ABBREVIATION

SYNONYMS (S)
ANTONYMS (A)

U cell (S)
Postembryonic E ectoblast (S)

Former name (e.g. in Sulston and Horvitz, 1977) of one of the rectal epithelial cells. Later renamed as U cell. Terminally differentiated in the hermaphrodite tail, but acts as a blast cell in the male.

See U cell

Pharyngeal epithelial cells.

A category of endosome likely to be involved in endocytosis and recycling of materials, but not yet well established histologically in C. elegans.

See Endosome

The temperature at which a group of animals tends to accumulate preferentially; it is often related to the temperature at which the animals have become previously acclimatized. C. elegans individuals can show very acute selectivity for this preferred temperature (Hedgecock and Russell, 1975).

This term encompasses both the processes of molting and exsheathment.

See Molt
See Exsheathment

Extracellular matrix (S)
Basal lamina (S)
Basement membrane(S)

A stem cell lying in the outer body wall that gives rise to epithelial cells, glia and neurons.

See Blast cell

Outermost layer of tissue in a developing embryo. This layer gives rise to the outer surface (skin) of the organism as well as the nervous system and other external organs and structures. In C. elegans, ectoderm includes the hypodermis, seam and interfacial epithelial cells and all their precursors, as well as blast cells that lie within the hypodermis such as P0-P12 until they differentiate.

See Hypodermis

Any parasite which lives on the exterior surface of its host animal or plant.

See Endoparasite
See Parasite

Zygote (S def.1)
Ovum (S def. 2)

1) A diploid cell produced by the union between two gametes, a sperm and an oocyte, and is surrounded by a protective outer shell (embryo).

2) A haploid reproductive cell (gamete) produced by the hermaphrodite C. elegans and develops into an embryo when fertilized by a sperm (oocyte).

Ovulation (S)
Oviposition (S)

The behavioral program that serves to move fertilized eggs down the uterus, through the vulva, and out of the worm onto the substrate. Egg-laying is controlled by the function of the vulval (vm1 and vm2 type) and uterine (um1 and um2 type) muscles. The uterine muscles contract to squeeze the eggs out of the uterus while the vulval muscles contract to open the vulval orifice. Two classes of motor neurons synapse onto these muscles; the two HSN's and the six VC's. HSN's are essential for egg-laying while VC's are not, as shown by laser ablation studies. HSN's are serotonergic as well as possibly cholinergic. All VC's are cholinergic and VC4 and VC5 are also serotonergic. Serotonin and levamisole, nicotinic Ach agonists, strongly induce egg-laying. Serotonergic and cholinergic pathways are suggested to act in parallel for this function (Weinshenker and Thomas, 1997).

C. elegans modulates its rate of egg laying in response to a variety of environmental conditions; absence of food as well as high osmolarity lead to suppression of egg laying, while the volatile attractant isoamyl alcohol stimulates egg laying in the absence of food (Sawin and Horvitz, 1991).

See Egg retention
See Bag of worms

A culture plate containing very many developing eggs. This may be produced by the “lay-off” method to produce semi-synchronous eggs, or by choosing a highly populous plate and gently washing off all hatched worms, leaving non-synchronized eggs behind. Synchronization can be achieved among the progeny by a “hatch-off” technique, either by picking individual eggs which have reached the desired age, or by allowing eggs to hatch over a narrow time window, and then collecting these recent hatchees by gentle washing.

See Lay-off
See Hatch-off

Congestion of the adult hermaphrodite uterus with excess fertilized eggs due to a decrease in the rate of egg-laying. This may result from changes in motor activity that govern the operation of the egg-laying muscles (as in conditions reducing the amount of serotonin released from HSN neurons), or may be due to developmental changes that cause the vulva to be malformed or closed, as in the Egl or Vul mutants (Desai and Horvitz, 1989; Han et al., 1990). Egg retention also occurs in wild type animals when food is scarce.

See Egg laying

A tough protective coating that covers the developing embryo very soon after fertilization of the oocyte. Most or all may be formed by secretion from within the embryonic tissue, but an outer "oolemma" layer is reportedly secreted by the uterine sheath (Anya, 1976; Bird and Bird, 1991). The eggshell consists of an external vitelline layer, a tough central layer made principally of chitin, and an internal lipid layer. The young L1 larva emerges from the eggshell about 10 hours after fertilization. Secretions from pharyngeal glands may weaken it just prior to hatching. Careful dissection can allow the outer chitinous layer to be removed without perturbing embryogenesis (see Schierenberg and Junkersdorf, 1992). Modest sized holes in the vitelline membrane, caused by laser ablation, will reseal and still allow embryogenesis. Many sources confuse the positions of the three layers, putting the vitelline layer inside rather than outside the chitinous layer for the C. elegans eggshell.
In common usage, the term eggshell is often equated solely with the chitinous layer.

See Chitinous layer
See Lipid layer
See Oolemma
See Pellucid layer
See Vitelline layer
See Vitelline membrane
See Zona pellucida

EGg Laying mutant phenotype.
There are two types of egl phenotype: 1) egl-d or egl refers to those mutants where an animal is defective in egg laying and retains its eggs (Trent et al., 1983; Desai and Horvitz, 1989); 2) egl-c refers to those animals that constitutively lay eggs. egl-c can be detected as more immature eggs being laid by mutants than those laid by wild type (reflecting decreased uterine residency time) or as an elevated rate of egg-laying relative to wild type in the absence of food (Barnes and Hekimi, 1997).

See Bag of worms
See Matricide

There are two types of electron microscopy, scanning (SEM) and transmission (TEM). SEM images the surface of the structure or organism, while TEM occurs on thin slices of the tissue and allows for very high magnification of the specimen.

Wormimage provides a searchable database of TEM images of many different C. elegans animals while Slidable Worm provides TEM images along the length of an animal.

For detailed methods, a number of electron microscopy techniques are available.

This term can refer to many separate developmental processes, including:

Elongation of the embryo: begins soon after the end of gastrulation, and is caused by circumferential squeezing by the hypodermal cells surrounding the embryo, followed by deposition of a cuticle layer to hold the worm in this new shape (Priess and Hirsh, 1986). Time for elongation to proceed is roughly 2 hrs. This form of elongation does not depend upon new growth in embryo volume or new cell divisions, but only on the reshaping of existing cells.

Elongation of the excretory canals: grow rapidly along the bodywall from the cell body during late embryogenesis and the first larval stage. The canal is simultaneously reshaped and grows rapidly in total size, with most new growth occurring at the canal tips (Buechner, 2002).

Elongation of a neuron: directed at the axon tip by the growth cone, where new growth is focused and the axon position is redirected along specific pathways (Wadsworth et al., 1996).          

A mutational phenotype where EMBryonic development is defective mostly leading to arrest at various stages.

See Embryonic lethal
See Embryonic arrest
See Let

A stage of development of C. elegans between the time that the oocyte is fertilized and the point at which the the mature embryo emerges from the eggshell at hatching as a young L1 larva.

See Embryonic stages

The cessation of normal developmental steps within the embryo, most often caused by a mutation or a physical defect. Besides mutation (Denich et al., 1984), embryonic arrest can also be induced in some cases by laser ablation of certain embryonic cells, laser surgery to fuse embryonic cells (Schierenberg, 1984), destruction of the vitelline membrane (Schierenberg and Junkersdorf, 1992), removal of egg cell cytoplasm (Laufer and von Ehrenstein, 1981), and/or interference with early cell-cell interactions (Priess and Thomson, 1987). Arrest is more severe than mere developmental delay or alterations in the order of cell divisions, which are more likely to result in reasonably normal overall development and production of a functional animal at hatching (Junkersdorf ).

Embryonic arrest is seldom if ever reversible, and therefore leads to lethality. However the aberrant embryo may continue to persist for hours or even permit some cell divisions to create a developmental monster.

See Arrest stage
See Let
See Monster
See Terminal phenotype

The longitudinal axis of the early embryo before gastrulation. The early embryo is oblong in shape, with the P granules sequestered at the posterior pole, opposite from the slightly narrower anterior pole.

A mutant phenotype in which some or all embryos suffer embryonic arrest, failing to progress to the L1 stage. Individual mutant alleles may arrest at characteristic developmental timepoints within embryogenesis. There are very many different categories of mutant within this broad designation.

See Let
See Monster

A form of basal lamina or glycocalyx which is secreted by the unfused hypodermal cells of the early embryo. It covers the embryo before the onset of elongation and is required to spread the forces of elongation equally over the embryo’s outer surface (Priess and Hirsh, 1986). This extracellular sheath lies on the apical surface of the hypodermis and is later replaced by the early cuticle.

EndoMitotic Oocytes phenotype. A mutant phenotype where meiotic maturation is not followed by ovulation and the mature oocyte is trapped in the gonad arm where it endomitotically replicates its DNA (Dang et al., 1996). Somatic sheath cell and spermatheca ablation also disrupts ovulation and causes Emo phenotype (McCarter et al., 1997). Besides the enlargement of their nuclei due to endomitosis, these oocytes are also subject to tearing forces as they enter the spermatheca. As a result they may break into several pieces, one containing the nucleus, and some smaller cytoplasts, which are formed as separate structures inside the proximal arm or inside the uterus.

The progenitor cell of the E and MS blastomeres. This was formerly called S₂ or EMSt, since it gives rise to “somatic” tissues: Endoderm, Mesoderm and Stomodeum.

See Founder cell

Free ending (S)
Bare ending (S)

A subclass of neurite end points which are often presumed to be sensory by their unique positions; sometimes used to ascribe a sensory function where no obvious physical specialization (such as a cilium) can be visualized, or where the apparent sensory features are diffuse.

See Dendrite

The innermost layers of the cuticle.

See Basal zone

A process by which a cell actively takes up material from its external environment by inward bending of the plasma membrane to create vesicles that encapsulate this material and carry it into the cytoplasm. There are multiple mechanisms for this process, including clathrin mediated uptake, caveolae-mediated uptake and clathrin- and caveolae-independent internalization.

See Coated vesicle
See Phagocytosis
See Pinocytosis

Chromosomal replication without nuclear or cellular division that results in a cell containing a highly enlarged nucleus with multiple copies (greater than 2X) of each chromosome (Rose et al., 1997). When this process occurs in the oocyte, it is called the Emo phenotype.

See Emo
See Endoreduplication

Any parasite that lives within the body of the host animal or plant.

See Ectoparasite
See Parasite

ER

A network of branching tubules and sacs extending throughout the cytosol forming a continuous sheet. Its membranes are the site of production for transmembrane proteins and lipids. Often, import of proteins occurs before the polypeptide is fully formed (co-translational). The ribosomes that synthesis the protein coat the surface of the ER creating regions called rough ER (regions without ribosomes are termed smooth ER).

See Rough endoplasmic reticulum
See Smooth endoplasmic reticulum

Multiple rounds of DNA replication that take place without chromosome condensation, segregation or cytokinesis. Endoreduplication results in enlarged, highly polyploid cells. This process is normally seen in intestinal nuclei during each larval lethargus which results in adult intestinal nuclei with 32 copies (32C) of each chromosome (Hedgecock and White, 1985). It is also seen in adult wild type hypodermal nuclei.

See Endomitosis

A nematode that retains two full layers of cuticle and hence gains extra protection against the exterior environment. This condition is not normally observed in C. elegans, but is common in some other nematode species.

See Molt

Soil dwelling nematodes that infect insects, including the larval stages of butterflies, moths, beetles and flies as well as adult crickets and grasshoppers.

A process at the end of gastrulation by which some cells migrate forward to cover the blastopore, covering the hole through which previous cells had entered inside the gastrula (Chisholm and Hardin, 2005).

Cortical layer (S)

External cortical envelope (S)

The outermost collagenous layer of the cuticle, which appears densely staining by electron microscopy, and may consist of a multi-layered membrane. It is underlain by successive collagenous cuticle layers, and is often coated on the outside by a noncollagenous matrix called the surface coat, or glycocalyx. The epicuticle can be considered the outermost portion of the cuticle’s “cortical zone” (Bird and Bird, 1991).

See Cortical layer

Hypodermis of C. elegans. These two terms refer to the same tissue and are used interchangeably in publications (Chin-Sang and Chisholm, 2000).

See Hypodermis
See Ectoderm

A blast cell that can give rise to epidermal cells, glia and neurons in C. elegans.

See Blast cell

Archaic (Golschmidt, 1903; Mclaren, 1976)

Pharyngeal gland

See Gland cell

Archaic term for the pharynx.
(Alternate spelling=Oesophagus)

A behavior by which an animal escapes a predator or unfriendly partner. For instance C. elegans may be repelled by chemosensory signals to evade some pathogenic bacteria (Schulenburg and Ewbank, 2004; Schulenburg and Muller, 2004).

A normal process by which the maturing vulva (before eversion) turns inside out and the lumen closes during late L4 stage (post eversion). However, this same process can be overdone in some developmental mutants to create a distinctive mutant phenotype, Evl, in which the vulval tissue projects visibly outward from the ventral side of the body.

See Everted vulva

A mutant phenotype in which the developing vulva everts out of the body to form an large outward bulge which generally leaves the animal unable to undergo normal egg- laying.

See Multivulva phenotype

A synaptic connection between two neurons whose stimulation leads to an increase in electrical activity in the postsynaptic cell (a depolarization).

The H-shaped structure made by the processes of the excretory canal cell. It extends almost the full length of the body on both sides of the animal, generally in contact with the lateral hypodermis and the pseudocoelom.

See Excretory system

exc cell

Excretory canal cell (S)

A protokidney cell with an H-shaped internal lumen that is suggested to collect and secrete salt solutions outward via the excretory sinus (Nelson et al., 1983; Buechner et al., 1999). The animal cannot survive if this cell is ablated or if its outlet (the excretory duct) is blocked.

See Excretory system

The extracellular sinus formed by the excretory duct cell and the pore cell.

See Excretory system

exc duct

Duct cell (S)

An interfacial epithelial cell which forms a lumen to receive the outflow of the excretory gland and excretory canal cells; this outflow is transported into the lumen of the excretory pore cell and then to the excretory pore.

See Excretory system

exc gl L
exc gl R

Secretory-excretory gland (S)

A pair of large cells in the head that fuse to form a single gland whose contents are released into the excretory duct through a specialized secretory membrane. Under most conditions the gland is filled with large secretory granules containing a dense matrix of unknown function; however, in the dauer larva these granules are absent and the gland is filled with complex spherical and tubular membranes (Nelson et al., 1983). It has been postulated that the granules may contribute to the glycocalyx covering the body cuticle (Nelson and Riddle, 1984).

See Excretory system

A highly specialized intercellular membrane junction that links the excretory canal cell, the excretory gland process, and the excretory duct cell, to permit the release of materials from the canal and gland into the duct and hence out of the body.

See Excretory system

The outlet of the excretory sinus to the exterior environment through the cuticle. Pore is located on the ventral side of the head, just behind the nerve ring.

See Excretory system

exc pore

exc socket cell (S)

An interfacial epithelial cell which links excretory duct to hypodermis.

See Excretory system

exc socket

exc pore cell (S)

A specific step in the defecation motor program.

See Defecation motor program

A form of molting in which a nematode sheds a retained outer cuticle layer. This process is common in infective nematode species, but not in C. elegans. Infective species may retain an older cuticle layer as a protective sheath until they successfully enter their final host.

See Molt

ECM

Basal lamina (S)
Basement membrane (S)

A complex mixture of long chain proteins and proteoglycans that lie on the outer surface of cell membranes of each tissue, in particular those at the basal pole. Much of the material is condensed into a uniform meshwork, the basal lamina, but some collagenous materials may extend further into the pseudocoelom between neighboring tissues. For more general information see Alberts et al., 2002.

See Basal lamina
See ECM
See Tendon

A pigmented granular structure found in pharyngeal muscles in some nematode species other than C. elegans (Burr and Webster, 1971; Bollerup and Burr, 1979). Such eyespots vary in color, are different from the background coloration of the rest of the pharynx, and usually organize into simple cup-shaped structures. Pigmented eyespots occur in other nematode species in association with sheath cells and a possible lens-like element in the bodywall of the head (Croll et al., 1972; Van de Velde and Coomans, 1988). Although lacking a detectable eyespot, C. elegans is reported to exhibit a behavioral response to light (Burr, 1985; Ken Miller, pers. comm.).