to the veined rapa whelk (continued):
The scientific name for this species is Rapana venosa,
with 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
might rapa whelks grow?
may grow to be quite large. The largest record in the literature
for the native range is 18.3 cm shell length from Taiwan. A length
of 12.1 cm has been published from the Black Sea. Several specimens
in excess of 15 cm shell length have been collected from Hampton
a rapa whelk look like?
rapa whelk (Figure 1 to the right) has a heavy short spired shell
with a large inflated body whorl and a deep umbilicus. 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. Most specimens have distinctive black veins throughout
the shell (see #1 in Figure 1 to the right); some animals have
black veins on the opercular lip as well. The columella is broad
and smooth (#2) and the siphonal canal is short (#3). The edge
of the outer opercular lip has small, elongate teeth (#4). Older
examples may have some flare to the outer lip. A very characteristic
feature of the species is the deep orange color found on the opercular
aperture and columella (also #4).
1: An adult veined rapa whelk
2: Home range of the rapa whelk.
do rapa whelks occur naturally?
are native to the Sea of Japan. In Chinese waters they occur 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 (Figure 2). 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 water surface water).
it eat and how?
are predatory snails that eat a variety of molluscs. They often
attack bivalves (oysters, clams, mussels) around the
region where the two valves meet, rather than boring a distinct
hole (Figure 3). The related species Rapana bezoar, is
also a generalist predator on molluscs, attacks other shallow
burrowing molluscs. This is a
characteristic that has been noted in collections of clam shells
from Hampton Roads.
3: A rapa whelk eating a hard clam.
history of events since the discovery of rapa whelks in Chesapeake
the initial report of rapa whelks 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.
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. Adult specimens as well as egg cases continue
to be reported from locations in the lower Chesapeake Bay. Rapa
whelk egg masses (Figure 4) or groups of egg cases resemble small
mats of yellow shag carpet and are quiet distinctive and noticeably
different from the egg cases of native snails.
4: Rapa whelk egg cases.