The Value of Biodiversity – Pain Relief and Cone Snails

By now, you are probably well aware that we are in a biodiversity crisis – we are losing species on the planets at a rate that may be unparalleled since the end of the Cretaceous period some 65 million years ago.  But how can we convey the importance of the loss of biodiversity? Talking about the extinction of the “warm fuzzy” mammals and birds helps, but often it is still hard to make a connection with these species because most of us do not interact with them, or their environments, on a daily basis.

What if we relate it to something we all understand…. such as pain? We have all experienced the ineffectiveness of pain medications in truly controlling pain. From headaches to the aftermath of surgery, there are really very few medications that truly control pain without having detrimental side effects on our bodies. Recent studies in cone snails (Genus Conus), which live on coral reefs, have unveiled a number of small peptide molecules, called conotoxins, that may be the next-generation of pain relievers. And since coral reefs are a threatened marine ecosystem, this may be the perfect way to talking about biodiversity.

Conus-geographicus

 

So first, a little about the cone snails. There are about 500 species of cone snails. Basically, cone snails come in two flavors,  hunters that prey on other snails in mid-level ocean waters, and ocean floor lurkers that feed on much larger fish. Of the two, the latter are the most deadly to humans. Because cone snails are not much faster than their land snail cousins, they have to work fast to kill their much quicker prey before it can be caught and eaten by other ocean predators. They do this through the use of a transparent “harpoon”, located on the end of their proboscis, that injects a fast-acting venom which can paralyze their prey within the span of two seconds, ensuring that the fish doesn’t swim out of the snail’s reach before dying.

While undeniably dangerous, what is remarkable about cone snails is in the incredible complexity of their venom. While many other venomous species, such as snakes or venomous fish, have two or three different kinds of toxins in their venom, cone snail venom contains over a hundred separate toxins, each specialized in disrupting the nervous systems of their prey. This makes cone snail venom powerful, paralytic, and most importantly, painless. One species of cone snail  (the geographic cone snail- or Conus geographus – shown above)   is also referred as the cigarette snail, since an individual who is stung by the snail has about as much time to live as it would take to smoke a cigarette.  Dozens of human deaths have been attributed to cone snail venom, and in many of these occurrences the victim is unaware of having been stung, as the toxins within the venom create a natural painkiller that, when refined by scientists, can be over a hundred times more powerful than morphine.

Today, scientists are working on developing painkillers for medical use that use the toxins present in cone snail venom. Studies have indicated that the conotoxin indirectly inhibits sodium channels in the neurons by interacting with GABA receptors (a form of neurotransmitter).  Here is a quick review of how channel proteins, such as sodium channels, work:

 

 

Initially, there were complications in using the conotoxins orally, since the compounds are easily broken down by the digestive system, which meant that in order to be used as a painkiller the toxin had to be injected directly into the spinal cord. However, researchers have been able to modify the structure of some of the conotoxins so that it is ring-shaped, which prevents it from being broken down by digestive enzymes. Animals studies of these compounds have been promising. If successful, these new painkillers could serve as a more effective, and non-addictive, alternative to morphine, helping improve the lives of people around the world suffering from painful afflictions and diseases.

The new interest in cone snails comes with a conservation warning, however. Cone snails are already at a risk from shell collectors, and should researchers develop a painkiller using cone snail venom, it’s very possible that overfishing could decimate this remarkable species.  The reefs that these species inhabit is also in danger, since overfishing, climate change and pollution are creating significant problems with this ecosystem. Estimates are that almost 20% of the coral reef ecosystems are already lost, and other 15% may be lost in the next 10 years. Because of this, several scientists are attempting to find a balance between harvesting cone sails for their medical properties and preserving the species’ survival and the survival of its native equatorial reefs.

 

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