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Glossary - L





5R and 5L are alternate lineage patterns of the hermaphrodite which are related by twofold rotational symmetry.

VU, Z1.ppa (Ventral Uterine precursor; generates uterus, spermatheca and spermatheca-uterine valve cells)

VU, Z1.ppp (Ventral Uterine precursor; generates uterus, spermatheca and spermatheca-uterine valve cells)

AC, Z4.aaa (Anchor Cell)

VU, Z4.aap (Ventral Uterine precursor; generates uterus, spermatheca and spermatheca-uterine valve cells)

See 5R
See Somatic primordium

"l" neuron

ADL cell (S)




Amphid neurons with dual ciliated sensory endings that project directly into nerve ring and take up FITC. This neuron mediates mediate social feeding behavior when aversive food signals are present (de Bono et al., 2002).

L1, L2, L3, L4   See Larva
L1 diapause  

See Diapause

L2d L2D A starved or stressed L2 larva adopts a somewhat slimmer body shape than a normal L2 animal before the molt into dauer larva stage. This slimmer animal is sometimes referred to as an L2d larva or predauer larva. The L2d retains the potential for continuous development and can molt to the L3 stage if environmental conditions improve (Golden and Riddle, 1984).
L/A switch  

Larval to adult changes in tissue development. This process is normally restricted to the final (fourth) molt, however, mutations in heterochronic genes advance or retard the timing of the L/A switch, resulting in larvae with adult hypodermis or adults with larval hypodermis (Rougvie, 2001).


Referring to the lips, or labia. Generally refers explicitly to the mechanosensory specializations, as opposed to the chemosensory (amphidial) specializations in the nose. These labial sensilla can be divided into two groups, the inner labials (ILs) and the outer labials (OLs), based upon their relative distance from opening of the buccal cavity. The cephalic sensilla (CEPs) have endings grouped closely to the OLs in C. elegans (and thus might also be considered as labials), but lie away from the lips in some other nematode species. This term is also used to refer to the two flaps which border the opening of the vulva; e.g. the vulval labia.

Labial nerve  

Any of six longitudinal nerves which extend from mechanosensors in the lips to the nerve ring.


Labial pore     A patent opening in the lip cuticle through which a chemosensory neuron cilium may be exposed to the environment, as in the amphids and inner labial sensilla.
Labial sheath  

Refers to the sheath cells of the inner labial sensilla, ILsh, of the nose.



Small (non-membrane bound) spaces in the cytoplasm.


A common reporter gene construct used to mark cells, organelles or proteins. If gene is expressed in the live animal, its expression can be visualized by light microscopy of fixed tissue by histochemical staining for the enzyme encoded by the lacZ gene (beta-galactosidase).

Lamella/ lamellae  

A set of closely spaced membrane leaflets which may be in continuity (spiral or folded into parallel leaflets), or in separate parallel bodies (onion-like, or stacked in a pile). They can look superficially like “myelin” but have no correspondence to it.

See Lamellar membrane
See Whorl

Lamellar body   A lipid storage and secretory vesicle which is surrounded by a membrane and contains prominent whorls of membranes. These bodies are common in some cell types, including hypodermis.
Lamellar membrane  

This term can refer to several distinctly different features involving broad flattened surfaces:

Many cells display characteristic stacks of membranous lamellae as a cytoplasmic organelle, such as gland cells, sheath cells, structural cells, etc, which may be involved in secretion, perhaps as a post-Golgi endosome or as large RER arrays.

Several epithelial cells (hypodermis, pore cell) display characteristic stacked lamellae in continuity with the apical plasma membrane (they are parallel invaginations), forming an organelle on the cell surface, perhaps involved in cuticle secretion, or alternately, providing a means for the plasma membrane to stretch or shrink as needed.

Some cells, often containing actin, extend broad flattened or ruffled cell extensions that are referred to as lamellae or lamellipodia.

See Lamellipodium
See Sheath lamellae
Stacked membrane

Lamellipodium/ lamellipod/ lamellipodia Membrane ruffles (S)

A broad flattened cell extension from an epithelial cell as it spreads across a surface or migrates in directed amoeboid movements, and also the cell extensions required during events such as gastrulation, cell intercalation, or embryonic enclosure. Similar broad extensions have also been noted from differentiating neuron cell bodies in some mutant backgrounds (Yang and Lundquist, 2005), at the tips of neuron growth cones (Chalfie, 1994 -cover photo in Science), from the somata of the CEP sheath cells to provide a glial wrapping of the nerve ring, and from the GLR somata as a scaffold for muscle arms of the nerve ring.

See Growth cone
Pseudopium / Pseudopod / Pseudopdia


A component of the nuclear lamina that forms a meshwork of intermediate filaments, localizing to subregions of the nuclear envelope, and functions in organizing nuclear structure and regulating nuclear events including cell cycle progression and chromosome segregation (Liu et al., 2000). C. elegans expresses a single B type lamin, LMN-1 (Liu et al., 2000; Reimer et al., 1993), in all cells with the exception of mature sperm cells (Liu et al., 2000). Lack of lamin results in embryonic lethality (Liu et al., 2000).

Larva/ larval Juvenile (S)
L1, L2, L3, L4 and dauer stage (S)

In the life cycle of C. elegans, upon hatching from the egg, the immature nematode progresses through intermediate developmental stages interrupted by a series of molts until finally reaching adulthood. The “larval stages” of C. elegans should perhaps be more properly termed “nymphal stages” since the animal does not undergo a true metamorphosis, but retains the same basic body plan and retains virtually all juvenile cells. Normal development progresses from egg to L1, L2, L3, L4 and then adult. Starved or stressed animals can enter a dauer larva stage after L2 and interrupt normal developmental progression. All larval stages are all pre-reproductive, lacking mature sexual organs.

See Dauer
See Post-dauer

Larvae accumulator     A class of genetic mutations that cause the affected adults to produce many live larvae but few or no adult progeny (Hirsh and Vanderslice, 1976).
Larval arrest

Arrest at the larval stage of development. Can occur by genetic mutation or environmental conditions such as starvation and sometimes may be reversed by a change in environmental conditions.

Larval lethal/ larval lethality

Mutations or culture conditions which cause death of the larva usually in early or late L1 stage, or less often in later larval stages. There are several distinctive body types associated with different causes of early larval lethality. For example, defects in excretory canal (kidney) function seem to lead to stiff rod-like corpses (as in some Ras pathway alleles), whereas some defects that result in starvation or nutritional deficits lead to thin scrawny body types, sometimes having the appearance of a normal head and pharyngeal region but only a very short withered body and tail. Developmental monsters less often survive to hatching, but when they do, will take on a more disorganized appearance and fail to grow.

See Developmental arrest

Late endosome  

A variety of membrane-bound vesicular organelles within the cell cytoplasm are termed “endosomes”, and they may act to shuttle cargoes to and from the cell surface (“the endocytic pathway”), the Golgi apparatus and the ER, or into degradative pathways. The late endosome brings material (from these other sources) into a degradative pathway, and can fuse with a lysosome to form a more advanced degradative organelle, the “secondary lysosome”.

Late pretzel stage Four fold stage (S)

A late stage of embryogenesis, just before hatching.

See Pretzel stage

Lateral cord


Lateral chord (S)


This term is used to include different anatomical structures within the C. elegans nervous system.

1) the lateral nerve cord

2) the lateral hypodermal cord

3) the combined lateral ridge of hypodermis and nerve

The left and right hypodermal cords form the largest hypodermal compartments in the body and contain many hypodermal nuclei. It is a syncytium connecting to the smaller dorsal and ventral cords via thin extensions running beneath the bodywall muscles.

There are several distinctly different lateral nerves with apparently different functions. A bilateral pair of small lateral nerve cords containing three interneuron processes each run along the lateral line, in close proximity to the seam cells, connecting the nerve ring and preanal ganglion. Bilateral sensory nerves run laterally near the dorsal and ventral limits of the lateral hypodermis while the anterior sensory nerves run along the dorsal limit and end near the vulval region. Similarly, the posterior sensory nerves run along the ventral limit, also ending in the vulval region.

See Hypodermal ridge

Lateral element  

Part of the synaptonemal complex formed during meiotic prophase. Proteins for a long ladderlike-core along which the sister chromatids align. The lateral elements run along each pair of sister chromosomes forming the sides of the ladder.

See Synaptonemal complex
See Central element

Lateral ganglion  

The left and right lateral ganglia lie beside the nerve ring in the head. They each contain about 50 neuron cell bodies and send their neuronal processes into the ring at its posterior margin either laterally or ventrally via the amphid commissures and ventral ganglion, but form no local neuropil separate from the nerve ring. The lateral ganglia are in close contact with the lateral hypodermal cords.

Lateral line Lateral cord (S)   The enlarged longitudinal hypodermal compartment, lateral seam cells and several embedded lateral nerves, including several mechanosensory nerves (touch dendrites).

See Hypodermal ridge
See Nerve
Touch dendrite

Lateral nerve Canal-associated nerve (S)  

There are several distinctly different lateral nerves with different functions. 

1) A bilateral pair of small lateral nerve cords containing three interneuron processes each run along the lateral line, in close proximity to the seam cells, connecting the nerve ring and preanal ganglion.

2) Bilateral sensory nerves run laterally near the dorsal and ventral limits of the lateral hypodermis. The anterior sensory nerves run along the dorsal limit and end near the vulval region. The posterior sensory nerves run along the ventral limit, also ending in the vulval region.

Lateral view Lateral aspect (S)   View of the side of the animal.



A thin film of bacteria used to feed nematodes in culture, usually on a “culture plate” containing a layer of agar onto which the lawn of bacteria is applied. Tracks can be seen on the lawn as the nematodes move through the bacteria.


A method to produce many partially synchronous progeny by placing 50-100 fertile adults on a single plate for several hours, permitting them to lay eggs, after which the adults are all removed. This produces an “egg plate”. Sometimes the population of eggs is further synchronized by a “subsequent hatch-off”, in which 3-fold embryos are picked off the egg plate and transferred to a new plate for 1 hour, after which any unhatched embryos are removed (McCarter et al., 1997).

See Egg plate
See Hatch-off

Leader cell migration  

Refers to directed cell migration by two somatic gonad cell types, the distal tip cell (in the hermaphrodite) and the linker cell (in the male).

See Distal tip cell
See Linker cell

Leader function


In the developing germline primordium, one somatic cell binds tightly over the distal portion and crawls along the bodywall, pulling and shaping the primordium into an extended cylindrical tube. During this process, the somatic cell may make several distinctive turns which forces the whole tube to bend or be redirected according to the actions of the “leader” cell. For the hermaphrodite gonad, the distal tip cells perform the leader function, one cell for each gonad arm, whereas in the male gonad, the single linker cell performs the leader function.

See Distal tip cell
See Linker cell

Leading cell    

In the process of epidermal enclosure of the embryo, several hypodermal cells migrate and extend arms across the ventral surface in advance of all others (Williams-Masson et al., 1997; Chisholm and Hardin, 2005), and later the same “leading cells” also initiate cell fusions of the hypodermal compartments prior to all others (Podbilewicz and White, 1994).

Learning and memory    

C. elegans displays very simple behaviors, but does show some ability to modify its actions based upon previous experiences as determined by sensory inputs such as chemosensation (Bargmann, 2006; Jansen in Hart, 2006) mechanosensation (Chalfie in Hart, 2006) and thermosensation (Mori in H art, 2006). These abilities may reflect behavior patterns encoded in the synaptic circuits, or plasticity based upon being able to modify the circuitry (Bernhard and van der Kooy, 2000; Zhang et al., 2005; Giles et al., 2005).

See Associative learning
See Habituation
See Neural plasticity
See Osmotic avoidance
See Sensitization

Leaving behavior


A sex drive displayed by well fed male adult C. elegans in which the animal chooses to ignore food and to wander in search of a suitable adult hermaphrodite partner. The animal’s motions are no longer guided by attention to food signals, but become strongly attuned to finding other nematodes via a pheromone signal (Lipton et al., 2004).

See Mate-finding
See Pheromone
See Wandering



A roller (rol) mutation which forces the animals to rotate around their long axis as they crawl resulting in movement in a circular path. Left handed rollers always turn leftwards as they roll, due to a twist in the exoskeleton producing left-handed helical treads, body musculatures and ventral nerve cords (Higgins and Hirsh, 1977).

See Roller



A characteristic of some nematode species (though not C. elegans) in which the male tail fan fails to extend posterior to the most posterior rays, allowing a thin cytoplasmic process to extend posteriorly from the fan. The lep mutants of C. elegans display this feature in the adult male tail.

See Peloderan
See Caudal alae
See Fan

Leptotene   An early stage in meiotic prophase progression, preceding zygotene. Germline cells in the “transition zone” of the distal gonad arm enter this stage coordinately.
Let   Lethal phenotype.
Lethargic movement   Slow movement of the body and general unresponsiveness to stimulation, commonly seen in very old adult animals and in many behavioral mutants, as well as in all animals during molting.

A behavior of the whole animal associated with times of molting (Cassada and Russell, 1975; Singh and Sulston, 1978). The animal becomes generally inactive or torpid for one to two hours prior to shedding of the cuticle. Pharyngeal pumping rates drop from 200 strokes per min to less than 1 per min. Movement by the bodywall muscles is also very low. Pumping is restored immediately before ecdysis. A second, very brief drop in pumping rate sometimes follows the molt. It is possible that during lethargus the nervous system undergoes selective rewiring, since new sets of neurons appear at several of these stages (late L1, late L2, etc). Increased oxygen uptake during lethargus (measured in other nematode species) has been ascribed to an increase in metabolic activity during this period, perhaps associated with these developmental changes. A less dramatic, but longer torpor is associated with the dauer larva.

See Dauer behavior
See Flipping
See Quietus


Levamisole is a synthetic imidazothiazole derivative that has been widely used in treatment of worm infestations in both humans and animals. As an anthelmintic, levamisole acts as a nicotinic agonist which activates an acetylcholine receptor in muscle. While acute exposure leads to paralysis and death, sublethal treatment at 0.1% animals enter rapid complete paralysis. Its action is reversible, and has often been used to devise mutant screens for defects in synaptic release (Lewis et al., 1980; 1987) or to block internal fertilizations by paralyzing the contractility of the somatic gonad (Argon and Ward, 1980; Doniach and Hodgkin, 1984).

See Anthelminthic

Life cycle

The progression of embryonic, larval stages and adulthood that commences after egg-laying, and results in new embryos being created by the next adult generation.

Life history



The sequential developmental stages and environments through which an animal proceeds. Such progressions are of particular importance in parasitic species, in which certain larval stages may be free-living, while others may require invasion into a host species in order to trigger further development or egg-laying. Some species can have several alternate life histories, depending upon which host they encounter first, or can live either as parasites or as free-living forms (Ashton and Schad, 1996).

Lifespan Longevity (S)

The length of time which an individual has lived. The longevity, or life expectancy, of an individual or species is generally the average amount of time expected to live under ideal conditions while maximum lifespan is the age of death for the oldest individuals.

Light touch Gentle touch (S)
Harsh touch (A)

The level of mechanical stimulus required to stimulate a behavioral response by the touch dendrites along the bodywall of the nematode. In C. elegans, gentle touch with an eyelash is sufficient to activate these receptors, whereas poking the animal with a metal wire evokes a different response (harsh touch) activated by separate sense cells.

See Gentle touch
See Harsh touch
See Touch response

Lima bean stage

Bean stage (S)


An intermediate stage in embryogenesis, immediately following the completion of gastrulation around 350-390 minutes after first cleavage. Cell number is at ~560 cells. At this time cell proliferation ceases and the embryo begins morphogenesis and elongation. The shape of the entire embryo within the eggshell resembles a lima bean. The next stage is called the comma embryo.

Lima bean stopper


  A common arrest stage in embryogenesis.

See Embryonic arrest




The exact sequence of cell divisions that gives rise to a particular set of mature (or intermediate stage) cells. In C. elegans, almost all patterns of cell lineage are repeated exactly from one animal to another for any given structure and have been characterized (Sulston and Horvitz, 1977; Sulston et al., 1983) and are apparently regulated by genetic programs operating in the nucleus of the parent cells (Sulston and Horvitz, 1981), whereas in higher animals cell lineages generally show high degrees of variation and unpredictability. Early portions of the embryonic lineage are conserved among many nematode species (von Ehrenstein and Schierenberg, 1980).

The process of vulval development has been closely studied and provides some insight into the complexity of cell signaling influences on lineage determination.

Lineage regulation    

A change in the lineage of one blast cell in compensation for nearby environmental changes, especially with regard to the loss of homologous sister blast cells or their progeny. This regulation may involve the replacement of lost cells nearby by altering the division pattern and/or cell fates of a blast cell’s daughters. Such regulation is unusual in C. elegans lineages, and virtually never allows for the full replacement of the total number of daughter cells, even if some cell fates can be replaced (Sulston and White, 1980; Sulston and Horvitz, 1981).

Linker cell   As a part of the somatic gonad of the male, the linker cell performs a “leader function” similar to that of the distal tip cell in the hermaphrodite gonad. As it migrates it leads the developing germline towards the tail tip to connect to the proctodeum. The linker cell later helps to form the opening of the vas deferens to the proctodeum, after which it undergoes a programmed cell death to allow this channel to open (Kimble and Hirsh, 1979). In this later role, the linker cell acts in rather similar fashion to the anchor cell of the female uterus, helping to connect the gonad to the exterior.

See Anchor cell
See Distal tip cell

Lip/ Lips


This term has multiple meanings, but structures called lips always consists of a fold or protuberance of hypodermal tissue covered by cuticle, bordering an opening into the body.

1) In the head, the opening to the buccal cavity is bordered by six-fold lips also knows as the labia They are named according to their relative positions: subdorsal, subventral or lateral.

2) At the opening of the vulva there are two-fold vulval “lips” both anterior and posterior to the opening.

3) In at least some species, folds at the cloaca in male tail are called lips.

4) At the anus, anal lips borders the opening on the anterior and posterior with the anterior lip being more prominent.

Lipid bilayer    

See Bilayer

Lipid layer Vitelline envelope (S)  

A component of the eggshell. This thin wispy layer lies underneath the chitin layer, just overlying the plasma membrane of the embryonic cells. It may break down in the hours before hatching (Bird and Bird, 1991). In many instances, this layer has been mislabeled the “vitelline membrane” or “inner vitelline membrane”, but the vitelline membrane is actually the outermost layer of the eggshell.

See Eggshell
See Vitelline membrane

Lipid raft

A microdomain within the cell membrane that is enriched with certain types of lipids such as cholesterol, glycolipids and sphingolipids. These domains are distinguished by their relative insolubility in nonionic detergents and their relative buoyancy in a density gradient.  Within a cell membrane such lipid collections can coassemble to form a “raft” which will derive special physical properties. Some lipid rafts have a tendency to form invaginations called caveolae, and some rafts attract special subsets of proteins to form local clusters.

See Caveola/ caveolae



A granular cytoplasmic substance in the intestine that increases in size and frequency in older nematodes (Clokey and Jacobsen, 1986).  It is autofluorescent and dark-staining, and useful as a biomarker for physiological aging in longevity studies (Herndon et al., 2002; Gerstbrein et al., 2005).

See AGE pigments

Liquid culture  

A method for growing large quantities of nematodes in well-aerated flasks of bacterial broth or axenic broth, rather than on typical culture plates of agar spread with a bacterial lawn.

See Axenic medium
See Defined medium

Locomotion/ locomotory activity


Self-propelled movement. In C. elegans, locomotion is generated by the action of a defined set of motor neurons and interneurons that signal the action of the body muscles.

See Crawling
See Deep ventral bend
See Foraging
See Kinesis
See Lethargus
See Nictation
See Roller
See Nose touch avoidance
See Quiescence
See Shortening
See Swimming
See Taxis
See Thrashing

Longitudinal migration



Migration of cells or neurons that extend towards the nose or tail rather than towards the sides of the animal.

Longitudinal muscles



All nematode somatic (striated) muscles run longitudinally. Hermaphrodites have 95 body wall muscle cells that are arranged as staggered pairs in four longitudinal bundles located in four quadrants. Males have 3 additional sets of sex-specific longitudinal muscles (anterior and posterior outer, anterior and posterior inner, and caudal) that contribute to the body wall musculature.

Longitudinal view

Longitudinal aspect (S)

  Any side view of the body, as opposed to a cross-section or "transverse view". This can include views from a dorsal or ventral aspect, or a left or right-side view.

A portion of the extended gonad where it bends back upon itself (reflexes) to form a proximal arm and a distal arm. Alternately, this term can refer to a specific type of continued turning in the forward motion of the animal which permits it to reverse direction without making any backward motions.

Loop stage Three-fold stage (S)   A late stage in embryogenesis during which the elongating embryo has begun to adopt a worm-like shape within the eggshell, and many events in tissue morphogenesis are proceeding. This stage immediately precedes the early pretzel stage.

Describes a form of track on the agar seen for some classes of uncoordinated (unc) mutants, in which the animals move forward in exaggerated circular paths, often turning continuously with little net progress across the plate.  This is a behavioral change, and not the same as the rolling motion caused by some cuticle defects (e.g. not like a “roller”) (Hawasli et al., 2004).

LSM Lateral submedial neuron

See CEP cell

Lumbar commissure

Lumbar-preanal commissure (S)
Lumbar-preanal nerve (S)
Lumbar nerve (S)
Ano-lumbar commissure (S)
Caudalid (archaic)

  Each left and right lumbar commissure connects one of the lumbar ganglia to the pre-anal ganglion via closely bundled processes passing circumferentially beneath the ventral bodywall muscles in the tail.


Lumbar ganglion



The left and right lumbar ganglia lie behind the pre-anal ganglion in the tail, in lateral positions. Each contains 12 neuron cell bodies that send most of their neuronal processes into the ventral nerve cord via lumbar commissures and the pre-anal ganglion. There is no local neuropil in these ganglia in the hermaphrodite, instead they form most synapses in the pre-anal ganglion. Most lumbar neurons have sensory functions. In the adult male tail, these two ganglia gain many additional neurons and have some local neuropil. The lumbar neurons lie in close association with the lateral hypodermis, and most are posterior to the anus.

Lumen/ lumena    

The interior of a vessel within a body such as of the pharynx, intestine, excretory gland, uterus, vulva, or spermatheca. It can also refer to the inner membrane space of the mitochondrion, golgi or ER.

Lysis   Typically refers to death of a cell by bursting. Can occur by osmotic or viral triggers that compromise the integrity of the cellular membrane. Also refers to the bursting of entire worms for preparation of DNA, RNA or proteins.

A membrane bound organelle that contains digestive enzymes for digesting macromolecules and disposing of unwanted materials such as phagocytosed bacterium and damaged organelles. Additionally, lysosomes aid in the recycling of the components of receptor-mediated endocytosis. Each pathway to degradation leads to the lysosome, regardless of the souce of the material (Alberts, 2002).

See also Wormbook chapters: Intracellular trafficking (Grant and Sato, 2006) and Autophagy in C. elegans (Meléndez and Levine, 2009).

Edited for the web by Laura A. Herndon. Last revision: September 19, 2011. This section should be cited as: Herndon, L.A. and Hall, D.H. 2009. Glossary L. In WormAtlas.  doi:10.3908/wormatlas.6.12