Question

What is pseudocoelom? Where is it located?

Answer 1

Hint: A Coelom or body cavity refers to a large fluid filled space or cavity present between the outer body wall and inner gut wall (walls of alimentary canal). The Coelom contains most of the visceral organs and is lined by mesoderm on all sides.

Complete answer:
Coelom is divided into three types:
1) Eucoelom: In this Coelom, the mesoderm is present between the ectoderm and endoderm. Eucoelom is also known as true Coelom. True Coelom is a body cavity in which mesoderm of the embryo provides a cellular lining peritoneum. The Coelom is filled with coelomic fluid secreted by the peritoneum. True Coelom is of two types: Schizocoelom and Enterocoelom. E.g., annelids, echinoderms and chordates.
2) Pseudocoelom: It is also known as false Coelom. It is the cavity present in the body but it is not completely lined by mesoderm. The mesoderm is present as scattered pouches in between the ectoderm and endoderm. This type of body cavity is known as pseudocoelom. The pseudocoelom is developed from the blastocoele of the embryo. Pseudocoelom is present only in invertebrates. Animals possessing pseudocoelom are known as Pseudocoelomates and the group of animals is known as Pseudocoelomates or Blastocoelomate. Pseudocoelomates lack blood vascular system, skeleton, segmentation, body wall and most of these are microscopic. e.g., Aschelminthes.
3) Acoelom: In this type, the body cavity or Coelom is absent in the body. There is no Coelom or cavity present between the body wall and gut wall. E.g., sponges, coelenterates and Platyhelminthes.

Note: Body cavity of arthropods and non-cephalopod molluscs is called haemocoel. Platyhelminthes are triploblastic acoelomate. In this three germ layers are present but there is no body cavity or Coelom is present between the body wall and gut wall.