What does pseudocoelomate mean?
A pseudocoelomate is an animal with a pseudocoel, a fluid-filled body cavity that is not completely lined by mesoderm. This arrangement differs from a true coelom, which is fully lined by mesoderm, and from the condition in an acoelomate, which has no fluid-filled body cavity at all. Nematodes, or roundworms, are the best-known examples. In a pseudocoelomate, the organs are not enclosed within a continuous body-cavity lining; they may lie freely in the cavity or remain attached to the body wall. The term is chiefly used in zoology, anatomy, and historical classifications of invertebrates. Although it describes a real structural distinction, it has become less prominent in modern evolutionary discussions, which focus more closely on evolutionary relationships among animal groups. It remains useful when the essential feature under discussion is the incomplete mesodermal lining of the body cavity.
An animal whose body cavity is not completely lined by mesoderm.
"The nematode is a pseudocoelomate with a fluid-filled pseudocoel."
Having a body cavity that is not completely lined by mesoderm.
"The diagram shows a pseudocoelomate body plan."
The plural is used when referring to animals characterized by a pseudocoel.
"Nematodes and rotifers are pseudocoelomates."
A pseudocoelomate has a body cavity that is almost, but not quite, a true coelom.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does pseudocoelomate come from?
The word combines the prefix pseudo-, from Greek pseudes meaning false, with coelomate, derived from Greek koilōm, meaning cavity. The resulting term literally indicates an animal resembling a coelomate but not possessing a true coelom. Related terms include pseudocoel, pseudocoelomous, and coelomate, all belonging to the same anatomical vocabulary based on the Greek word for a hollow cavity.
Related word forms
How pseudocoelomate is actually used
The term is chiefly used in zoology and comparative anatomy. It is more technical than ordinary descriptions of the animals concerned, and modern classification often discusses relationships among animal groups rather than relying on the traditional category by itself.
Easily confused with pseudocoelomate
A coelomate has a true coelom, a body cavity completely lined by mesoderm, whereas a pseudocoelomate has a cavity that is only partially lined.
An acoelomate lacks a fluid-filled body cavity altogether, while a pseudocoelomate has a pseudocoel that is not completely lined by mesoderm.