Schizocoely

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Schizocoely (adjective forms: schizocoelous or schizocoelic) is a process by which some animal embryos develop. The schizocoely mechanism occurs when secondary body cavities (coeloms) are formed by splitting a solid mass of mesodermal embryonic tissue. [1] [2] All schizocoelomates are protostomians[ contradictory ] and they show holoblastic, spiral, determinate cleavage.

Contents

Etymology

The term schizocoely derives from the Ancient Greek words σχίζω (skhízō), meaning 'to split', and κοιλία (koilía), meaning 'cavity'. [3] [4] This refers to the fact that fluid-filled body cavities are formed by splitting of mesodermal cells.

Taxonomic distribution

Animals called protostomes develop through schizocoely for which they are also known as schizocoelomates.

Schizocoelous development often occurs in protostomes, [1] [5] [6] as in phyla Mollusca, Annelida, and Arthropoda. Deuterostomes usually exhibit enterocoely; [7] however, some deuterostomes like enteropneusts can exhibit schizocoely as well. [8]

Embryonic development

The term refers to the order of organization of cells in the gastrula leading to development of the coelom. In mollusks, annelids, and arthropods, the mesoderm (the middle germ layer) forms as a solid mass of migrated cells from the single layer of the gastrula. The new mesoderm then splits, creating the pocket-like cavity of the coelom.

See also

Related Research Articles

<span class="mw-page-title-main">Mesoderm</span> Middle germ layer of embryonic development

The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.

<span class="mw-page-title-main">Bilateria</span> Animals with embryonic bilateral symmetry

Bilateria is a large clade or infrakingdom of animals called bilaterians, characterised by bilateral symmetry during embryonic development. This means their body plans are laid around a longitudinal axis with a front and a rear end, as well as a left–right–symmetrical belly (ventral) and back (dorsal) surface. Nearly all bilaterians maintain a bilaterally symmetrical body as adults; the most notable exception is the echinoderms, which have pentaradial symmetry as adults, but are only bilaterally symmetrical as an embryo. Cephalization is a characteristic feature among most bilaterians, where the special sense organs and central nerve ganglia become concentrated at the front end.

<span class="mw-page-title-main">Coelom</span> The main body cavity in many animals

The coelom is the main body cavity in many animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it remains undifferentiated. In the past, and for practical purposes, coelom characteristics have been used to classify bilaterian animal phyla into informal groups.

<span class="mw-page-title-main">Gastrulation</span> Stage in embryonic development in which germ layers form

Gastrulation is the stage in the early embryonic development of most animals, during which the blastula, or in mammals the blastocyst, is reorganized into a two-layered or three-layered embryo known as the gastrula. Before gastrulation, the embryo is a continuous epithelial sheet of cells; by the end of gastrulation, the embryo has begun differentiation to establish distinct cell lineages, set up the basic axes of the body, and internalized one or more cell types including the prospective gut.

<span class="mw-page-title-main">Blastocoel</span> Fluid-filled or yolk-filled cavity that forms in the blastula

The blastocoel, also spelled blastocoele and blastocele, and also called cleavage cavity, or segmentation cavity is a fluid-filled or yolk-filled cavity that forms in the blastula during very early embryonic development. At this stage in mammals the blastula is called the blastocyst, which consists of an outer epithelium, the trophectoderm, enveloping the inner cell mass and the blastocoel.

A germ layer is a primary layer of cells that forms during embryonic development. The three germ layers in vertebrates are particularly pronounced; however, all eumetazoans produce two or three primary germ layers. Some animals, like cnidarians, produce two germ layers making them diploblastic. Other animals such as bilaterians produce a third layer between these two layers, making them triploblastic. Germ layers eventually give rise to all of an animal's tissues and organs through the process of organogenesis.

<span class="mw-page-title-main">Gestational sac</span> Cavity of fluid surrounding an embryo

The gestational sac is the large cavity of fluid surrounding the embryo. During early embryogenesis, it consists of the extraembryonic coelom, also called the chorionic cavity. The gestational sac is normally contained within the uterus. It is the only available structure that can be used to determine if an intrauterine pregnancy exists until the embryo can be identified.

The archenteron, also called the gastrocoel, the primitive digestive tube or the primitive gut, is the internal cavity of the primitive gastrointestinal tract that forms during gastrulation in a developing animal embryo. It develops into the endoderm and mesoderm of the animal.

<span class="mw-page-title-main">Animal embryonic development</span> Process by which the embryo forms and develops

In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell (spermatozoon). Once fertilized, the ovum becomes a single diploid cell known as a zygote. The zygote undergoes mitotic divisions with no significant growth and cellular differentiation, leading to development of a multicellular embryo after passing through an organizational checkpoint during mid-embryogenesis. In mammals, the term refers chiefly to the early stages of prenatal development, whereas the terms fetus and fetal development describe later stages.

<span class="mw-page-title-main">Neurula</span> Embryo at the early stage of development in which neurulation occurs

A neurula is a vertebrate embryo at the early stage of development in which neurulation occurs. The neurula stage is preceded by the gastrula stage; consequentially, neurulation is preceded by gastrulation. Neurulation marks the beginning of the process of organogenesis.

<span class="mw-page-title-main">Lateral plate mesoderm</span>

The lateral plate mesoderm is the mesoderm that is found at the periphery of the embryo. It is to the side of the paraxial mesoderm, and further to the axial mesoderm. The lateral plate mesoderm is separated from the paraxial mesoderm by a narrow region of intermediate mesoderm. The mesoderm is the middle layer of the three germ layers, between the outer ectoderm and inner endoderm.

<span class="mw-page-title-main">Enterocoely</span> Development process of some animals

Enterocoelom describes both the process by which some animal embryos develop and the origin of the cells involved. In enterocoely, a mesoderm is formed in a developing embryo, in which the coelom appears from pouches growing and separating from the digestive tract. As the incipient coelomic epithelium originates from archenteral diverticula, the endoderm therefore gives rise to the mesodermal cells.

Convergent extension (CE), sometimes called convergence and extension (C&E), is the process by which the tissue of an embryo is restructured to converge (narrow) along one axis and extend (elongate) along a perpendicular axis by cellular movement.

<span class="mw-page-title-main">Human embryonic development</span> Development and formation of the human embryo

Human embryonic development or human embryogenesis is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, the development of the human body entails growth from a one-celled zygote to an adult human being. Fertilization occurs when the sperm cell successfully enters and fuses with an egg cell (ovum). The genetic material of the sperm and egg then combine to form the single cell zygote and the germinal stage of development commences. Human embryonic development covers the first eight weeks of development, which have 23 stages, called Carnegie stages. At the beginning of the ninth week, the embryo is termed a fetus. In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs.

The urbilaterian is the hypothetical last common ancestor of the bilaterian clade, i.e., all animals having a bilateral symmetry.

<span class="mw-page-title-main">Phoronid</span> Phylum of marine animals

Phoronids are a small phylum of marine animals that filter-feed with a lophophore, and build upright tubes of chitin to support and protect their soft bodies. They live in most of the oceans and seas, including the Arctic Ocean but excluding the Antarctic Ocean, and between the intertidal zone and about 400 meters down. Most adult phoronids are 2 cm long and about 1.5 mm wide, although the largest are 50 cm long.

<span class="mw-page-title-main">Protostome</span> Clade of animals whose mouth develops before the anus

Protostomia is the clade of animals once thought to be characterized by the formation of the organism's mouth before its anus during embryonic development. This nature has since been discovered to be extremely variable among Protostomia's members, although the reverse is typically true of its sister clade, Deuterostomia. Well-known examples of protostomes are arthropods, molluscs, annelids, flatworms and nematodes. They are also called schizocoelomates since schizocoely typically occurs in them.

<span class="mw-page-title-main">Ectoderm specification</span> Stage in embryonic development

In Xenopus laevis, the specification of the three germ layers occurs at the blastula stage. Great efforts have been made to determine the factors that specify the endoderm and mesoderm. On the other hand, only a few examples of genes that are required for ectoderm specification have been described in the last decade. The first molecule identified to be required for the specification of ectoderm was the ubiquitin ligase Ectodermin ; later, it was found that the deubiquitinating enzyme, FAM/USP9x, is able to overcome the effects of ubiquitination made by Ectodermin in Smad4. Two transcription factors have been proposed to control gene expression of ectodermal specific genes: POU91/Oct3/4 and FoxIe1/Xema. A new factor specific for the ectoderm, XFDL156, has shown to be essential for suppression of mesoderm differentiation from pluripotent cells.

In evolutionary developmental biology, inversion refers to the hypothesis that during the course of animal evolution, the structures along the dorsoventral (DV) axis have taken on an orientation opposite that of the ancestral form.

This glossary of developmental biology is a list of definitions of terms and concepts commonly used in the study of developmental biology and related disciplines in biology, including embryology and reproductive biology, primarily as they pertain to vertebrate animals and particularly to humans and other mammals. The developmental biology of invertebrates, plants, fungi, and other organisms is treated in other articles; e.g terms relating to the reproduction and development of insects are listed in Glossary of entomology, and those relating to plants are listed in Glossary of botany.

References

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  7. Satoh, Gouki; Harada, Yoshito; Satoh, Nori (September 2000). "The expression of nonchordate deuterostome Brachyury genes in the ascidian Ciona embryo can promote the differentiation of extra notochord cells". Mechanisms of Development. 96 (2): 155–163. doi:10.1016/S0925-4773(00)00395-6. PMID   10960780. S2CID   6732563.
  8. Kaul-Strehlow, Sabrina; Stach, Thomas (2011-05-11). "The pericardium in the deuterostome Saccoglossus kowalevskii (Enteropneusta) develops from the ectoderm via schizocoely". Zoomorphology. 130 (2): 107. doi:10.1007/s00435-011-0125-0. ISSN   1432-234X. S2CID   22199440.