Haemocoel The body cavity of arthropods and molluscs, which is filled with blood. The haemocoel is an enlarged blastocoel (see blastula), which greatly reduces the coelom (this is restricted to the cavities of the gonads and excretory organs). The haemocoel can act as a hydrostatic skeleton. Nereis is a genus of polychaete worms in the family Nereidae. It comprises many species, most of which are marine, including the sandworm (Nereis virens) and the common clam worm (Nereis succinea). Nereis possess setae and parapodia for locomotion. They may have two types of setae, which are found on the parapodia. Acicular setae provide support. Locomotor chaetae are for crawling, and are the bristles that are visible on the exterior of the Polychaeta.
No, it is not present in nereis.
Nereis has true body cavity i.e. coelom..
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