''Naja annulata'' (formerly ''Boulengerina annulata''), commonly known as the banded water cobra or the ringed water cobra, is a species of
water cobra
''Naja'' is a genus of venomous elapid snakes commonly known as cobras (or "true cobras"). Members of the genus ''Naja'' are the most widespread and the most widely recognized as "true" cobras. Various species occur in regions throughout Afric ...
native to western and central
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
.
The species is one of the two species of water cobra in the world, the other one being the Congo water cobra (''
Naja christyi
''Naja christyi'' (formerly ''Boulengerina christyi)'', commonly known as the Congo water cobra or Christy's water cobra, is a species of venomous snakes belonging to the family Elapidae. The species is native to Sub-Saharan Africa.
This speci ...
'').
Description
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 in length, but they can grow to a maximum of .
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
Burundi
Burundi (, ), officially the Republic of Burundi ( rn, Repuburika y’Uburundi ; Swahili language, Swahili: ''Jamuhuri ya Burundi''; French language, French: ''République du Burundi'' ), is a landlocked country in the Great Rift Valley at the ...
,
Cameroon
Cameroon (; french: Cameroun, ff, Kamerun), officially the Republic of Cameroon (french: République du Cameroun, links=no), is a country in west-central Africa. It is bordered by Nigeria to the west and north; Chad to the northeast; the C ...
,
Central African Republic
The Central African Republic (CAR; ; , RCA; , or , ) is a landlocked country in Central Africa. It is bordered by Chad to the north, Sudan to the northeast, South Sudan to the southeast, the DR Congo to the south, the Republic of th ...
,
Democratic Republic of Congo
The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
,
Republic of Congo
The Republic of the Congo (french: République du Congo, ln, Republíki ya Kongó), also known as Congo-Brazzaville, the Congo Republic or simply either Congo or the Congo, is a country located in the western coast of Central Africa to the w ...
,
Equatorial Guinea
Equatorial Guinea ( es, Guinea Ecuatorial; french: Guinée équatoriale; pt, Guiné Equatorial), officially the Republic of Equatorial Guinea ( es, link=no, República de Guinea Ecuatorial, french: link=no, République de Guinée équatoria ...
,
Gabon
Gabon (; ; snq, Ngabu), officially the Gabonese Republic (french: République gabonaise), is a country on the west coast of Central Africa. Located on the equator, it is bordered by Equatorial Guinea to the northwest, Cameroon to the north ...
,
Rwanda
Rwanda (; rw, u Rwanda ), officially the Republic of Rwanda, is a landlocked country in the Great Rift Valley of Central Africa, where the African Great Lakes region and Southeast Africa converge. Located a few degrees south of the Equator ...
, and the province of
Cabinda in
Angola
, national_anthem = " Angola Avante"()
, image_map =
, map_caption =
, capital = Luanda
, religion =
, religion_year = 2020
, religion_ref =
, coordina ...
, as well as along the Burundian, Tanzanian and Zambian shores of
Lake Tanganyika
Lake Tanganyika () is an African Great Lake. It is the second-oldest freshwater lake in the world, the second-largest by volume, and the second-deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. ...
. 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,
[ 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 underwater for up to 10 minutes and diving to depths of . 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.[
It preys almost exclusively on fish.][ It may also prey on frogs, toads, and other amphibians.][
]
Venom
The venom of this species is not well studied, but it is believed that the venom is dangerously neurotoxic
Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specificall ...
, like that of most elapids
Elapidae (, commonly known as elapids ; grc, ἔλλοψ ''éllops'' "sea-fish") 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 Emydocep ...
. A study listed the intraperitoneal (IP) 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-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
Elapidae (, commonly known as elapids ; grc, ἔλλοψ ''éllops'' "sea-fish") 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 Emydocep ...
have some of the lowest intraperitoneal LD50 values of any African ''Naja'' species studied thus far, and have high concentrations of potent postsynaptic neurotoxins.[
]
Taxonomy
References
* Mark O'Shea, Tim Halliday
Professor Timothy Richard Halliday was a British herpetologist and artist.
He was born on 11 September 1945 in Marlborough, Wiltshire, to Edna (née Barlow), was a housemistress at Marlborough College and her husband, Jack Halliday, a biology ...
, ''Reptiles and amphibians'' ()
{{Taxonbar, from=Q2703922
annulata
Snakes of Africa
Reptiles of Angola
Vertebrates of Burundi
Reptiles of Cameroon
Reptiles of the Central African Republic
Reptiles of the Democratic Republic of the Congo
Reptiles of Gabon
Reptiles of Tanzania
Reptiles of Zambia
Reptiles described in 1876
Taxa named by Wilhelm Peters