Perhaps the most infamous method of venom delivery is through fangs.
Fangs are essentially specialised teeth used to inject venom directly into the body of another organism. They are most commonly found in reptiles, but have also evolved in arachnids such as the Funnel-Web Spider. This post will focus on the most advanced fangs seen in reptiles, which can be found on Vipers. Vipers are famous for their long fangs which act as syringes to inject large amounts of venom into their prey.
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| A Bush Viper, native to sub-Saharan Africa, and a great looking snake! |
Each kill made by a Komodo Dragon is a narrative in itself.
After tracking down a likely prey item such as a buffalo, a Komodo Dragon will charge towards it and latch onto any part of the body. It does not need to go for the windpipe like other large predators, it does not even need to overpower its prey. In fact, after a brief struggle, the Komodo Dragon releases the buffalo, leaving a nasty, but easily survivable flesh wound. After escaping with its life, it runs far away and continues with its life. In the coming days, however the buffalo becomes weaker and weaker.The bite area is now horrifically infected, and the animal is fighting for life. Another day passes and the buffalo can no longer remain standing, and within a matter of hours, it succumbs and dies. This is when the Komodo Dragon reappears. After following the scent of the animal for days, often with several other dragons, it begins to eat, sparking a feeding frenzy as more dragons arrive.
It has long been thought that the Komodo Dragon utilised bacteria in its mouth to inflict a lethal infection in its prey. However, in more recent observations, it has been noted that a bitten prey item experiences symptoms that bacterial infections do not induce, and that the death is alot faster than a bacterial infection alone could cause.
When analysing the jaw area of a Komodo Dragon, small venom glands were found. Saliva samples confirmed the presence of a venom that can prevent blood clotting, cause muscle paralysis and a decrease in blood pressure.
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| The potent saliva of a Komodo Dragon. |
This shows that it is entirely possible to deliver venom with simple teeth, so how did the advanced hollow fangs arise?As with all evolutionary debates, it is about fitness. The more venom administered the better. A prey item that dies in a few minutes is less energy-draining for the predator than one that takes days to die, and it also reduces the amount of time the predator needs to stay out in an environment where they are not the top predator. This is perhaps the reason why snakes have evolved such potent venom in comparison to monitors, as snakes are often preyed upon, while the much larger Komodo Dragon and Perentie are not.
The question now is how did simple teeth turn into the hypodermic needles seen in some snakes today? The answer involves an intermediate stage. Many animals, during their embryonic stages of life, show physical traits which are similar to an ancestral group. A key example of this is the tail seen on human embryos during development. In other words, the embryonic stages of animals gives us an insight into some of the traits of its ancestors. Before the fangs of a viper erupt from its gum, they are not hollow. Instead, they are grooved, and as development continues and the fang erupts, this groove is enclosed to form a hollow structure. Grooved teeth can be seen today in many venomous snakes lizards, and they facilitate the transport of venom the gland in the mouth of the animal to the body of the prey.
It is hypothesised that the grooved tooth is the intermediate stage between a simple tooth and a hollow fang. In time, individuals with a deeper groove became dominant, due to their ability to administer more venom. The deep groove eventually closed over completely, and turned what was once a tooth into a hypodermic needle.
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| A useful diagram showing the different parts of a snake's venom delivery system. |
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| The impressive fangs of a Gaboon Viper. |
The Evolution of Nature's Deadliest Weapon
Sources:
http://www.nature.com/news/2010/101117/full/news.2010.617.html - Accessed 18Mar14
http://www.mapoflife.org/topics/topic_388_Venom-and-venom-fangs-in-snakes-lizards-and-synapsids/ - Accessed 18Mar14
http://en.wikipedia.org/wiki/Sinornithosaurus - Accessed 18Mar14
http://news.nationalgeographic.com.au/news/2009/05/090518-komodo-dragon-venom.html- Accessed 22Mar14
http://www.youtube.com/watch?v=JcEapEccNIc Accessed 26Mar14
Images:
http://sciencelakes.com/data_images/out/25/8850662-bush-viper-snake.jpg Accessed 29Mar14
http://upload.wikimedia.org/wikipedia/commons/b/b4/Bitis_gabonica_fangs.jpg -Accessed 29Mar14
http://jeanbont.pbworks.com/f/1299294821/snake%20fangs%20and%20venom.png -Accessed 29Mar14
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwnScSHSR-4z9m4CCzSnD-guyCAEeBiQBbu0C9oJpsND9s7aNI-uqRXkGKzCe9664_xFxR-hnAM9Bj4IyHl3daITWW4Ph_dlti-VWD2fZlG5evIFN6HvSarZV3IxTypojKkZN_PiGmaOnv/s1600/koodo+dragon+saliva.jpg -Accessed 29Mar14
http://www.youtube.com/watch?v=JcEapEccNIc - Accessed 30 Mar14
Absolutely fascinating! Whenever humans come up with a good idea (e.g. hypodermic needles), one only has to look to nature to find that it came up with the idea first (as you so rightly note here). Adders and vipers are my favourite group of snakes, most likely because they are generally so “lazy”, but can be surprisingly fast! I’ve heard that Puff adders (which, like Gaboon vipers, have amazingly powerful bites) have the fastest striking speed of all snakes – any truth there? Also, what is the difference between a viper and an adder, because I’ve heard Gaboon vipers referred to as adders? Very nice post!
ReplyDeleteThe puff adder is considered to have the fastest strike of any snake, however this title is somewhat disputed. The death adder also has an incredibly fast strike, and is reportedly as fast if not faster than the puff adder. I wish I could say for certain, but after much research, I have been unable to find a definitive and accurate study on the striking speed of snakes.
DeleteTo answer your second question, the terms viper and adder are interchangeable. They both refer to any snake of the family Viperidae. However, despite the death adder’s name, it is not in fact a member of the viper family. Like most of Australia’s venomous snakes, it is an elapid. The term death adder was used because of its viper-like appearance and behaviour.
I really like your blog! Always found venemous animals so interesting! I didn't know that the Komodo Dragon actually had venom, I have always thought the bite from this animal was dangerous due to bacterias, but know I know better:) also fascinating how you explain about the intermediate stage, never thought about how simple teeth have been modified to fangs, cool:)
ReplyDeleteReally cool blog love the bush viper pic. Lots of really interesting information in here. However I wonder if the advantages for snakes with enclosed fangs was not that they can deliver more venom but less. Venom as you probably know is a very expensive resource hence why snakes commonly dry bite. Enclosed fangs ensure venom is injected directly into the victim and therefore is less wasteful. Either less venom has to be produced or more can be saved?
ReplyDelete