- Cone snail
name = Cone snails
image_width = 250px
image_caption = Geography cone, "Conus geographus"
familia = Conidae
familia_authority = Linnaeus, 1758
subdivision_ranks = Genera
subdivision = "
Leptoconus"The cone snails or cone shells, sometimes simply known as "cones", (family Conidae), are a taxonomicfamily of medium-sized to large, sophisticated predatorysea snails, marine gastropod mollusks.
The shells of cone snails are shaped roughly like an
ice-cream cone. The narrow end of the cone shell is the anterior end, and the wide end shows the usually very low spire of the gastropod shell.
These snails hunt and immobilize prey using a modified
radular tooth along with a poison gland containing neurotoxins; this is launched out of its mouth in a harpoon-like motion.
venomshows great promise as a source of new, medically important substances. [ [http://molinterv.aspetjournals.org/cgi/content/full/7/5/251 MI - Sign In Page ] ] [http://www.fhcrc.org/about/pubs/quest/natures_brew.html]
Live cone shells should not be handled, as they are capable of "stinging" humans with unpleasant results. The sting of very small cones is no worse than a bee sting, but the sting of a few of the larger species of tropical cone snails can be fatal to human beings.
The shells of cone snails are often brightly colored and intricately patterned.
This family is typically found in warm and tropical seas and oceans worldwide. However, some species are rather adapted to temperate environments, such as the Cape coast of South Africa, and indeed are endemic to these regions. There are about 500 different species.
Many tropical cone snails live in or near
coral reefs. Subtropical species may be found under rocks in the lower intertidal and shallow subtidal zones.
The shells of cone snails are often brightly colored, and have interesting patterns, although in some species the color patterns may be partially or completely hidden under an opaque layer of
Some species of cone snails can grow up to 23 cm in length and are found in tropical or subtropical waters.
Cone snails are carnivorous, generally eating marine
worms, small fish, mollusks, and even other cone snails. Because cone snails are slow-moving, they use a venomous harpoon(called a toxoglossan radula) to capture faster-moving prey such as fish. The venom of a few larger species is powerful enough to kill a human being.
Harpoon and venoms
The cone snail's harpoon is a modification of the
radula, an organ in molluscs which acts as both tongueand teeth. The harpoon is hollow and barbed, and is attached to the tip of the radula inside the snail's throat. When the snail detects a prey animal nearby, it turns its mouth - a long flexible tube called a proboscis- towards the prey. The harpoon is loaded with venom and, still attached to the radula, is fired from the proboscis into the prey by a powerful muscular contraction. The venom paralyzes small fish almost instantly. The snail then retracts the radula, drawing the subdued prey into the mouth. After the prey is digested, the cone snail will regurgitate any indigestible material such as spines and scales, along with the disposable harpoon.
The venom of cone snails contains hundreds of different compounds, and its composition varies widely from one species of cone snail to another. The toxins in these various venoms are called
conotoxins. These are various peptides, each targeting a specific nerve channel or receptor. Some cone snail venoms also contain a pain-reducing toxin, which the snail uses to pacify the victim before immobilising and then killing it. Some cone snail venoms contain a tetrodotoxin, which is similar to the paralytic neurotoxins found in pufferfish, the blue-ringed octopus, and the Rough-skinned Newt.
Relevance to humans
Risk of being stung
The bright colors and patterns of cone snails are attractive to the eye, and therefore people sometimes pick up the live animals and hold them in their hand for a while. This must not be done, because the snail may fire its harpoon in self-defense.
The "sting" of many of the smaller cone species may be no worse than that of a bee or hornet sting,Fact|date=June 2008 but in the case of a few of the larger tropical species,clarifyme handling the snail can have fatal consequences. About 30 human deaths have been recorded from cone snail envenomation.Fact|date=June 2008
One species, the Geography cone, "
Conus geographus", is also known colloquially as the "cigarette snail," a humorous exaggeration stating that, when stung by this creature, the victim will have only enough time to smoke a cigarette before dying. [ [http://publications.nigms.nih.gov/findings/sept02/snails.html NIGMS - Findings, September 2002: Secrets of the Killer Snails ] ] [ [http://animals.nationalgeographic.com/animals/invertebrates/geographers-cone-snail.html Geographic Cone Snail, Geographic Cone Snail Profile, Facts, Information, Photos, Pictures, Sounds, Habitats, Reports, News - National Geographic ] ] In the case of these larger species of cone snail, there may be risk of the harpoon penetrating gloves or wetsuits.
Symptoms of a cone snail sting include intense
pain, swelling, numbness and tingling. Symptoms can start immediately or can be delayed in onset for days. Severe cases involve muscle paralysis, changes in vision and respiratory failurethat can lead to death. There is no antivenom, and treatment involves providing life supportuntil the venom is metabolised by the victim.
Medical use of the venom
The venom of some cone snails, such as the Magician cone, "Conus magus", shows much promise for providing a non-addictive pain reliever 1000 times as powerful as, and possibly a replacement for,
morphine. Many peptides produced by the cone snails show prospects for being potent pharmaceuticals, such as AVC1, isolated from the Australian species, the Queen Victoria cone, "Conus victoriae". This has proved very effective in treating post-surgical and neuropathic pain, even accelerating recovery from nerve injury. The first painkiller Ziconotidederived from cone snail toxins was approved by the U.S. Food and Drug Administrationin December 2004 under the name "Prialt". Other drugs are in clinical and preclinical trials, such as compounds of the toxin that may be used in the treatment of Alzheimer's disease, Parkinson's disease, and epilepsy.Fact|date=June 2008
Due to the intricate color patterns of cone shells, they have been called the most popular collectible shells. [ [http://www.worldwideconchology.com/Conidae.htm Conidae - worldwideconchology ] ] [ [http://www.coneshell.net/pages/g_gloriamaris.htm Conus gloriamaris ] ]
"Conus gloriamaris", the Glory of the Seas cone, was in earlier centuries one of the most famous and sought-after seashells, with only a few specimens in private collections. This apparent rarity meant that shells of this species fetched very high prices, until finally the habitat for this cone was discovered, and sizable populations were located, bringing the price down dramatically. [ [http://www.oceanlight.com/lightbox.php?sp=Conus_gloriamaris Conus gloriamaris, Glory of the Seas Cone photos, Phillip Colla Natural History Photography :: Online Photo Search ] ]
Naturally-occurring, beachworn, cone shell "tops" (the broken-off spire of the shell, which often has a hole worn at the tip) can function as beads without any further modification. In
Hawaiithese natural beads were traditionally collected from the beach drift in order to make puka shelljewelry.
Since it is hard to obtain enough naturally-occurring cone tops, almost all modern puka shell jewelry uses cheaper imitations, cut from thin shells of other species of mollusk, or even made of plastic.
* [http://grimwade.biochem.unimelb.edu.au/cone/index1.html Cone snail and conotoxins page]
* [http://biology.burke.washington.edu/conus/catalogue/index.php The "Conus" Biodiversity website]
* [http://research1t.imb.uq.edu.au/conoserver/ ConoServer]
* [http://www.worldwideconchology.com/Conidae.htm Conidae] from worldwide.conchology.com. Scroll down for many photographs.
* [http://www.theage.com.au/news/creative--media/painkiller-comes-out-of-its-shell/2005/07/24/1122143728598.html Pain-killer comes out of its shell] (The Age news article)
* [http://news.bbc.co.uk/1/hi/sci/tech/4846504.stm Venomous snails aid medical science] (BBC News Article).
* [http://www.coneshell.net ConeShell Collection Giancarlo Paganelli]
* [http://www.youtube.com/watch?v=B3qf8kawojk Cone Snail Video]
* [http://www.cnn.com/2008/LIVING/wayoflife/04/08/deadly.animals/index.html Deadly Critters That Might Save Your Life] (CNN)
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