The term "periwinkle" doesn't just refer to a color or a type of flower. It is also the name of a common snail native to the northeastern European and Russian coasts of the Atlantic Ocean. The periwinkle snail, or littorina littorea, is also found in North America, where it is considered an invasive species after its accidental introduction in the mid-1800s. Highly valued for their taste, periwinkle snails are eaten in places all over the world.
The periwinkle snail, also called the common winkle, is a type of marine snail. It prefers intertidal zones, areas that are above water at low tide and below water at high tide, but also takes up residence in estuaries and tide pools. The winkle snails commonly cling to rocks or structures to steady themselves and provide a measure of protection against predators.
Another benefit of the periwinkle snail's affinity for rocks is that it affords the gastropods an abundant food source. Although the snails are technically omnivorous, the bulk of their diet comes from algae. Periwinkle snails also eat smaller invertebrates such as barnacle larvae.
The common winkle shell is an irregular oval shape with a sharply pointed edge that sometimes wears down due to erosion. The shells are thick and hefty with multiple bands of colors ranging from gray to brown with an interior color of dark brown. At maturity, the snails measure between 0.39 to 0.47 inches (9.9 to 11.93 millimeters) long, and between 1.18 to 2 inches (29.97 to 50.8 millimeters) tall.
A single periwinkle snail can live between five and ten years. Each year, a single female can lay 10,000 to 100,000 eggs, which hatch into larvae four to seven weeks later. Not all of the larvae make it to adulthood, with many thousands falling victim to predators and harsh sea conditions. Still, enough survive to make the periwinkle snail a common sight on Atlantic beaches.
Humans have long enjoyed a comfortable relationship with the periwinkle snail. Shells from the creatures have been found in Scottish shell piles dating back to at least 7,500 BCE. They're common in British and Irish cuisine, and they are sold by the bag. African and Asian cooks regard the snails as a delicacy. Common winkle parts are sometimes used as bait for catching fish.
Not everybody welcomes the periwinkle snail as a beneficial creature. Periwinkles in America are invasive. They take up resources used by native species, harming those species and altering the natural environment and ecology. As a result of accidental introduction, the periwinkle is found on both the Pacific and Atlantic coasts of North America and is considered one of the predominant species after wiping out several native species.