(Buchholz and Peters, 1876)
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 cobras 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 2.7 metres (8.9 ft). 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.
Distribution and habitat
This species is found in parts of central and western Africa, in Cameroon, Central African Republic, Democratic Republic of Congo, Republic of Congo, Equatorial Guinea, Gabon, Rwanda, and the province of Cabinda in Angola. It is largely an aquatic species and rarely is found far away from water. It can be found along lakes and rivers in forest and well-wooded savanna terrain where cover is sufficient, most commonly along lowland forested, bushy or wooded banks of lakes, rivers, and streams.
Behavior and diet
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 under water for up to 10 min and diving to depths of 25 metres (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.
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.
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 (N. christyi toxin) residue 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 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 the lowest intraperitoneal LD50 of any African Naja species studied thus far and have high concentrations of potent postsynaptic neurotoxins.
|Subspecies||Taxon author||Common name||Geographic range|
|N. a. annulata||Buchholz and Peters, 1876||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)||Storm's water cobra||Burundi, Tanzania|
- "Boulengerina annulata". ITIS Standard Report Page. ITIS.gov. Retrieved 16 February 2012.
- Spawls, Stephen; Branch, Bill (1995). Dangerous Snakes of Africa. London, UK: Blandford Press. pp. 55–56. ISBN 0-7137-2394-7.
- "Boulengerina annulata - General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid, Antivenoms". Clinical Toxinology Resource. University of Adelaide. Retrieved 16 February 2012.
- "Boulengerina annulata". Armed Forces Pest Management Board. United States Department of Defense. Retrieved 16 February 2012.
- Weinstein, Scott A.; James J. Schmidt; Leonard A. Smith (30 March 1991). "Lethal toxins and cross-neutralization of venoms from the African water cobras, Boulengerina annulata annulata and Boulengerina christyi". Toxicon 29 (11): 1315–1327. doi:10.1016/0041-0101(91)90118-B. PMID 1814007. Retrieved 12 May 2012.
- "Boulengerina annulata stormsi". ITIS Standard Report Page. ITIS.gov. Retrieved 25 February 2012.
- Mark O'Shea, Tim Halliday, Reptiles and amphibians (ISBN 957-469-519-0)