Deadly Cone Snails: Characteristics, Toxins, Deaths and Drugs | Sea Life, Islands and Oceania

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CONE SNAILS

20120518-cone shell Rhizoconus_mustelinus_01.JPG
cone shell Rhizoconus mustelinus
There are 500 species in the “ Conus” genus. Their shells feature and endless variety of intricate patterns created from repeating triangles, strips, spots and cobblestones. They range in size from grape-size to pear-size and are among the slowest moving of all mollusks. They rely on their poison for both defense and to catch prey. Some cone snails are quite aggressive. They can actively reach out to sting prey or potential predators. [Source: Wikipedia]

Cone snails are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature), heterothermic (have a body temperature that fluctuates with the surrounding environment) and have bilateral symmetry (both sides of the animal are the and venomous. /=\

Many cone species are found around the Caroline Islands of Micronesia and Palau. Demand for cone snails for their shell. meat and toxins (for medical purposes) plus loss of habitat and global climate changes have caused a dramatic reduction in the numbers of cone snails. The problem is so severe that several species may threatened with extinction.

Most cone snail species are not listed as vulnerable, threatened, or Endangered. They have not been evaluated for the International Union for Conservation of Nature (IUCN) Red List and have no special status according to the Convention on the International Trade in Endangered Species (CITES).

Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems

Cone Snail Characteristics, Predators and Behavior

Cone snails are nocturnal (active at night), motile (move around as opposed to being stationary) and solitary. There is no data of any sort of home range. They sense and communicate with vision, touch and chemicals usually detected by smelling. Their three main methods of perception used are visual (eyes to detect light), tactile (using its foot) and chemoreception (detecting dissolved chemicals in the water). It is likely that food and potential mates are detected using all three of these senses.

According to Animal Diversity Web: A calcareous, smooth shell covers the mollusk’s soft body. The shell spire is obconical (having a length of less than or equal to 10 percent of the entire structure) featuring coronation (small bumps) at and above the shoulder along the edges of the larger whorls. The spire is concave with smooth sutures and a prominent point at the protoconch apex. The body whorl terminates in an elongated aperture that has a width of about 1/3 of the overall shell width. [Source: Miranda Hall, Animal Diversity Web (ADW) /=]

During their larval period cone snails face many predators such as fishes and filer-feeding invertebrates that consume zooplankton. As adults, they have to be concerned about mollusk-eating vertebrates such as sea turtles and rays, and human shell collectors. Their radular teeth and toxic harpoons serve as a defense mechanism against potential predators. /=\

Cone Snail Feeding and Attacks

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Cone snail eating a fish
Cone snails feed on other mollusks, worms and fish. They detect prey with siphons that take in water and shoot it over their gills. After shoot hit they then pull their prey slowly back to their shell and engulf it. Cone snails have transformed their radula into a kind of gun that shoots small glassy, poison harpoons. The harpoons are excreted with enough force to penetrate a diver’s wetsuit.

Cone snails are inactive during the day, burying themselves in the sand to camouflage themselves for both protection and hunting. At night the snails actively hunt food.Geography cone snails live under the sand and use their chemical-sensing proboscis to sense passing-by prey. When prey comes close the snail’s proboscis rears up and shoots a hollow harpoon into the victim’s flesh and pumps in venom. Death is almost instantaneous.

According to Animal Diversity Web: Some researchers hypothesize that male cone snails may exhibit territoriality in their hunting grounds. Observations show that snails hunt with two methods used by other Conus species: the hook-and-line method and the net-hunting method. In the hook-and-line method, the snail slowly approaches its prey, waving its proboscis like a lure to attract the fish before stinging the fish with its radula. The fish jerks violently for a few moments and is injected with a paralyzing excitotoxin venom that stiffens the fish, allowing the cone snail to swallow it whole. Several hours or days later, the snail regurgitates the fish’s bones. Another method is net-hunting, wherein a fish is engulfed in one mouthful before being harpooned with the radular tooth. [Source: Miranda Hall, Animal Diversity Web (ADW) /=]

Deadly Cone Snails

All cone snails are venomous and capable of stinging. The sting of many of the smaller species is roughly equivalent to a bee or hornet sting, but the sting of a few of the larger tropical fish-eating species, such as Conus geographus, Conus tulipa and Conus striatus, can be fatal. Other dangerous species include Conus pennaceus, Conus textile, Conus aulicus, Conus magus and Conus marmoreus.

Cone snails have been described as "the deadliest creatures on the planet, for their size." Small creatures with beautiful shells found in the South Pacific and Indian Oceans, they inject venom with short barbs into their victim. The poison can cause paralysis an even death in fish and humans. Humans are rarely deliberately attacked. Deaths and injuries often have been the result of divers innocently pocketing the shells and finding out the harpoons can penetrate swimsuits.

Symptoms of a cone snail sting may include an excruciating pain at the penetrated area, much worse than a bee’s sting. As the pain fades, numbness soon sets in, followed by dizziness, slurred speech, and respiratory paralysis. Death can follow within half an hour afterward, but this is rare. Presently, there is no known anti-venom. Applied pressure on the wound, immobilization and artificial respiration (mouth-to-mouth resuscitation) are the only recommended treatments for victims. [Source: Miranda Hall, Animal Diversity Web (ADW)]

Cone Snail Toxin

Cone snail on fire coral
Some cone snail toxins are among the most powerful produced in the animal kingdom. A single creature can carry enough poison to kill a dozen people. The poison is potent and fast-acting nerve agents for which there is known antidote or antivenin.. If it was otherwise cone snail prey could escape before the cone snail could catch it. Death can occur is less than 30 minutes. The venom contains an analgesic so the victim feels almost no pain.

Cone snails poisons are known as conotoxins, which consist of chains of amino acids called peptides. Each species produces 50t o 100 different kinds. Often the way the peptides are combined and mixed varies each time the poison is injected. Conantokins ("sleeper peptides") from the geographic cone snail are a complex mix of short-chain peptides that affect a number of neural receptors in fish and mammals. It is estimated that the conantokins in one geographic cone snail sting can kill 15 people, maybe more. [Source: Miranda Hall, Animal Diversity Web (ADW)]

Powerful toxins (lethal dose): 1) anthrax (0.0002); 2) geographic cone snail (0.004); 3) textrodoxotine in the blue ring octopus and puffer fish (0.008); 4) inland taipan snake (0.025); 5) eastern brown snake (0.036); 6) Dubois’s sea snake (0.044); 7) coastal taipan snake (0.105); 8) beaked sea snake (0.113); 9) western tiger snake (0.194); 10) mainland tiger snake (0.214); 11) common death adder (0.500). Lethal doses is defined as the amount in milligrams needed to kill 50 percent of the animals tested.

Geography Cone Snails — the Deadliest Species

The “ Conus geographus” (geographic cone snail) is the most deadly cone snail. It contains a venom so powerful that human victims quickly go into a coma and die within several hours.

Geographic cone snails are native to Australia, the Indian Ocean and Pacific Ocean. They are are most often found along the northern shores of Australia, ranging from coast around Brisbane, Queensland in the east to Darwin, Northern Territory in central-northern Australia to Exmouth, in Western Australia. Rare sightings (and recorded fatalities) have also been reported in New Caledonia. They have been seen as far west as the east coast of Africa. [Source: Miranda Hall, Animal Diversity Web (ADW) /=]

Geographic cone snails live in tropical areas and reside in coastal areas on the sea bottom as well as intertidal (littoral) zones on the shores. They are typically found at depths of zero to 200 meters (656 feet) in areas with fragmented coral reefs and sandy bottoms. They are less commonly found in deeper waters.

Geography Cone Snail Characteristics and Behavior

Geography Cone Snail

Geographic cone snails range in weight from 13.3 to 62 grams (0.47 to 2.19 ounces), with an average weight is 38.8 grams (1.37 ounces) They range in length from seven to 15 centimeters (2.8 to 6 inches). Both sexes are roughly equal in size and look similar.[Source: Miranda Hall, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: The outer shell’s coloration ranges from ground colors of white, cream, or rose pink overlain with brown or red mottled patterns arranged in horizontal spirals along the body whorl. The shell is covered with a thin yellowish layer of protein-based material called the periostracum, forming tufts on the spire, on the spiral rows, and along the body whorl, following the sculpture of the shell. This protein covering gives the cone a roughened appearance. /=\

The most obvious features of the geographic cone snail are the foot, which extends from the aperture; two small eyes borne on eyestalks, and two features associated with their feeding habits: the proboscis, an extendable protrusion in the oral region that expands to swallow its prey, and the siphon, an extension of the mantle tissue, used for chemoreception of its prey. The cone snail uses a elaborately scuplted, hollow radular tooth (housed in the proboscis) as a harpoon to incapacitate its prey. Venom glands produce deadly toxins and digestive enzymes, and these are injected into the snail’s prey through the radular tooth. ) /=\

Geographic cone snails are nocturnal (active at night). They hunting at night when its fish prey are the least active or at rest. Generally, they crawl on top of the substrate, or crawl while buried beneath the sand. Diet consists of small- (3-to-5-centimeter) and medium- (10-to-13-centimeter) sized-fishes that fit into its rostrum (mouth). Larger snails (8 to 8.7 centimeters) are able to capture and ingest larger fishes between 13 and 14 centimeters in length. /=\

People Who Died After Being Stung by Conus Geographus

At least 30 people have died from cone snail attacks. According to Goldfrank's Toxicologic Emergencies, about 27 human deaths can be firmly attributed to cone snail envenomation, though the real number is likely much higher; some three dozen people are estimated to have died from geography cone envenomation alone.

The “ Conus geographus” (geographic cone snail) of Australia is the most deadly cone snail. It contains a venom so powerful that victims quickly go into a coma and die within several hours. This species has been nicknamed the "cigarette snail", a reference that implies the victim has only enough time to smoke a cigarette before dying after being stung.

Visitors to the Queensland Museum can see a shell from a specimen that killed a man, causing only fatality on the Great Barrier Reef from a marine animal. The man was collecting shells. He picked up the cone snail and put it in his pocket and was fatally stung through his clothes.

One young man who picked up geographic cone shell thought it would make a nice gift for his girlfriend. He put the shell on his shoulder to show his friends. The animal stung him with its needle-like radula. He was dead a short time later. Despite the potency of their toxins, people eat them in the Philippines and Samoa as a delicacy.

Cone Snail Sting Symptom and Treatments

Geography Cone Snail

Symptoms of a more serious cone snail sting include intense, localized pain, swelling, numbness and tingling and vomiting. Symptoms can start immediately or can be delayed for days. Severe cases involve muscle paralysis, changes in vision, and respiratory failure that can lead to death. If stung, one should seek medical attention as soon as possible. [Source: Wikipedia]

According to the National Library of Medicine: The initial symptoms of envenomation vary depending on the species of cone snail and the victim. When stung by a large cone snail, one may feel anything from a sharp pricking sensation to unbearable pain. At the envenomation site, local numbness, ischemia (restricted blood and oxygen flow), cyanosis (bluish-purple hue to the skin) and necrosis (body tissue death) may occur and sometimes involves entire regions of the body. [Source: Sasha Kapil; Stephen Hendriksen; Jeffrey S. Cooper, “Cone Snail Toxicity”, National Library of Medicine, January 2, 2023]

Given that the affected neurotransmitter pathways exist throughout the body, the toxin can spread and systemic symptoms may develop. These progress from initial weakness, sweating, and visual changes to generalized muscle paralysis, respiratory failure, cardiovascular collapse, and coma. If a patient is untreated, death is rapid and often occurs within one to five hours. Less severe envenomations, resulting from contact with smaller species, are milder in their toxic effects. These effects are also variable and may include numbness, paresthesias, and limb immobility.

The most important intervention after cone snail envenomation is to seek urgent hospital-based therapy and to ensure that the patient’s airway, breathing, and circulation remain intact. Once the patient arrives at the hospital, mechanical ventilation and supportive therapies are enacted. While in transport, some additional methods can be utilized to prevent venom spread. Pressure immobilization involves bandaging the limb starting at the distal end (fingers or toes) and moving toward the axial joints. This technique has been suggested to prevent further injury following envenomation. The wrapping should be tight but not to the point that circulation is affected. There should be a frequent examinations to ensure that the most distal parts (i.e., fingers, toes) remain pink. It is suggested that these bandages should be removed for 90 seconds and reapplied every 10 minutes, but this should in no way impact the speed of transport to a hospital.

Additional reports have suggested that hot water (40̊to 50̊ C, 104̊ to 122̊F) may be effective for pain relief after cone snail envenomation. More reports are needed before this becomes standard of care, but at this time it is primarily based on anecdotal data.

Cone Snail Mating, Reproduction and Development

Cone snails are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). They engage in internal reproduction in which sperm from the male parent fertilizes an egg from the female parent and are monogamous (having one mate at a time). [Source: Miranda Hall, Animal Diversity Web (ADW) /=]

Cone snails engage in seasonal breeding. Geographic cone snails breed once a year between April and September when the waters are warm. The number of offspring ranges from 1000 to 5000, with the average number of offspring being 2500. The gestation period ranges from two to three days. The average gestation period is three days and the age in which they become independent ranging from 15 to 25 days.

Cone shells employ a “lay em and leave em” strategy of egg laying. There is no parental involvement in the raising of young. Females and males reach sexual maturity at six to 12 months. According to Animal Diversity: Published observations on reproductive behavior were made in aquaria, and direct observations on ritual courtships or competition for a mate in the wild is lacking. Some researchers hypothesize that male cone snails may exhibit territoriality to ensure access to potential mates. /=\

During copulation, the male mounts the female using its foot. It inserts about 2/3 of a ribbon-like organ called the verge (analogous to a penis) into the female’s opening near the anal notch. This position is maintained for at least 15 minutes before the male retracts its verge. Two to three days later, the female lays several capsules eggs on a smooth, hard surface, where they develop into larvae in twenty days. No information is available as to whether mating occurs singly or at multiple times across the lifespan. /=\

Cone snail species from nine subgenera.
Top row: fish-hunting cone snails (from left to right: Conus geographus (Gastridium), Conus magus and Conus consors (Pionoconus), Conus purpurascens (Chelyconus)), middle row: snail-hunting cone snails (Conus marmoreus (Conus), Conus textile and Conus ammiralis (Cylinder), Conus omaria (Darioconus)), bottom row: worm-hunting species (Conus imperialis and Conus regius (Stephanoconus), Conus pulicarius (Puncticulis), Conus mustelinus (Rhizoconus)). Shells not to scale.

Very little is known of the cone shell’s natural history from neoteny to adulthood. After the mating ritual, clusters of egg sacs (about 40 eggs per sac) are extruded and attached on a suitable hard surface. The eggs incubate within their capsule for 10 to 15 days before maturing into the larval stage. After twenty days, the transparent shells and bodies are visible, and they break from their capsules and drift in the plankton as meroplanktonic veliger larvae (a temporary zooplanktonic stage of the lifecycle). The larval diet is unknown, but assumed to be smaller plankton. Only a low percentage of cone snail larvae survive to metamorphose into benthic (bottom-dwelling) juveniles, and even fewer survive to reach adulthood. Planktonic survival rate is affected by weather and oceanographic factors such as water temperature, salinity, and ocean currents, as well as abundance of secondary consumers in the water column. /=\

Cone Snail Drugs

Some scientists believe that cone snails possess more potential medicines than any other organism. With 500 different species producing 50 to 100 chemicals each that adds up to 25,000 to 50,000 chemicals that could be used to make medicines. Cone snails contain analgesics and compounds that hold the potential for treating cancer and nervous system conditions such as epilepsy and stroke.

Of the tens of thousands of cone snail conotoxins out there only about 100 have been studied. Many have been found to bind to ion-channel receptions, holes in cell membranes that allow changes to take place that can cause or stop diseases. Milking the venom from cone snails is no easy task because the animal can bend it radula to almost every direction to sting at from virtually any angle, The venom is extracted by a Brisbane-based biotechnology company called Xenome by dangling fish in front of the snail. After the snail strikes the fish and kills it the venom is extracted from the fish.

According to Animal Diversity Web: The potential therapeutic and economic benefits from conantokins have great potential. Conantokins are antagonists to the nicotinic aceytlcholine receptors (the means by which the cone snails paralyze their prey) and N-Methyl-D-aspartic acid (NMDA) receptors, which (in humans) are involved with pain reception, drug and alcohol withdrawal symptoms, memory, and learning. Con-G, one of the conantokins from the geographic cone snail, is a potent analgesic, particularly for nociceptive pain (pain that warns the body of tissue injury or other serious damage). [Source: Miranda Hall, Animal Diversity Web (ADW)]

Con-G specifically acts on the NR2B NMDA receptor subtype, which means it is more selective than morphine for treating chronic neuropathic pain found in patients suffering from cancer, arthritis, shingles, diabetes, and AIDS. Therefore, smaller doses can be used, and Con-G does not seem to be addictive or to have side effects in the therapeutic dose range, unlike morphine. In addition, since NMDA receptors are involved with memory, conantokins can potentially be used in treating Alzheimer's and Parkinson's diseases, and possibly used as anti-convulsants in epilepsy or as a means of alleviating drug-induced withdrawal symptoms. In addition, Con-G has been found to act as a neuroprotective agent in brain ischemia from strokes. (Jimenez, 2009; Livett, et al., 2004; Sprackland, 2005) /=\

Prialt — the Cone-Snail-Derived Drug

Prialt is a synthetic derivative of the toxin of the “conus magnus”, the magician’s cone, a cone snail which kills prey in its swamp habitat. It is an extremely powerful painkiller, up to 1,000 stronger than morphine but is non addictive. Baldomero Olivera from the University of Utah, who extracted the peptide from the snail told Smithsonian magazine, “I thought if these snails were so powerful that they could paralyze the nervous system, smaller doses of the compounds from the venoms might have beneficial effects....Cones snails are of exceptional interest because the molecules they make are very small and simple, easily reproducible.”

Prialt is already valued in the hundreds of millions of dollars. It has proved to very promising treating people with chronic, serious pain. It works by interfering the with the transfer of signals between nerve cells in the spinal chord and other parts of the body. One man whose spine was crushed by sawmill accident told Smithsonian magazine that he suffered excruciating pain for years that even morphine didn’t help. He started taking Prialt and said the pain went away after three days. Scientists are studying Prialt to make treatments for epilepsy.

According to the TerSera, the drug’s maker: PRIALT® (ziconotide) intrathecal infusion (25 mcg/mL, 100 mcg/mL) is a prescription medicine used to treat severe chronic pain in adults who cannot take other treatments or when other treatments do not work, stop working, or cause bothersome side effects. PRIALT can only be delivered by or under the direction of a doctor who injects the medicine into your spinal fluid through a special device (a procedure called intrathecal infusion) and should only be used in patients who are appropriate for the procedure. [Source: TerSera Therapeutics LLC]

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023