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Roundworm

Caenorhabditis elegans (Maupas 1899)

Brief Summary

    Caenorhabditis elegans: Brief Summary
    provided by wikipedia
    "C. elegans" redirects here. For other uses, see C. elegans (disambiguation).

    Caenorhabditis elegans (/ˌsiːnoʊræbˈdaɪtəs ˈɛləɡænz/) is a free-living (not parasitic), transparent nematode (roundworm), about 1 mm in length, that lives in temperate soil environments. It is the type species of its genus. The name is a blend of the Greek caeno- (recent), rhabditis (rod-like) and Latin elegans (elegant). In 1900, Maupas initially named it Rhabditides elegans, Osche placed it in the subgenus Caenorhabditis in 1952, and in 1955, Dougherty raised Caenorhabditis to the status of genus.

    C. elegans is an unsegmented pseudocoelomate and lacks respiratory or circulatory systems. The majority of these nematodes are hermaphrodites and a few are males. Males have specialised tails for mating that include spicules.

    In 1963, Sydney Brenner proposed research into C. elegans primarily in the area of neuronal development. In 1974, he began research into the molecular and developmental biology of C. elegans, which has since been extensively used as a model organism. It was the first multicellular organism to have its whole genome sequenced, and as of 2012, is the only organism to have its connectome (neuronal "wiring diagram") completed.

    Brief Summary
    provided by EOL authors
    Caenorhabditis elegans is a small (~1mm long) nematode worm (roundworm) in the family Rhabditidae. It is cosmopolitan in distribution, with reproductive stages found most reliably in rotting fruits and surrounding soil. When food is plentiful, a fertilized egg completes embryogenesis, passes through four larval stages, and attains reproductive maturity in only three days at room temperature. As with most terrestrial nematodes, under stressful conditions an alternative third larval stage specialized for dispersal, the dauer larva, may be formed. In soil, C. elegans is often found in the dauer form. The reproductive mode of C. elegans involves a mixture of self-fertile hermaphrodites and males (this system was derived relatively recently from an ancestral male/female system). The transparency, anatomical simplicity, rapid development, and mix of outcrossing and selfing in C. elegans led American nematologist Ellsworth Dougherty and British molecular geneticist Sydney Brenner to champion this species as a model organism for basic biological research beginning in the 1970s. By the early 1980's, Brenner and colleagues had carried out pioneering studies investigating the invariant cell lineages, neuroanatomy, and aspects of the genome of C. elegans. This rich body of work garnered the attention of many more researchers and quickly led to C. elegans becoming one of the most widely studied laboratory organisms in the fields of genetics, cell biology, development, aging, evolution, and neuroscience. In 1998, C. elegans became the first animal to have its entire genome sequence determined and it remains at the forefront of functional genomics.

Comprehensive Description

Distribution

    Distribution
    provided by Animal Diversity Web

    Caenorhabditis elegans live in temperate regions in many parts of the world (Nicholas 1975).

Morphology

    Morphology
    provided by Animal Diversity Web

    Caenorhabditis elegans have elongated cylindrical bodies, tapered at both ends, with smooth skin, no segmentation, and no appendages. Adults grow to approximately 1mm in length. Exactly 959 cells compose Caenorhabditis elegans, and their bodies are transparent; therefore, individual cells are easily observed with a microscope (Edgley 1999).

Habitat

    Habitat
    provided by Animal Diversity Web

    Caenorhabditis elegans are terrestrial organisms. They live primarily in soil (Lee & Atkinson 1977). The soil must have a constant level of moisture, so that the worm can move in the film of water and draw water from the soil. The soil must also have a moderate oxygen content. Worms may not be able to penetrate soils with high clay content. For ideal movement, the worm should be about three times as long as the diameter of the soil particles ( Nicholas 1975). Worms are also found in or on rotting vegetation above ground (Edgley 1999).

Trophic Strategy

    Trophic Strategy
    provided by Animal Diversity Web

    Caenorhabditis elegans are bacteriovorous; they feed on various types of bacteria that live in soil and on rotting vegetation. They feed by ingesting bacteria in suspension or on detritus (Nicholas 1975).

Life Expectancy

    Life Expectancy
    provided by Animal Diversity Web

    Average lifespan
    Status: captivity:
    0.16 years.

Reproduction

    Reproduction
    provided by Animal Diversity Web

    Caenorhabditis elegans have two naturally occurring sexes, a male and a self-fertilizing hermaphrodite; females do not naturally occur. The majority of individuals are hermaphrodites; males usually comprise no more than 0.20% of the natural population. The number of males can be increased, however, by raising the temperature at the onset of sexual maturity (Nicholas 1975). Hermaphrodites are protandrous; the individuals produce sperm first and then produce eggs (Blaxter 1999). Most commonly, worms will simply fertilize their own eggs (Bird 1991). However, the males that do exist copulate with hermaphrodites, thus mixing up the gene pool in the population (Nicholas 1975). Eggs are laid within two to three hours of fertilization and hatch approximately twelve hours later. The worms develop into adults in four larval stages; this generally takes about three days when the temperature ranges from 20 to 25 degrees Celsius (Blaxter 1999). Temperature plays a major role in the development of Caenorhabditis elegans. The worms' average lifespan is two to three weeks (Edgley 1999).

    Images of Caenorhabditis elegans and sperm: http://www.mcb.arizona.edu/Wardlab/gallery.html (Muhlrad 1998)

    Average age at sexual or reproductive maturity (male)
    Sex: male:
    3 days.

    Average age at sexual or reproductive maturity (female)
    Sex: female:
    3 days.

Conservation Status

    Conservation Status
    provided by Animal Diversity Web

    Caenorhabditis elegans are not endangered or threatened; they are found in large numbers in nature.

    US Federal List: no special status

    CITES: no special status

Benefits

    Benefits
    provided by Animal Diversity Web

    This species has no known negative impact on humans.

    Benefits
    provided by Animal Diversity Web

    Caenorhabditis elegans are used often in scientific research; they are considered a model organism and are easy to study due to their transparency. They are bred for use as laboratory specimens.

Other Articles

    Untitled
    provided by Animal Diversity Web

    Caenorhabditis elegans are often called C. elegans or simply 'the worm' because they are a model species. C. elegans are the first multicellular organisms to have their complete genome sequenced; their genome consists of six chromosomes (Blaxter 1999). The genes of the worm are studied to determine how the complex processes of embryogenesis, development, disease, and aging occur. This research is leading to a better understanding of the specific roles of genes in other organisms, including humans (Edgley 1999). For example, scientists are investigating the role that different genes play in the aging process of C. elegans with the hope that much of what they learn will lead to a better understanding of the complex process of aging in humans. Scientists are also experimenting with various ways to slow or reverse the aging process; techniques developed could then be tested in humans (Blaxter 1999).

    Image of Caenorhabditis elegans: http://www.soton.ac.uk/~djab/ce.htm (Avery 2000)