Conus is a large genus of small to large predatory sea snails, marine gastropod molluscs, with the common names of cone snails, cone shells or cones. Conus snails are all venomous. Live ones should be handled with care or not handled at all, because they are all capable of stinging humans with unpleasant results. The species that are most dangerous to humans are the larger ones that prey on small bottom-dwelling fish. The other species hunt and eat marine worms or mollusks. Cone snails use a hypodermic-like modified radula tooth and a venom gland to attack and paralyze their prey before engulfing it. The tooth is sometimes likened to a dart or a harpoon. It is barbed and can be extended some distance out from the mouth of the snail, at the end of the proboscis.
Stonefishes are venomous, dangerous, and even fatal to humans. It is the most venomous fish in the world currently known. They are found in the coastal regions of Indo-Pacific oceans. The vernacular name of the species, the stonefish, derives from the stonefish's ability to camouflage itself with a grey and mottled color similar to the color of a stone. Swimmers may not notice them, and may inadvertently step on them, triggering a sting. When the stonefish is disturbed, it may inject an amount of venom proportional to the amount of pressure applied to it.
Pufferfish are generally believed to be the second–most poisonous vertebrates in the world, after the golden poison frog. Certain internal organs, such as liver, and sometimes the skin, are highly toxic to most animals when eaten; nevertheless, the meat of some species is considered a delicacy in Japan, Korea and China when prepared by chefs who know which part is safe to eat and in what quantity. Puffer's (tetrodotoxin) deadens the tongue and lips, and induces dizziness and vomiting, followed by numbness and prickling over the body, rapid heart rate, decreased blood pressure, and muscle paralysis. The toxin paralyzes diaphragm muscles and stops the person who has ingested it from breathing. People who live longer than 24 hours typically survive, although possibly after a coma lasting several days.
Blue Ringed Octopus
They are currently recognized as one of the world's most venomous marine animals. Despite their small size and relatively docile nature, they can prove a danger to humans. They can be recognized by their characteristic blue and black rings and yellowish skin. The blue-ringed octopus is 12 to 20 cm (5 to 8 inches), but its venom is powerful enough to kill humans. There is no blue-ringed octopus antivenom available. The octopus produces venom that contains tetrodotoxin, 5-hydroxytryptamine, hyaluronidase, tyramine, histamine, tryptamine, octopamine, taurine, acetylcholine, and dopamine. Tetrodotoxin blocks sodium channels, causing motor paralysis and respiratory arrest within minutes of exposure, leading to cardiac arrest due to a lack of oxygen. The toxin is produced by bacteria in the salivary glands of the octopus.
Although a few species are harmless or even useful to humanity, most are a nuisance because they suck blood from vertebrates, many of them attacking humans. In feeding on blood various species of mosquitoes transmit some of the most harmful human and livestock diseases. Some authorities argue accordingly that mosquitoes are the most dangerous animals on earth.
Poison Dart Frog
These species are diurnal and often have brightly-colored bodies. Although all wild dendrobatids are at least somewhat toxic, levels of toxicity vary considerably from one species to the next and from one population to another. Many species are critically endangered. These amphibians are often called "dart frogs" due to the Amerindians' indigenous use of their toxic secretions to poison the tips of blowdarts. However, of over 175 species, only three have been documented as being used for this purpose and none come from the Dendrobates genus, which is characterized by the brilliant color and complex patterns of its members. The most poisonous of these frogs, the golden poison frog (Phyllobates terribilis), has enough toxin on average to kill ten to 20 men or about ten thousand mice.
Box jellyfish are known for the extremely potent venom produced by some species. They are among the most venomous creatures in the world. Stings from these and a few other species in the class are extremely painful and sometimes fatal to humans. Once a tentacle of the box jellyfish adheres to skin, it pumps nematocysts with venom into the skin, causing the sting and agonizing pain.