Veined Rapa Whelk

The shell of Rapana venosa is globose (rounded) and heavy, possessing a very short spire, a large body whorl, a strong columella and a deep umbilicus. The aperture is large and roughly ovate. Ornamentation is present externally as axial ribs, smooth spiral ribs ending in blunt knobs at both the shoulder and body whorl, and internally as small elongated teeth disposed along the outer lip margin. The external color varies from gray to reddish-brown, with dark brown dashes on the spiral ribs. Some specimens may have distinctive black/dark blue vein-like coloration patterns throughout the inner portions of the shell, usually originating from each individual tooth at the outer lip.

A diagnostic feature for this species is the deep orange color found in the aperture and on the columella. The height of the shell can reach up to 180 mm (about 7 in).

This species is native to the marine and estuarine waters of the western Pacific, from the Sea of Japan, Yellow Sea, East China Sea and the Bohai Sea.

Rapana venosa is included in Russia's Red Book as threatened with extinction. The original known habitat for this species was the Far East, but since 1947 it has been found in the Black Sea, and its shell became a popular souvenir in Crimea. Recently this species has been found as an exotic in the Chesapeake Bay, on the eastern coast of the United States.

Veined rapa whelks are carnivorous selective predatory gastropods whose main diet consists of a variety of other mollusk species, mainly epifaunal bivalves such as oysters (Crassostrea virginica) and mussels (Mytilus galloprovincialis, Modiolus and Geukensia), but also clams (Anadara inaequivalvis, Chamelea gallina, Tapes philippinarum, Venus verrucosa, and the northern quahog Mercenaria mercenaria). Prey are chosen by the whelk according to their species and size. Most snails feed by drilling a hole into their bivalve prey, but rapa whelks usually smother their prey by wrapping around the hinged region of the shell and feed by introducing their proboscis between the opened valves. The whelk can also secrete a thick mucus that may or may not contain biotoxins to weaken the prey. Shell drilling, however, is also not unknown in this species.

Veined rapa whelks favor compact sandy bottoms, in which they can burrow almost completely. The native habitat of this species is a region of wide annual temperature ranges, comparable to other localities. Fleeing cold waters in the winter, this species may migrate to warmer, deeper waters, thereby evading cool surface waters. This fertile sea snail is extremely versatile, tolerating low salinities, water pollution and oxygen deficient waters.

Rapana venosa is dioecious, which means each individual organism belonging to this species is distinctly male or female. In this species' native range, mating occurs for extended periods of time, mainly during the winter and spring. It reproduces by internal fertilization, after which it lays clusters of egg cases that resemble small mats of white to yellow shag carpet, mainly during spring and summer. One adult female can lay multiple egg cases throughout the season. Each cluster contains 50-500 egg cases, and each egg case may contain 200-1000 eggs. The pelagic veliger larvae (a larval form common to various marine and fresh-water gastropod and bivalve mollusks) then hatch, persisting in the water column for 14 to 80 days and feeding primarily on plankton. They eventually settle on the ocean floor where they develop into hard-shelled snails.