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

Species

Noble pen shell

Pinna nobilis(3 photos)

Critically EndangeredUp to 120 cm2–30mPosidoniaSand

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.

Observed at

Tascó Petit(Illes Medes)Roca Muladera(Tossa de Mar)La Calita(La Herradura)

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