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Topic: Cnidarian


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In the News (Sat 28 Nov 09)

  
  Cnidaria
Cnidarians are diploblastic -- that is, the body and tentacles consist of two cell layers, the endoderm (sometimes referred to as the gastrodermis) and the ectoderm (the epidermis).
All cnidarians are carnivorous, with cnidae and tentacles active in prey capture.
The text-book depiction of the typical cnidarian life cycle is an alternation between a medusa and a polyp (termed metagenesis), the former the sexually reproductive stage and the latter the asexual stage.
tolweb.org /Cnidaria   (2407 words)

  
  Introduction to Cnidaria   (Site not responding. Last check: )
Cnidarians are incredibly diverse in form, as evidenced by colonial siphonophores, massive medusae and corals, feathery hydroids, and box jellies with complex eyes.
Cnidarians are united based on the presumption that their nematocysts have been inherited from a single common ancestor.
Many thousands of cnidarian species live in the world's oceans, from the tropics to the poles, from the surface to the bottom.
www.ucmp.berkeley.edu /cnidaria/cnidaria.html   (190 words)

  
  NationMaster - Encyclopedia: Cnidarian
Cnidarians get their name from cnidocytes, which are specialized cells that carry stinging organelles.
Cnidarians are highly evident in the fossil record, having first appeared in the Precambrian era.
The nematocysts are the cnidarians main form of offence or defense and function by a chemical or physical trigger that causes the specialized cell to eject a barbed and poisoned hook that can stick into, ensnare, or entangle prey.
www.nationmaster.com /encyclopedia/Cnidarian   (810 words)

  
 Marine biodiversity: Cnidarians
With nearly 2.700 species, hydrozoans are less known of all the animals integrating cnidarians, consequence of their small size (from few millimetres, of smaller ones, to little bit more than 10 centimeters of larger ones), which generally cause that they are unobserved by most divers.
The cnidarian body consists of a central blind sac, the coelenteron (= gastrovascular cavity), enclosed by a body wall comprising two epithelia, the outer epidermis and the inner gastrodermis.
Cnidarians are ammonotelic and diffusion across the body and tentacle surface eliminated the ammonia from the body.
www.bioaqua.net /mnp/biodiversidad/cnidarians.asp   (803 words)

  
 Kids.Net.Au - Encyclopedia > Cnidarian   (Site not responding. Last check: )
The cnidarians are a large phylum (of 10,000 species) of relatively simple Animals, found exclusively in aquatic environments.
Cnidarians are well-known in the fossil record and date back to at least the Cambrian.
The cnidarian body is radially symmetric and diploblastic - that is, composed of two layers of tissues, which are not differentiated into organs.
www.kids.net.au /encyclopedia-wiki/cn/Cnidarian   (379 words)

  
 cnidarian
Cnidarians (also known as coelenterates) are diploblastic, with two cell layers (ectoderm and endoderm) separated by mesoglea, and have radial symmetry.
Unique to cnidarians are stinging cells known as cnidocytes (nematocytes), which are used for defense or capturing prey.
Cnidarians exist both as free-swimming medusae (such as jellyfish) and as sedentary polyps.
www.daviddarling.info /encyclopedia/C/cnidarian.html   (187 words)

  
 Cnidarian Introduction
Cnidarians are have two true tissue layers (an outer epidermis and an inner gastrodermis) separated by a connective tissue layer called the mesoglea.
Two body types are seen in cnidarians; the polyp is a sessile, cylindrical form in which the oral end (mouth and tentacles) is directed upward and the aboral end is attached to the substrate.
The nervous system of cnidarians consists of a diffuse network of neurons called a nerve net in which any direction of conduction is possible, a useful property for animals with radial symmetry.
bioweb.uwlax.edu /zoolab/Table_of_Contents/Lab-3a/Cnidarian_Introduction/cnidarian_introduction.htm   (214 words)

  
 Diversity :: Animals Fanlisting
Cnidarians, also known as coelenterates, are a diverse group of aquatic, invertebrate animals armed with microscopic stinging structures.
Cnidarians have many shapes and they range in size from microscopic hydrozoans to jellyfishes that are 2 m (7 ft) in diameter with tentacles 30 m (100 ft) long.
Cnidarians are invertebrates (animals that lack a backbone), but the ectoderm of some cnidarians, including hard corals and some hydrozoans, may form a skeleton-like structure externally.
www.kandosii.net /fan/animals/animals_cnidarians.php   (1126 words)

  
 Spartanburg SC | GoUpstate.com | Spartanburg Herald-Journal   (Site not responding. Last check: )
Cnidarians get their name from cnidocytes, which are specialized cells that carry stinging organelles called cnidocysts.
The basic body shape of a cnidarian consists of a sac with a gastrovascular cavity, with a single opening that functions as both mouth and anus.
The nematocysts are the cnidarians' main form of offence or defense and function by a chemical or physical trigger that causes the specialized cell to eject a barbed and poisoned hook that can stick into, ensnare, or entangle prey or predators, killing or at least paralysing its victim.
www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=cnidarian   (2625 words)

  
 Diversity :: Animals Fanlisting   (Site not responding. Last check: )
Cnidarians have many shapes and they range in size from microscopic hydrozoans to jellyfishes that are 2 m (7 ft) in diameter with tentacles 30 m (100 ft) long.
Cnidarians are invertebrates (animals that lack a backbone), but the ectoderm of some cnidarians, including hard corals and some hydrozoans, may form a skeleton-like structure externally.
Some cnidarians alternate between polyp and medusa at different stages of their life cycles, some cnidarians live solely as polyps, and others only as medusae.
kandosii.net /fan/animals/animals_cnidarians.php   (1126 words)

  
 About corals, anemones, and their kin
Cnidarians have nematocysts, which are specialized structures (produced by certain cells) that function in food capture and defense.
Many species of cnidarians depend on their algal symbionts for the majority of their energy needs, and loss of their zooxantheallae (as sometimes occurs under stressful conditions) can be lethal to the animal.
Cnidarians that depend on zooxanthellae include all of the reef-building stony corals, many of the soft corals and gorgonians, many species of anemomes, some jellyfish, and others.
www.augsburg.edu /biology/aquaria/SpecialTopicsFiles/AboutCoralsAnemonesAndKin.html   (1812 words)

  
 Cnidarians - National Zoo| FONZ
Cnidarians are either polyps, such as sea anemones or coral, or free-floating medusae, such as jellyfish.
Cnidarians live in aquatic environments and inhabit all depths, from the sandy substrate up to the surface.
Cnidarians have no need for a brain or a heart; instead, these animals have specialized tissues to coordinate basic bodily functions.
nationalzoo.si.edu /Animals/Invertebrates/Facts/cnidarians   (456 words)

  
 Oceanlink | marine sciences education and fun
The cnidarian body is composed of three basic layers: an outer epithelium called the epidermis, an inner layer called the gastrodermis and between these, a middle extracellular layer called the mesoglea.
Populations of cnidarians are known to fluctuate significantly in accordance with a variety of environmental parameters.
Cnidarians have two body forms, one is free-swimming and is called a medusa, and the other is stationary and is called a polyp.
oceanlink.island.net /ask/cnidaria.html   (9979 words)

  
 Cal Coast Divers Marine Ecology Pages: Phyla Cnidarians
The body of cnidarians are comprised of an outer cell layer exposed to the environment called the epidermis and the internal cell lining the gastrodermis.
Cnidarians have only one body cavity, named the coelenteron, which is responsible for digesting the cnidarians prey.
Carnivorous cnidarians capture their food with the stinging nematocysts located all along their tentacles which are triggered by their prey as the prey swims by unassumingly.
www.calcoastdivers.com /ecology/cnidarians.html   (824 words)

  
 BioMed Central | Full text | Transcriptome analysis of a cnidarian - dinoflagellate mutualism reveals complex ...
Cnidarian – dinoflagellate intracellular symbioses are one of the most important mutualisms in the marine environment.
Such a role is consistent with the increased expression of this protein in the symbiotic state, and with evidence that lipids are translocated from the algal symbiont to the host cell [27].
This function is particularly intriguing with regard to cnidarian – dinoflagellates symbioses as Plasmodium is a member of the apicomplexa, a sister taxon to the dinoflagellates [36,37].
www.biomedcentral.com /1471-2164/7/23   (6455 words)

  
 Cnidarian
Nematocysts are used for defense and to sting and paralyze prey, ranging from plankton to fish.
Cnidarians have a simple body plan with two epithelial cell layers: the epidermis and gastrodermis, separated by a gelatinous mesoglea ("middle glue").
The mesoglea ranges from a thin, gluelike layer in the freshwater hydras to a thick, gelatinous layer in the jellyfish.
www.biologyreference.com /Ce-Co/Cnidarian.html   (258 words)

  
 cnidarian - Search Results - MSN Encarta
Cnidarians, also known as coelenterates, diverse group of aquatic, invertebrate animals armed with microscopic stinging structures.
Jellyfish, common name for any of the invertebrate animals making up two classes of the cnidarian phylum.
The basic body shape of a cnidarian consists of a sac containing a gastrovascular cavity with a single opening that functions as both mouth and anus.
encarta.msn.com /cnidarian.html   (236 words)

  
 Cnidaria
The mouth is surrounded by tentacles studded with microscopic stinging capsules known as nematocysts that are the agents of offense and defense.
All cnidarians are carnivorous, with cnidae and tentacles active in prey capture.
The four extant cnidarian classes are identifiable as early as the Ordovician (Robson 1985), but evolutionary relationships among them have been the subject of much debate (e.g.
www.tolweb.org /tree?group=Cnidaria&contgroup=Animals   (2407 words)

  
 26
Cnidarians are soft-bodied animals with stinging tentacles arranged in circles around their mouth.
Cnidarians have two true tissue layers that are separated by various amounts of a non-cellular gelatinous material called mesoglea.
Cnidarians are aquatic animals that exhibit radial symmetry and stinging structures called nematocysts on their tentacles.
ohs-bio.www1.50megs.com /ch26/Ch_26_Textbook.htm   (9116 words)

  
 Cnidarian Research - www.ecolevol.de - ITZ   (Site not responding. Last check: )
Cnidarian species are often used as model organisms in evolutionary studies (of development, cell biology, gene families, etc.) because Cnidaria diverged relatively early in the history of Metazoa.
While it is possible that character states in cnidarians are ancient, features under study in a given cnidarian species may certainly be derived at some level within Cnidaria and it could be misleading to assume the opposite.
In addition, we use these cnidarians in studies aimed at understanding the evolution of regulatory genes and animal body plans.
ecolevol.de /cnida.html   (255 words)

  
 Wonders of the Seas: Cnidarians   (Site not responding. Last check: )
All Cnidarians have tentacles with stinging cells in their tips which are used to capture and subdue prey.
In fact, the phylum name "Cnidarian" literally means "stinging creature." The stinging cells are called cnidocytes and contain a structure called a nematocyst.
Most Cnidarian's nematocysts are not harmful to humans, as the stinger cannot penetrate sufficiently into human skin to inflict any harm.
www.oceanicresearch.org /cnidarian.html   (690 words)

  
 Wonders of the Sea: Cnidarians   (Site not responding. Last check: )
The polypoid is the configuration of corals and anemones, with the tentacles and mouth generally facing up, and the other side affixed to a substrate or connected to a colony of other creatures of the same species.
Cnidarians are said to be the simplest organisms at the tissue grade of organization.
Cnidarian ecology is a complex subject because it is cnidarians, in particular corals that are the builders of some of the richest and most complex ecosystems on the planet.
www.oceaninn.com /guides/cnidarians.htm   (1767 words)

  
 ADW: Cnidaria: Information
Cnidarians are radially or biradially symmetric, a general type of symmetry believed primitive for eumetazoans.
Cnidarians have two basic body forms, medusa and polyp.
A nematocyst discharges when a prey species or predator comes into contact with it, driving its threads with barb and poison into the flesh of the victim by means of a rapid increase in hydrostatic pressure.
animaldiversity.ummz.umich.edu /site/accounts/information/Cnidaria.html   (479 words)

  
 Cnidarians
Most cnidarians are considered carnivores because of their ability to actually catch food with their stinging cells called nematocysts.
The cnidarian classes Anthozoa (corals) and Hydrozoa have calcified skeletons of aragonite and calcite and a good fossil record, whereas the long fossil record of the class Scyphozoa (jelly fish) is comprised mostly of molds and casts.
Geologically the anthozoans are the most important of the cnidarians because their polyps often produce calcitized skeletons that are readily preserved as fossils.
paleo.cortland.edu /tutorial/Cnidarians/cnidarians.htm   (975 words)

  
 Cnidarian - Qwika
The basic body shape of a cnidarian consists of a sac with a gastrovascular...
The cnidarian is composed of two layers of tissue...
Being a cnidarian it is diploblastic, having an ectoderm and...
www.qwika.com /find/Cnidarian   (301 words)

  
 Về một loài Sưá biển - Mang Luoi Tuoi Tre Viet Nam Len Duong - lenduong.net
Các nhà sinh vật học nghiên cứu quá trình tiến hoá xem loài cnidarian như một di tích của quá trình tiến hoá.
Cnidarian có thể là đại diện cho quá trình tiến hoá giai đoạn tiếp theo, thu nhận các đặc tính của ô tế bào và hệ thống thần kinh đơn giản.
Giờ đây ông cho rằng cnidarian không phải đơn giản là một trong những loài động vật hình thành trước tiên trong giai đoạn bùng nổ Cambrian, mà là một trong những loài nằm trong giai đoạn này, sự tiến hoá của nó chịu quy luật điều khiển của các loài động vật ăn thịt.
www.lenduong.net /article.php3?id_article=14851   (2282 words)

  
 The Shape of Life . Cnidaria | PBS
Many cnidarian species exist in two different body forms during their life cycle: the free-swimming form, called the medusa (a jellyfish for instance), and the stationary form called the polyp (which resembles a tiny sea anemone).
Cnidarians have a defined top and bottom and are made up of two layers of tissue that include nerve and muscle cells.
This body, formed from tissues with organized groupings of muscles and nerves, allowed ancestral cnidarians to be the first animals on the planet to show animated behavior.
www.pbs.org /kcet/shapeoflife/animals/cnidaria.html   (161 words)

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