Jameson's mamba

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Jameson's mamba
closeup of scales on body and head of snake
Subsp. jamesoni, Korup National Park
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Dendroaspis
Species:
D. jamesoni
Binomial name
Dendroaspis jamesoni
(Traill, 1843)[2]
Dendroaspis jamesoni distribution.svg
Range of Jameson's mamba
Synonyms[3]
  • Elaps jamesoni
    Traill, 1843
  • Dendraspis jamesoni
    Günther, 1858
  • Dendroaspis jamesoni
    Schmidt, 1923

Jameson's mamba (Dendroaspis jamesoni) is a species of highly venomous snake native to equatorial Africa. A member of the mamba genus Dendroaspis, it is slender with dull green upperparts and cream underparts and generally ranges from 1.5 to 2.2 m (4 ft 11 in to 7 ft 3 in) in length. Described by Scottish naturalist Thomas Traill in 1843, it has two recognised subspecies; the nominate subspecies from central and west Sub-Saharan Africa and the eastern black-tailed subspecies from eastern Sub-Saharan Africa, mainly western Kenya.

Predominantly arboreal, Jameson's mamba preys mainly on birds and mammals. Its venom consists of both neurotoxins and cardiotoxins. Symptoms of envenomation in humans include pain and swelling of the bite site, followed by swelling, chills, sweating abdominal pain and vomiting, with subsequent slurred speech, difficulty breathing and paralysis. Fatalities have been recorded within three to four hours of being bitten. The venom of the eastern subspecies is around twice as potent as that of the nominate subspecies.

Taxonomy and etymology[edit]

Jameson's mamba was first described as Elaps jamesoni in 1843 by Thomas Traill, a Scottish doctor, zoologist and scholar of medical jurisprudence.[4] The specific epithet is in honour of Robert Jameson, Traill's contemporary and the Regius Professor of Natural History at the University of Edinburgh where Traill studied.[5] In 1848, German naturalist Hermann Schlegel created the genus Dendroaspis, designating Jameson's mamba as the type species.[6] The generic name is derived from the Ancient Greek words dendron (δένδρον), "tree", and aspis (ἀσπίς) "asp".[7] The genus was misspelt as Dendraspis by French zoologist Auguste Duméril in 1856,[8] and generally uncorrected by subsequent authors. In 1936, Dutch herpetologist Leo Brongersma corrected the spelling to the original.[9]

In 1936, British biologist Arthur Loveridge described a new subspecies D. jamesoni kaimosae, from a specimen collected from the Kaimosi Forest in western Kenya, observing that it had fewer subcaudal scales and a black (rather than green) tail.[10] Analysis of the components of the venom of all mambas places Jameson's mamba as sister species to the western green mamba (Dendroaspis viridis), as shown in the cladogram below.[11]

king cobra (Ophiophagus hannah)

Jameson's mamba – western subspecies (Dendroaspis j. jamesoni)

Jameson's mamba – eastern subspecies (Dendroaspis j. kaimosae)

western green mamba (Dendroaspis viridis)

eastern green mamba (Dendroaspis angusticeps)

black mamba (Dendroaspis polylepis)

Description[edit]

Jameson's mamba is a long and slender snake with smooth scales and a tail which typically accounts for 20 to 25% of its total length. The total length (including tail) of an adult snake is approximately 1.5–2.2 m (4 ft 11 in–7 ft 3 in). It may grow as large as 2.64 m (8 ft 8 in).[12] The general consensus is that the sexes are of similar sizes, although fieldwork in southeastern Nigeria found that males were significantly larger than females.[13] Adults tend to be dull green across the back, blending to pale green towards the underbelly with scales generally edged with black. The neck, throat and underparts are typically cream or yellowish in colour. Jameson's mamba has a narrow and elongated head containing small eyes and round pupils. Like the western green mamba, the neck may be flattened. The subspecies D. jamesoni kaimosae, which is found in the eastern part of the species' range, features a black tail, while central and western examples typically have a pale green or yellow tail.[12] The thin fangs are attached to the upper jaw and have a furrow running down their anterior surface.[4]

Scalation[edit]

The number and pattern of scales on a snake's body play a key role in the identification and differentiation at the species level.[14] Jameson's mamba has between 15 and 17 rows of dorsal scales at midbody, 210 to 236 (Subsp. jamesoni) or 202 to 227 ventral scales (Subsp. kaimosae), 94 to 122 (ssp jamesoni) or 94 to 113 (Subsp. kaimosae) divided subcaudal scales, and a divided anal scale.[a] Its mouth is lined with 7 to 9 (usually 8) supralabial scales above and 8 to 10 (usually 9) sublabial scales below, the fourth ones located over and under the eye.[16] Its eyes have three preocular, three postocular and one subocular scale.[12]

Distribution and habitat[edit]

green snake on a tree
Subsp. jamesoni navigating a tree, Korup National Park
green snake on a tree from above
Dorsal view of scales

Jameson's mamba occurs mostly in Central Africa and West Africa, and in some parts of East Africa.[3] In Central Africa it can be found from Angola northwards to the Democratic Republic of the Congo, Republic of the Congo, Central African Republic, and as far north as the Imatong Mountains of South Sudan.[12] In West Africa it ranges from Ghana eastwards to Togo, Nigeria, Cameroon, Equatorial Guinea and Gabon.[3] In East Africa it can be found in Uganda, Kenya, Rwanda, Burundi and Tanzania.[12] The subspecies D. jamesoni kaimosae is endemic to East Africa and chiefly found in western Kenya, where its type locality is located, as well as in Uganda, Rwanda, and the adjacent Democratic Republic of the Congo.[3] It is a relatively common and widespread snake, particularly across its western range. Fieldwork in Nigeria indicated the species is sedentary.[13]

Found in primary and secondary rainforests, woodland, forest-savanna and deforested areas at elevations of up to 2,200 metres (7,200 ft) high,[12] Jameson's mamba is an adaptable species; it persists in areas where there has been extensive deforestation and human development. It is often found around buildings, town parks, farmlands and plantations.[12] Jameson's mamba is a highly arboreal snake, more so than its close relatives the eastern green mamba and western green mamba, and significantly more so than the black mamba.[13]

Behaviour and ecology[edit]

Jameson's mamba is a highly agile snake. Like other mambas it is capable of flattening its neck in mimicry of a cobra when it feels threatened, and its body shape and length give an ability to strike at significant range. Generally not aggressive, it will typically attempt to escape if confronted.[12][13]

Breeding[edit]

In Nigeria males fight each other for access to females (and then breed) over the dry season of December, January and February;[13] mating was recorded in September in the Kakamega Forest in Kenya.[17] Jameson's mamba is oviparous; the female lays a clutch of 5–16 eggs; in Nigeria laying was recorded from April to June, and most likely soon after November in Uganda.[17] Egg clutches have been recovered from abandoned termite colonies.[13]

Diet and predators[edit]

Jameson's mamba has been difficult to study in the field due to its arboreal nature and green coloration. It has not been observed hunting but is thought to use a sit-and-wait strategy, which has been reported for the eastern green mamba. The bulk of its diet is made up of birds and tree-dwelling mammals,[13] such as cisticolas, woodpeckers, doves, squirrels, shrews and mice.[17] Smaller individuals of under 100 cm (40 in) in length have been recorded feeding on lizards such as the common agama, and toads. There is no evidence they have adapted to hunting terrestrial rodents such as rats,[13] though they have been recorded eating rodents in Kenya, and have accepted them in captivity.[17]

The main predators of this species are birds of prey, including the martial eagle, bateleur, and the Congo serpent eagle. Other predators may include the honey badger, other snakes, and species of mongoose may also occasionally prey on the Jameson's mamba.[18]

Venom[edit]

green snake closeup
Subsp. kaimosae, the more venomous subspecies
green snake on a tree from below
Subsp. kaimosae from beneath, showing ventral scales

Jameson's mamba is classified as a Snake of Medical Importance in Sub-Saharan Africa by the World Health Organization,[b][19] although there are few records of snakebites.[17] Field observations over a 16-year period in the Niger Delta in southern Nigeria found that both humans and snakes were most active in rural areas during the rainy season, April to August, hence rendering this a peak period for snakebite. As well as succumbing to snakebites, workers were reported to have perished from falling from trees after encountering Jameson's mambas in the canopy of trees in palm oil plantations.[20] Snake bites are rare in cities but more common in forested areas in countries such as the Democratic Republic of the Congo; the country's poor infrastructure and lack of facilities render access to antivenom difficult.[21]

Like other mambas, the venom of the Jameson's mamba is highly neurotoxic.[22] Symptoms of envenomation by this species include pain and swelling of the bite site. Systemic effects include generalised swelling, chills, sweating abdominal pain and vomiting, with subsequent slurred speech, difficulty breathing and paralysis. Death has been recorded within three to four hours of being bitten;[17] there is an unconfirmed report of a child dying within 30 minutes.[22] With an average intravenous murine median lethal dose (LD50) of 0.53 mg/kg,[c] the venom of the eastern subspecies kaimosae is twice as potent as that of the nominate subspecies jamesoni at 1.2 mg/kg. The reason for this is unclear as the venom compositions are similar between the two subspecies, though kaimosae has higher concentrations of the potent neurotoxin-1.[11]

Similarly to the venom of most other mambas, Jameson's mamba's contains predominantly three-finger toxin agents as well as dendrotoxins. Other toxins of the three-finger family present include alpha-neurotoxin, cardiotoxins and fasciculins.[11] Dendrotoxins are akin to kunitz-type protease inhibitors that interact with voltage-dependent potassium channels, stimulating acetylcholine and causing an excitatory effect,[24] and are thought to cause symptoms such as sweating.[25] Unlike that of many snake species, the venom of mambas has little phospholipase A2.[11] Although cardiotoxins have been isolated in higher proportions from its venom than other mamba species, their role in toxicity is unclear and probably not prominent.[22]

Treatment[edit]

The speed of onset of envenomation means that urgent medical attention is needed.[17] Standard first aid treatment for any bite from a suspected venomous snake is the application of a pressure bandage, minimisation of the victim's movement, and rapid conveyance to a hospital or clinic. Due to the neurotoxic nature of green mamba venom, an arterial tourniquet may be beneficial.[26] Tetanus toxoid is sometimes administered, though the main treatment is the administration of the appropriate antivenom.[27] Trivalent and monovalent[d] antivenoms for the black, eastern green and Jameson's mambas became available in the 1950s and 1960s.[29]

Notes[edit]

  1. ^ A divided scale is one split down the midline into two scales.[15]
  2. ^ Snakes of Medical Importance include those with highly dangerous venom resulting in high rates of morbidity and mortality, or those that are common agents in snakebite.[19]
  3. ^ The strength or toxicity of snake venom is traditionally measured using the LD50 (lethal dose 50%) test; in essence, injecting a certain amount of toxin into number of mice and recording what dose kills half of them.[23]
  4. ^ A monovalent antivenom is specific for one toxin or species, while a polyvalent one is effective against multiple toxins or species.[28]

References[edit]

  1. ^ Luiselli, L., Wagner, P., Branch, W.R. & Howell, K. 2021. Dendroaspis jamesoni. The IUCN Red List of Threatened Species 2021: e.T13265784A13265793. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T13265784A13265793.en. Downloaded on 18 September 2021.
  2. ^ "Dendroaspis jamesoni". Integrated Taxonomic Information System. Retrieved 8 March 2015.
  3. ^ a b c d Uetz, Peter. "Dendroaspis jamesoni (Traill, 1843)". The Reptile Database. Retrieved 27 April 2012.
  4. ^ a b Traill, Thomas (1843). "Description of the Elaps Jamesoni [sic], a New Species from Demerara". Edinburgh New Philosophical Journal. 34: 53–55 – via Internet Archive.
  5. ^ Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. ISBN 978-1-4214-0135-5. (Dendroaspis jamesoni, p. 133).
  6. ^ "Dendroaspis". Integrated Taxonomic Information System. Retrieved 9 December 2013.
  7. ^ Liddell, Henry George; Scott, Robert (1980). A Greek-English Lexicon (Abridged ed.). Oxford University Press. pp. 109, 154. ISBN 978-0-19-910207-5.
  8. ^ Duméril, Auguste Henri André (1856). "Note sure les Reptiles du Gabon". Revue et magasin de zoologie pure et appliquée (in French). 2 (8): 553–562 [557–558].
  9. ^ Brongersma, Leo Daniel (1936). "Herpetological note XIII". Zoologische Mededelingen. 19: 135.
  10. ^ Loveridge, Arthur (1936). "New tree snakes of the genera Thrasops and Dendraspis from Kenya Colony". Proceedings of the Biological Society of Washington. 49: 63–66.
  11. ^ a b c d Ainsworth, Stuart; Petras, Daniel; Engmark, Mikael; Süssmuth, Roderich D.; Whiteley, Gareth; Albulescu, Laura-Oana; Kazandjian, Taline D.; Wagstaff, Simon C.; Rowley, Paul; Wüster, Wolfgang; Dorrestein, Pieter C.; Arias, Ana Silvia; Gutiérrez, José M.; Harrison, Robert A.; Casewell, Nicholas R.; Calvete, Juan J. (2018). "The medical threat of mamba envenoming in sub-Saharan Africa revealed by genus-wide analysis of venom composition, toxicity and antivenomics profiling of available antivenoms". Journal of Proteomics. 172: 173–189. doi:10.1016/j.jprot.2017.08.016. PMID 28843532.
  12. ^ a b c d e f g h Spawls, Stephen; Howell, Kim; Drewes, Robert; Ashe, James (2002). A Field Guide to the Reptiles of East Africa. Bloomsbury. pp. 463–464. ISBN 978-0-7136-6817-9.
  13. ^ a b c d e f g h Luiselli, Luca; Francesco M. Angelici; Godfrey C. Akani (2000). "Large elapids and arboreality: the ecology of Jameson's green mamba (Dendroaspis jamesoni ) in an Afrotropical forested region". Contributions to Zoology. 69 (3): 147–155. doi:10.1163/18759866-06903001.
  14. ^ Hutchinson, Mark; Williams, Ian (2018). "Key to the Snakes of South Australia" (PDF). South Australian Museum. Government of South Australia. Archived from the original (PDF) on 18 July 2019. Retrieved 19 August 2021.
  15. ^ Macdonald, Stewart. "snake scale count search". Australian Reptile Online Database. Retrieved 3 May 2019.
  16. ^ Chippaux, Jean-Phillipe; Jackson, Kate (2019). Snakes of Central and Western Africa (1 ed.). Johns Hopkins University Press. p. 109. ISBN 978-1-4214-2719-5.
  17. ^ a b c d e f g Spawls, Steve; Branch, Bill (2020) [1995]. The Dangerous Snakes of Africa. Bloomsbury. pp. 123–125. ISBN 978-1-4729-6028-3.
  18. ^ Mattison, Chris (1987). Snakes of the World. Facts on File, Inc. p. 164.
  19. ^ a b WHO Expert Committee on Biological Standardization. "Guidelines for the production, control and regulation of snake antivenom immunoglobulins" (PDF). WHO Technical Report Series, No. 964. pp. 224–226. Retrieved 1 January 2019.
  20. ^ Akani, Godfrey C.; Ebere, Nwabueze; Franco, Daniel; Eniang, Edem A.; Petrozzi, Fabio; Politano, Edoardo; Luiselli, Luca (2013). "Correlation between annual activity patterns of venomous snakes and rural people in the Niger Delta, southern Nigeria" (PDF). Journal of Venomous Animals and Toxins Including Tropical Diseases. 19 (1): 2. doi:10.1186/1678-9199-19-2. PMC 3707103. PMID 23849681.
  21. ^ Cunningham, Hugh Kinsella (9 September 2019). "How Snakebites Became an Invisible Health Crisis in Congo". Pulitzer Center. Retrieved 31 July 2021.
  22. ^ a b c van Aswegen, G.; van Rooyen, J.M.; Fourie, C; Oberholzer, G (1996). "Putative cardiotoxicity of the venoms of three mamba species". Wilderness & Environmental Medicine. 7 (2): 115–21. doi:10.1580/1080-6032(1996)007[0115:PCOTVO]2.3.CO;2. PMID 11990104.
  23. ^ "Snake Venom". School of Chemistry. University of Bristol. Retrieved 18 September 2021.
  24. ^ Laustsen, Andreas Hougaard; Lomonte, Bruno; Lohse, Brian; Fernández, Julián; Gutiérrez, José María (2015). "Unveiling the nature of black mamba (Dendroaspis polylepis) venom through venomics and antivenom immunoprofiling: Identification of key toxin targets for antivenom development". Journal of Proteomics. 119: 126–142. doi:10.1016/j.jprot.2015.02.002. PMID 25688917.
  25. ^ Hodgson, Peter S.; Davidson, Terence M. (1996). "Biology and treatment of the mamba snakebite". Wilderness and Environmental Medicine. 7 (2): 133–145. doi:10.1580/1080-6032(1996)007[0133:BATOTM]2.3.CO;2. PMID 11990107.
  26. ^ Dreyer, S. B.; Dreyer, J. S. (November 2013). "Snake Bite: A review of Current Literature". East and Central African Journal of Surgery. 18 (3): 45–52. ISSN 2073-9990.
  27. ^ Gutiérrez, José María; Calvete, Juan J.; Habib, Abdulrazaq G.; Harrison, Robert A.; Williams, David J.; Warrell, David A. (2017). "Snakebite envenoming" (PDF). Nature Reviews Disease Primers. 3 (3): 17063. doi:10.1038/nrdp.2017.63. PMID 28905944. S2CID 4916503.
  28. ^ Whyte, Ian (2012). "Antivenom update" (PDF). Australian Prescriber. 35 (5): 152–155.
  29. ^ Marais, Johan (2011). A Complete Guide to the Snakes of Southern Africa. Penguin Random House South Africa. ISBN 978-1-920544-64-5.