the salient features exhibited by Polychaetes?

Polychaetes are marine segmented worms distinguished by paired, bristle-bearing parapodia on nearly every segment, a well-developed sensory head, separate sexes, and indirect development via a trochophore larva.

Salient features of Polychaetes:

1. Habitat: Predominantly marine; a few burrow in sand/mud or live in tubes.
2. Body: Elongated, segmented (metamerically), bilaterally symmetrical, with a well-developed, distinct head (prostomium + peristomium) bearing sensory structures — eyes, tentacles, and palps.
3. Parapodia: Each body segment (except the first and last) typically bears a pair of lateral, fleshy, paddle-like appendages called parapodia, used for locomotion (crawling/swimming) and, since they are richly vascularised, also for respiration.
4. Setae (chaetae): Numerous bristle-like chitinous setae project in bundles from each parapodium (hence "Poly-chaeta" = many setae), aiding grip and movement.
5. Clitellum: Typically absent (in contrast to Oligochaeta, which have a clitellum for cocoon formation).
6. Sexes: Mostly dioecious (sexes separate), unlike the hermaphroditic Oligochaeta and Hirudinea. …