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Meloidogyne Incognita

Meloidogyne incognita

The meloidogyne incognita is a nematode. It is an important plant parasite. It is classified in parasitology as a root-knot nematode; in other words, it prefers to attack the root of its host plant. When it attacks the roots of the plants, it sets up a feeding where it deforms the root cells and establishes giant cells. The roots become knarled or nodulated, hence the term "root-knot" nematode. Category:Parasites

Nematode


Adenophorea
   Subclass Enoplia
   Subclass Chromadoria
Secernentea
   Subclass Rhabditia
   Subclass Spiruria
   Subclass Diplogasteria The roundworms (Phylum Nematoda from Gr. nema, nematos "thread" + ode "like") are one of the most common phyla of animals, with over 20,000 different described species. 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 locations as diverse as Antarctica and oceanic trenches. Further, there are a great many parasitic forms, including pathogens in most plants and animals, humans included. Only the Arthropoda are more diverse. The roundworms were originally named the Nemata by Nathan Cobb in 1919. Later they were demoted to a class Nematoda in the Aschelminthes, and then restored to phylum Nematoda.

Morphology

Roundworms are tripoblastic protostomes with a complete digestive system. They are thin and are round in cross section, though they are actually bilaterally symmetrical. The body cavity is reduced to a narrow pseudocoelom. The mouth is often surrounded by various flaps or projections used in feeding and sensation. The portion of the body past the anus or cloaca is called the "tail." The epidermis secretes a layered cuticle made of keratin that protects the body from drying out, from digestive juices, or from other harsh environments, as well as in some forms sporting projections that aid in locomotion. This cuticle is shed as the animal grows. Most free-living nematodes are microscopic, though a few parasitic forms can grow to several metres in length. There are no circular muscles, so the body can only undulate from side to side. Contact with solid objects is necessary for locomotion; its thrashing motions vary from mostly to completely ineffective at swimming. Roundworms generally eat bacteria, algae, fungi and protozoans, although some are filter feeders. Excretion is through a separate excretory pore. Reproduction is usually sexual. Males are usually smaller than females (often very much smaller) and often have a characteristically bent tail for holding the female for copulation. During copulation, one or more chitinized spicules move out of the cloaca and are inserted into genital pore of the female. Amoeboid sperm crawl along the spicule into the female worm. 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. Roundworms have a simple nervous system, with a main nerve cord running along the ventral side. Sensory structures at the anterior end are called amphids, while sensory structures at the posterior end are called phasmids.

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 meiobenthos. One roundworm of note is Caenorhabditis elegans, which lives in the soil and has found much use as a model organism.

Parasitic species

Parasitic forms often have quite complicated life cycles, moving between several different hosts or locations in the host's body. Infection occurs variously by eating uncooked meat with larvae in it, by entrance into unprotected cuts or directly through the skin, by transfer via blood-sucking insects, and so forth. Important parasites on humans include whipworms, hookworms, pinworms, ascarids, and filarids. The species Trichinella spiralis, commonly known as the trichina worm, occurs in rats, pigs, and humans, and is responsible for the disease trichinosis. Baylisascaris usually infests wild animals but can be deadly to humans as well. Haemonchus contortus is one of the most abundant infectious agents in sheep around the world, causing great economic damage to sheep farms.

Phylogeny

The common presence of a pseudocoelom is no longer considered evidence that the pseudocoelomate phyla are all related, but a few groups are still probably close relatives of the Nematoda. Of special note here are the Nematomorpha, or horse-hair worms, which have larvae parasitic in arthropods and free-living adults. The Arthropods have also been considered to be possible relatives of these groups, the common process of ecdysis (molting) being evidence for this. Together, the molting animals form the clade Ecdysozoa.

External links


- http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html
- http://www.nematodes.org/
- [http://faculty.ucr.edu/%7Epdeley/lab/taxonomy.html Nematode Virtual Library]
- [http://www.ifns.org/ International Federation of Nematology Societies] Category:Parasites
- ko:선형동물 ms:Cacing Gelang ja:線形動物

Parasitology

Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question, but by their way of life. This means it forms a synthesis of other disciplines, and draws on techniques from fields such as cell biology, bioinformatics, molecular biology, immunology, genetics and ecology. The parasitic mode of life is the most common on the planet, with representatives from all major taxa, from the simplest unicellular organisms to complex vertebrates. Every free-living species has its own unique species of parasite, so the number of parasitic species greatly exceeds the number of free living species.

Fields

The study of these diverse organisms means that the subject is often broken up into simpler, more focused units, which use common techniques, even if they are not studying the same organisms or diseases. Much research in parasitology falls somewhere between two or more of these definitions. In general, the study of prokaryotes fall under the field of bacteriology rather than parasitology.

Medical parasitology

One of the largest fields in parasitology, medical parasitology is the study of those parasites which infect humans. These include unicellular organisms such as Plasmodium spp., the organism which causes malaria, Leishmania donovani, the organism which causes leishmaniasis and multicellular organisms such as Schistosoma spp., Wuchereria bancrofti and Necator americanus. Medical parasitology can involve drug development, epidimiological studies and study of zoonoses.

Veterinary parasitology

The study of parasites which cause economic losses in agriculture or aquaculture operations, or which infect companion animals. Examples of species studied are Lucilia cericata, the blowfly, which lays eggs on the skins of farm animals, the maggots hatch and burrow into the flesh, distressing the animal and causing economic loss to the farmer, Otodectes cynotis, the cat ear mite, responsible for Canker, and Gyrodactylus salaris, a monogenean parasite of salmon, which can wipe out populations which are not resistant.

Parasite ecology and population genetics

The study of parasites can reveal information about their relationship with the host (eg. influences on mortality rate) and relationships between different populations of host species. This technique is commonly applied in fisheries biology, where parasites are used to identify different populations of the same fish. This forms an interesting application of the Red Queen hypothesis.

Taxonomy and phylogenetics

The huge diversity within the parasitic animals creates a challenge for biologists to describe and catalogue them. Recent developments in using DNA to identify separate species and to investigate the relationship between groups at various taxonomic scales has been enormously useful to parasitologists, as many parasites are highly degenerate, disguising relationships between species.

See also


- Important publications in parasitology
- Parasitologists

External links


- [http://asp.unl.edu American Society of Parasitologists]
- [http://www.parasite.org.au Australian Society for Parasitology]
- [http://www.gla.ac.uk/departments/ibls/II/parasitology/bsp/public_html British Society for Parasitology]
- [http://www.ips.ioz.ac.cn/Parasitologye.htm Chinese Society of Parasitology]
- [http://http://www.parazitologie.cz Czech Society for Parasitology]
- [http://www.parasitologyindia.org Indian Society of Parasitology]
- [http://www.icompa-xi.org International Congress of Parasitologists]
- [http://parasitology-soc.md.huji.ac.il/ Israel Society for Parasitology, Protozoology and Tropical Diseases]
- [http://jsp.tm.nagasaki-u.ac.jp/~parasite/ Japanese Society of Parasitology]
- [http://www.parasitol.or.kr/eng/ Korean Society for Parasitology]
- [http://www.parasitologie.nl Nederlandse Vereniging voor Parasitologie]
- [http://nzsp.rsnz.govt.nz/ New Zealand Society for Parasitology]
- [http://www.hi.is/pub/sbsp/ Scandinavian and Baltic Societies for Parasitology]
- th:ปรสิตวิทยา

Category:Parasites

Category:Parasitology ja:Category:寄生虫

Categorie:Nationaal park van Queensland

Queensland

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