Syrinx aruanus, the Australian trumpet also know as the Giant whelk below is a huge snail, the world's largest, that can grow to 91 cm long and weigh 25 kg! It is found in the intertidal zone down to around 50 m deep around the northern Australian coast, southern New Guinea and Indonesia. It is carnivorous and feeds on polychaete worms. It has a long proboscis (up to 25 cm) and it uses this to reach into the tubes of its prey. Females produce large egg cases (15 cm), which they attach to rocks, shells or gorgonian corals. It is sometimes eaten by humans and is used for fish bait.
The Turnip whelk, Busycon coarctatum below can be found down the East Mexican coast, and in contrast to the Lightning whelk, below, the turnip whelk coils clockwise.
The Lightning whelk, Busicon contrarium, right, is found in shallow water from New Jersey down to Texas in estuaries, creeks and around oyster beds. Adults can grow up to 41 cm long. The sexes are separate. They prey on clams, forcing the clam shell open with their foot, and holding open with the edge of their own shell.
Its common name comes from the lightning bolt shaped stripes seen on juvenile shells.
The Dog whelk, Atlantic dogwinkle, Nucella lapillus, below, was used to make purple dye in Britain right up until the Romans invaded. It is found around the European and North West Atlantic coasts, mainly on rocky shores, where it prefers sheltered positions and crevices. Fully grown individuals are up to 4 cm long, and have a life expectancy of 6 years or more.
The Dog whelk preys on shelled molluscs and crustaceans. Its radula bores a hole in the shell of the prey, at the same time as its foot secretes shell-softening chemicals. Once through the shell digestive enzymes are secreted turning the prey's body into soup. To consume a barnacle takes about a day, and a mussel about a month. Boring into a the tough shell of a limpet takes about 3 days. Mussels have developed a good defence against the dog whelk. They tie it down using byssus threads and leave the whelk to starve. Up to 30% of dog whelks invading mussel beds end up this way. It is prey for birds and crabs.
TBT (tributyl-tin), a chemical found in anti-fouling paint used on boats causes female dog whelks to develop a penis and sperm duct at less than 1 part per trillion. At 5 parts per trillion females are unable to release eggs, and the population will die out.