We're all familiar with top 10 lists of "the most deadly" animals, but what makes these animals deadly? In today's Feed the Data Monster (FtDM) read, we'll touch on the distinctions between the world's most venomous animals and what, on a molecular level, makes them so dangerous.
Now, before we jump into the list, one important distinction we need know is the difference between poison and venom. Often times, people confuse the two terms in thinking that they mean the same thing. However, this is not the case. A poisonous organism is toxic because it is touched or ingested. A venomous organism is associated with being toxic because it delivers its poison via some form of injection. Let's go over a few examples to clarify this distinction.
Hippomane mancinella [the manchineel tree], a species native to the tropical regions of the Americas, is poisonous. If you touch the tree, you will come in contact with phorbol, which causes severe skin irritation. Crotalus atrox [the Western diamondback rattlesnake], on the other hand, is a venomous animal found in the deserts of Mexico and the United States. You can touch a rattlesnake and be fine, but if it bites you then you're in trouble! This injection [which harbors proteolytic enzymes, metalloproteinases, cytotoxins, and myotoxins that ultimately destroy/impact blood flow] is why the animal is referred to as venomous. Plants and fungi can only be poisonous because they don't "attack", whereas animals can be classified as venomous [i.e. snakes, spiders, scorpions] or poisonous [i.e. pufferfish, poison dart frogs, salamanders]. Even so, it's easy to see how the line between poison and venom can be blurry. Chemically harmful microorganisms are simply classified as "toxic".
Varanus komodensis [the komodo dragon] is an animal that we once confused as poisonous because of the bacteria living in its mouth. Today, thanks to the findings by the quirky Dr. Bryan Fry and his colleagues, we now know that the komodo dragon actually has glands that release venom through its mouth.
So, what are the advantages to being poisonous v. venomous anyway? Well, it depends. Organisms belonging to either party can use their toxins as defense mechanisms, to capture prey, or both. Though, it is more common that poisonous organisms have evolved in this way as a line as defense and that venomous organisms evolved as a means of developing sophisticated predation/defense combo methods.
Now, finally, onto that list we've all been waiting for...just kidding! It's difficult to "rank" how venomous or poisonous an organism is because the references used are often inconsistent. Additionally, new research on venom/poison is continuously produced. The big question, then, is how were existing lists created? Well, that's hard to say too.
A quick Google search for "top venomous animals" will easily show discrepancies between lists and links. And that's because it's almost impossible to compare animals of completely different groups to one another, which makes sense. A dog's hair is much different from human hair, just like a box jellyfish is much different from a blue-ringed octopus. The majority of venomous rankings out there are based on how quickly a reference animal, such as a human, dies from an injection. Nevertheless, this too can vary. Each individual response differs depending on their age, sex, and genetic composition. This is also true for the perpetrator [the poisonous or venomous animal]. Not to mention, as we've gone through via a few living examples, the chemical composition of the poison or venom differs between taxonomical groupings.
One form of ranking that's more accurate and consistent is a comparison within groupings. For example, there are some rankings between venomous spiders. This makes sense, since the venom in a spider species will be more similar in chemical composition to other spiders in contrast to comparing spider venom to cone snail and ant venom. A continued emphasis on the ranking and understanding of venom chemical composition within a taxonomical group first, before comparing between taxonomical groups, is thus crucial to our understanding of how venomous a given species is amongst all known venomous organisms.
Perhaps all this talk about poisonous and venomous organisms is causing onset paranoia of them, especially when considering how difficult it is to rank poison or venom potency between groupings. Fear not! One thing we can measure is how many deaths are caused by what organisms annually. Actually, Bill Gates organized a team to accomplish just that and display it in an infographic form for 2014. What this infographic tells us is that venomous and poisonous organisms are responsible for a minority of human deaths. This makes sense because, as mentioned before, poisonous and venomous organisms have evolved for defense and/or catching prey [and we know humans aren't prey for any of these organisms]. So, ultimately, safety from poisonous and and venomous organisms boils down to respecting boundaries. Moreover, there is a lot of biomedical promise in researching the chemical composition of poisons and venoms, showing the value in the conservation of these organisms. For example, did you know that Prialt, an analgesic [painkiller] for chronic pain, is derived from Conus magus venom [which is known to kill a human in an average of 13 minutes]?
Questions? Comments? Confusions?
Until next time, FTDMers, stay hungry!