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My research paper
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by HELERI on April 11, 2001
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Hello everybody! I am writing for advice and suggestions on the paper I have pasted from my computer below. I have had it edited by many great people and have found out for myself that I am tackling a HUGE subject and will probably never finish this. I'm writing this paper to make it understandable for the lay people and herp lovers who are shady in the area of venomous squamates. And YES, Birds are put under the class Reptilia! Anyhow, here it is. I hope it fits...
Venomous Squamates
Robert Villa
1125 E. Missouri St.
Tucson, AZ 85714
herpguyrobert@aol.com
Table of contents:
General classification/categorization of venomous squamates
Secretion glands and venom injection mechanisms in venomous squamates
Prevention and care of venomous snakebite while seeking medical help
The future of reptiles
Acknowledgements
Glossary
Bibliography
General classification/categorization of venomous squamates
Squamates are a group of animals that belong to a class of animals called reptiles. Reptiles are ectothermic vertebrates (with the exception of birds) that are divided into four major groups. They are:
REPTILES
* Crocodylia (Crocodiles & Alligators)
* Squamata (Snakes & Lizards)
* Chelonia (Turtles and Tortoises)
* Rhynchocephalia (Tuataras-the only ones of their kind)
* Aves (Birds)
Squamates are the only order of reptile that has the ability to produce venom. There are about 6,402 species of squamates recognized. Here’s how venomous snakes are categorized:
SQUAMATES
Ophidia (Snakes)-Comprised of three major groups:
Leptothyphlopidae-Blindsnakes, not venomous
Boidae-Boas and pythons, not venomous
Colubroideae-Comprised of four families: Viperidae, Elapidae, Colubridae, and Atractaspidae. Atravtaspidae has no venomous species.
Viperidae (pitvipers &Vipers)-These snakes are stout bodied animals with arrow-like heads and are special since they have syringe-like front fangs that fold back in the mouth when not in use, as opposed to fangs fixed to the maxilla (upper jaw) or fangs at the rear of the maxilla (See chapter two.)
*Pitvipers (North & South America, and Asia)-The name pit viper is the name given to these highly evolved and successful clad of snakes because of heat detecting pits just below the nostrils (loreal pits). These pits detect heat, and are used to find/detect prey/predators. These are snakes commonly known in the Southwestern United States as rattlesnakes. Why rattles? Scientists think that millions of years ago rattlesnakes developed rattles to warn mega fauna (land mammals like bison and wild horses) of their presence on the ground so they wouldn’t get trampled on. Rattlesnakes still use the rattle as a means of warning and presence. There are however some variations on the theme as far as pit vipers go. Some pit vipers in Central & South America, and Asia have no rattles. These pit vipers, along with their ability to detect heat, writhe their tails on the ground as a fake lure to attract their prey.
*Vipers (Africa, Australia, and Europe)-These are Old World snakes that look a lot like pit vipers but have no rattles or pits.
Elapidae (Cobras and their relatives)-These snakes include cobras, coral snakes, kraits, Australian endemics, mambas and sea snakes . Their fangs are fixed to the maxilla and are not capable of retracting, therefore these fangs are small as opposed to the vipers fangs. Coral snakes are restricted to the New World, and sea snakes are restricted to warm tropical waters.
Colubridae- Colubrids are the most widespread and common of all snakes. Most snakes are colubrids and are venomous to some extent. Venomous colubrids are rear-fanged (fangs situated at the back end of the maxilla) and deliver venom through a groove in the fang. In the New World these include garter snakes and hognose snakes. In the Old World these include boomslangs and vine/tree snakes.
Lizards(Squamata)
Helodermatidae(Gila monsters and beaded lizards)-The only venomous lizards on the planet.
Secretion glands and venom injection mechanisms in venomous squamates
Before venom was available to snakes, snakes had to rely on suffocating their prey by means of circulatory arrest (stopping the circulation of blood). Now that they had the ability to use venom, they could kill their prey faster without having to risk injury to themselves. Venom is stored in a venom sack or gland below the skin, running from just before the nose to the back of the eye. There are however some exceptions. All rear-fanged snakes, the Colubrids, and envenomate their prey differently than other snakes. This gland is named the Duvernoy’s gland, after George Louis Duvernoy, the French anatomist who discovered it. Instead of a venom sack, venom is stored in a system of branched tubes that run from before the nose to the back of the eye underneath the skin as in where venom sacks would be located. Venom more like a toxic saliva and when the snake bites down on it’s query the venom from Duvernoy’s gland runs down the grooved fangs. Generally speaking, there are three main types of toxins produced by snakes in their venom: hemotoxic, cardiovascular, and neurotoxic. Hemotoxins destroy the veins & capillaries and causes necrosis and swelling; cardiovascular toxins shutdown the heart and lungs and thus cause low blood pressure; neurotoxins affect the nervous system and cause drooping eyelids, and uncontrollable muscle spasms. The chart below shows the snake families with the general characteristics of their venom. It would not be appropriate to associate certain venom types to certain snake families. Snakes usually associated with hemotoxic venom, such as viperids, could give a bite with neurotoxic symptoms. The nature of a snake’s bite really depends on the snake itself and the circumstances in which the snake deals with.
SQUAMATES
Ophidia(snakes)-Comprised of three major groups
Leptothyphlopidae-Blindsnakes, not venomous
Boidae-Boas and python, not venomous
Colubroideae- comprised of the families: Viperidae, Elapidae, Colubridae, and Atractapiidae. Atractaspidae has no venomous species.
Viperidae (Vipers & pitvipers)-These snakes have long, independently movable front fangs that fold back in the mouth when not in use. Replacement fangs rest above the ones in use. This has made viperids very successful. The injection mechanism of the viperids emulates that of a hypodermic needle. The jaw muscles-pump, the venom gland-barrel, the fang-needle. When the snake opens it’s mouth, the fangs retract forward while the jaw muscles squeeze out the venom gland’s contents through the fangs and into the victim. Venom is mostly comprised of enzymes and hemotoxins.
Elapidae (Cobras and their relatives)-These snakes include cobras, coral snakes, kraits, sea snakes and some Australian endemics. Their fangs are fixed to the front of the maxilla and are not capable of retracting, therefore these fangs are small as opposed to the vipers fangs. Their fangs are either hollow or deeply grooved and inject venom in the same way as viperids. Venom is mostly comprised of neurotoxins.
Colubridae-All colubrids are venomous to some degree and most are not capable of delivering a fatal bite to humans. Most species’ venom is only toxic to small reptiles, amphibians, birds and mammals. However, some species of Colubrids can kill humans. In the Old World these include the boomslangs and twig snakes. There aren’t vary many species in the New World that can cause a serious bite to man, but they do exist. Colubrids in South America have caused nearly fatal bites, and colubrids in North America, the hognose and garter snakes, have caused swelling, numbing and irritation of the arm. Most species don’t even have rear fangs big enough to penetrate the skin. Since their fangs are situated at the rear of the maxilla, colubrids have to “chew” whatever they are envenomating until their fangs penetrate the prey. Meanwhile the toxic venom from Duvernoy’s gland envenomates the victim.
Lizards(Squamata)
Helodermatidae(Gila monsters and beaded lizards)-The only venomous lizards on the planet. Venom is injected through grooved teeth in the mandible.
Species/Lethal dose of venom(mg.)/Amount injected (mg.)
Crotalus durissus-
Neotropical rattlesnake 3 10
Crotalus scutulatus-
Mojave rattlesnake 7 70
Crotalus horridus atricauddatus-
Timber rattlesnake 15 140
Crotalus adamanteus-
Eastern diamondback rattlesnake 70 400
Crotalus atrox-
Western diamondback rattlsnake 120 400
Agkistrodon contortrix-
Copperhead 370 900
Oxyuranus australis-Taipan 1 44
Prevention and care of venomous snakebite while seeking medical help
Prevention-This describes the many ways of avoiding the bite of a dangerous snake. Most of us will never come across a rattlesnake in the wild. A study indicated that fifty percent of snakebite victims are males under the age of thirty who are interacting with the snake and/or are intoxicated. However, there are certain people that tend to see them now and then. This could include telephone company field workers, ranchers, hunters, hikers, campers and others. These kinds of people usually plan snakebite prevention into their daily lives. (Keep in mind that most snakes are crepuscular and nocturnal and are not out during our active hours.) Below are several guidelines for avoiding snakebites.
1. Wear appropriate footwear such as boots, chaps or high-top hiking shoes.
2. Step up onto logs or rocks rather than over them.
3. Don't place your hands on unseen ledges or into animal holes.
4. Don't turn rocks or boards over with bare hands. Use a tool.
5. Don't try to kill, catch or molest a venomous snake or Gila monster. Leave them alone.
6. Don't hike by yourself.
7. Learn what dangerous snakes in your area look like. Get a book.
8. Watch where you are walking.
9. Identify everything before you pick it up.
10. Don’t touch anything that can hurt you. If you don’t know if it can hurt you, don’t touch it.
11. Always look under things before picking them up, and whenever possible, before stepping on or around them.
12. Look under things from a distance (use a tool to lift, then look).
13. Always use a flashlight when you are out at night.
14. Do not pick up a “dead” rattlesnake. It may not be dead, and even if it is, it may still bite (reflexively) and envenomate.
15. Don’t walk barefoot or in open-toed shoes in the desert.
What to do-This describes measures taken in the field to minimize the effects of the bite of a venomous snake. Treatment at a hospital should always be sought.
Below is a list of do's and don'ts when dealing with snakebite first aid.
1. .Have another individual drive to medical care for treatment.
2. Remain calm and inactive
3. Don't make incisions over the snakebite.
4. Don't immerse a limb in ice water.
5. Don't constrict the flow of blood
6. Don’t use suction device or mouth to extract some venom. If performed this
may help increase the effects of the bite. This procedure should not be
performed.
Bibliography
Greene, Harry W. Snakes: The evolution of mystery in nature., Berkley at Los Angeles. University of California Press 1997 p. 77-206; 215-263
Rubio, Manuel, Rattlesnake: Portrait of a Predator., Smithsonian Institution Press, Washington DC
Walls, Jerry G., Rattlesnakes: Their natural history and care in captivity, T.F.H. Publications Neptune City, NJ 1996
Preston, Todd, “Venom: The practical poison” REPTILES Oct. 1998: Vol. 6 p. 76-83
Lichtenhan, J, Brad M.D., “What Reptile Enthusiasts Should Know About Snakebite” REPTILES August 1995 Vol. 6. p. 76-85
Norris, Robert M.D./Minton, Sherman M.D. “Snake Venom Poisoning: What the Herpetoculturist needs to know” The Vivarium Journal May/June 1995: Vol. 6 p. 4-9
Grenard, Steve “Is Snake Venom Evolving?” Natural History July 2000 Vol. 109 p. 44-46
Grenard, Steve “Snakebite: Are ‘Non-poisonous’ Colubrids Really Harmless?” Reptile & Amphibian Hobbyist Sept./Oct. 1994 p. 51-63
Arizona Poison Control System/Tucson Herpetological Society “Venomous Reptiles” 1996
Meyers, Bob American International Rattlesnake Museum www.rattlesnakes.com Abequerque, NM
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RE: My research paper
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Anonymous post on April 12, 2001
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It looks fine Robert. It's a thorough overview. But I don't know if laypeople wouldn't get lost in the herpetology jargon. They like to read about snakes, but they want and need it a little more simplified.
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RE: My research paper
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by filthy on April 12, 2001
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Excellent.
But as Anon said, it might be a little slow going for the guy on the street.
One minor correction: C. h. atricaudatus is the Canebrake Rattlesnake. C, h. horridus is the Timber. As long as I can remember, and that's a right good while, there has been an on-going argument as to whether these should be ssp., or the Canebrake classified as merely a color morph of horridus. It continues today and I doubt if there will be a satisfactory resolution to it in my lifetime. At last report, they've both been classified as C. horridus.
It if further interesting to note that there was - perhaps still is - a push to classify one of the Timber morphs in the northwestern part of their range as a ssp.
Myself, I say horridus and atricaudatus are ssp., but I have no official standing.
luck,
f
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RE: My research paper
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by BloodSerpent on April 16, 2001
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Nice looking paper! One quick note- atractaspidae do indeed possess venom. Look under mole vipers such as the stiletto snake (I don't know if I spelled that right). Interestingly enough, its fangs are positioned through to the outside of its mouth. Otherwise, seems great.
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