coelomate

Examples of coelomate in the following topics:

• Animal Characterization Based on Features of Embryological Development

  • Triploblasts can be differentiated into three categories: those that do not develop an internal body cavity called a coelom (acoelomates), those with a true coelom (eucoelomates), and those with "false" coeloms (pseudocoelomates) .
  • Eucoelomates (or coelomates) have a true coelom that arises entirely within the mesoderm germ layer and is lined by an epithelial membrane.
  • Although still functional, these are considered false coeloms.
  • The coelom of most protostomes is formed through a process called schizocoely, when a solid mass of the mesoderm splits apart and forms the hollow opening of the coelom.
  • These pouches eventually fuse to form the mesoderm, which then gives rise to the coelom.

• Superphylum Ecdysozoa

  • The other idea about the phylogeny of the Ecdysozoa is called the coelomate hypothesis.
  • There were three types, or grades, of organization: the Acoelomata (no coelom), the Pseudocoelomata (partial coelom), and the Eucoelomata (true coelom).
  • With the introduction of molecular phylogenetics, the coelomate hypothesis was abandoned, although some molecular, phylogenetic support for the Coelomata continued until 2005.

• Types of Skeletal Systems

  • A hydrostatic skeleton is one formed by a fluid-filled compartment within the body: the coelom.
  • The organs of the coelom are supported by the aqueous fluid, which also resists external compression.
  • Movement in a hydrostatic skeleton is provided by muscles that surround the coelom.
  • The muscles in a hydrostatic skeleton contract to change the shape of the coelom; the pressure of the fluid in the coelom produces movement.

• Phylum Annelida

  • Annelids include segmented worms, such as leeches and earthworms; they are the most advanced worms as they possess a true coelom.
  • Annelids show the presence of a true coelom, derived from embryonic mesoderm and protostomy.
  • Each segment is limited by a membranous septum that divides the coelomic cavity into a series of compartments.
  • Additionally, the segmentation of the body wall may not correspond to the internal segmentation of the coelomic cavity.

• Superphylum Lophotrochozoa

  • This layer multiplies into a band which then splits internally to form the coelom; this protostomic coelom is termed schizocoelom.

• Skin, Gills, and Tracheal Systems

  • In animals that contain coelomic fluid instead of blood, oxygen diffuses across the gill surfaces into the coelomic fluid.

• The Evolution of Reproduction

  • These organisms produce sperm and eggs from undifferentiated cells in their coelom, storing them in that cavity.
  • When the coelom becomes filled, the cells are released through an excretory opening or by the body splitting open.
  • These types of reproductive systems developed in insects (compared to annelids which have a coelom for storage).

• Phylum Platyhelminthes

  • The Platyhelminthes are flatworms that lack a coelom; many are parasitic; all lack either a circulatory or respiratory system.

• Phylum Nemertea

  • The circulatory system is derived from the coelomic cavity of the embryo.
  • Although these are called blood vessels, since they are of coelomic origin, the circulatory fluid is colorless.

• Phylum Mollusca

  • The mantle cavity develops independently of the coelomic cavity.