In details

Celomato, acelomao and pseudocelomao animals


The animals that have cheloma are called cheloma.

All chords are chelomated, as are mollusks (slugs, oysters), annelids (earthworms) and echinoderms (starfish, sea urchins).

There are triblastic animals in which the mesoderm delimits one part of the cavity, the other part being delimited by the endoderm. These animals are called pseudocelomates, because the celoma is only true when it is completely covered by the mesoderm. This is the case of nematodes, whose best known representative is the roundworm (Ascaris lumbricoides), a parasite of the human intestine.

In some animals the only cavity that forms in the embryo is the archenter, so they are called accelerated.

The following scheme shows schematic cross sections in acelomata, pseudocelomata and chelomato organisms: