Coral snake

Coral snake
Coral snake (Micrurus sp.)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Species

See text.

Coral snakes are a large group of elapid snakes that can be subdivided into two distinct groups, Old World coral snakes and New World coral snakes. There are 16 species of Old World coral snake in three genera (Calliophis, Hemibungarus and Sinomicrurus), and over 65 recognized species of New World coral snakes in three genera (Leptomicrurus, Micruroides, and Micrurus). Genetic studies have found that the most basal lineages are Asian, indicating that the group originated in the Old World.[1][2]

North American coloration patterns

Coral snakes in North America are most notable for their red, yellow/white, and black colored banding. (However, several nonvenomous species have similar coloration, including the scarlet snake, genus Cemophora; some of the kingsnakes and milk snakes, genus Lampropeltis; and the shovelnose snakes, genus Chionactis.) In some regions, the order of the bands distinguishes between the non-venomous mimics and the venomous coral snakes, giving rise to quite a few mnemonics along the lines of "Red and yellow, kill a fellow. Red and black, venom lack." Another helpful mnemonic, is "Yellow, Red, Stop!" referencing the order of traffic lights. In any case, remembering that yellow touches both other colors can indicate a cause for caution. However, this reliably applies only to coral snakes native to North America: Micrurus fulvius (Eastern or common coral snake), Micrurus tener (Texas coral snake), and Micruroides euryxanthus (Arizona coral snake), found in the southern and western United States. Coral snakes found in other parts of the world can have distinctly different patterns, have red bands touching black bands, have only pink and blue banding, or have no banding at all.

Most species of coral snake are small in size. North American species average around 3 feet (91 cm) in length, but specimens of up to 5 feet (150 cm) or slightly larger have been reported. Aquatic species have flattened tails acting as a fin, aiding in swimming.

Behavior

Coral snake showing typically reclusive behavior of hiding under rotting wood. This one was over 30 inches (76 cm) long, but less than an inch (2.5 cm) across.

Coral snakes vary widely in their behavior, but most are very elusive, fossorial snakes which spend the vast majority of their time buried beneath the ground or in the leaf litter of a rainforest floor, coming to the surface only when it rains or during breeding season. Some species, like Micrurus surinamensis, are almost entirely aquatic and spend most of their lives in slow-moving bodies of water that have dense vegetation.

Coral snakes feed mostly on smaller snakes, lizards, frogs, nestling birds, small rodents, etc.

Like all elapid snakes, coral snakes possess a pair of small hollow fangs to deliver their venom. The fangs are positioned at the front of the mouth.[3][4] The fangs are fixed in position rather than retractable, and rather than being directly connected to the venom duct, they have a small groove through which the venom enters the base of the fangs.[5][6] Because the fangs are relatively small and inefficient for venom delivery, rather than biting quickly and letting go (like vipers), coral snakes tend to hold onto their prey and make chewing motions when biting.[5][7] The venom takes time to take full effect.[6]

Coral snakes are not aggressive or prone to biting and account for less than one percent of the number of snake bites each year in the United States.The life span of coral snakes in captivity is about 7 years.[8]

Distribution

Eastern coral snake, Micrurus fulvius

New World coral snakes exist in the southern range of many temperate U.S. states. Coral snakes are found in scattered localities in the southern coastal plain from North Carolina to Louisiana, including all of Florida. They can be found in pine and scrub oak sandhill habitats in parts of this range but sometimes inhabit hardwood areas and pine flatwoods that undergo seasonal flooding.[9]

There is controversy about the classification of the very similar Texas coral snake as a separate species. Its habitat, in Texas, Louisiana, Arkansas, and sometimes in Oklahoma due to floods in the Red River, is separated from the eastern habitat by the Mississippi River. The coral snake population is most dense in the southeast United States, but coral snakes have been spotted as far north as Kentucky.[10]

The Arizona coral snake, clearly a separate species and genus, is found in central and southern Arizona, extreme southwestern New Mexico and southward to Sinaloa in western Mexico. It occupies arid and semiarid regions in many different habitat types including thornscrub, desert-scrub, woodland, grassland and farmland. It is found in the plains and lower mountain slopes from sea level to 5800 feet (1768 m); often found in rocky areas.[11]

Danger to humans

New World coral snakes possess one of the most potent venoms of any North American snake. However, relatively few bites are recorded due to their reclusive nature and the fact they generally inhabit sparsely populated areas. According to the American National Institutes of Health, there are an average of 15–25 coral snake bites in the United States each year.[12]

When confronted by humans, coral snakes will almost always attempt to flee, and bite only as a last resort. In addition, coral snakes have short fangs (proteroglyph dentition) that cannot penetrate thick leather clothing. Any skin penetration however, is a medical emergency that requires immediate attention. Coral snakes have a powerful neurotoxin that paralyzes the breathing muscles; mechanical or artificial respiration, along with large doses of antivenom, are often required to save a victim's life. There is usually only mild pain associated with a bite, but respiratory failure can occur within hours.

Antivenom shortage

The bite of a coral snake may soon be more dangerous, in part because bites are so uncommon. Production of coral snake antivenom in the United States ceased because it is not profitable. According to Pfizer, the owner of the company that used to make Coralmyn, it would take over $5–$10 million to put toward researching a new synthetic antivenom. The cost was too large for the small number of cases presented each year. The American antivenom stock expired in 2008, but the U.S. Food and Drug Administration has extended the expiration date every year through at least 2013.[13] Foreign pharmaceutical manufacturers have produced other coral snake antivenoms, but the costs of licensing them in the United States have stalled availability (see above).[14] Instituto Bioclon is developing a coral snake antivenom.[15] In 2013, Pfizer was reportedly working on a new batch of antivenom but had not announced when it would become available.[13]

Old World

Genus Calliophis

Main article: Calliophis
Wikispecies has information related to: Calliophis

Species in this genus are:

Nota bene: A binomial authority in parentheses indicates that the species was originally described in a different genus.

Genus Hemibungarus

Main article: Hemibungarus
Wikispecies has information related to: Hemibungarus

Species in this genus are:

Genus Sinomicrurus

Main article: Sinomicrurus

Species in this genus are:

New World

Genus Leptomicrurus

Genus Micruroides

Wikispecies has information related to: Micruroides

Genus Micrurus

Wikispecies has information related to: Micrurus

Mimicry

New World coral snakes serve as models for their Batesian mimics, false coral snakes, snake species whose venom is less toxic, as well as for many nonvenomous snake species that bear superficial resemblances to them. The role of coral snakes as models for Batesian mimics is supported by research showing that coral snake color patterns deter predators from attacking snake-shaped prey,[16][17] and that in the absence of coral snakes, species hypothesized to mimic them are indeed attacked more frequently.[18] Species that appear similar to coral snakes include:

References

  1. ↑ Slowinski, J. B. and Keogh J. S. (April 2000). "Phylogenetic Relationships of Elapid Snakes Based on Cytochrome b mtDNA Sequences". Molecular Phylogenetics and Evolution 15 (1): 157–164. doi:10.1006/mpev.1999.0725. PMID 10764543.
  2. ↑ Slowinski, J. B., Boundy, J. and Lawson, R. (June 2001). "The Phylogenetic Relationships of Asian Coral Snakes (Elapidae: Calliophis and Maticora) Based on Morphological and Molecular Characters". Herpetologica 57 (2): 233–245. JSTOR 3893186.
  3. ↑ Eastern Coral Snake (Micrurus fulvius), Savannah River Ecology Library.
  4. ↑ Coral Snakes: Rear fanged? Grooved fangs? Primitive?
  5. 1 2 Eastern Coral Snake
  6. 1 2 "Coral Snakes: Micrurus f. fulvius". Retrieved 24 November 2009.
  7. ↑ Coral Snakes: Colors, Bites, Farts & Facts, Live Science.
  8. ↑ "Eastern Coral Snake". Animals national Geographic.
  9. ↑ University of Georgia, Savannah River Ecology, Snakes of Georgia and South Carolina
  10. ↑ Western Connecticut State University
  11. ↑ Arizona-Sonora Desert Museum
  12. ↑ "Snake bites: MedlinePlus Medical Encyclopedia". Nlm.nih.gov. 2010-01-13. Retrieved 2010-11-16.
  13. 1 2 Breen, David (12 October 2013). "Risk from coral-snake bites grows as antivenin dwindles". Orlando Sentinel. Retrieved 25 May 2014.
  14. ↑ "Antivenom Shortages – Cost of Antivenom Production Creates Shortages". Popular Mechanics. 2010-05-10. Retrieved 2010-11-16.
  15. ↑ "Our Products – Coralmyn". Bioclon.com.mx. Retrieved 2010-11-16.
  16. ↑ Brodie III, Edmund D. (1993). "Differential avoidance of coral snake banded patterns by free-ranging avian predators in Costa Rica". Evolution 47 (1): 227–235. doi:10.2307/2410131.
  17. ↑ Brodie III, Edmund D., Moore, Allen J. (1995). "Experimental studies of coral snake mimicry: do snakes mimic millipedes?". Animal Behavior 49 (2): 534–6. doi:10.1006/anbe.1995.0072.
  18. ↑ Pfennig, David W., Harcombe, William R., Pfennig, Karin S. (2001). "Frequncy-dependent Batesian mimicry". Nature 410 (6826): 323. doi:10.1038/35066628. PMID 11268195.

Further reading

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