Bivalves
The reef's filter feeders — look for giant clams with electric-blue mantles in the tropics, or fan mussels standing upright in Mediterranean seagrass. Most stay clamped shut, but giant clams react to your shadow with a slow, dramatic close.
Last updated April 2026
Noble pen shellPinna nobilis3 photos
The largest Mediterranean bivalve — a huge, fan-shaped shell up to 120 cm tall, embedded upright in sandy Posidonia beds. Critically endangered and fully protected.
Stands upright in seagrass meadows, filtering water — never touch or disturb. A mass mortality event since 2016 has made sightings rare and precious.
© Jouni Kuisma
© Jouni Kuisma
© Jouni Kuisma
Rough penshellPinna rudis1 photos
© Jouni Kuisma
Observed at
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