Beware the Deadly Beauty of the Marbled Cone Snail – by AquaViews


marbled cone snailThe unique marbled cone snail is found from the southern tip of India to Okinawa, Japan, and southeast to New Caledonia and Samoa. It feeds on other snails, including some within its own species. When it attacks its prey, it sticks out its long white proboscis to shoot a poison-laden harpoon, sometimes attacking its prey multiple times over. The prey becomes paralyzed and its muscles begin to relax irreversibly. Once the prey lies flaccid outside its shell, the snail can begin to devour it. The species is found in fairly shallow water, typically on coral reef platforms or lagoon pinnacles, as well as in sand, under rocks, or among sea grass. The marbled cone snail is unusual among marine snails in that it is quite active during the day, and not strictly nocturnal.

Some of the peptide toxins found in the venom have been characterized, one of which is being developed as a potential drug for pain. The venomous toxins are produced in the venom duct, which is attached to a large bulb called the venom bulb. The venom bulb contracts to push venom into the harpoons, similar to squeezing a pipette to force liquid out. The longest dissected venom duct is over three feet long and came from a cone snail that was only five inches long!

The harpoons are evolutionarily modified teeth that are stored in a radular sac. The harpoon is like a disposable, hypodermic needle. Once the cone snail uses a harpoon to inject venom into its prey, it is discarded. The snail must reload another harpoon before it can strike again. Thankfully for snail, they have around twenty harpoons at various developmental stages in storage so a snail will always have another harpoon ready to load and use. The venom is made of a small number of amino acids. Cone snails have the ability to make hundreds of toxins and deliver a cocktail, or mixture of toxins, when injecting its prey with venom.

marbled cone snailIn the nervous system communication can be stopped by blocking certain ion channels. These channels open to let a chemical signal travel from neuron to neuron. Eventually the signal reaches a muscle cell that tells it to contract. This is how you can bend your finger and kick a ball. Cone snail toxins, called conotoxins, block these channels. When the channels are blocked, communication in the nervous system stops. This causes paralysis.

Different toxins stop different channels. Some channels control just our skeletal muscles, some control our heart muscles, and some control our organs. Based on the type of snail, the toxin might cause different kinds of paralysis. The moral of this story seems to be not to mess with the marbled cone snail under any circumstances when you see one, lest you become a target for its painful harpoon!

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