Cerastes (genus)

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Cerastes is a genus of small, venomous vipers. Common names: horned vipers,Mallow D, Ludwig D, Nilson G. 2003. True Vipers: Natural History and Toxinology of Old World Vipers. Krieger Publishing Company. ISBN 0-89464-877-2. North African desert vipers.Spawls S, Branch B. 1995. The Dangerous Snakes of Africa. Ralph Curtis Books. Dubai: Oriental Press. 192 pp. ISBN 0-88359-029-8. Three species are currently recognized, all of which are found in the deserts or semi-deserts of northern Africa and the Middle East.

Contents

1 Description
2 Behavior
3 Feeding
4 Reproduction
5 Venom
6 Species
7 Taxonomy
8 Cited references
9 External links
10 See also

Description

C. cerastes, with horns.

Cerastes are small snakes, averaging less than 50 cm in length, but are relatively stout in appearance. The head is broad, flat, distinct from the neck. The head covered with tubercularly keeled scales, which usually number 15 or more across, and a supraorbital horn may be present over each eye in some species. The snout is short and wide and the eyes, which are set well forward, are small to moderate in size. The body is short, stout and cylindrically depressed. The tail is short and tapers abruptly behind the vent.U.S. Navy. 1991. Poisonous Snakes of the World. New York: Dover Books. (Reprint of US Govt. Printing Office, Washington D.C.) 133 pp. ISBN 048626629X. The scales are small, with serrated keels, in 23-35 rows at midbody.

Although Cerastes are often referred to as horned vipers, only two larger species, C. cerastes and C. gasperettii, are known to have horns, and even these species do not always have them. Individuals with and without horns occur within the same populations and even within the same litters.Werner YL, Verdier A, Rosenman D, Sivan N. 1991. Systematics and zoogeography of Cerastes (Ophidia: Viperidae) in the Levant: 1, Distinguishing Arabian from African "Cerastes cerastes." The Snake, The Japan Snake Institute, Yabuzuka Honmachi, Nittagun, Gunma Prefecture, Japan, 23:90-100.Sterer Y. 1992. A mixed litter of horned and hornless Cerastes cerastes. Israel Journal of Zoology, 37:247-9.

When present, each horn consist of a single long, spinelike scale that can be folded back into an indentation in the postocular scale. They fold back in response to direct stimulation, thus streamlining the head and easing passage through burrows.Cohen AC, Meyers BC. 1970. A function of the horn in the sidewinder rattlesnake Crotalus cerastes, with comments on other horned snakes. Copeia, American Society of Ichthyologists and Herpetologists, 3:574-5. Horns occur more often in individuals from sandy deserts as opposed to stony deserts.Schnurrenberger H. 1959. Observations on behavior in two Libyan species of viperine snake. Herpetologica, Herpetologist's League, 15:70-2. Specimens without horns have a prominent brow ridge instead.

The purpose of the horns is the subject of much speculation. One theory is that they to allow a buildup of sand above the eyes while keeping it out of the eyes themselves. Another, more recent theory is simply that the horns serve to break up the outline of the head, making them harder for prey animals to spot.

Behavior

This genus is nocturnal and terrestrial (not known to climb into bushes), often hiding by burying themselves in the sand. Although often described as slow moving, these snakes are also capable of sidewinding. When doing so, that can move quickly across the sand.

Cerastes species are not known to be particularly ill-tempered ("fairly placid"), but when threatened they will often stand their ground and form C-shaped coils that are rubbed together to produce a rasping or crackling sound, similar to Echis. With enough provocation, they will strike from this position.Green HW. 1988. Antipredator mechanisms in reptiles. In: Gans C, editor. The Biology of the Reptilia. Vol. 16. New York: Academic Press. pp 212-317.

These snakes are capable of "sinking" quickly down into loose sand, using their keeled, angled and serrated lateral scales in a rocking motion. This process begins at the tail and moves forward until the entire head is buried and only the eyes and nostrils are exposed. They can bury themselves this way whether in an outstretched or a coiled position. See [video].

Feeding

These are ambush predators that lie buried in the sand, waiting for prey to happen by. Their diet consists mainly of rodents, birds and lizards.

Reproduction

All three species lay eggs. However, those of C. vipera hatch within hours of deposition as opposed to many weeks -- something not previously observed in other African snakes, most of which lay eggs that hatch weeks later or give birth to live young.

Venom

Unlike Echis, to which they bear a passing resemblance, Cerastes species are not known to be ill-tempered and their venom, which is a cytotoxin, is not particularly potent. Bites can be painful and should always be taken seriously, but little venom is injected and few fatalities are known. Bites do occur, especially in the Suez Canal region, but no statistical data in available.Kramer E, Schnurrenberger H. 1958. Zur Schlangenfauna von Libyen. Die Aquarien- und Terrarien-Zeitschrift XI.2., 1.2.:57-9.Mohamed AH, Khaled LZ. 1966. Effect of venom of Cerastes cerastes on nerve tissue and skeletal muscle. Toxicon, Great Britain, 3:233-4.Mohamed AH, Abdel-Baset A, Hassan A. 1980. Immunological studies om monovalent and bivalent Cerastes antivenin. Toxicon, Great Britain, 18:384-7.

Species

Species	Authority	Subsp.*	Common name	Geographic range
C. cerastes	Linnaeus, 1758	3	Desert horned viper	Egypt, Libya, Tunisia, Algeria, Morocco, Mauritania, Mali, Niger, Israel, Sudan, Oman
C. gasperettii	Leviton & Anderson, 1967	1	Arabian horned viper	United Arab Emirates, Yemen, Oman, Israel, Jordan, Iraq, Kuwait, Saudi Arabia, south-west Iran
C. vipera	Linnaeus, 1758	0	Sahara sand viper	Egypt (Sinai), Libya, Tunisia, Algeria, Morocco, Mauritania, Mali, Niger, Israel

*) Not including the nominotype (typical form).

Taxonomy

Although it would seem that Laurenti changed his mind in 1768 and decided to name this genus Aspis, instead of Cerastes as he did earlier, this did not come to pass. The ICZN later placed the name Cerastes on the Official List of Generic Names in Zoology (name no. 1539), while the name Aspis was placed on the Official Index of Invalid Generic Names in Zoology (name no. 1630).Opinions and Declarations rendered by the International Commission on Zoological Nomenclature, 1963:191

Cited references

External links

Genus [Cerastes] at the [EMBL Reptile Database]
Integrated Taxonomic Information System - [Cerastes]