Naja annulata | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Squamata |
Suborder: | Serpentes |
Family: | Elapidae |
Genus: | Naja |
Subgenus: | Boulengerina |
Species: | N. annulata |
Binomial name | |
Naja annulata | |
Synonyms [2] | |
Naja annulata (formerly Boulengerina annulata), commonly known as the banded water cobra or the ringed water cobra, is a species of water cobra native to western and central Africa.
The species is one of the two species of water cobra in the world, the other one being the Congo water cobra ( Naja christyi ).
It is a large, heavy-bodied snake with a short, broad and flat head with an indistinct canthus and distinct from the neck. It has medium-sized dark eyes with round pupils. The body is cylindrical; the tail is long. The scales are smooth and glossy, in 21–23 rows at midbody. Adults grow to an average of 1.4 to 2.2 metres (4.6 to 7.2 ft) in length, but they can grow to a maximum of 2.8 metres (9.2 ft). [3] Scales are smooth, indicating the largely aquatic life of this species. It is capable of spreading a narrow, yet impressive hood. Body colors are mostly glossy brown, grayish-brown, or reddish-brown with black bands all along the body. The belly is pale yellow, while the tail is wholly black. [4] [5]
This species is found in parts of central and western Africa, in Burundi, Cameroon, Central African Republic, Democratic Republic of Congo, Republic of Congo, Equatorial Guinea, Gabon, Rwanda, and the province of Cabinda in Angola, as well as along the Burundian, Tanzanian and Zambian shores of Lake Tanganyika. It is largely an aquatic species and rarely is found far away from water. It can be found along lakes and rivers in forested and well-wooded savanna terrain where cover is sufficient, [4] most commonly along lowland forested, bushy or wooded banks of lakes, rivers, and streams. [5]
It is a secretive species and is seldom encountered by humans. It is active by day and night, though it is usually more active by day. This largely aquatic snake spends most of its time in the water. It is an excellent swimmer and is capable of remaining underwater for up to 10 minutes and diving to depths of 25 m (82 ft). It is a slow mover on land, and it tends to hide among rocks, in holes, or overhanging tree roots at the shoreline. It also makes use of any man-made structures, such as bridges and jetties, to hide. It is generally not aggressive, and if approached in water, it will swim away swiftly and on land will attempt to escape into water. If threatened on land, it will rear up and spread its narrow, yet prominent hood and it may hiss loudly, but it tends not to make any forward movements. It will only bite when provoked. [3] [4]
It preys almost exclusively on fish. [4] It may also prey on frogs, toads, and other amphibians. [5]
The venom of this species is not well studied, but it is believed that the venom is dangerously neurotoxic, like that of most elapids. A study listed the intraperitoneal (IP) LD50 of this species at 0.143 mg/kg. [6]
Venoms of the water cobras were assayed for lethality, proteolytic activity and protein content. Naja annulata annulata and Naja christyi venoms averaged 89% protein and lacked proteolytic activity. The murine intraperitoneal LD50 of N. a. annulata and N. christyi venoms were 0.143 and 0.120 mg/kg, respectively. Polyvalent antivenom produced by the South African Institute of Medical Research neutralized 575 and 200 LD50 of N. a. annulata and N. christyi venoms/ml antivenom, respectively. Cation exchange chromatography resolved four lethal peaks from N. a. annulata venom and six lethal peaks from N. christyi venom. The major lethal peaks (about 12% of total venom protein) were purified further with molecular sieve chromatography and were characterized as 61- (N. a. annulata toxin) and 62-residue (N. christyi toxin) polypeptides with four half-cystines. Elucidation of the complete amino-acid sequences indicated that these toxins belonged to the short-chain class of postsynaptic neurotoxins. Short-chain neurotoxins 1 from N. a. annulata and N. christyi had murine intraperitoneal LD50 values of 0.052 and 0.083 mg/kg, respectively, and showed over 80% homology with N. nigricollis alpha toxin. Reverse-phase analysis of another peak present in both venoms resolved a toxin that had an N-terminus identical to N. christyi short-chain neurotoxin 1. These fractions also contained toxins readily separable from the short-chain isotoxin by preparative reverse-phase chromatography. Amino-acid sequencing of the first 28 residues indicated that both toxins were long-chain neurotoxins with identical N-termini. The LD50 of long-chain neurotoxins 2 from N. a. annulata and N. christyi venoms were 0.086 and 0.090 mg/kg, respectively. The venoms of these little-known elapids have some of the lowest intraperitoneal LD50 values of any African Naja species studied thus far, and have high concentrations of potent postsynaptic neurotoxins. [6]
Subspecies | Taxon author | Common name | Geographic range |
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N. a. annulata | Buchholz and Peters, 1876 [2] | Banded water cobra, ringed water cobra | Cameroon, Central African Republic, Democratic Republic of Congo, Republic of Congo, Equatorial Guinea, Gabon, Rwanda, Cabinda |
N. a. stormsi | (Dollo, 1886) [2] | Storm's water cobra | Burundi, Tanzania |
The king cobra is a venomous snake endemic to Asia. The sole member of the genus Ophiophagus, it is not taxonomically a true cobra, despite its common name and some resemblance. With an average length of 3.18 to 4 m and a record length of 5.85 m (19.2 ft), it is the world's longest venomous snake. The species has diversified colouration across habitats, from black with white stripes to unbroken brownish grey. The king cobra is widely distributed albeit not commonly seen, with a range spanning from the Indian Subcontinent through Southeastern Asia to Southern China. It preys chiefly on other snakes, including those of its own kind. This is the only ophidian that constructs an above-ground nest for its eggs, which are purposefully and meticulously gathered and protected by the female throughout the incubation period.
Elapidae is a family of snakes characterized by their permanently erect fangs at the front of the mouth. Most elapids are venomous, with the exception of the genus Emydocephalus. Many members of this family exhibit a threat display of rearing upwards while spreading out a neck flap. Elapids are endemic to tropical and subtropical regions around the world, with terrestrial forms in Asia, Australia, Africa, and the Americas and marine forms in the Pacific and Indian Oceans. Members of the family have a wide range of sizes, from the 18 cm (7.1 in) white-lipped snake to the 5.85 m king cobra. Most species have neurotoxic venom that is channeled by their hollow fangs, and some may contain other toxic components in various proportions. The family includes 55 genera with around 360 species and over 170 subspecies.
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Naja is a genus of venomous elapid snakes commonly known as cobras. Members of the genus Naja are the most widespread and the most widely recognized as "true" cobras. Various species occur in regions throughout Africa, Southwest Asia, South Asia, and Southeast Asia. Several other elapid species are also called "cobras", such as the king cobra and the rinkhals, but neither is a true cobra, in that they do not belong to the genus Naja, but instead each belong to monotypic genera Hemachatus and Ophiophagus.
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