EVERYDAY SCIENCE

Detailed explanation-1: -An acoelomate is an animal which lack a coelom, or formal body cavity. True body cavities form only in multicellular organisms with true tissues. Within this group, the eumetazoa, there are the organisms like coral and jellyfish, which have only 2 basic tissues. The triploblastic eumetazoa have 3 tissue types.

Detailed explanation-2: -Acoelomates are triploblastic animals lacking a fluid-filled body cavity (Fig. 3.17 A). The flatworms (phylum Platyhelminthes) and ribbon worms (phylum Nemertea) are examples of acoelomates.

Detailed explanation-3: -The body cavity of a true coelomate is lined with mesodermal cells. In acoelomates, the mesodermal cells attach to the sides of other cells, via an extracellular matrix. They are devoid of the body cavity. Thus, the organs formed are completely surrounded by the mesoderm.

Detailed explanation-4: -Among the acoelomate phyla, the members of Platyhelminthes (flatworms) have no body cavity, and the space between the gut and the body wall, when present, is filled with a spongy organ tissue of mesodermal cells through which tissue fluids may percolate.