Venomous apparatus

Introduction

The snake venom inoculator apparatus consists of a salivary gland, referred to as a venom gland, connected by a channel to one or more hooks, then defined as hooks or canaliculate tooth. There are different structures of this device that varies according to the families of snakes. In viperids, this structure is called solenoglyphic and is distinguished by relatively long hooks which, when unused are retracted along the maxillary maxilla. At the time of use, including possible muscle stretching, visible during and after ingestion of prey, the hooks are deployed forward as shown in Figures A and B below. (Goyffon, M., & Chippaux, J. P. (1990)).

Morphology – composition

The venom gland, located behind the eyes, consists of two parts. The first, main, synthesizes and stores the venom while the second, placed upstream, activates the venom during its passage (Rollard, C., Chippaux, J.P., & Goyffon, M. (2015)). Venom can be stored for a long time but remains active even after long periods of fasting; Moreover, the glands being controlled by independent muscles, the amount injected is thus dependent on the choice of the snake. When the snake plants its hooks, two important points must be distinguished. The first is that the venom flow time inside the prey is shorter than the penetration time of the hooks. A suction mechanism seems to avoid any unnecessary flow thus saving a maximum of venom. The second point is that the injected venom is more important in a defensive situation than in a predatory situation (Young, B. A., & Zahn, K. (2001)). This last point clearly brings the proof of competence to the contextual analysis of ophidians.

Popeia fucata - Dentition solénoglyphe - Appareil innoculateur - Pahang Province Malaisie - Credit: Manuel Ebert
Popeia fucatus – Solenoglyphic Teeth – Inoculators- Pahang Province (Malaisie) – Credit: Manuel Ebert

The mode of action, whose dual objective of quickly immobilizing prey and starting digestion is governed by the composition that may vary according to sex, age, season and environmental parameters, but also by the snake diet. (Zelanis, A., Andrade-Silva, D., Rocha, M.M., Furtado, M.F., Serrano, S.M., Junqueira-de-Azevedo, I.L., & Ho, P.L. (2012)). Moreover it has been shown that there may be differences in the two venom glands of the same specimen (Rollard, C., Chippaux, J.P., & Goyffon, M. (2015)).

In order to achieve these goals, venoms are composed mainly of enzymes and toxins.

The term toxin is generic and defines molecules of variable molecular weight with an action on the name whose suffix is ​​attached. Ex: Nephrotoxin is a toxin, the nature of which is not known, which acts on the kidneys.

The “-toxins” can be enzymes, large proteins, that cut another protein (always the same) or to transform it into another protein that will have a different mode of action, or to change its role in the cell or organism.

The “toxins” may also be peptides. That is, small, and therefore low molecular weight proteins that replace or combine with other molecules in the body to modify or prevent their function. These are the “toxins” as we hear about it. (Chippaux, J.P., private exchange, 2015).

While it is commonly accepted that the usefulness of venom is to kill prey, it is also regularly conveyed the idea that it would also serve to predigate prey. Studies in Taiwan on Trimeresurus gracilis and Viridovipera stejnegeri seem to invalidate this hypothesis (Chu, C. W., Tsai, T. S., Tsai, I.H., Lin, Y.S., & Tu, M.C. (2009)).

Sources:

CHIPPAUX, J. P., & Goyffon, M. (2006). Envenimations et intoxications par les animaux venimeux ou vénéneux. I. Généralités. Médecine tropicale, 66(3), 215-220.

Goyffon, M., & Chippaux, J. P. (1990). Animaux venimeux terrestres. Encyclopédie Médico-Chirurgicale.

Rollard, C., Chippaux, J. P., & Goyffon, M. (2015). La fonction venimeuse.

Young, B. A., & Zahn, K. (2001). Venom flow in rattlesnakes: mechanics and metering. Journal of experimental biology, 204(24), 4345-4351.

Zhang, X. C., Kearney, A., Gibbs, F. J., & Hack, J. B. (2016). Snakebite! Crotalinae Envenomation of a Man in Rhode Island. Rhode Island medical journal (2013), 99(1), 25.

Zelanis, A., Andrade-Silva, D., Rocha, M. M., Furtado, M. F., Serrano, S. M., Junqueira-de-Azevedo, I. L., & Ho, P. L. (2012). A transcriptomic view of the proteome variability of newborn and adult Bothrops jararaca snake venoms. PLoS Negl Trop Dis, 6(3), e1554.

Chan, T. Y. K., & Hung, L. K. (2010). Digital gangrene following a green pit viper bite. Southeast Asian J Trop Med Public Health, 41(1), 192-94.

Chen, C. M., Wu, K. G., Chen, C. J., & Wang, C. M. (2011). Bacterial infection in association with snakebite: A 10-year experience in a northern Taiwan medical center. Journal of Microbiology, Immunology and Infection, 44(6), 456-460.

Liu, P. Y., Shi, Z. Y., Lin, C. F., Huang, J. A., Liu, J. W., Chan, K. W., & Tung, K. C. (2012). Shewanella infection of snake bites: a twelve-year retrospective study. Clinics, 67(5), 431-435.

Chen, Y. C., Chen, M. H., Yang, C. C., Chen, Y. W., Wang, L. M., & Huang, C. I. (2007). Trimeresurus stejnegeri envenoming during pregnancy. The American journal of tropical medicine and hygiene, 77(5), 847-849.

WANG, W., LI, Q. B., & CHEN, Q. F. (2013). Analysis of Different Clinical Characteristics of Two Kinds of Trimeresurus Stejnegeri Snakebites in Guangxi Province. Chinese General Practice, 19, 040.

Chu, C. W., Tsai, T. S., Tsai, I. H., Lin, Y. S., & Tu, M. C. (2009). Prey envenomation does not improve digestive performance in Taiwanese pit vipers (Trimeresurus gracilis and T. stejnegeri stejnegeri). Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 152(4), 579-585.