Central Asian Pit Viper
by Jay Sharp
The Central Asian pit viper, with a cadre of closely related and widely distributed subspecies and species, has raised considerable confusion about its taxonomic classification. The snake has "been the subject of considerable taxonomic instability..." as one authority said.
It varies in pattern and color within the specific species. According to some sources, it attacks aggressively, posing a serious danger. According to others, it withdraws timidly, posing little danger. Its venom composition may vary with its locality -- highly toxic according to some, mildly toxic according to others -- posing problems in designing treatment for bites. It has several different common names, for instance, Central Asian viper, Asiatic pit viper, Mongolian pit viper, mamushi and Amur viper, and it also has several different scientific names, for instance, Trigonocephalus intermedius, Ancistrodon intermedius and Haly intermedia. The snake comes with uncertainty in its characterization.
Characteristics of the Central Asian Pit Viper
The Central Asian pit viper bears a taxonomic relationship at the family (Viperidae) level with the new world copperhead, the cottonmouth water moccasin and the cantil viper as well as the Siberian pit viper, the Malayan pit vipers and others. Each of these species is distinguished by a heat-sensing pit on each side of its head, between the eye and the nostril. The pit functions as a thermoreceptor, which serves to convey differences in temperatures.
- Size and Weight: About three quarters the size of the copperhead, of the eastern and southeastern United States, the Central Asian pit viper measures about 15 to 30 inches in length. Typical of pit vipers, it has a relatively stocky body with a fairly narrow neck and a short and tapered tail.
- Head: The snake has a flattened, triangular-shaped head with eyes that have elliptical-shaped pupils. On each side of its head, it has a dark stripe that extends from the back of the eyes to the hinges of the jaw. It has a forked tongue that it uses to capture odor particles from the air and a Jacobsen's organ, in the roof of its mouth, to "smell" the particles. It uses its heat-sensing pits, especially in the darkness of night, to find and evaluate potential prey and to locate thermally comfortable retreats. Like all members of its taxonomic family, it has hypodermic-needlelike fangs -- actually modified teeth -- that flick forward, into a biting position, when the snake opens its mouth, and that fold backward, against the roof of the mouth, when the snake closes its mouth. The venom glands -- its reservoirs of venom -- are located near the hinges of the jaw.
- Colors: Although it varies in color and pattern within the species, the Central Asian pit viper, generally, has several dozen irregularly shaped, dark crossbands, or splotches, that saddle its back, from its neck to its tail, overlying a much lighter base color. Sometimes the bands may be partially bordered with an even darker outline. The snake has a lighter-colored belly, which may be heavily or lightly speckled.
- The Heat-sensing Pits: The sensitivity of the snake's heat-sensing pits would likely compare with that of other pit vipers, although that has apparently not been investigated thoroughly. It can probably use its pits -- in effect, infrared sensors -- to "see" heat signals with only slight differences. It can distinguish between the "heat signature" of potentially vulnerable prey and that of larger and potentially threatening animals.
Distribution, Habitat and Diet
The Central Asian pit viper occurs across a vast range, extending from the Caspian Sea east-northeastward to the Gobi Desert and from northern Iran and Afghanistan northward to southern Russia. It favors rocky grasslands, scrublands and open woodlands, said the Armed Forces Pest Management Board's Living Hazards Database. It "Feeds primarily on rodents, lizards, frogs and large insects," according to Clinical Toxinology Resources. It also likely preys on birds.
Behavior and Life Cycle
Given the limited research, the snake raises many questions about its behavior and life cycle. It does, however, seem reasonable that it would follow the model of close relatives within the Viperidae family.
The Central Asian pit viper would likely stay active throughout the day, except in hot weather, when it would become most active around twilight, say some sources. Conversely, it hunts mainly at night, according to Michael Allaby, "Biomes of the Earth: Grasslands." It travels with a sidewinding motion, much like that of the American Southwest's sidewinder rattlesnake. It may ambush prey from a low-lying shrub. If harassed, it may become aggressive, flattening its body against the earth and vibrating its tail in warning preparatory to striking. Otherwise, the snake would behave fairly listlessly.
The snake's courtship behavior seems to be little known, but the female, ovoviviparous, hatches her eggs inside her body, producing, once a year, a litter of some three to twelve, several-inch-long live young. The young Central Asian pit viper, able to feed and defend itself from the start, would mature sexually within a few years. It would breed in the spring or fall. It might live for ten to twenty years.
When it strikes, the Central Asian pit viper, like its Viperidae kin, opens it mouth nearly 180 degrees, with it fangs projected forward. When it drives home its fangs, it uses specialized muscles to express the venom glands, controlling the amount of venom it injects. It immediately withdraws, prepared to strike again.
According to a study by Shaanxi Normal University graduate students in 2007, the Central Asian pit viper is "the most toxic pit-viper species usually seen in northwest China and part of north China, and it is responsible for the most snakebite accidents in these area[s]." By comparison, said the Armed Forces Pest Management Board, "Not much is known," about the snake's venom, and the snake has inflicted no "confirmed fatalities."
In all likelihood, the snake's venom comprises a cocktail of dozens of proteins and enzymes, a few of them toxic. Likely, said the AFPMB, the venom is both neurotoxic, attacking the nervous system swiftly, and hemotoxic, attacking the cardiovascular system more slowly.
The snake's victims will experience pain, swelling and, possibly, rapid or irregular heartbeat. They may also, said Adrienne B. Ari, Military Medicine, exhibit "the following symptoms: difficulty seeing, seeing double, difficulty in opening the mouth, speaking, and swallowing, and difficulty getting out of bed the morning after the bite," all an indication of the beginning of muscle paralysis. Additionally, suggests Sean P. Bush, MD, Loma Linda University School of Medicine, the victim may experience bleeding into the tissues surrounding the bite. Unfortunately, as the AFPMB said, there is "no known specific antivenom currently available."
The viper's venom, with its wide variety of chemical compounds, has "potential use [in the] medical field," said the Shaanxi Normal University graduate students. Components might, for instance, be extracted for use in thinning blood and dissolving blood clots -- an important part of the treatment for stroke victims or for potential stroke or heart attack victims. Snake venom components have already been extracted for use in treating blood disorders in Asia, Europe and Latin America.
The Central Asian pit viper does not appear to be in danger. It is not included in the International Union for the Conservation of Nature's Red List of threatened species.
- According to the New World Encyclopedia, there are more than 150 species of pit vipers, which occur in North, South and Central America and in Central and East Asia and Eastern Europe.
- A pit viper's heat-sensing pits may be so sensitive that they can detect temperature differences of no more than a few hundredths of a degree Fahrenheit. It can track down and strike prey in utter darkness.
- The pit viper's venom delivery system is highly evolved, ranked by many scientists as the most sophisticated in all of nature.
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