Snake scale

Scales have been modified over time to serve other functions such as "eyelash" fringes, and protective covers for the eyes[2] with the most distinctive modification being the rattle of the North American rattlesnakes.

This permits replacement of old worn out skin, disposal of parasites and is thought to allow the snake to grow.

The ventral (or belly) scales, which are large and oblong, are especially low-friction, and some arboreal species can use the edges to grip branches.

[3] Snakes pick up vibrations from both the air and the ground, and can differentiate the two, using a complex system of internal resonances (perhaps involving the scales).

To prevent loss of moisture, reptilian skin lost the softness and moisture of amphibian skin and developed a thick stratum corneum with multiple layers of lipids, which served as an impermeable barrier, as well as providing protection from ultraviolet light.

The surfaces of the dermis and epidermis of all reptilian scales form a single contiguous sheet, as can be seen when the snake sheds its skin as a whole.

Often, snake scales have pits, tubercles and other fine structures which may be visible to the naked eye or under a microscope.

Other more advanced snakes have special large symmetrical scales on the head called shields or plates.

[12] Some snakes, such as the short seasnake Lapemis curtus, may have spinelike and juxtaposed scales[8] while others may have large and non-overlapping knobs as in the case of the Javan mudsnake Xenodermus javanicus.

The rattle is made up of a series of loosely linked, interlocking chambers that when shaken, vibrate against one another to create the warning signal of a rattlesnake.

[13] At birth, a rattlesnake hatchling has only a small button or 'primordial rattle' which is firmly attached to the tip of the tail.

[16] Snake scales are not discrete but extensions of the epidermis hence they are not shed separately, but are ejected as a complete contiguous outer layer of skin during each moult, akin to a sock being turned inside out.

[9] Moulting serves a number of functions – firstly, the old and worn skin is replaced, secondly, it helps get rid of parasites such as mites and ticks.

Renewal of the skin by moulting is supposed to allow growth in some animals such as insects, however this view has been disputed in the case of snakes.

In many cases the cast skin peels backward over the body from head to tail, in one piece like an old sock.

[9] Scale arrangements are important, not only for taxonomic utility, but also for forensic reasons and conservation of snake species.

[20] The number of rows range from ten in Tiger Ratsnake Spilotes pullatus; thirteen in Dryocalamus, Liopeltis, Calamaria and Asian coral snakes of genus Calliophis; 65 to 75 in pythons; 74 to 93 in Kolpophis and 130 to 150 in Acrochordus.

Identification of cephalic scales is most conveniently begun with reference to the nostril, which is easily identified on a snake.

[13] Sometimes snakes have enlarged scales, either single or paired, under the tail; these are called subcaudals or urosteges.

[30][31] In other places with large biodiversity, such as Myanmar, publications caution that venomous and non-venomous snakes cannot be easily distinguished apart without careful examination.

Species identification using scales requires a fair degree of knowledge about snakes, their taxonomy, snake-scale nomenclature as well as familiarity with and access to scientific literature.

Distinguishing by using scale diagrams whether a snake is venomous or not in the field cannot be done in the case of uncaught specimens.

[34]: 190  Most books or websites provide an array of traits of the local herpetofauna, other than scale diagrams, which help to distinguish whether a snake in the field is venomous or not.

[29][35]: 52 In certain regions, presence or absence of certain scales may be a quick way to distinguish non-venomous and venomous snakes, but used with care and knowledge of exceptions.

For example, in Myanmar, the presence or absence of loreal scales can be used to distinguish between relatively harmless Colubrids and lethally venomous Elapids.

[32] In South Asia, it is advisable to take the snake which has bitten a person, if it has been killed, and carry it along to the hospital for possible identification by medical staff using scale diagrams so that an informed decision can be taken them as to whether and which anti-venom is to be administered.

[36] Snakes have been a motif in human culture and religion and an object of dread and fascination all over the world.

The vivid patterns of snake scales, such as the Gaboon Viper, both repel and fascinate the human mind.

[37] Snakeskin, with its highly periodic cross-hatch or grid patterns, appeals to people's aesthetics and have been used to manufacture many leather articles including fashionable accessories.

[39] Animal lovers in many countries now promote the use of artificial snakeskin instead, which are easily produced from embossed leather, patterned fabric, plastics and other materials.