Who cares about toxins?

Atheris matildae

Ever since humans made the link between interactions with toxic creatures and illness or death, both a fascination and fear of these animals developed. Both venomous and poisonous found in toxic creatures have long been used to give an evolutionary advantage and play a vital role in prey capture, immobilization and defence. As the species evolved so did the toxins they use providing an immense library of active proteins (Fox and Serrano, 2007).

Ranitomeya variablis

Toxins of all kinds have been a focal point of much research within the last 70 years, we have gained a lot of knowledge on how these toxins cause the effects they do on their prey or attackers (Fox and Serrano, 2007). These dramatic and highly specific effects led to the investigation of using these protein cocktails for therapeutic uses (Fox and Serrano, 2007). Despite this it has only become prevalent in the past two decades to mine these biological wonders for treatment, detection, diagnosis and research on an ever growing and seemingly endless list of diseases. While very much a developing field treatments for Hypertension, angina, coronary angioplasty, chronic pain, diabetes and many forms of cancer have been created and are currently being used globally (Takacs and Nathan, 2014). With an estimated 20 million toxins remaining unexplored these will no doubt produce many more (Takacs and Nathan, 2014). This extensive assemblage will be a major source of novel therapeutics in the years to come (Takacs and Nathan, 2014).

Maybe those who allow hate to cloud their vision of these creatures will one day see the benefit of their existence, not only their sheer biological elegance, efficiency and beauty but also in their medicinal benefits to all.

References
Fox, J.W. and Serrano, S.M., 2007. Approaching the Golden Age of Natural Product Pharmaceuticals from Venom Libraries: An Overview of Toxins and Toxin-Derivatives Currently Involved in Therapeutic or Diagnostic Applications. Current Pharmaceutical Design, Vol:13, No:28, pp.2927-2934.
Takacs, Z., Nathan, S., 2014. Animal Venoms in Medicine. In: Wexler, P. (Ed.), Encyclopedia of Toxicology, 3rd edition vol 1. Elsevier Inc., Academic Press, pp. 252-259.
Images
Ranitomeya variablis: https://www.flickr.com/photos/reptiles4all/14002572367/in/photolist-kGJBVB-prYMqt-pHUdZR-gmkwk6-kdcZhz-pqEcKP-rqpEkd-hFm8jU-uwcFQk-quhfDR-prsT4M-q1DjjH-8RiiWU-8SmGSj-qTELsq-qXmmTJ-qkN961-nkmQVv-oPjuA9-99CajC/
Atheris matildae: https://www.flickr.com/photos/reptiles4all/15570371547/in/photolist-kGJBVB-prYMqt-pHUdZR-gmkwk6-kdcZhz-pqEcKP-rqpEkd-hFm8jU-uwcFQk-quhfDR-prsT4M-q1DjjH-8RiiWU-8SmGSj-qTELsq-qXmmTJ-qkN961-nkmQVv-oPjuA9-99CajC

Antivenom

Australia is notorious for is venomous creatures in particular the venomous snakes. Taipans, brown snakes, tiger snakes and death adders strike fear into the hearts of many people. Despite these species harbouring some incredibly toxic venoms, snake bites in Australia resulting in fatalities is now a rare incidence. Why so?

Desert death adder (Acanthophis pyrrhus) a species with a strong postsynaptic toxin component.

Production of high quality and relatively easily sourced antivenom, education of the public and quality medical care all are essential in reducing fatalities (White & Meier, 1995).

Antivenom comes in two forms;
Polyvalent antivenoms are a fantastic idea conceptually. The idea of having a wide-ranging effective antivenom to cover most if not all species would truly change the medicinal treatment of bites. This level of effectiveness however, has not been reached (White & Meier, 1995). Polyvalents are often used as a last alternative as reactions, often worse than the response to the venom, are common (White & Meier, 1995). Many other side effects are common and effectively counteracting all components of the venom is far from certain.

Monovalent antivenoms are highly specific and are produced to counteract the venom from one species. These serums may still cause reaction but are far less common. Due to their specific nature they also target most if not all of the venom component. These factors make monovalent a much safer option to treat a patient with a known envenomation (White & Meier, 1995).

Red-headed krait (Bungarus flaviceps baluensis) a species with strong presynaptic neurotoxin components.

Most dangerous Australian snake’s venom is dominated by postsynaptic neurotoxins. Neurotoxins are classed into postsynaptic and presynaptic depending on what area of the neuron is impacted (White & Meier, 1995). Bites from presynaptic neurotoxins often take a long time to manifest with few symptoms initially, however, after a certain length of time the neuron is permanently damaged and antivenom is no longer effective (White & Meier, 1995). Postsynaptic neurotoxins work oppositely with a fast onset of symptoms but reacts much more effectively to antivenom even hours after the envenomation (White & Meier, 1995).

References
White, J. and Meier, J., 1(995). Handbook of clinical toxicology of animal venoms and poisons (Vol. 236). CRC Press.

Images by Nick Weigner

Snakes of the sea

Sea snakes occupy a huge amount of the worlds' oceans filling various niches from the pelagic going Yellow bellied sea snake (Pelamis platura) to the Australian beaked sea snake (Enhydrina zweifeli) that regularly ventures into freshwater rivers (Cogger, 2014). However, all ‘true’ sea snakes are in the subfamily Hydrophiinae and share the same reproductive strategy of viviparity. The Sea kraits (Laticaudae subfamily, not to be confused with true sea snakes or land kraits of the Bungarus genus) show superficial similarities to true sea snakes with their largely marine habit, flattened paddle-like tail and highly toxic venom. Their habit of terrestrial exploitation for mating, laying eggs and digestion led to their own subfamily classification. In fact sea snakes are more closely related to the terrestrial elapids than the sea kraits (Cogger, 2014).

Laticauda colubrina

Pelamis platura

Sea snake and sea kraits are a prime example of convergent evolution both developing the analogous characteristic of the paddle shaped tail to aid in movement through water (McDowell, 1969). The tail of sea kraits is a simple paddle supported by unmodified vertebrae unlike the highly modified vertebrae of the true sea snakes (Fig.1). Even within the true sea snakes the paddle tail has evolved separately many times (Sanders et al, 2012).

Fig.1 Sections of modified vertebrae to aid in support of paddle tail of six sea snake species (Sanders et al, 2012).

Both families belong to the family Elapidae and are proteroglyphs (Cogger, 2014). Venom from both Hydrophiinae and Laticaudae species are often potently neurotoxic and have caused many fatalities globally (Tamiya et al, 1983; Heatwole, 1969). Most deaths occur in S.E Asia where a high diversity of both subfamilies is found, a strong reliance on net fishing practices and poor medical facilities all contribute to a heightened incidence of fatalities (Heatwole, 1969). Most species of both Sea snakes and Sea krait are notoriously docile however the curious nature of some species is often mistaken for aggression and causes an inflammatory reaction from divers (Cogger 2014).



References
Cogger, H., (2014). “Reptiles and amphibians of Australia.” 7th ed. CSIRO Publishing.

Heatwole, H., (1999). “Sea snakes.” (No. ed. 2). Krieger Publishing Company.

McDowell, S.B., (1969). “Notes on the Australian sea-snake Ephalophis greyi M. Smith (Serpentes: Elapidae, Hydrophiinae) and the origin and classification of sea-snakes.” Zoological Journal of the Linnean Society, Vol: 48, No: 3, pp. 333–349.

Sanders, K.L., Rasmussen, A.R. and Elmberg, J., (2012). Independent innovation in the evolution of paddle-shaped tails in viviparous sea snakes (Elapidae: Hydrophiinae). Integrative and comparative biology, First published online May 24, 2012 doi:10.1093/icb/ics066.

Tamiya, N., Sato, A., Kim, H.S., Teruuchi, T., Takasaki, C., Ishikawa, Y., Guinea, M.L., McCoy, M., Heatwole, H. and Cogger, H.G., (1983). “Neurotoxins of sea snakes genus Laticauda.” Toxicon, Vol:21, No:3 pp.445-447.

Images
Pelamis platura: Cogger, H. (2014). “Reptiles and amphibians of Australia.” 7th ed. CSIRO Publishing.
Laticauda colubrina :https://www.robertharding.com/preview/860-282736/banded-sea-krait-surface-amatildecopydatildecopye-islet-new-caledonia/