Editing Coelom (section)

== Pseudocoelomates ==
In some [[protostome]]s, the embryonic [[blastocoele]] persists as a body cavity. These protostomes have a fluid filled main body cavity unlined or partially lined with tissue derived from mesoderm.

This fluid-filled space surrounding the internal [[organ (anatomy)|organ]]s serves several functions like distribution of nutrients and removal of waste or supporting the body as a [[hydrostatic skeleton]].

A '''pseudocoelomate''' or '''blastocoelomate''' is any [[invertebrate]] [[animal]] with a three-layered body and a [[Body cavity|pseudocoel]]. The coelom was apparently lost or reduced as a result of [[mutation]]s in certain types of [[gene]]s that affected early development. Thus, pseudocoelomates evolved from coelomates.<ref>Evers, Christine A., Lisa Starr. ''Biology:Concepts and Applications.'' 6th ed. United States:Thomson, 2006. {{ISBN|0-534-46224-3}}.</ref> "Pseudocoelomate" is no longer considered a valid [[Taxonomy (biology)|taxonomic group]], since it is not [[monophyletic]]. However, it is still used as a descriptive term.

Important characteristics:
* lack a vascular blood system
** [[diffusion]] and [[osmosis]] circulate nutrients and waste products throughout the body.
* lack a skeleton
** hydrostatic pressure gives the body a supportive framework that acts as a skeleton.
* no segmentation
* body wall
** epidermis and muscle
** often [[syncytial]]
** usually covered by a secreted cuticle
* most are microscopic
* parasites of almost every form of life (although some are free living)
* [[eutely]] in some
* loss of [[larval]] stage in some
* possibly [[pedomorphism]]

===Pseudocoelomate phyla===
Bilaterian pseudocoelomate phyla according to Brusca and Brusca,:<ref name=Brusca />

*[[Nematoda]] (roundworms)
*[[Nematomorpha]] (horsehair worms)
*[[Loricifera]]
*[[Priapulida]]
*[[Kinorhyncha]]
*[[Rotifera]], including [[Acanthocephala]] (spiny-headed worms)<ref>{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S105579031500370X | doi=10.1016/j.ympev.2015.11.017 | title=Phylogeny of Syndermata (Syn. Rotifera): Mitochondrial gene order verifies epizoic Seisonidea as sister to endoparasitic Acanthocephala within monophyletic Hemirotifera | date=2016 | last1=Sielaff | first1=Malte | last2=Schmidt | first2=Hanno | last3=Struck | first3=Torsten H. | last4=Rosenkranz | first4=David | last5=Mark Welch | first5=David B. | last6=Hankeln | first6=Thomas | last7=Herlyn | first7=Holger | journal=Molecular Phylogenetics and Evolution | volume=96 | pages=79–92 | bibcode=2016MolPE..96...79S }}</ref><ref>[https://web.archive.org/web/20180410121327id_/http://biosoc.pk/wp-content/uploads/2015/12/5-50-15-Rotifers-Safari.pdf Study of Rotifers of Safari Zoo Lake Lahore in Relation to Physico-chemical Parameters]</ref>