Alex Mustard / A young veined octopus (coconut octopus: Amphioctopus marginatus) shelters in an empty bivalve shell by pulling the two halves together with its arms. Lembeh Strait, Molucca Sea, Sulawesi, Indonesia.

Philippe Clement / Dog cockle (Glycymeris glycymeris) shell split in to the two halves showing the inside and the outside, Normandy, France

Philippe Clement / Common mussel (Mytilus edulis) shell, both halves separated, Belgium

Jane Burton / Buff Pekin {Gallus gallus domesticus} hatch sequence 3/9. The chick begins to push the two halves of the shell apart