Question

Why is the body cavity of the roundworm called a pseudocoelom?

Answer 1

the body cavity is not a true coelom ie psudocoelamate means (its is a fluid filled body cavity lying inside the external body wall where alimentary canal and digestive system are suspended

Answer 2

The pseudocoelom is a fluid-filled body cavity lying inside the external body wall of the nematode that bathes the internal organs, including the alimentary system and the reproductive system (PeriFIG 1). This body cavity is called a “pseudocoelom” because it is not fully lined by mesodermal cells as in the true “coelomic cavity” of vertebrates. The C. elegans pseudocoelom is bounded by basal laminae (BL) that cover the hypodermis, the nervous tissues, the gonad and the intestine (PeriFIG 2) (Bird and Bird, 1991). The pseudocoelom contains the coelomocytes (see Coelomocyte Section), provides the turgor-hydrostatic pressure for the animal as a whole, functions as a lubricant between tissues, and provides a medium for intercellular signaling and nutrient transport.