The "roundworms" or "nematodes" (phylum
Nematoda) are the most diverse phylum of
pseudocoelomatesBy the broadest definition, a body cavity is any fluid filled space in a multicellular organism. However, the term usually refers to the space, located between an animal’s outer covering and the outer lining of the gut cavity, where internal organs develop...
, and one of the most diverse of all
animalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
s. Nematode
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
are very difficult to distinguish; over 80,000 have been described, of which over 15,000 are parasitic. It has been estimated that the total number of described and undescribed roundworms might be more than 500,000. Unlike cnidarians or flatworms, roundworms have a digestive system that is like a tube at both ends.
Habitats
Nematodes have successfully adapted to nearly every
ecological nicheIn ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different school if the members of these schools utilize significantly different...
from marine to fresh water, from the polar regions to the tropics, as well as the highest to the lowest of elevations. They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in the locations as diverse as
Antarctica| style="border-top:solid 1px #ccd2d9; padding:0.4em 1em 0.4em 0; vertical-align:top;" | 14,000,000 km
2 280,000 km
2 13,720,000 km
2 |-! style="border-top: solid 1px #ccd2d9; padding: 0.4em 1em 0.4em 0; vertical-align: top;...
and
oceanic trenchThe oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor....
es. They represent, for example, 90% of all life on the seafloor of the Earth. Their many parasitic forms include
pathogenA pathogen , infectious agent, or germ, is a biological agent that causes disease or illness to its host....
s in most plants and animals (including humans.) Some nematodes can undergo
cryptobiosisCryptobiosis is a metabolic state of life entered by an organism in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. In the cryptobiotic state, all metabolic procedures stop, preventing reproduction, development, and repair...
.
Taxonomy and systematics
The group was originally defined by
Karl RudolphiKarl Asmund Rudolphi was a Swedish-born naturalist, who is credited with being the "father of helminthology"....
in 1808 under the name
Nematoidea, from
Ancient GreekAncient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...
νῆμα (
nêma, nêmatos, 'thread') and -eiδἠς (
-eidēs, 'like'). The vernacular word "nematode" is a corruption of this taxon, reclassified as
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
Nematodes by Burmeister in 1837 and ordo
Nematoda by K. M. Diesing in 1861.
At the origin, the taxon
Nematoidea applied to both roundworms and horsehair worms. Along with
Acanthocephala, Trematoda and
Cestoidea, it formed the group
Entozoa. The first differentiation of roundworms from horsehair worms, though erroneous, is due to von Siebold (1843) with orders
Nematoidea and
Gordiacei (
Gordiacea). They were classed along with
Acanthocephala in the new phylum
Nemathelminthes (today obsolete) by Gegenbaur (1859). Then the taxon
Nematoidea has been promoted to the rank of phylum by
Ray LankesterSir E. Ray Lankester KCB, FRS was a British zoologist, born in London.An invertebrate zoologist and evolutionary biologist, he held chairs at University College London and Oxford University. He was the third Director of the Natural History Museum, and was awarded the Copley Medal of the Royal...
(1877) including the family
Gordiidae (horsehair worms). In 1919,
Nathan CobbNathan Augustus Cobb born in Spencer, Massachusetts is known as "the father of nematology in the United States".He provided the foundations for nematode taxonomy and described over 1000 different nematode species...
proposed that roundworms should be recognized alone as a phylum. He argued that they should be called
nema(s) in English rather than "nematodes" and defined the taxon
Nemates (Latin plural of
nema). For ITIS, the taxon
Nematoda is invalid.
Since Cobb was the first to exclude all but nematodes from the group, the valid taxon should be
Nemates Cobb 1919 or
Nemata Cobb 1919.
Phylogeny
The relationships of the nematodes and their close relatives among the protostomian Metazoa are unresolved. Traditionally, they were held to be a lineage of their own, but in the 1990s it was proposed that they form a
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
together with
moultIn biology, moulting signifies the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life-cycle.Moulting can involve the epidermis , pelage In biology, moulting (or molting, also known as sloughing, shedding or for...
ing animals such as
arthropodAn arthropod is an invertebrate that has an exoskeleton , a segmented body, and jointed attachments called appendages. Arthropods are animals belonging to the Phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s. This group has been named
EcdysozoaThe Ecdysozoa are a grouping of protostome animals, including the Arthropoda , Nematoda, and several smaller phyla. They were first defined by Aguinaldo et al. in 1997, based mainly on trees constructed using 18S ribosomal RNA genes...
. However, the
monophylyIn common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it consists of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly...
of the Ecdysozoa was never unequivocally accepted: while most researchers consider at least the placement of arthropods as more distant relatives of
annelidThe annelids, collectively called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches. They are found in marine environments from tidal zones to hydrothermal vents, in freshwater, and in moist terrestrial environments...
s — with which they were formerly united — to be warranted, the presumed close relationships of the nematodes and relatives with the arthropods has been a major point of contention.
Even though the amount of data since accumulated in regard to this problem is staggering, the situation seems if anything less clear these days.
DNA sequenceA DNA sequence or genetic sequence is a succession of letters representing the primary structure of a real or hypothetical DNA molecule or strand, with the capacity to carry information as described by the central dogma of molecular biology....
data, initially strongly supporting the Ecdysozoa hypothesis, has become rather equivocal on ecdysozoan monophyly, and is simply unable to
refuteFalsification may mean:*The act of disproving a proposition, hypothesis, or theory. *Forgery, the act of producing something that lacks authenticity with the intent to commit fraud or deception...
either a close or a more distant relationship between the arthropod and nematode lineages. That the roundworms have a large number of peculiar apomorphies and in many cases a parasitic lifestyle confounds morphological analyses. Genetic analyses of roundworms suggest that — as is also indicated by their unique morphological features — the group has been under intense
selectiveNatural selection is the process by which heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations...
pressure during its early radiation, resulting apparently in accelerated rates of both morphological and molecular
evolutionIn biology, evolution is change in the genetic material of a population of organisms from one generation to the next. Though changes produced in any one generation are normally small, differences accumulate with each generation and can, over time, cause substantial changes in the population, a...
. Furthermore, no distinctive apomorphies of Ecdysozoa are known; even moulting has recently been confirmed to occur outside the presumed clade.
Conversely, the identity of the closest living relatives of the Nematoda has always been considered to be well resolved. Morphological characters and molecular phylogenies agree with placement of the roundworms as sister taxon to the parasitic horsehair worms (Nematomorpha); together they make up the
Nematoida. Together with the
ScalidophoraScalidophora is a group of marine pseudocoelomate invertebrates, consisting of the three phyla Kinorhyncha, Priapulida, and Loricifera. The members of the group share a number of characteristics, including introvert larvae and moulting of the cuticle...
(formerly Cephalorhyncha), the Nematoida form the Introverta. It is entirely unclear whether the Introverta are, in turn, the closest living relatives of the enigmatic Gastrotricha; if so, they are considered a clade
CycloneuraliaCycloneuralia is a grouping of animals.The name derives from the position of the brain around the pharynx....
, but there is much disagreement both between and among the available morphological and molecular data. The Cycloneuralia or the Introverta — depending on the validity of the former — are often ranked as a superphylum.
Nematode systematics
Due to the lack of knowledge regarding many nematodes, their systematics is contentious. Traditionally, they are divided into two
classIn biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
es, the
AdenophoreaAdenophorea is a class of nematodes. They are unsegmented worms.Characteristics of adenophorea are:* amphids always post-labial, variable shape, pore-like to elaborate* deirids are not seen* phasmids are generally absent...
and the
SecernenteaSecernentea are the main class of nematodes, characterised by numerous caudal papillae and an excretory system possessing lateral canals. Like all nematodes, they have no circulatory or respiratory system....
, and initial
DNA sequenceA DNA sequence or genetic sequence is a succession of letters representing the primary structure of a real or hypothetical DNA molecule or strand, with the capacity to carry information as described by the central dogma of molecular biology....
studies suggested the existence of five
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
s:
- Dorylaimia
- Enoplia
Enoplia are a subclass of the roundworms. Most are free-living, but the group includes the order Trichurida, which includes whipworms and trichina worms. The anterior sensory structures are well developed, while the posterior ones are not.-External links:*...
- Spirurina
- Tylenchina
- Rhabditina
As it seems, the
SecernenteaSecernentea are the main class of nematodes, characterised by numerous caudal papillae and an excretory system possessing lateral canals. Like all nematodes, they have no circulatory or respiratory system....
are indeed a natural group of closest relatives. But the "Adenophorea" appear to be a paraphyletic assemblage of roundworms simply retaining a good number of ancestral traits. The
EnopliaEnoplia are a subclass of the roundworms. Most are free-living, but the group includes the order Trichurida, which includes whipworms and trichina worms. The anterior sensory structures are well developed, while the posterior ones are not.-External links:*...
do not seem to be monophyletic either but to contain two distinct lineages. The old group "
ChromadoriaThe Chromadoria are a subclass of the class Adenophorea, . Members of this subclass' bodies usually have annules, their amphids elaborate and spiral, and they all have three esophageal glands. They usually live in marine sediments, although they can live elsewhere...
" seem to be another paraphyletic assemblage, with the
MonhysteridaThe Monhysterida are an order in the phylum Nematoda. Usually the stoma in Monhysterida is funnel shaped and lightly cuticularized, but it is sometimes spacious and heavily cuticularized and they always have protrusible teeth. They are either simply spiral or circular.-External links:*...
representing a very ancient minor group of nematodes. Among the Secernentea, the Diplogasteria may need to be united with the
RhabditiaSubclass Rhabditia is mostly composed of parasitic nematodes , though there are some free-living species as well...
. while the Tylenchia might be paraphyletic with the Rhabditia.
The understanding of roundworm systematics and phylogeny as of 2002 is summarised below:
Phylum Nematoda
- Basal order Monhysterida
The Monhysterida are an order in the phylum Nematoda. Usually the stoma in Monhysterida is funnel shaped and lightly cuticularized, but it is sometimes spacious and heavily cuticularized and they always have protrusible teeth. They are either simply spiral or circular.-External links:*...
- Basal subclass/Class Enoplia
Enoplia are a subclass of the roundworms. Most are free-living, but the group includes the order Trichurida, which includes whipworms and trichina worms. The anterior sensory structures are well developed, while the posterior ones are not.-External links:*...
- Basal subclass/Class Dorylaimia
- Class Secernentea
Secernentea are the main class of nematodes, characterised by numerous caudal papillae and an excretory system possessing lateral canals. Like all nematodes, they have no circulatory or respiratory system....
- Subclass Diplogasteria (disputed)
- Subclass Rhabditia
Subclass Rhabditia is mostly composed of parasitic nematodes , though there are some free-living species as well...
(paraphyletic?)
- Subclass Spiruria
Subclass Spiruria comprises mostly parasitic secernentean nematodes. In an alternate classification, they are treated as suborder Spirurina, with the orders listed here being ranked as infraorders....
- Subclass Tylenchia (disputed)
- "Chromadoria
The Chromadoria are a subclass of the class Adenophorea, . Members of this subclass' bodies usually have annules, their amphids elaborate and spiral, and they all have three esophageal glands. They usually live in marine sediments, although they can live elsewhere...
" assemblage
Reproduction
Reproduction is usually sexual. Males are usually smaller than females (often much smaller) and often have a characteristically bent tail for holding the female for copulation. During copulation, one or more
chitinChitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world. It is the main component of the cell walls of fungi, the exoskeletons of arthropods, such as crustaceans Chitin...
ized
spiculeSpicules are tiny spike-like structures of diverse origin and function found in many organisms, such as the copulatory spicules of certain nematodes or the grains on the skin of some frogs....
s move out of the cloaca and are inserted into genital pore of the female.
AmoeboidAmoeboids are single-celled life-forms characterized by an irregular shape."Amoeboid" and "amoeba" are often used interchangeably even by biologists, and especially refers to a creature moving by using pseudopods. Most references to "amoebas" or "amoebae" are to amoeboids in general rather than to...
spermThe term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
crawl along the spicule into the female worm. Nematode sperm is thought to be the only
eukaryotic cellEukaryotic Cell is an academic journal published by the American Society for Microbiology. The title is commonly abbreviated EC and the ISSN is 1535-9778 for the print version, and 1535-9786 for the electronic version....
without the globular protein G-actin.
Eggs may be embryonated or unembryonated when passed by the female, meaning that their fertilized eggs may not yet be developed. In free-living roundworms, the eggs hatch into larva, which eventually grow into adults; in parasitic roundworms, the life cycle is often much more complicated.
Nematodes as a whole possess a wide range of modes of reproduction. Some nematodes, specifically
HeterorhabditisHeterorhabditis is a genus of nematodes belonging to the order Rhabditida. All species of this genus are obligate parasites of insects, and some are used as biological control agents for the control of pest insects.- Uses:...
spp., undergo a process called
endotokia matricida: intrauterine birth causing maternal death. Some nematodes, like other animals (for example segmented worms), are hermaphroditic. The hermaphroditic nematode keeps its self-fertilized eggs inside its uterus until they hatch. The juvenile nematodes will then ingest the parent nematode. This process is significantly promoted in environments with a low or reducing food supply. The nematode model species
Caenorhabditis elegansCaenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
and
C. briggsaeCaenorhabditis briggsae is a small nematode, closely related to Caenorhabditis elegans. The differences between the two species are subtle. The male tail in C. briggsae has a slightly different morphology than C. elegans. Other differences include changes in vulval precursor competence and the...
exhibit
androdioecyAndrodioecy is a reproductive system found in species composed of a male population and a distinct hermaphrodite population. Such species are rare....
, which is very rare among animals. The single genus
Meloidogyne (root-knot nematodes) exhibit a range of reproductive modes including sexuality (amphimixis), facultative sexuality, meiotic parthenogenesis (automixis) and mitotic parthenogenesis (
apomixisIn botany, apomixis is replacement of the normal sexual reproduction by asexual reproduction, without fertilization...
).
Free-living species
In free-living species, development usually consists of four molts of the cuticle during growth. Different species feed on materials as varied as algae, fungi, small animals, fecal matter, dead organisms and living tissues. Free-living marine nematodes are important and abundant members of the
meiobenthosMeiofauna are small benthic invertebrates that live in both marine and fresh water environments . The term Meiofauna loosely defines a group of organisms by their size, larger than Microfauna but smaller than Macrofauna, rather than a taxonomic grouping...
. They play an important role in the decomposition process, aid in recycling of nutrients in marine environments and are sensitive to changes in the environment caused by pollution. One roundworm of note is
Caenorhabditis elegansCaenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
, which lives in the soil and has found much use as a
model organismA model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms...
.
C. elegans has had its entire genome sequenced, as well as the developmental fate of every cell determined, and every neuron mapped.
Parasitic species
Nematodes commonly parasitic on humans include ascarids (
Ascaris), filarids,
hookwormThe hookworm is a parasitic nematode worm that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. Necator americanus predominates in the Americas, Sub-Saharan...
s,
pinwormThe pinworm , also known as threadworm or seat worm, is a common human intestinal parasite, especially in children...
s (
Enterobius) and
whipwormThe human whipworm , is a roundworm, which causes trichuriasis when it infects a human large intestine. The name whipworm refers to the shape of the worm; they look like whips with wider "handles" at the posterior end.-Life Cycle:The female T. trichiura produces 2,000–10,000 single celled eggs per...
s (
Trichuris trichiura). The species
Trichinella spiralis, commonly known as the trichina worm, occurs in rats, pigs, and humans, and is responsible for the disease
trichinosisTrichinosis, also called trichinellosis, or trichiniasis, is a parasitic disease caused by eating raw or undercooked pork and wild game infected with the larvae of a species of roundworm Trichinella spiralis, commonly called the trichina worm. There are eight Trichinella species; five species are...
.
BaylisascarisBaylisascaris is a genus of roundworms that infest more than fifty animal species.-Life cycle:Baylisascaris eggs are passed in feces and become active within a month. They can remain viable in the environment for years, withstanding heat and cold...
usually infests wild animals but can be deadly to humans as well.
Dirofilaria immitus are Heartworms known for causing
HeartwormHeartworm is a parasitic roundworm that is spread from host to host through the bites of mosquitoes. The heartworm is a type of filaria, a small thread-like worm. The definitive host is the dog but it can also infect cats, wolves, coyotes, foxes and other animals, such as ferrets, sea lions and...
disease by inhabiting the hearts, arteries, and lungs of dogs and some cats.
Haemonchus contortusHaemonchus contortus, also known as red stomach worm, wire worm or Barber's pole worm, is very common parasite and one the most pathogenic nematode of ruminants. Adult worms are attached to abomasal mucosa and feed on the blood....
is one of the most abundant infectious agents in sheep around the world, causing great economic damage to sheep farms. In contrast,
entomopathogenic nematodeEntomopathogenic nematodes are soil-inhabiting, lethal insect parasitoids that belong to the phylum Nematoda, commonly called roundworms. The term entomopathogenic comes from the Greek word entomon, meaning insect, and pathogenic, which means causing disease...
s parasitize insects and are considered by humans to be beneficial.
One form of nematode is entirely dependent upon
fig waspFig wasps are wasps of the family Agaonidae which pollinate figs or are otherwise associated with figs, a coevolutional relationship that has been developing for at least 80 million years....
s, which are the sole source of
figFIG may refer to:*Common fig, a large, deciduous shrub native to southwest Asia and the eastern Mediterranean region.*Ficus, a genus of about 850 species of woody trees, shrubs in the family Moraceae.-Acronym:* Fédération Internationale de Gymnastique...
fertilization. They prey upon the wasps, riding them from the ripe fig of the wasp's birth to the fig flower of its death, where they kill the wasp, and their offspring await the birth of the next generation of wasps as the fig ripens.
Plant parasitic nematodes include several groups causing severe crop losses. The most common genera are
AphelenchoidesAphelenchoides is a genus of plant pathogenic foliar nematodes.The most important species of these are A. ritzemabosi, the chrysanthemum foliar nematode; A. fragariae, the spring crimp or spring dwarf nematode of strawberry, which also attacks many ornamentals; and A...
(foliar nematodes),
DitylenchusDitylenchus is a genus of plant pathogenic nematodes....
,
Globodera (potato cyst nematodes),
HeteroderaHeterodera is a soybean cyst nematode. Heterodera was first reported from Japan in 1916. Studies at that time showed that the nematode had been present in Japan since 1881. The soybean cyst nematode was first reported in the United States in 1954 and in Canada in 1987...
(soybean cyst nematodes),
Longidorus,
Meloidogyne (root-knot nematodes),
Nacobbus,
PratylenchusPratylenchus is a genus of nematodes. Many of the species in this genus are plant pathogens....
(lesion nematodes),
Trichodorus and
XiphinemaXiphinema is a genus of plant-parasitic roundworms.- List of species :* Xiphinema abrantinum Roca & Pereira, 1991.* Xiphinema aceri Chizhov & al., 1986.* Xiphinema aequum Roca & Lamberti, 1988....
(dagger nematodes). Several phytoparasitic nematode species cause histological damages to roots, including the formation of visible galls (e.g. by root-knot nematodes), which are useful characters for their diagnostic in the field. Some nematode species transmit plant viruses through their feeding activity on roots. One of them is
Xiphinema indexXiphinema index is a plant pathogenic nematode.- External links :*...
, vector of GFLV (
Grapevine Fanleaf VirusGrapevine fanleaf virus is a plant pathogenic virus of the family Comoviridae.-External links:**...
), an important disease of grapes.
Other nematodes attack bark and forest trees. The most important representative of this group is
Bursaphelenchus xylophilusBursaphelenchus xylophilus is a nematode that infects pine trees and causes pine wilt...
, the pine wood nematode, present in Asia and America and recently discovered in Europe.
Nematodes in agriculture
Depending on the species, a nematode may be beneficial or detrimental to plant health.
From an agricultural perspective, there are two categories of nematode: predatory ones, which will kill garden pests like
cutwormThe term cutworm is used for the larvae of many species of moth. Most cutworms are in the moth family Noctuidae, however, many noctuid larvae are not cutworms. Cutworms are notorious agricultural and garden pests. They are voracious leaf, bud, and stem feeders and can destroy entire plants...
s, and pest nematodes, like the
root-knot nematodeRoot-knot nematodes are plant-parasitic nematodes from the genus Meloidogyne. They exist in soil in areas with hot climates or short winters. About 2000 plants are susceptible to infection by root-knot nematodes and they cause approximately 5% of global crop loss...
, which attack plants and those that act as
vectorsIn biology, the term vector may be used in different contexts:*Vector , an organism, often an invertebrate arthropod, that transmits a pathogen from reservoir to host...
spreading
plant virusPlant viruses are viruses affecting plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses are defined as viruses pathogenic to higher plants...
es between crop plants.
Predatory nematodes can be bred by soaking a specific recipe of leaves and other
detritusDetritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
in water, in a dark, cool place, and can even be purchased as an
organicThe organic movement broadly refers to the organizations and individuals involved worldwide in the promotion of organic farming, which they believe to be a more sustainable mode of agriculture...
form of
pest controlPest control refers to the regulation or management of a species defined as a pest, usually because it is perceived to be detrimental to a person's health, the ecology or the economy....
.
Rotations of plants with nematode resistant species or varieties is one means of managing parasitic nematode infestations. For example, marigolds, grown over one or more seasons (the effective is cumulative), can be used to control nematodes. Another is treatment with natural antagonists such as the fungus
gliocladium roseum.
ChitosanChitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine...
is a natural biocontrol that elicits plant defense responses to destroy parasitic cyst nematodes on roots of sobyean, corn, sugar beets, potatoes and tomatoes without harming beneficial nematodes in the soil.. Furthermore
soil steamingSoil steam sterilization is a farming technique that sterilizes soil with steam in open fields or greenhouses. Pests of plant cultures such as weeds, bacteria, fungi and viruses are killed through induced hot steam which causes their cell structure to physically degenerate. Biologically, the...
is an efficient method to kill nematodes before planting crop.
CSIRO has found
http://www.publish.csiro.au/paper/AP04081 that there was 13- to 14-fold reduction of nematode population densities in plots having Indian mustard (
Brassica junceaBrassica juncea, also known as mustard greens, Indian mustard and leaf mustard, is a species of mustard plant. Sub-varieties include Southern Giant Curled Mustard, which resembles a headless cabbage such as Kale, but with a distinct horseradish-mustard flavor...
) green manure or seed meal in the soil.
Hundreds of
Caenorhabditis elegansCaenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
were featured in a research project on NASA's
STS-107STS-107 was a space shuttle mission by NASA using the Space Shuttle Columbia, launched January 16, 2003. This was a multi-disciplinary microgravity and Earth science research mission with a multitude of international scientific investigations conducted continuously during 16 days in orbit.The...
space mission (which ended in the
Space Shuttle Columbia DisasterThe Space Shuttle Columbia disaster occurred on February 1, 2003, when the Space Shuttle Columbia disintegrated over Texas during re-entry into the Earth's atmosphere, with the loss of all seven crew members, shortly before it was scheduled to conclude its 28th mission, STS-107.The loss of Columbia...
).
See also
- Ascariasis
Ascariasis is a human disease caused by the parasitic roundworm Ascaris lumbricoides. Perhaps as many as one quarter of the world's people are infected, and ascariasis is particularly prevalent in tropical regions and in areas of poor hygiene...
: A human disease caused by the parasitic roundworm Ascaris lumbricoides
- Chitosan
Chitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine...
(Natural Biocontrol for Agricultural & Horticultural use of nematodes)
- Caenorhabditis elegans
Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
: An important model organismA model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms...
often used to study cellular differentiationIn developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a single zygote to a complex system of...
, sometimes simply referred to as "worm" by scientists.
- List of parasites (human)
- Toxocariasis
Toxocariasis is a zoonotic, helminthic infection of humans caused by the dog roundworm or cat roundworm . Humans normally become infected by ingestion of embryonated eggs from contaminated sources. Humans are accidental hosts, which inhibits L2 larvae maturation within humans...
: A helminth infection of humans caused by the dogThe dog is a domesticated form of the Gray Wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The domestic dog has been one of the most widely kept working and companion animals in human history...
or catThe cat , also known as the domestic cat or housecat to distinguish it from other felines and felids, is a small carnivorous mammal that is valued by humans for its companionship and its ability to hunt vermin and household pests...
roundworm, Toxocara canisToxocara canis is worldwide distributed helminth parasite of dogs and other canids. T. canis are gonochorists, adult worms measure from 9 to 18 cm, are yellow-white in color, and occur in the intestine of the definitive host. In adult dogs, the infection is usually asymptomatic. By the...
or Toxocara catiToxocara cati is worldwide distributed parasite of cats and other felids and it is one of the most common nematode of cats. Adult worms are localised in gut of the host. In adult cats, the infection is usually asymptomatic. However, massive infection in juvenile cats can be fatal.-External links:*...
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UFThe University of Florida is a public land-grant, sea-grant, space-grant major research university located on a campus located in Gainesville, Florida, in the United States. The university traces its origins to 1853, and has continuously operated on its present Gainesville campus since the fall...
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IFASThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
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