Veined rapa whelk

The veined rapa whelk, Rapana venosa, is a species of large predatory sea snail, a marine gastropod mollusk or whelk, in the family Muricidae, the rock shells. This large sea snail has become an invasive species in many different localities around the world

Distribution

This species is native to the Sea of Japan area: the East China Sea, the Bohai Sea and the Yellow Sea.

As an invasive species

It appears to be the case that the spread of this species outside its natural range has been made possible by the larval stage being transported along with ballast water in the hulls of ships.

Rapa whelks were first found in the Black Sea in the 1940s. Within a decade this mollusk had spread along the Caucasian and Crimean coasts and moved into the Sea of Azov. From 1959 to 1972, its range extended into the northwest Black Sea to the coastlines of Romania, Bulgaria and Turkey

Rapas have also become established in the Adriatic and Aegean seas.

They have been found at at least one location along the southeast coast of South America.

In the United States the first specimen discovered was in August 1998 by members of the Virginia Institute of Marine Science (VIMS) Trawl Survey Group in Hampton Roads, Virginia In the lower Chesapeake Bay of the eastern United States adult specimens as well as egg cases are continually being reported.

Reasons for the survival of this invasive species

The thick strong shell of the rapa whelk is arguably its strongest advantage over native whelks, because rapas can easily prey on local whelks, whereas local whelks are unable to successfully attack rapas. The thick shell also means that predators such as sea turtles are unable to feed on the invasive species, and can only feed on local whelk populations. Once the rapa whelk reaches adulthood, it exists unchecked in the local population, and can consume and reproduce freely.