Tears of Venom: Hydrodynamics of Reptilian Envenomation

Young, Bruce A.; Herzog, Florian; Friedel, Paul; Rammensee, Sebastian; Bausch, Andreas R.; Hemmen, J. Leo van

doi:10.1103/physrevlett.106.198103

Cited by 23 publications

(19 citation statements)

References 11 publications

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“…First, we measured the rheological behavior of the venom fluid. The results confirm trends documented by Balmert et al [21] and Young et al [22], i.e., that the venom showed a shear-thinning behavior. This implies that flow is less viscous at high shear rates.…”

Section: Discussionsupporting

confidence: 91%

3D Flow in the Venom Channel of a Spitting Cobra: Do the Ridges in the Fangs Act as Fluid Guide Vanes?

et al. 2013

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The spitting cobra Naja pallida can eject its venom towards an offender from a distance of up to two meters. The aim of this study was to understand the mechanisms responsible for the relatively large distance covered by the venom jet although the venom channel is only of micro-scale. Therefore, we analysed factors that influence secondary flow and pressure drop in the venom channel, which include the physical-chemical properties of venom liquid and the morphology of the venom channel. The cobra venom showed shear-reducing properties and the venom channel had paired ridges that span from the last third of the channel to its distal end, terminating laterally and in close proximity to the discharge orifice. To analyze the functional significance of these ridges we generated a numerical and an experimental model of the venom channel. Computational fluid dynamics (CFD) and Particle-Image Velocimetry (PIV) revealed that the paired interior ridges shape the flow structure upstream of the sharp 90° bend at the distal end. The occurrence of secondary flow structures resembling Dean-type vortical structures in the venom channel can be observed, which induce additional pressure loss. Comparing a venom channel featuring ridges with an identical channel featuring no ridges, one can observe a reduction of pressure loss of about 30%. Therefore it is concluded that the function of the ridges is similar to guide vanes used by engineers to reduce pressure loss in curved flow channels.

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Section: Discussionsupporting

confidence: 91%

3D Flow in the Venom Channel of a Spitting Cobra: Do the Ridges in the Fangs Act as Fluid Guide Vanes?

et al. 2013

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“…Most prior research has focussed on the spitting behavior itself, treating it as a peculiar oddity in nature without investigating associated evolutionary trends (e.g., venom composition) [16], and it has been described at the morphological [17,18], mechanical [12,19,20] and behavioural levels [13,21]. Hooding is a distinctive characteristic of the genera Hemachatus , Naja and Ophiophagus and members of these genera are found in Africa and Asia [22].…”

Section: Introductionmentioning

confidence: 99%

How the Cobra Got Its Flesh-Eating Venom: Cytotoxicity as a Defensive Innovation and Its Co-Evolution with Hooding, Aposematic Marking, and Spitting

Panagides

Jackson

Ikonomopoulou

et al. 2017

Toxins

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The cytotoxicity of the venom of 25 species of Old World elapid snake was tested and compared with the morphological and behavioural adaptations of hooding and spitting. We determined that, contrary to previous assumptions, the venoms of spitting species are not consistently more cytotoxic than those of closely related non-spitting species. While this correlation between spitting and non-spitting was found among African cobras, it was not present among Asian cobras. On the other hand, a consistent positive correlation was observed between cytotoxicity and utilisation of the defensive hooding display that cobras are famous for. Hooding and spitting are widely regarded as defensive adaptations, but it has hitherto been uncertain whether cytotoxicity serves a defensive purpose or is somehow useful in prey subjugation. The results of this study suggest that cytotoxicity evolved primarily as a defensive innovation and that it has co-evolved twice alongside hooding behavior: once in the Hemachatus + Naja and again independently in the king cobras (Ophiophagus). There was a significant increase of cytotoxicity in the Asian Naja linked to the evolution of bold aposematic hood markings, reinforcing the link between hooding and the evolution of defensive cytotoxic venoms. In parallel, lineages with increased cytotoxicity but lacking bold hood patterns evolved aposematic markers in the form of high contrast body banding. The results also indicate that, secondary to the evolution of venom rich in cytotoxins, spitting has evolved three times independently: once within the African Naja, once within the Asian Naja, and once in the Hemachatus genus. The evolution of cytotoxic venom thus appears to facilitate the evolution of defensive spitting behaviour. In contrast, a secondary loss of cytotoxicity and reduction of the hood occurred in the water cobra Naja annulata, which possesses streamlined neurotoxic venom similar to that of other aquatic elapid snakes (e.g., hydrophiine sea snakes). The results of this study make an important contribution to our growing understanding of the selection pressures shaping the evolution of snake venom and its constituent toxins. The data also aid in elucidating the relationship between these selection pressures and the medical impact of human snakebite in the developing world, as cytotoxic cobras cause considerable morbidity including loss-of-function injuries that result in economic and social burdens in the tropics of Asia and sub-Saharan Africa.

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“…the mangrove and banded snakes) have grooved fangs located near the back of their jaws. Unlike vipers, these snakes leave their fangs embedded as their venom works its way down the groove and into the wound (Young et al, 2011). However, colubrid fangs also lack ornamentation (their grip is maintained through muscle action), as they still must be removed after injection.…”

Section: Injection/removalmentioning

confidence: 99%

Making a point: shared mechanics underlying the diversity of biological puncture

Anderson

2018

Journal of Experimental Biology

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A viper injecting venom into a target, a mantis shrimp harpooning a fish, a cactus dispersing itself via spines attaching to passing mammals; all these are examples of biological puncture. Although disparate in terms of materials, kinematics and phylogeny, all three examples must adhere to the same set of fundamental physical laws that govern puncture mechanics. The diversity of biological puncture systems is a good case study for how physical laws can be used as a baseline for comparing disparate biological systems. In this Review, I explore the diversity of biological puncture and identify key variables that influence these systems. First, I explore recent work on biological puncture in a diversity of organisms, based on their hypothesized objectives: gripping, injection, damage and defence. Variation within each category is discussed, such as the differences between gripping for prey capture, gripping for dispersal of materials or gripping during reproduction. The second half of the Review is focused on specific physical parameters that influence puncture mechanics, such as material properties, stress, energy, speed and the medium within which puncture occurs. I focus on how these parameters have been examined in biology, and how they influence the evolution of biological systems. The ultimate objective of this Review is to outline an initial framework for examining the mechanics and evolution of puncture systems across biology. This framework will not only allow for broad biological comparisons, but also create a baseline for bioinspired design of both tools that puncture efficiently and materials that can resist puncture.

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Tears of Venom: Hydrodynamics of Reptilian Envenomation

Cited by 23 publications

References 11 publications

3D Flow in the Venom Channel of a Spitting Cobra: Do the Ridges in the Fangs Act as Fluid Guide Vanes?

3D Flow in the Venom Channel of a Spitting Cobra: Do the Ridges in the Fangs Act as Fluid Guide Vanes?

How the Cobra Got Its Flesh-Eating Venom: Cytotoxicity as a Defensive Innovation and Its Co-Evolution with Hooding, Aposematic Marking, and Spitting

Making a point: shared mechanics underlying the diversity of biological puncture

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