Last fall, marine scientists said they knew too little about the fist-sized Asian snail discovered in area waters to fear it as an ecological threat.

But now it's time to be frightened, they say. Nearly everything that scientists at the Virginia Institute of Marine Sciences have since learned about the veined rapa whelk has made them worried that the alien species poses a serious threat to the region's seafood industry.

Scientists are just beginning to realize the prodigious reproductive habits of the snail. In what could be a summer-long onslaught, watermen and researchers have watched as the animals have begun laying millions of egg cases in Hampton Roads -- clusters of inch-long, pale yellow stalks that resemble patches of shag carpeting.

The potential for devastation of native shellfish is not far-fetched. The rapa whelk has a taste for native oysters, but it prefers clams. A full-grown whelk can devour two large chowder clams a week.

What are the common and scientific names?

The species is commonly referred to as the Veined Rapa Whelk or the Asian Rapa Whelk. The descriptor "veined" comes from distinctive shell markings.

The scientific name is Rapana venosa, the first description being given by Valenciennes in 1846. The species was also described by Crosse in 1861 as Rapana thomasiana with the common name Thomas's Rapa Whelk being applied. It is now generally agreed that these are the same species and that Rapana venosa, being the earlier description, has precedent. Within the scientific classification it is considered to be a member of the family Muricidae, a family of predatory marine snails.

What does it look like?

The Veined Rapa Whelk has a heavy short spired shell with a large inflated body whorl and a deep umbilicus. The aperture is large and ovate, the columella is broad and smooth. The edge of the outer lip has small, elongate teeth. Older examples may have some flare to the outer lip, although this does not appear to be related to sexual maturity, which can occur at small size. Smooth spiral ribs develop regular blunt knobs at the shoulder and the periphery of the body whorl. Fine spiral ridges are crossed by low vertical riblets. The color is variable from gray to red brown, with dark brown dashes on the spiral ribs, although older specimens can be quite eroded on the outside. A very characteristic feature of the species is the deep orange aperture and columella. Rapana venosa grows to be quite large. The largest record in the literature for the native range is 18.3 cm shell height from Taiwan. A length of 12.1 cm has been published from the Black Sea. A specimen in excess of 15 cm has been collected from Hampton Roads, Virginia.

What is the natural range?

Rapana venosa is native to the Sea of Japan. In Chinese waters it occurs with two other closely related species, Rapana bezoar and Rapana rapiformis. Rapana venosa is restricted to the Yellow Sea, the East China Sea and the Bohai Sea. Rapana bezoar occurs off the southern provinces bordering the South China Sea and is more widely distributed in the Western Pacific, and the Indian Ocean. Rapana rapiformis occurs in the East and South China Seas. This is a region of wide annual temperature ranges, comparable to that of the Chesapeake Bay. In winter populations may migrate from estuarine waters into deeper water (possibly to avoid freezing surface water).

What does it eat and how?

Rapana venosa is a predatory gastropod with prey range of molluscs. It often attacks bivalve (oysters, clams, mussels) prey by rasping around the region where the two valves meet, rather than boring a distinct hole. The related species Rapana bezoar, also a generalist predator on molluscs, attacks other shallow burrowing molluscs by boring the edge of the shell. This is a characteristic that has been noted in collections of clam shells from Hampton Roads.

A short history of events since the discovery of Rapana venosa in the Chesapeake Bay

Since the initial report of Rapana venosa in Hampton Roads following collection of a specimen by members of the VIMS Trawl Survey Group information has been distributed through the news media and by personal communication with a number of people in the fishing industry and academia. A short Rapana venosa information site was added to the VIMS world wide web site (http://www.vims.edu/rapana/) with a request to contact VIMS if you had information on the species in Hampton Roads or further afield. These activities have resulted in a number of calls to VIMS to report records of observation or collection and thereby increased our knowledge of the distribution of Rapana venosa in the lower Chesapeake Bay.

In addition to the information dissemination approach a field sampling day was organized for August 24, 1998 in Hampton Roads using the Virginia Marine Resources Commission vessel R/V Baylor to re-examine the location of collection of the Rapana venosa for further adults or egg cases as evidence of active breeding of Rapana venosa in Hampton Roads. In addition to VIMS and VMRC staff, the field party included Dr. Yuri Kantor of the Russian Academy of Science, Moscow (Dr. Kantor is currently visiting at the Smithsonian Institution in Washington D.C), Dr. Guido Pastorino, a visiting fellow at Smithsonian Institution, and Ms. Raye Germon of the curatorial staff at the Smithsonian Institution. Although no additional adult specimens were collected on August 24th, we did succeed in collecting the distinctive egg cases of Rapana venosa attached to plant material retrieved in the trawl (shown in the picture to the right). The egg cases were returned live to the wet laboratory at VIMS and successfully induced to hatch, thereby releasing larval forms for further study.

Information on Veined Rapa Whelk reporting and bounty system

What should I do if I find (or think that I have found) a Veined Rapa Whelk?

Look at pictures of Veined Rapa Whelks and compare these pictures with pictures of local whelks and with your specimen. Pay particular attention to:

• The shell coloration - are there any black veins along the shell mouth?
• The shell thickness
• The shell height
• The thickness and texture of the shell columella

If you think you have found a Rapana, contact Roger Mann or Juli Harding at VIMS by phone (804/684-7360 or 804/684-7302) or electronic mail (rmann@vims.edu, jharding@vims.edu). Please make sure to give a contact name and phone number so that we can return your call.

What is the "bounty system" and how does it work?

The Virginia Saltwater Commercial Fishing Development Fund, administered through the Virginia Marine Resources Commission, and the Virginia Sea Grant Program both have approved funds to assist VIMS in mapping the distribution of the Rapa Whelk in the Virginia portion of the Chesapeake Bay and its major subestuaries. We are using these funds to support a bounty on the whelks at the rate of $5 per whelk through 18 December 1998. After 18 December, the rate will be lowered to $2 per animal in an effort to continue the program. If the whelk is alive when you catch it, please try and keep it alive by placing it in a bucket with river water.

To be eligible for the bounty, you must give the following information to VIMS personnel when the whelk is picked up or when you deliver the whelk:

1. Date of collection.
2. Specific collection location
3. Bottom type at the collection site
4. Water depth at the collection site