Others'are fertilized internally, in the intertentacular organ or in the coelom.
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A coelom is a cavity lined by an epithelium derived from mesoderm.
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The coelom can be used for diffusion of gases and metabolites etc.
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Initially the intraembryonic coelom is one continuous space.
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A few, such as Priapulids, have no coelom, but they may have descended from schizocoelomate ancestors.
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Hence the coelom of the arthropod is reduced to small areas around the reproductive and excretory systems.
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Secondary gymnovarian ovaries shed ova into the coelom from which they go directly into the oviduct.
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These groups have a reduced coelom, called a pseudocoelom.
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Oxygen seems to be distributed by the fluid of the coelom.
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More examples
Celom: a cavity in the mesoderm of an embryo that gives rise in humans to the pleural cavity and pericardial cavity and peritoneal cavity
The coelom ("sea-lum") is a fluid filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages. Loss of coelom is correlated with reduction in body size. ...
A body cavity is any fluid-filled space in a multicellular organism other than those of vessels (such as blood vessels and lymph vessels). The term usually refers to the space located between an animalu2019s outer covering (epidermis), and the outer lining of the gut cavity, where internal organs develop.
A fluid-filled cavity within the body of an animal. The digestive system is suspended within the cavity, which is lined by a tissue called the peritoneum
(Coelomic) extensions in the body wall in the form of canals between longitudinal muscle bands.
In animals, a body cavity between the body wall and the digestive system that forms during preadult development.
A fluid-filled body cavity in animals, lined with tissue of mesodermal origin, housing the internal organs.
A body cavity completely lined with mesoderm.
A fluid-filled space in the mesoderm of more advanced organisms which divides the gut muscles from those of the body wall. This provides a protective place for specialised organs, which are held in position, supported and lubricated. The main advantages are: