Michel Roggo / Watermilfoil (Myriophyllum spicatum) with some stems supporting clusters of Zebra mussel (Dreissena polymorpha) Lake Neuchatel, Switzerland. Highly commended in the Plants category of the Wildlife Pho...

Alex Hyde / Pea Crab (Pinnotheres pisum) inside a Common Mussel (Mytilus edulis). This small crab parasitises a number of bivalve species including mussels, living in the host's mantle cavity. Normandy, France. J...

Alex Mustard / Noble pen shell (Pinna nobilis), a large bivalve shell (this individual was about 60cm/2ft), endemic to the Mediterraean, grows vertically from a bed of Caulerpa algae. Calasetta, Island of Sant'Antio...

Alex Mustard / Decorative sea silk, woven from the spun byssus threads produced by the large bivalve mollusc, the Noble pen shell (Pinna nobilis). Calasetta, Island of Sant'Antioco, Sardinia, Italy. Mediterranean Se...

Franco Banfi / Pen shell (Pinna nobilis) in seagrass meadow of Nepture grass (Posidonia oceanica), Ischia Island, Italy, Tyrrhenian Sea, Mediterranean

Pete Oxford / Amber penshell (Pinna carnea) amongst sea grass, Coral Reef Island, Belize Barrier Reef, Belize

LYNN M. STONE / Ruddy Turnstone (Arenaria interpres) foraging on shoreline, feeding on a pen shell (Pinna sp), Sanibel Island, Florida, USA

Daniel Gomez / Fish experts Leandro Sousa + Mario Pinna attching fish to ROV. Brazil

Jose B. Ruiz / Noble pen shell {Pinna noblis} Mediterranean.

Jose B. Ruiz / Noble pen shell {Pinna nobilis} Mediterranean

Juergen Freund / Penshell {Pinna carnea} in seagrass on seabed Caribbean sea

Jack Perks / Common carp (Cyprinus carpio) swimming in a river, feeding on Zebra mussels (Dreissena polymorpha). The animal swims out of the frame. London, UK.