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Unexpected lack of specialisation in the flow properties of spitting cobra venom

Avella, Ignazio, Barajas-Ledesma, Edgar, Casewell, Nicholas ORCID: https://orcid.org/0000-0002-8035-4719, Harrison, Robert, Rowley, Paul, Crittenden, Edouard, Wüster, Wolfgang, Castiglia, Riccardo, Holland, Chris and van der Meijden, Arie (2021) 'Unexpected lack of specialisation in the flow properties of spitting cobra venom'. The Journal of Experimental Biology, Vol 224, jeb229229.

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Abstract

Venom spitting is a defence mechanism based on airborne venom delivery used by a number of different African and Asian elapid snake species (‘spitting cobras’; Naja spp. and Hemachatus spp.). Adaptations underpinning venom spitting have been studied extensively at both behavioural and morphological level in cobras, but the role of the physical properties of venom itself in its effective projection remains largely unstudied. We hereby provide the first comparative study of the physical properties of venom in spitting and non-spitting cobras. We measured the viscosity, protein concentration and pH of the venom of 13 cobra species of the genus Naja from Africa and Asia, alongside the spitting elapid Hemachatus haemachatus and the non-spitting viper Bitis arietans. By using published microCT scans, we calculated the pressure required to eject venom through the fangs of a spitting and a non-spitting cobra. Despite the differences in the modes of venom delivery, we found no significant differences between spitters and non-spitters in the rheological and physical properties of the studied venoms. Furthermore, all analysed venoms showed a Newtonian flow behaviour, in contrast to previous reports. Although our results imply that the evolution of venom spitting did not significantly affect venom viscosity, our models of fang pressure suggests that the pressure requirements to eject venom are lower in spitting cobras than in non-spitting cobras.

Item Type: Article
Subjects: QU Biochemistry > QU 4 General works
WD Disorders of Systemic, Metabolic or Environmental Origin, etc > Animal Poisons > WD 400 General works
WD Disorders of Systemic, Metabolic or Environmental Origin, etc > Animal Poisons > WD 410 Reptiles
Faculty: Department: Biological Sciences > Department of Tropical Disease Biology
Digital Object Identifer (DOI): https://doi.org/10.1242/jeb.229229
Depositing User: Cathy Waldron
Date Deposited: 12 Apr 2021 16:50
Last Modified: 12 Apr 2021 16:50
URI: https://archive.lstmed.ac.uk/id/eprint/17574

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