Question

What is call the animals which have pseudocoelom?

Answer 1

…a fluid-filled body cavity, the pseudocoelom, which, unlike a true coelom, does not have a cellular peritoneal lining. Most of the pseudocoelomates (e.g., the classes Nematoda and Rotifera) are small and none possess an independent vascular system.

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Answer 2

Nematodes or roundworms (see Nematoda), rotifers (see Rotifera), acanthocephalans (spiny-headed worms), kinorhynchs (see Kinorhyncha) and nematomorphs or horsehair worms (see Nematomorpha) are pseudocoelomates.