Lower phyla in the animal kingdom such as Cnidarians, Porifera, and Ctenophora.
Acoelomate animals, for example, flatworms, do not have a body cavity. Their organs are held in place by mesodermal tissues that are semi-solid.
Pisces or fish have true internal body cavity.
The presence or absence of a coelom (body cavity) is a key characteristic in the classification of animals. Animals can be categorized as acoelomates (no body cavity), pseudocoelomates (body cavity between mesoderm and endoderm), or coelomates (body cavity within mesoderm). This classification is important in understanding the evolutionary relationships and anatomical differences among animal groups.
Coelom is a greek work literally meaning body cavity.A body cavity is a space between the alimentary canal and body wall. When it is lined by a layer of mesoderm, then it is called a true coelom. Depending upon this the animals are classified intoAcoelomates - Animals which don't have body cavity. Eg: PlatyhelminthesPseudocoelomates - Animals in which the body cavity is formed from embryonic blastocoel. This blastocoel acts as a body cavity in adults. Eg: AschelminthesSchizocoelomates - Animals in which the body cavity formed by splitting of mesoderm. Eg: Annelida, Arthropoda and MolluscaEnterocoelomates - Animals in which body cavity is derived from entero-mesoderm. Eg: Echinodermata, Hemichordata and chordata.
the body cavity that surrounds the gut in invertebrates
There are two principal body cavities the dorsal (posterior) body cavity and the ventral (anterior) body cavity.
Animals that have three layers of embryonic tissue with organs in a cavity completely lined with the mesoderm are called triploblastic animals.
Acoelomate
mantle
Complex animals tend to have specialized cells, bilateral symmetry, cephalization, and a body cavity.
Body cavities in organisms are referred to as coeloms, and animals that have them are called coelomates. An organism that has a false body cavity, or a psuedocoelom, are called psuedocoelomates.
The type of body cavity shared by all mollusks is pseudocoelom is a false statement. The correct answer is coelom.
eucoelomate (true guts) possessing a cavity coelom between the body wall and the gut. (zoology)