Nereis is an aquatic annelid. Its parapodia help it swim.
- Nereis is a genus of Polychaeta worms in the family Nereidae.
- They possess setae and parapodia for locomotion.
- Every segment of the body, besides the peristomium and the anal segment, bears on either side a flat, fleshy, hollow and vertical flap-like outgrowth called parapodia.