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Mediterranean invasive species factsheet

MOLLUSCS

Reproduction Common name: Rapa whelk

Knobs towards the spire
identification Striped lines on
entire shell

Scientific Name:
Rapana venosa
Picture

Key identifying features
Brief history
This large marine snail, 11–13 cm in shell length, has Deep umbilicus
a heavy, short, sculptured shell with a large inflated
body whorl that gives it a spherical appearance. It is
nearly as wide as it is long. The colour of the shell
can vary from light grey to dark brown, often with light
stripes along the spiral ribs.

An obvious distinguishing feature is the deep orange
colour of the inside of the aperture, which contains
small, elongate teeth on the outer lip. It has a short,
wide siphonal canal and pronounced knobs leading
to the spire, which are more or less evident
depending on the erosion of the shell. Juvenile
individuals do not have the orange aperture and the
spire is relatively higher.

Field identification signs and habitat
The rapa whelk lives at depths of 2–40 m on sandy
and rocky mixed bottoms in marine and brackish
estuarine and, less frequently, inner lagoon waters. It
often lies buried in the sand to avoid predators and
preys on other mollusc species, such as oysters and
clams. It tolerates low salinities, polluted waters and
oxygen-deficient waters.

Reproduction
Artificial breakwaters, jetties and other man-made
marine structures are optimal sites for its
reproduction. At such sites rapa whelks congregate
to mate and lay their eggs. They reproduce
continuously from April to September at temperatures
of 12–28 °C. Eggs are deposited in elongated (up to
2 cm) egg capsules that change colour from pale
yellow to almost black as the embryos develop. After
two weeks free swimming larvae are released into
the water column; they later metamorphose into Rapana venosa. Photo: Guido and P. Poppe
juvenile whelks and migrate to the sea bottom.

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