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Snails that shoot poison darts

© Esther Wullschleger

It is highly recommended not to touch any organisms while diving in a coral reef: Either it harms you or you harm it. Venom is a common mean to defend oneself among coral reef creatures, or to use as a weapon against prey. Especially cone snails have some impressive toxins. But, maybe you are lucky to see one or the other cone snail hunting for food by shooting a poison dart at its prey.

If a small fish comes by, the cone snail Conus purpurascens fires a harpoon-like dart at it. Within seconds the highly effective toxin in the dart paralyses the victim, and the snail puts its long and flexible mouth part forward to gulp the prey immediately. This hunting behavior may sound strange in the ear of people not familiar with snails, given that snails are known as extremely sluggish animals! Some cone snail species are equipped with a veritable "ordnance depot": a dozen of darts ready to fire in all directions, even backwards. And some have toxins that can be dangerous to humans. On the other hand, human collectors are a serious danger to cone snails, because the picturesque shells of these snails are on high demand. The rare Conus gloriamaris, the "Glory of the Sea", has been traded at audaciously high prizes.

Cone snails live in coastal sea areas in the temperate and tropical climate zone. They aren't confined to coral reefs - some species live in deeper sea and some on rocky ground. The different species hunt and feed on small marine organisms such as fish, other snails or worms. Due to their effective toxin, the relatively large fish-eating species are of potential danger to humans.

Conus geographus from the Indopacific region reaches 13 centimetres of shell length and has been allegedly the cause of a number of human deaths. Confirmed deaths through cone snails occurred once uninformed tourists collected cone shells in the Pacific region. It is advised to attain immediate medical attention if stung by a cone snail. If possible, note down a description of the cone snail type in question.

Cone snails do not show aggressiveness towards humans and will only sting in defense when disturbed (victims are usually careless shell collectors). Keep in mind that collecting live shells threatens biodiversity and requires a permit. The unique venoms of some cone snails are investigated in medical science because of their pharmacological qualities. New treatments in development, based on these toxins, might help against neurological auto-immune diseases, cancer or chronic pain. However, fears are great that many cone snails are in serious threat due to habitat distruction and exploitative collecting - both for their shells and for medical research.