Cone shells are marine shells, and they are part of the family conidae

Cone Snails

Ken Carter

Cone snails are marine snails that belong to the family Conidae, genus Conus. There are more than 600 species known. The size of the cone shell varies among species, and ranges from 20mm to180mm. The shells of the cone snail are very smooth and each species has its own unique design. The shells are covered in a periostracum, which is the hard chitinous covering that protects the shell from the erosive action of water.

The trunk of the cone shell is where the proboscis is located. The proboscis is a muscular extendible projection of the snail’s body that helps it to move around and become more familiar with the surrounding area. It is also the location of the radula and serves as the cone snail’s mouth. The radula is where the spear (teeth) is located. The teeth have evolved into a harpoon-like feature that is equipped with a lethal poison. The foot of the cone snail is a big muscle that enables the critter to move around and cling onto things. On the left side of the head there is a siphon, an extendible tube that pumps the water from and into the gills located at the base of the siphon. It’s open below, protrudes from the sand and allows the animal to breathe while buried in the sand. The cone snails are organisms with separated sexes (dioecious). When they mate and produce fertile eggs, each of the egg sacks is filled with about 500-700 eggs. The cone snail’s habitat is warm tropical water, and they can be found in coral reefs or sand flats around certain beaches. The greatest population of cone snails is in the Great Barrier Reef off the coast of Australia.

Cone snails are classified by what they feed on. The piscivorous cone snails are fish eaters, and two examples are Conus striatus and Conus geographus. These are the types that have the most toxic venom, because the fish has to be paralyzed or killed before it has a chance to swim away. These snails are also the most dangerous to humans. The molluscivorous cone snails feed on other mollusks and a few examples are Conus textile and Conus marmoreus. These types of cone snails are known to be cannibals, for example Conus textile’s main diet consists of other cone snails. Vermivorous pecies are the worm eaters and are the smallest of all.

When the snails have detected prey and it is in striking distance, the radula shoots out much like a harpoon and penetrates any exposed tissue and releases the venom. If the prey hasn’t escaped in time, it will be immobilized and engulfed through the proboscis. The venom is different among species and has evolved in a way to paralyze a specific prey. Small peptides are the active components of the venom, ranging from 12-30 amino acids that are highly constrained due to the high density of disulphide bonds. The venom prevents neuronal communication (communication between brain and body), and often paralyzes the diaphragm which inhibits breathing.

Due to the beautiful designs on their shells, cone snails make for a desired collector’s item, so a lot of people pick them up get stung. There have been several non-lethal attacks reported, some of the symptoms of the not to severe cases will include slight pain, mild numbness, drowsiness, and fatigue. In the more severe cases symptoms will include extreme pain and numbness, painful headaches, stomach cramps, difficulty breathing, and temporary paralysis. There have been several lethal encounters reported but only 3 have been confirmed. One of the 3 confirmed cases happened in Hawaii; an eye witness reported 2 cone snails bit a victim in the neck causing death in 3 seconds!

But there is one advantage to the extremely poisonous venom, it makes for a good resource in medical studies for future treatments. The venom of Conus magus is currently under study in the US as a possible treatment for Ischaemia in stroke patients. Some species’ venom that target potassium channels in their prey might help researchers develop a treatment for hypertension. Conantokins from fish hunting cone snails are currently under study and hopefully will result in treatment of epilepsy and Parkinson’s disease. In Melbourne, Australia the venom of Conus geographus, Conus catus, and Conus marmoreus is helping researchers develop new pain medication. This would be a great breakthrough, eventually replacing morphine, because morphine is a tolerant drug and it takes more dosage to deliver the same amount of pain relief if you have used it before. The medication from the cone snails would not be tolerant and could be to up 100 times more powerful than morphine.

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