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Mediterranean invasive species factsheet

MOLLUSCS

Reproduction Hinged with 2 small teeth ‘Ears’ present
Common name: Rayed pearl oyster

identification

Scientific Name:
Pinctada imbricata radiata
Picture

Key identifying features
Brief history
The shell is rounded and irregular in shape, the two
valves being flattened and developing obliquely in
one direction. The side of the shell where the two
valves are hinged forms a straight line with a short,
rounded ‘ear’ at one end. One valve is more convex
than the other; thus the whole shell is variable in
thickness. On the upper surface are irregular
concentric ribs and along the edge are scaly spines. oysters attach in clusters of several to many
The shell is brown-purple occasionally mixed with individuals by means of byssal threads, and may
green, pale yellow or white. The interior is covered form assemblages consisting of pearl oyster shells,
with nacre. Shell length is usually 5–6 cm, sometimes worm tubes, algal clumps and anemones, which
up to 10 cm. camouflage the pearl oyster shells. They tolerate a
wide range of water temperatures (13–35 °C).

Field identification signs and habitat
This oyster is found at depths of 5–25 m attached to Reproduction
hard surfaces (natural or artificial) such as rocks, This oyster commonly begins life as a male and
nets, buoys and docks, as well as in seagrass when larger than 3 cm it changes sex, becoming
meadows on sandy-muddy sediments, usually in female. Spawning occurs in the water column mainly
marine habitats with relatively rough hydrodynamic in summer and early autumn, but reproduction can
conditions. It may also attach to the shells of the occur all year around. Free-swimming larvae then
noble pen shell Pinna nobilis or other animals. The metamorphose into juvenile pearl oysters.

Pinctada radiata. Photo: B. Michele Pinctada radiata. Photo: M. Draman

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