Cone snails, or cones, are highly venomous sea snails of the family Conidae.
Fossils of cone snails have been found from the Eocene to the Holocene epochs. Cone snail species have shells that are roughly conical in shape. Many species have colorful patterning on the shell surface. Cone snails are almost exclusively tropical in distribution.
All cone snails are venomous and capable of stinging. Cone snails use a modified radula tooth and a venom gland to attack and paralyze their prey before engulfing it. The tooth, which is likened to a dart or a harpoon, is barbed and can be extended some distance out from the head of the snail at the end of the proboscis.
Cone snail venoms are mainly peptide-based, and contain many different toxins that vary in their effects. The sting of several larger species of cone snails can be serious, and even fatal to humans. Cone snail venom also shows promise for medical use.
Distribution and habitat
There are over 900 different species of cone snails. Cone snails are typically found in warm tropical seas and oceans worldwide. Cone snails reach their greatest diversity in the Western Indo-Pacific region. While the majority of cone snails are found in warm tropical waters, some species have adapted to temperate/semi-tropical environments and are endemic to areas such as the Cape coast of South Africa, the Mediterranean, or the cool subtropical waters of southern California (Californiconus californicus).
Cone snails are found in all tropical and subtropical seas. They live on a variety of substrates, from the intertidal zone and deeper areas, to sand, rocks or coral reefs.
Shell
Cone snails have a large variety of shell colors and patterns, with local varieties and color forms of the same species often occurring. This variety in color and pattern has led to the creation of a large number of known synonyms and probable synonyms, making it difficult to give an exact taxonomic assignment for many snails in this genus. As of 2009, more than 3,200 different species names have been assigned, with an average of 16 new species names introduced each year.
The shells of cone snails vary in size and are conical in shape. The shell is whorled in the form of an inverted cone, with the anterior end being narrower. The protruding parts of the top of the whorls, that form the spire, are in the shape of another more flattened cone. The aperture is elongated and narrow with the sharp operculum being very small. The outer lip is simple, thin, and sharp, without a callus, and has a notched tip at the upper part. The columella is straight.
The larger species of cone snails can grow up to in length. The shells of cone snails are often brightly colored with a variety of patterns. Some species color patterns may be partially or completely hidden under an opaque layer of periostracum. In other species, the topmost shell layer is a thin periostracum, a transparent yellowish or brownish membrane.
Physiology and behavior
Cone snails are carnivorous. Their prey consists of marine worms, small fish, molluscs, and other cone snails. Cone snails are slow-moving, and use a venomous harpoon to disable faster-moving prey.
The osphradium in cone snails is more specialized than in other groups of gastropods. It is through this sensory modality that cone snails are able to sense their prey. The cone snails immobilize their prey using a modified, dartlike, barbed radular tooth, made of chitin, along with a venom gland containing neurotoxins.
Molecular phylogeny research has shown that preying on fish has evolved at least twice independently in cone snails.
Harpoon
Cone snails use a harpoon-like structure called a radula tooth for predation. Radula teeth are modified teeth, primarily made of chitin and formed inside the mouth of the snail, in a structure known as the toxoglossan radula. Each specialized cone snail tooth is stored in the radula sac, except for the tooth that is in current use.