Cone Snail Toxicity

Excerpt

Experienced and novice scuba divers are drawn to warm, tropical seas, but when traveling to these areas, divers must practice additional cautionary measures to avoid predators specific to these environments. One example is the Conus genus, which includes over 500 different species of predatory snails. While humans are not the intended prey for these mollusks, naive divers may inadvertently pick up cones with the intention of keeping them as souvenirs. The handful of humans that are stung by a cone snail is often subject to a venom potent enough to immediately paralyze and eventually kill its prey. The venom from one cone snail has a hypothesized potential of killing up to 700 people.

The Conus genus, within the Conidae family, is a group of predatory gastropod mollusks. The spiral shells of the snail are the life-long habitat for the indwelling predator. As the snail continues to grow, it builds upon its patterned shell. All members of the genus appear similar, but many different Conus species fall under this umbrella, some of which pose a greater threat to humans than others. Cone snails range in size from a few centimeters up to 29 cm long. These snails sense prey within their environment using an appendage called a siphon. While some species do have eyestalks, the siphon provides a more sensitive method of locating prey, as well as performing additional respiratory functions. There is variability in the prey each Conus species tends to hunt. Some feed on worms (vermivores), others on mollusks (molluscivores), and those most toxic to humans feed on fish (piscivores). Knowing these specific feeding patterns makes differentiation of deadly Conus species easier; though all cone snails are capable of envenomation. The geographic cone is the most toxic of the known species, and several human deaths have resulted from envenomation. Humans are not typical cone snail prey and envenomation is most likely to occur during handling. Unsurprisingly, envenomation occurs most often on the palms and fingers.

Within piscivorous snails, two primary methods of hunting have been documented: hook and line versus net hunting. The species that utilize the hook-and-line method use an additional appendage called a proboscis. Within the proboscis is a tooth or harpoon, coated with species-specific venom. This proboscis can extend to all parts of the shell and handling. Only a certain part of the cone does not protect from envenomation. The second method of hunting also involves a venom-covered harpoon, but instead, the snail opens its mouth to catch fish and the harpoon is released within the mouth. Once a harpoon is engaged, it is discarded. At any time, a cone snail has about twenty harpoons in various stages of growth and development.