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| Cephalorhyncha |
CephalorhynchaScalidophora 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 cutitle (ecdysis). Their closest relatives are thought to be the Panarthropoda and Nematoda; they are thus placed in the group Ecdysozoa.
The two species in the genus Markuelia, known from fossilized embryos from the middle Cambrian, are thought to be stem Scalidophorans.
The group was formerly considered a single phylum, Cephalorhyncha, with three classes.
Category:Animals
PseudocoelomateA pseudocoelomate is an animal like a roundworm or rotifer. These animals have a body cavity, but it is not completely lined with a mesoderm. The mesoderm is the middle layer of tissue and cells which composes body structures into muscles and systems. The lack of this structure causes pseudocoelomates to be classified separately from other animals classified as coelomates.
Modern molecular phylogenies have brought into question whether coelomates and pseudocoelomates are actually independent lineages.
See also
Aschelminthes
Sources
- Biology. Sixth Edition by Solomon, Berg and Martin ISBN 0-534-39175-3
Category:Animals
Phylum (biology):For use of the word in linguistics, see Phylum (linguistics)
Phylum (plural: phyla) is a taxon used in the classification of life, adopted from the Greek phylai the clan-based voting groups in Greek city-states. (Although the International Code of Botanical Nomenclature allows the use of the term "Phylum", the term "Division" is almost always used by botanists.) Phyla represent the largest generally accepted groupings of animals and other living things with certain evolutionary traits, although the phyla themselves may sometimes be grouped into superphyla (e.g. Ecdysozoa with eight phyla, including arthropods and roundworms, and Deuterostomia with the echinoderms, chordates, hemichordates and arrow worms).
The best known animal phyla are the Mollusca, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Echinodermata, and Chordata, the phylum humans belong to. Although there are approximately 35 phyla, these nine include the majority of the species. Many phyla are exclusively marine, and only one phylum is entirely absent from the world's oceans: the Onychophora or velvet worms.
External links
Etymology:
- [http://www.bartleby.com/61/54/P0275400.html American Heritage Dictionary]: New Latin phylum, from Greek phūlon, class.
- [http://www.etymonline.com/index.php?l=p&p=15 Online Etymological Dictionary]: from Gk. phylon "race, stock," related to phyle "tribe, clan," and phylein "bring forth" of physikos "pertaining to nature," from physis "nature"
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Kinorhyncha
Cyclorhagida
Homalorhagida
Kinorhyncha (Gr. kinema motion + rhyncho snout) is a phylum of small (1 mm or less) marine pseudocoelomate invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos. They are sometimes called mud dragons.
They are segmented, with a body consisting of a head, neck, and a trunk of eleven segments. They do not have external cilia, but instead have a number of spines along the body, plus several circles of spines around the head, which they use for locomotion, withdrawing the head and pushing forward, then holding with the spines while drawing up the body. The spines are part of a cuticle secreted by the epidermis; this is molted several times while growing to adulthood. The head is completely retractable, and is covered by a set of neck plates called placids when retracted.
Kinorhynchs eat diatoms and whatever else they can find in the mud.
There are two sexes that look alike, and the larvae are free-living, but little else is known of their reproductive process.
Their closest relatives are thought to be the phyla Loricifera and Priapulida. Together they consitute the Scalidophora.
The two groups of Kinorhynchs are still generally characterized as orders rather than classes, about 150 species are known.
Order Cyclorhagida
- Suborder Cyclorhagae
- Family Echinoderidae
- Family Zelinkaderidae
- Family Centroderidae
- Family Dracoderidae
- Suborder Conchorhagae
- Family Semnoderidae
- Suborder Cryptorhagae
- Family Cateriidae
Order Homalorhagida
- Suborder Homalorhagae
- Family Pycnophyidae
- Family Neocentrophyidae
External link
- [http://www.ucmp.berkeley.edu/phyla/ecdysozoa/cephalorhyncha.html Introduction to the Cephalorhyncha]
- [http://biodidac.bio.uottawa.ca/thumbnails/catquery.htm?maxrows_old=&StartRow=1&maxrows=8&kingdom=Animalia&phylum=Kinorhyncha Drawings of Kinorhyncha]
Category:Animals
Loricifera
Loricifera is a small phylum of marine sediment-dwelling animals with about a dozen known species. The phylum was discovered in 1983 by Reinhardt Kristensen. The animals have a head, mouth and digestive system as well as a set of specialized umbrella skeleton like scales at each end that are used to move the animals. There is no circulatory system and no endocrine system. The body cavity is a pseudocoelom with a mouth and an anus. The animals are bisexual and probably oviparous. They have no fossil record.
Their closest relatives are thought to be the Kinorhyncha and Priapulida with which they constitute the taxon Scalidophora.
Category:Animals
ja:胴甲動物
Panarthropoda
- Phylum Arthropoda
- Phylum Onychophora
- Phylum Tardigrada
Panarthropoda is a taxon combining the phyla Arthropoda, Tardigrada and Onychophora. Originally, they were considered to be closely related to the annelids, grouped together as the Articulata, but newer studies place them among a group called the Ecdysozoa.
Common characters of the Panarthropoda include:
- presence of legs
- presence of claws
- ventral nervous system
- segmented body
Category:Animals
Nematoda
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
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ko:선형동물
ms:Cacing Gelang
ja:線形動物
Ecdysozoa
Panarthropoda
Arthropoda
Onychophora
Tardigrada
Scalidophora
Kinorhyncha
Priapulida
Loricifera
Nematoda
Nematomorpha
The Ecdysozoa are a group 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 group is also strongly supported by morphological characters, and can be considered as including all animals that shed their exoskeleton (see ecdysis). Groups corresponding roughly to the Ecdysozoa had been proposed previously by Perrier in 1897 and Seurat in 1920 based on morphology alone.
The most notable characteristic shared by ecdysozoans is a three-layered cuticle composed of organic material, which is periodically molted as the animal grows. This process is called ecdysis and gives the group its name. Ecdysozoans lack locomotory cilia, produce amoeboid sperm, and their embryos do not undergo spiral cleavage as in most other protostomes. Various other features are found in the group - for instance, both tardigrades and roundworms have a triradiate pharynx.
The Ecdysozoa include the following phyla: Arthropoda, Onychophora, Tardigrada, Kinorhyncha, Priapulida, Loricifera, Nematoda and Nematomorpha. A few other groups, such as the gastrotrichs, have been considered possible members but lack the main characters of the group, and are now placed elsewhere. The Panarthropoda are distinguished by a segmented body plan, and as such were traditionally believed to have evolved from the Annelida (segmented worms), together comprising the Articulata. However, they do not have many other characteristics in common, so it now appears that they developed segmentation separately.
The non-panarthropod members of Ecdysozoa have been grouped as Cycloneuralia but they are more usually considered paraphyletic.
References
- Aguinaldo, A. M. A., J. M. Turbeville, L. S. Linford, M. C. Rivera, J. R. Garey, R. A. Raff, & J. A. Lake, 1997. Evidence for a clade of nematodes, arthropods and other moulting animals. Nature 387: 489-493.
- Wagele, J. W., T. Erikson, P. Lockhart, & B. Misof, 1999. The Ecdysozoa: Artifact or monophylum? J. Zoo. Syst. Evol. Research 37: 211-223.
External links
- [http://www.ucmp.berkeley.edu/phyla/ecdysozoa.html UCMP-Ecdysozoa introduction]
- http://www.palaeos.com/Kingdoms/Animalia/Ecdysozoa.html
- http://nema.cap.ed.ac.uk/tardigrades/Tardigrades_and_Ecdysozoa.html
- http://chuma.cas.usf.edu/~garey/articulata.html
- http://chuma.cas.usf.edu/~garey/essential.html
Category:Animals
Markuelia Markuelia denotes a genus of fossil worm from the Middle Cambrian period that encompasses two known species, Markuelia hunanensis and Markuelia secunda, which are presumably the closest known relatives to three modern taxa of bilaterian animals: the Loricifera, Kinorhyncha and Priapulida.
Found in Hunan province in southern China and in eastern Siberia, these fossils represent many developmental stages from the first cell divisions to the time of hatching and therefore offer not only a unique opportunity to study the development of Lower Cambrian animals, but also yield remarkable insights into the phylogeny of the whole taxon, today known by the name of Scalidophora.
Category:Fossils
Category:Annelids (worms)
Category:Animals
Animals are a major group of organisms, classified as the kingdom Animalia. This category includes animals, their study, and their classification.
Category:Eukaryotes
ko:분류:동물
ja:Category:動物
BanswaraBanswara is a city in Banswara District in south Rajasthan in India. Banswara princely state was founded by Maharawal Jagmal Singh. It gets the name from dominance of "bans" or bamboo forests. It is also known as 'City of Hundred Islands', due to presence of numerous islands in the Mahi River, which flows through Banswara.
Category:Cities and towns in Rajasthan
Category:Cities in Malwa
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