On first glance they appear to simply be bland , bleach-white seashells , but when viewed under ultraviolet light they are transformed . Scientists have used a new technique to reconstrcut the colourful patterns on 28 fossilised cone snail shells that are up to 6.6 million years old . The technique has allowed researchers to look millions of years into the past to see how these once elaborately decorated shells would have once looked . The fossilised cone snail shells have bleached over time , like the one labelled A , but under ultraviolet light traces of pigment still in the shells are revealed , labelled B , allowing their colours to be reconstrcuted ( C ) Instead of being a simple white colour , they were infact covered in streaks of orange , purple , blue and even large pokadots . The scientists now believe the cone snail shells , which come from the northern Dominican Republic , include 13 entirely new species . A deadly tropical sea snail uses a super-potent form of insulin to subdue its fish prey , scientists have discovered . The geographic cone snail ( Conus geographus ) uses the chemical to cause a plunge in blood sugar , leaving the fish sluggish and unable to swim to safety . In this way the snail is able to entrap whole schools of small fish . C. geographus is one of the most venomous creatures on Earth , and known to have killed dozens of people in accidental encounters . It hunts in two ways , both by releasing toxins into the water and by firing a harpoon-like poison-tipped tooth into its prey.No antidote exists for a cone snail sting , which contains a mixture of nerve agents . The new research has uncovered one highly unusual ingredient in the cone snail 's venom cocktail - weaponised insulin . In tests , a synthetic version of the hormone - made from shorter protein chains than normal insulin - lowered the blood sugar levels of adult zebrafish . Injected into water , it also reduced the movements of fish larvae . There are about 30 recorded instances of people being killed by cone snails , some of which have attractive and collectible shells . Dr Jonathan Hendricks , a paleontologist at the San Jose State University who led the research , said that the lack of colouration in many fosisilised cone snail shells made them difficult to identify . He said : 'Original coloration patterns — if not the actual colors themselves —sometimes become visible when fossil shells are illuminated with ultraviolet light , which causes formerly pigmented regions of the shell to fluoresce . 'Once a specimen has been photographed under UV light , it is possible to use photoediting software to reconstruct the original shell coloration pattern . 'This is done by creating a reversed , negative image , which causes bright , fluorescing markings to become darkened , corresponding with regions that were once pigmented . ' Dr Hendricks used the ultraviolet technique to examine a range of fossilised shells that were discovered in the Cibao Valley of the northern Dominican Republic . Although it is now a rich and fertile inland valley , millions of years ago during the Neogene it was covered by ocean . All cone snails are venomous and predatory , with many species still around today . They use a harpoon like tooth that injects venom into their prey . In some cases the cone snail toxins are lethal to humans while many have a painful sting . Due to their bright colours and patterns they are often handled by unwary humans , leaving them vulnerable to stings . There are around 700 species of cone snail still living in tropical seas worldwide and around 1,000 species have been found in the fossil record . This image shows three of the fossil shells studied by the scientists as they currently appear without colour . Scientists used UV light to reveal tiny traces of the pigment left in the shell and the patterns they once had . However , identifying these can often be tricky as over time the bright pigments in the shells fade . Exposing them to ultraviolet light causes any remaining organic matter in the shells - like pigment - to fluoresce . It is thought that these compounds in the shells oxidise over time and so light up when UV light is shined on them . Dr Hendricks , whose work is published in the journal Public Library of Science One , compared the cone snail shells he examined with the patterns of those of modern Caribbean cone snails . He found that many of the fossils showed similar patterns , indicating that some modern species belong to lineages that have survived in the Caribbean for millions of years . UV light allowed scientists to peer back millions of years to reconstruct shell patterns and colours as above . Dr Hendricks said : 'This approach — combined with the exceptional Neogene fossil record of the Dominican Republic , as well as other regional fossil deposits — has the potential to provide a detailed understanding of the evolutionary and biogeographic development of the modern western Atlantic cone snail fauna . 'Clearly much more work needs to be done to better understand the compounds responsible for shell coloration . 'That said , it seems that oxidation - caused either naturally by exposure of shells to sunlight over prolonged periods of time , or artificially by soaking in bleach for several days - plays a role in causing formerly pigmented regions of fossil shells to fluoresce under UV light , though the reason is not currently understood . ' C. geographus ( above ) is one of 700 existing cone snail species and is one of most venomous living animals .
Fossilised cone snail shells found in Caribbean of Dominican Republic . In visible light they appear to be a plain white colour as the pigments faded . Under ultraviolet light , however , the vivid patterns and colours fluoresce . Scientists were able to reconstruct how the ancient species once looked .