Underwater Worlds

Explore the rich biodiversity of the world's oceans with bivalves, shellfish, sea urchins, cephalopods & molluscs. This exhibition is currently closed.

No Wheelchair Access No Wheelchair Access

The greatest variety of body shapes and lifestyles occupied the top floor of the Museum among the many groups of invertebrate animals. Many of these are marine creatures or land-living relatives of animals that show their greatest diversity in the world’s oceans. Echinoderms are animals with five-fold symmetry, the most obvious examples being starfish. Sea cucumbers such as Psolus phantapus are less obvious members of this group. They live on the sea floor and can spray out their internal organs if attacked by a predator. Being entangled in this sticky mess keeps the predator occupied while the sea cucumber moves away.

Heterocentrotus mammillatusSea urchins have a hard outer casing and use spines to deter predators. One of the most beautiful examples is the slate pencil urchin Heterocentrotus mammillatus from the Gilbert Islands in the Pacific Ocean.

Shellfish come in an amazing variety of shapes and sizes, mostly related to their lifestyles. This biological diversity is placed into three major groups within the molluscs – gastropods, bivalves and cephalopods. Molluscs with coiled shells are known as gastropods, a term that covers familiar snails, the limpets with their simple shells and even slugs without shells at all. The Australian red triton Charonia lampas on display is cut to show the internal spiral structure of a typical gastropod. Emperor helmet shells of the species Cassis madagascariensis from the West Indies were popular among Italian cameo workers who carved delicate intaglios, which stand out on the coloured layers of the shell.

Bivalves have two halves to the shell and include the familiar cockles and mussels. Tropical waters have a dazzling array of coloured bivalves including the Pacific thorny oyster Spondylus princeps of the western American coast. The noble pen shell Pinna nobilis attaches its shell to the sea floor with strands of strong tissue known as byssus. A 19th-Century fashion in Italy was to make gloves with this gold coloured thread.

Cephalopods are also molluscs, even if few living species apart from the nautilus have shells. Their ancestors include the famous ammonites, which thronged the seas when dinosaurs were alive. Modern cephalopods are highly intelligent creatures and include the white-spotted octopus Polypus macropus, on display in the form of a coloured glass model. Like other octopuses they can find their way through a laboratory maze and squeeze their soft bodies through the tightest gap. This allows them to escape predators but also to hunt their prey, which they bite with a horny beak.