snakes background info

8/3/2019 Snakes Background Info

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Snakes Background InformationRevised 5/2011

LESSON PLAN VOCABULARY

Adaptation Brille Constrictor EctothermEndotherm Infrared Vision Jacobsons Organ Low Frequency Hearing

Poisonous Reptile Scales SheddingVenomous

CA SCIENCE CONTENT STANDARDS (updated by CDE 10/98):

Students know producers and consumers (herbivores, carnivores, omnivores, and decomposers) are

related in food chains and food webs and may compete with each other for resources in an ecosystem.

(4.2b)

Students knowmany multicellular organisms have specialized structures to support the transport of

materials. (5.2a)

Students know populations of organisms can be categorized by the functions they serve in an ecosystem.

(6.5a)


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Snakes

OVERVIEWThere has always been something of a mysteryabout snakes. How can they move so quicklywithout legs? How can they kill their prey with onlya single bite? How they can swallow an animal

many times larger than them whole? It is littlewonder that there are so many myths and legendsabout these fascinating creatures.

The first known snake, Lapparentophis defrennei,first appeared about 100-150 million years agoduring the Cretaceous period in the region that isnow known as North Africa. To the best of ourknowledge it is believed that they originated from agroup of lizards that lost their legs over time inresponse to a burrowing lifestyle that made legsredundant. Today there are nearly 3,000 distinct

species of snakes in almost every country of theworld as they have evolved and adapted to adiverse range of habitats and climates.

What is a snake? On a basic level snakes arereptiles, they have a backbone, but to take it to thenext level lets discuss classification. This is thescientific method of establishing the relationshipbetween different organisms and arranging them ina way that reflects these relationships. Moving fromgeneral to specific, the classification system putsanimals in different classes, then orders, suborders,

superfamilies, and families. Snakes belong to theclass Reptilia, and the order Squamata. Within theSquamata are three suborders: Serpentes(snakes), Sauria (lizards), and Amphisbaenia(amphisbaenians). The suborder of serpents isfurther broken into two superfamiles, theScolecophidia and the Alethinophidia. It has beennoted however that snake classification is inconstant flux as new discoveries are found and astechnology advances allowing scientist to gaingreater depth on the relationship between familiesand species.

In general, snakes are discussed in terms of beingeither constrictors or venomous. Constrictorsasphyxiate their prey by first ambushing their preyand then looping themselves around the victim andsqueezing it until it stops breathing. Venomoussnakes bite their prey, injecting a toxin into thevictim.

CHARACTERISTICS AND ADAPTATIONSContent Standards 4.2b, 5.2a

Because snakes are unable to migrate like otherbirds or mammals they are at the mercy of theconditions of their surroundings and because everyenvironment is different, each species of snakeshas, over time, evolved in a variety of ways in orderto survive. The following information will discuss in

detail the external and internal make up of snakesand varying behaviors among species.

Most snakes prefer a temperature range ofbetween 70F and 95F (21C and 35C,respectively), but snakes cannot internallyreproduce or regulate their body temperaturesufficiently because they are ectotherms, meaningthat their body temperature is dependent uponoutside sources such as the heat or the sun, andconsequently, can only be regulated by basking orseeking shade. Snakes maintain their temperature

through a combination of behavioral and externalmethods. One example of an external method is if asnake is too cold they would move to some placehotter (pretty simple!), and vice-versa. A behavioralmethod would be like flattening themselves out somore of the sun hits them, or that many snakesgroup together to conserve energy. A high bodytemperature is an essential component in thedigestion of food as well as behavior. At low bodytemperatures snakes become slow and sluggishand body functions decrease. In very cool placessnakes may have to bask in the sun more

frequently and change positions continuous. This ispartly why snakes species are more numerous inwarmer tropical areas and why species diversityfalls off toward the poles.

The few species that can withstand freezingtemperature of regions closer to the poles areinvariably small and dark in color so they can warmup quickly. They hibernate in the winter and somespecies such as the garter snake, produce asubstance to prevent damage if ice crystals forminside their cells. These cold dwelling snakes

typically give live birth because by basking they areable to provide a more conducive environment fordeveloping embryos then if they were to lay eggs.On the flip side, snakes that live in the desert orextremely warm regions tend to be active only partof the year or in the evening hours and will live nearrocky outcrops or in canyons near water sourceswhere they can find water and protection.


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Ectotherms have an advantage over mammalswhen it comes to food sources. Since they do notneed to use their metabolic energy for foodproduction like mammals, which are endothermicthey are able to exploit scarce seasonal foodsources. It has been noted that snakes can live offof a meagerly 10 percent of the food need by otherbirds or mammals of the same size. Furthermore,these amazing creatures can actually shut downtheir systems for months if food is scarce.

Size and ShapeLook, Ma, No hands or feet Fundamentally allsnakes look the same, meaning they are all longand thin without any limbs. But between speciesshape and size can vary considerably. Forexample, within the group classified as boas,species can range in length from as large as theAnaconda, who averages 33ft, to as tiny as therubber boa, who rarely exceeds 2 feet!

Staying on the subject of length, the six largestsnakes belong one of two families: the boas or thepythons. The Big Six includes the greenanaconda, reticulated python, Python molurus(from India), python sebae(from Burma), theMorelia amethistina(form Australia), and last butnot least, the common boa, which grows to anaverage of 10ft. Large snakes such as these arerare simply due to the fact that they need to eat alot and their size forces them to forge food byambushing their prey making food a limitedresource. Second, snakes of this size take a long

time to heat up so being the endotherms that theyare, these particular large snakes have to live at ornear the tropics.

The three most primitive families: leptotyphlopids,anomalepids, and typhlopids total about 300species or about 10% of all snakes. Snakes withinthese families rarely grow larger than 12inches.Because snakes of such tiny dimensions requireless to eat and can heat up more quickly they havesome advantage when it come to surviving,however their size makes them a delicacy to prey,

including other snakes.

Snakes are not all round! Depending on how eachspecies lives and hunts determines the shape oftheir body. For example, burrowing and aquaticsnakes benefit from having a rounded undersidesimply because that shape is most conducive tosurviving and maneuvering in their environment.Snakes that are long and thin tend to be arboreal ortree-dwelling snakes. This thinness helps them to

be quick to hunt down their prey. These treehuggers must also be light in weight in to ensurethe branches can hold them and their long tailsallow them to hang down at varying lengths to plucktheir prey if need be. These snakes also tend tohave bodies that are flattened on either side as wellas on the bottom which makes them rigid in orderfor them to cantilever their bodies outward,supporting their own weight as they cross frombranch to branch. Country snakes, such as thesand snake, whipsnake, and racers, are also longand thin which helps them move quickly in throughvegetation to capture their prey. These snakeshave a flattened underside that allows them tograsp irregular surfaces. Short snakes such as theviper and some species of pythons do not goaround chasing prey, instead they ambush. Theirbodies are heavier, acting like an anchor whenlunging forward to strike its prey.

ScalesThe scaly skin of snakes provides both protectionfrom outside elements and the much neededflexibility to maneuver without limbs. Just as theshape of snakes varies from one species to anotherso do scales. Depending on the habitat and lifestyleof snakes each type of scale serves a specificpurpose. However, before diving into the differenttypes of scales, lets look at the function of scales.

A snakes skin is made up of two parts: scales,made up of keratin (the same thing as fingernails)

which are the thicker areas and the thinner areasbetween the scalescalled interstitial skin orinterscalar skin. Thescales lie similarly tothat of roof shingles.This means that if youwere to run your fingerfrom head to toe it

would be really smooth, but if you were to run yourfingers in the opposite direction the scales wouldget caught, making it not only uncomfortable to you

but to the snakes as well. The thinner skin isstretchable and makes the skin elasticity and veryflexible. Scales serve three main purposes. First,protection from the environment, some defenseagainst parasites, small predators, or biting insects,and from the snakes won prey which often fightsback. Second, scales help with locomotion.Because scales tend to be irregularly, particularlyon the underside, it helps the snake to grip theground, pulling itself forward or vertically. Third,


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scales help to minimize water loss throughevaporation, which for desert dwelling snakes isquite an important attribute.

There are four main types of scales: Dorsal scales,ventral scales, head scales, and subcaudal scales.Dorsal scales are found on the back and the side ofthe snakes and are usually arranged in rows. Onvipers, these scales are keeled where as inburrowing snakes they are smooth. Ventral scalesrest on the underside of the snake and are smoothin nature which helps aid in maneuverability. Thehead scales includes the scale at the tip of the nosecalled the rostral scale; the subocular scale that lies

just below the eyes, and the labial scale that restjust around the mouth. Again, depending on thespecies of snake, these scales can vary in size.Subcaudal scales are found beneath the snakestails. These are similar to the ventral scales, butmay be singular or paired.

The cells containing pigments are located in thescales and give each snake species itscharacteristic pattern and coloration. Coloration ofscales is largely dependent on a snakes habitat,helping them to blend into the surroundings. Therainbow boa has a particular structure to the cells inthe surface of its scales that causes light to reflectand refract creating a psychedelic, iridescent effect.There are a few species that can change shadewithin minutes and some species change colorthroughout their lifetime.

Evolution has helped to create unique superpowered-like scales in some species of snakes.Take the Desert Horned Viper who sports twohorns on either side of its head just above its eyesmaking it look more like a dragon than a snake.This fellow hides itself in the sands of the SaharaDesert allowing only its eyes and horns to piercethe surface. A few species have tails that end in asharp point that can be used to stab any predatorthat tries to mess with them. The rattlesnakesrattle is also an example of a specialized scale.

As the snake sheds, theses particular scales ontheir tail stay in place forming the rattle that can bevibrated to send out a warning sound.

Snakes grow but not their scales so they mustshed their layers, doing so an average of about

once a month.Snakes will rubtheir nose onsomething rough to

get begin the shedding process and will crawl alongrough surfaces to help remove the outer layerwhich comes off inside out.

Anatomy and StructureThe anatomy of the snake has much in commonwith other vertebrates despite its elongated shape.Snakes have a backbone; rely on the samesystems to survive (respiratory, circulatory,digestive, excretory, reproductive, and nervous),and many of the same organs. The main differenceis the placement and shape of these organs, whichare determined by the narrowness of its body.Snakes inhale and exhale through their mouth andtrachea. Most species of snakes have only onefunctioning lung. The exception to this is the boaand the python who have a right lung. Thereforethe right lung is exceptionally large, stretching athird of the entirelength of the snake.

To allow breathwhile swallowinglarge prey, somespecies of snakeshave a tracheal lungwhich is actually anextension of theright lung. Anotherneat adaptation tothe respiratorysystem is themuscular wind pipe

that they can force forward under their preyallowing them to continue to breathe as well. Theircirculatory system is the same to that of mostanimal except that their heart has only threechambers instead of four.

Snakes begin digestion in the mouth where oralglands secrete digestive juices while the snake isfeeding. Because the snake swallows its preywhole the throat and esophagus are muscular,helping to push food into the stomach, which is awide section of the gut. Large and small intestines

are shorter than in other animals and food thatgoes undigested is simple expelled. Interestinglysnakes lack a bladder. Waste is filtered through thekidneys and is excreted as a white, crystallinematerial that contains very little water, helping toconserve moisture.

Like other mammals and reptiles, snakes useinternal fertilization. Males have elongated testesand a pair of copulatory organs, the hemipenes.


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Sperm is carried to the testes to the hemipenesthroughway of the ureter. Female will either havestaggers ovaries or in some cases only one ovary.The brain and the spinal cord, which runs thelength of the backbone, help to make up thenervous system of a snake. Though the nervoussystem is simplified in snakes due to their lack oflimbs, they dohave additionalnerves thatserve theJacobsonsorgan. TheJacobsonsorgan is anadditional organlocated in theroof of thesnakes mouth.Snakes use this organ to sense prey, sticking their

tongue out to gather scents and touching it to theopening of the organ when the tongue is retracted.It brings those senses back inside its mouth to theJacobsons organ where the molecules areanalyzed and passed on to the brain. The forkedtongue can even tell which direction the prey hasgone. This forked tongue though is useless when itcomes to taste. Snakes have no taste buds!

Made up of a skull, spine, and ribs, the skeleton ofa snake is most notable for its strength andflexibility of its spine and its unusually large number

of vertebrae- ranging from 120 in smaller speciesand up to 500 in larger species. Compared to the24 vertebrae in humans, that is a lot!

The jaws and skulls of snakes have evolved overtime in response to feeding habits. For example,primitive snakes have limited flexibility in their jaws,therefore limiting their food source to termites andants. The more advanced snakes eat larger preyand thus require a larger capacity. In these moreevolved snakes, the bones in the jaw that wouldotherwise be fused, are delicate and loose, and

have the ability to move apart from each otherwhen the jaw is opened wide. Theses bones areable to move forward, backwards, and outwardsindependently from each other allowing the snaketo hook its teeth on to its prey and drag it into itsmouth.

Depending on a snakes feeding habit they will haveeither a large number of teeth or barely any at all.Teeth are loosely attached to the surface of the

jawbone on its inner edge rather than being rootedin a socket. Teeth are constantly being dislodgesbut grow in quickly, even fangs when present, arereplaced throughout a snakes life.Snakes with fangs are divided into two categories:opistoglyphous, or rear-fanged snakes; andproteroglyphous, or front-fanged snakes. Thevipers, cobras, and the burrowing asps belong tothe family of front-fanged snakes. These snakesfangs are hollow so that the venom can flow alongthe length, exiting at the tips and penetrating intoprey.

On the subject of venom, venom is produced frommodified saliva, a mixture of proteins and enzymesthat originally served as a means of digesting theprey. The stronger these digestive juices, the morevenomous the snake is. The toxicity of venomvaries from species to species. Some venom isspecialized according to the prey. For example, it

might affect a lizard but not a bird of the same size.Not all venom has the same effect either. Thecobra venom affects the nervous system where asthe venom of the viper affects the blood cells. Thevenom of many sea snakes is fast acting, affectingthe muscle. I know you are wondering what themost dangerous snakes are so here you have it:the black mamba, king cobra, and the Australianinland taipan. But these snakes are rare, killing onlya handful of people each year. Venomous must notbe confused with poisonous. Poison is toxic bytouch and would have to be on the outer surface of

the snake if that was the case. There are nopoisonous snakes.

All snakes are carnivores, but within the over 3,000species of snakes that exist are many differentfeeding habits. Snakes are stellar hunters, huntingby sneakiness, speed, or scent. If prey is too largeto swallow first snakes will kill it first by eitherconstricting or injecting venom into their prey.Constrictors are more common than venomoussnakes, most often associated with the boa.Constrictors will wrap themselves around the prey

and strangle it until it stops breathing beforeconsuming is.

Most snakes have poor eye sight, forcing them torely on other senses for hunting or defendingthemselves against predators. Most burrowingsnakes can only distinguish between light and dark.The remaining species have one of three types ofpupils. The shape of a snakes pupil indicates theprobable period of its hunting activity. Generally


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snakes with round pupils are diurnal and huntduring the day and snakes with vertical pupils arenocturnal, hunting at night. Horizontal pupils arefound in only a few species of tree snakes, givingthem binocular vision which helps them move frombranch to branch.

Another feature unique to snakes eyes is ocularscale, known as the brille. This transparent scalehelps to protect the eye from damage becausesnakes lack eyelids and they do not blink. Duringthe shedding process the brille will becomes cloudywhite and will shed too.

A snakes ability to sense sound is unique sincethey have no external ears. Instead they sense orhear vibrations in the ground. The vestiges of theinternal structure of the ear are still present in theform of a small bone called the stapes, which helpsto transmit vibrations to the inner ear when the jaw

of the snake is low to the ground. In addition to thevibration of potential prey or predators, snakes areable to pick up low frequency airborne sounds.There are two species, the pit viper and the boids,have a sort of sixth sense that allows them to catchtheir prey blinded. This is made possible throughinfrared vision or heat vision. Infrared rays havelonger wavelengths than those of visible light,signifying the presence of warm-blooded prey inthree dimensions. These snakes have heat pitslocated just below the eye and directed forward.These pits allow them to detect even the smallest

changes in heat around them. By analyzing theheat on either side of its head, the snake can figureout with precision the range and position of its preyin sheer darkness.

A SNAKES NICHEContent Standard 6.5a

The fundamental role that snakes play in anecosystem is a simple one. As one part of thegreater food chain, they prevent overpopulation andprovide food for hungry predators, especially whenthey are young. Their importance to humans is less

pronounced but still significant.

Insect and Rodent ControlSnakes impose an important check on rodentpopulations. Some of the most venomous snakes inthe world such as the Indian cobra actually preventthe spread of disease-carrying rodents, even inurban centers, so their usefulness often outweighstheir danger.

Prey

Snakes themselves are often used for food. Birds

of prey will eat many snakes.

Human Interactions

Though humans generally try to avoid interactionwith snakes, they do occasionally bear an importantrole. For instance, the venom of a snake is usedoften to derive vaccines, and snake scales areconsidered fashionable in many cultures.

FUN SNAKE FACTS

The rattlesnake's rattle consists of six to 10layers of scales, which fail to shed andmake that distinctive sound when the tail isshaken as a warning. Eventually the oldersegments will slough as the rattle

lengthens. A snake's heart can slide 1 to 1 1/2 times its

length from its normal position, to allow thepassage of swallowed prey. This isbecause of the relative mobility of thepericardial sac, which surrounds the heart.

Snakes can have over 300 pairs of ribs.

Out of about 3,000 species of snakes, onlyabout 350 have venom that is dangerous tohumans.

Snakes are the deadliest animal on earth,

killing over 100,000 people each year. Some snakes can reach a length of about

36 feet (11 meters).

SNAKES OF THE SAN BERNARDINONATIONAL FOREST

Southern Rubber BoaCharina bottae umbratica

Rubber boas belong to thefamily Boidae, boas, a


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family of nonvenomous snakes which includes 43species. The genus Charina consists of fourspecies, three of which are found in North Americaand one in Africa. The name Charina comes fromthe Greek and means graceful or delightful.This small docile snake looks like a giantearthworm. It is active at dawn and dusk, especiallyduring rainy periods. This small snake rangesbetween 12- 18 long.

The Southern Rubber Boa is found only in riparianhabitats in San Bernardino and San JacintoMountains, while the Northern Rubber Boa is foundin much of Northern California.

A so called intergrade between the Northern andSouthern Rubber boa is found in Los PadresNational Forest. This intergrade is genetically morerelated to the northern rubber boa but looks like thesouthern rubber boa.

Rubber boas live in damp woodland and coniferousforest, large grassy meadows, and moist sandyareas along rock streams from sea level to 9,200feet. They endure cold better than most othersnakes and are ovoviviparous, which means thatfemales retain the eggs inside their bodies until theyoung hatch. Mating takes place immediately afterthe end of hibernation, and the snakelets are bornin August through the first three weeks ofSeptember. Each female bears two to eight young.

The Southern Rubber Boa has been listed as oneof Californias threatened species since 1971. Theprincipal cause for the species' decline is habitatloss due to resort development, OHV activities,logging, and wood gathering.

Mojave RattlerCrotalus scutulatus

The often mis-named "Mojave Green" has the mostpotent venom of any rattlesnake in North America.

Its poison is about 16 times more powerful than thatof the Sidewinder. They can be identified by theirtriangular-shaped head and diamond-shapedmarkings along their body, and of course, rattles.They are brown in color in the lower elevations anddarken to a green in the higher regions near themountains. Their eggs hatch within them soanywhere from 4 to 24 baby snakes are born live ina litter.

The Mojave rattlesnake is the most dangerous ofrattlesnakes in the Mojave Desert. Its venom, whichit uses to immobilized its prey and defend itself,attack both the nervous system with nuerotoxinsand the bloodstream with hemotoxins. It lookssimilar to a diamondback rattlesnake, havingdiamond shapes along its back. Its color will varyfrom green-gray in higher, mountain elevations, toyellowish tones found more often in the lowerportions of its range. Adults range from 2-4 feet in

length.

The creosote bush, found in the 2,000 to 4,000 footelevation is the primary, but not the only habitat ofthis snake. They feed primarily on small rodents. Itwill not come looking for trouble, nor will it run fromit!

Striped WhipsnakeMasticophis taeniatus

Striped whipsnakes are fairly common in suitablehabitats. In California their range is restricted to

Great Basin habitats east of the Sierra/Cascadecrest from northeastern Siskiyou Co. and ModocCo. south to the northern Mojave Desert in SanBernardino Co. Absent from higher elevations inthe Warner Mountains. Elevation to 2850 m (9400ft). Important habitats in California include eastsidepine, pine-juniper, sagebrush, bitterbrush, anddesert scrub.


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A visually oriented, active predator, the stripedwhipsnake forages on the ground and in the lowbranches of bushes and small trees. When foragingon the ground whipsnakes often hold their headhigh off the ground. They are known to takeprimarily lizards and snakes but also take smallmammals, birds, and even insects

When not active this species seeks cover under orin dense vegetation, in rocky crevices, or in oraround surface objects. During winter individualshibernate in dens in rocky accumulations . At othertimes, whipsnakes may return to these dens ifconditions become particularly inclement.

Males are thought to defend a small area around afemale during the period of courtship and mating.Territorial defense sometimes involves physicalcombat. Males are not aggressive toward eachother during other seasons or in the absence of

females.

Courtship, involving the rubbing of portions of thefemale's body with the head and neck of the male,occurs soon after emergence from thehibernaculum in the spring. Three to 10 eggs aredeposited, often in communal nests, in June andJuly. Hatching occurs in late August or September.

The striped whipsnake is an active, diurnal, visuallyoriented predator, similar to the Californiawhipsnake, which occurs in less arid habitats.

Whipsnakes are taken by a variety of predatorsincluding mammals, diurnal birds of prey and othersnakes.

Mountain KingsnakeLampropeltis zonata parvirubra

The California Mountain Kingsnake is found in themountains of California, southern Oregon andnorthern Baja Mexico. Eggs are laid 3-9 in a clutchsometime in July and August hatching inSeptember and October. Hatchlings are 6-7"; anadult may exceed three feet, but most are between20 40 inches long. The head is generally allblack. Having colorful triads the length of the body.

They are found in the mountain ranges between3,000 up 8,000 feet elevation. They primarily eatlizards, however adults will eat rattlesnakes (hencethe name "Kingsnake"). They begin hibernationsometime in October, emerging sometime in mid-March. breeding occurs from the end of April till themiddle of June.

San Bernardino Ringneck SnakeDiadophis punctatus modestus

The ringneck snake is found along the southernCalifornia coast from the Santa Barbara area southalong the coast to San Diego County, and inlandinto the San Bernardino mountains. It is a small,thin snake with smooth scales. Gray, blue-gray,blackish, or dark olive dorsal coloring, with a brightorange to reddish underside, speckled with blackmarkings. The underside of the tail is a brightreddish orange.

Though it is mildly venomous, it is not considereddangerous to humans. It has enlarged non-groovedteeth in the rear of the upper jaw and a mild venomwhich may help to incapacitate small prey. Thistwo-toned snake flashes its orange belly whenintimidated or scared, trying to scare off predators.

These snakes are between 1016 inches long.This snake is rather secretive - usually found underthe cover of rocks, wood, bark, boards and othersurface debris, but occasionally seen moving onthe surface on cloudy days, at dusk, or at night.

Their diet consists of slender salamanders andother small salamanders, tadpoles, small frogs,small snakes, lizards, worms, slugs, and insects.As far as reproduction, the ringneck will lay eggs inthe summer, sometimes in a communal nest.

GLOSSARY

Adaptation A characteristic that enables a livingthing to survive in its environment


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Brille A clear scale that covers a snakes eyeConstrictorA type of snake that kills its prey by

suffocation

Ectotherm Animals that are unable to regulate

their temperature internally

Endotherm Animals that are able to regulatetheir temperature internally

Infrared Vision Vision outside the visiblespectrum at its red end, where thermal waves arepicked upJacobsons Organ Either of a pair of small pitsthat are used by reptiles and amphibians as asense organ for smell.Low Frequency Hearing Wave frequencies thatlie below the range of human hearing.Poison A biological toxin absorbed throughepithelial linings such as the skin or gut (notinjected like venom)Reptile-Any of various cold-blooded, usually egg-

laying, vertebrates having an external covering ofscales or horny plates and breathing by means oflungs.Scales -Small, flattened, rigid plates forming part ofthe external body covering of reptiles andamphibiansShedding The routine molting or sloughing off ofcells, as in the loss of scales on snakes and fur onmammalsVenomous Having a venom-producing gland andthe ability to inflict a poisoned wound.

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