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Brittle pen shell

Distribution : Mediterranean and eastern Atlantic; often described in deeper habitats and uncommon in recreational diving. Not equated with Pinna nobilis.

A brittle pen shell encounter happens at a boundary: some shell projects while the rest and its anchoring threads remain buried. That interface can explain its life without extracting the animal for a complete view.

Habitat of Brittle pen shell Habitat
Sand, Mud, Gravel
Depth range of Brittle pen shell Depth
20-600 m
Biological group of Brittle pen shell Group
Ecological role of Brittle pen shell Role
Filter feeder

WHAT DOES IT LOOK LIKE?

The brittle pen shell has thin brown brittle valves with an elongated triangular outline. A narrow anterior end enters sediment while the broader posterior region projects above. Concentric lines and variably expressed radial ribs mark the surface. Byssus threads attach to buried stones or shell debris. The exposed opening may remain incompletely closed without automatically indicating damage or death.

WHERE DOES IT LIVE?

Documented occurrence covers Mediterranean and eastern Atlantic waters. Mud, sand and muddy gravel are principal substrates. It can live down to around 600 m. Shallow records exist, but the species is not a routine first-metres encounter. Atlantic and Mediterranean frequency or population observations should retain their locality.

WHAT DOES IT EAT?

Filtering uses suspended organic particles. Entry and exit openings occupy the posterior region above sediment, maintaining exchange while the base is anchored. Tube worms, barnacles and other epibionts may use valves as support.

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Brittle pen shell

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Filter-feeding species

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