Shell

VHS cover

*Shell* is the thirteenth and final episode of the second season of Eyewitness. The topic of the episode is about animals (and some plants) that use shells for survival, their evolutionary history and cultural relevance to people. The episode aired on 8th July 1996.

*Shell* is based on a book that was first published in 1989, and has been republished on several occasions including in 1995, 1998, 2000 and 2013.

## Episode

### Introductory sequence

A scallop shell opens to show a rotating coconut. As the coconut spins around to its open half a Hermann’s tortoise is shown crawling inside it; it crawls off-screen and leaves the white background.

### Episode outline

Click here for the full transcript for Shell.

The shell is one of nature’s most successful creations, being adopted by hundreds of thousands of species that range from the desert to deepest ocean. All creatures have some strategy for survival such as camouflage, safety in numbers or active fleeing. At first, a shell seems more of a liability than an asset as they are heavy, inflexible and slow a creature down. But the design has been altered little in millions of years and is highly successful.

Shells set out on the evolutionary race millions of years ago. Today we understand how these fossils originated but, in the past, they gave rise to explanations, such as in 15th century Whitby, England where ammonite fossils were thought to be serpents beheaded and turned to stone by the Saxon abbess Saint Hilda. In many places, the landscape is made from shells - shells crushed into rock have created mountains, gorges, limestone and chalk cliffs.

The shells we find on the beach today are often the homes of sea snails. The snail grows its calcium shell around a central shaft like a spiral staircase, secreting calcium from the soft tissue of the mantle. The mantle can also add colour to the shells. Most shells spiral to the left as they grow, but some go the other way. In Hinduism the shankh shell, a type of conch, symbolises the origin of existence.

The spiral shell is shared by a group of single-shelled creatures collectively called gastropods. Land snails are gastropods that move by lubricating themselves with mucus, but can only move slowly. Double-shelled snails, or bivalves, don't even try to move around. Oysters, mussels and clams all filter food from the water, and their main defence is to simply clam up and slam their shells shut. While they have many determined predators, shellfish have stuck with their steady defence.

The shell-bound life poses few problems a little ingenuity can’t solve. Sea snails use bubble rafts to reach their toxic Portuguese man-o-war prey, while cone shells use their own toxins to kill fish. Japanese carrier shells have a sticky coating that it attaches debris with to fool predators. Some shelled molluscs can move quickly when escaping, such as the cockle and scallop. Scallops have multiple eyes to help them spot predators. The scallop shell often appears in art and religious symbolism.

As well as protection against predators, shells protect against the elements. Some shells resist coastal waves with ingenious solutions, such as the burrowing piddock and edible date mussel. Byssus thread is used by many shellfish, which can be as strong as steel cable. In Italy, byssus thread was woven into fine golden cloth.

Shelled animals on land use different strategies. Tortoise shells are an extension of their backbone, with double protection from both the exoskeleton and an internal skeleton. The scorpion has no internal skeleton, but its shell has joints made of tough and flexible chitin. Woodlice also have articulated armour plating, with some able to curl up into an impregnable ball. Although the resemblance may not be obvious, woodlice are close relatives of crabs and lobsters.

The lobster’s armour works just as that of a medieval knight. It provides protection, but movement is ponderous and exhausting. The lobster has the advantage of being supported by water. Spiny lobsters migrate in groups to escape predators. Most crustaceans have to shed their shells and grow a new one, as the armour does not grow with the animal. This is a dangerous time, as without the hard shell they are defenceless.

Shells can provide protection that faster but more vulnerable animals may envy, but some shellfish do without the protection altogether. Cuttlefish and squid have tiny internal shells to support their mass of flesh and muscle. This group includes the giant squid, the largest of the invertebrates.

Humans have been fond of shellfish since the earliest times, often as a source of food. The ancient Romans extracted a valuable purple dye from the murex shell. Other shells have been used as currency. Wampum were discs cut from Quahog clam shells and used as money by native Americans, while in Africa and the South Seas the cowrie was legal tender. The exchange rate for buying livestock with cowrie shells is provided.

Coconuts protect their seeds with a hairy outer shell, which helps them drift on the ocean. Both humans and the coconut crab appreciate the coconut as food. For humans, the coconut provides food, fuel and livelihood, and is subject to religious ceremonies in India. While coconuts are excellent marine travellers, barnacles can outdo them by clinging to the hulls of ships.

A tiny mollusc, the shipworm, gives ships larger problems. They can burrow through wooden hulls and secrete a protective lining. This method was copied by Marc and Isambard Brunel when they were digging their tunnel beneath the River Thames. The nautilus also provided inspiration for the design of the first submarine.

Coral reefs are made up of the exoskeletons of billions of tiny coral polyps, each secreting its own limestone shell. Even smaller shelled creatures exist as plankton, a swirling snowstorm of microscopic creatures that form a food source for marine giants such as whales and basking sharks. The biggest seashell belongs to the giant clam, which can grow as big as a baby elephant. Legend says their vice-like grip can trap unwary divers who put a foot in them.

True or not, divers are prepared to face real danger to gather pearls from oysters. The process of how and why an oyster creates a pearl is outlined, including the ancient fashion to create tiny pearl Buddhas from freshwater mussels. While oysters make pearls, some shellfish deal with threats more directly, such as the spiny sea urchin. Some tortoises and turtles use sheer size as a means of avoiding attack.

Sea turtles leave the sea to lay their eggs, while land crabs make the opposite journey when they breed. Of all shells, the bird’s eggshell is perhaps the most perfect. They can resist enormous pressure while still being thin enough for a chick to peck its way out. Shells feature in mythology around the world, from cosmic eggs to the Mayan god Quetzalcoatl, who was born from a snail shell. Many shelled creatures started out on their evolutionary journey early and have survived unchanged. They’re onto a winner, an evolutionary design that has stood the test of time.

## Animal species filmed for the programme

### Studio footage

* Hermann’s tortoise, *Testudo hermanni*
* Common shore crab, *Carcinus maenas*
* Domestic chicken, *Gallus domesticus*
* East African giant land snail, *Lissachatina fulica*
* Imperial scorpion, *Pandinus imperator*
* Spur-thighed tortoise, *Testudo graeca*
* Crested porcupine, *Hystrix sp*.
* Red-necked wallaby, *Notamacropus rufogriseus*
* European rabbit, *Oryctolagus cuniculus*
* European lobster, *Homarus gammarus*
* Common rough woodlouse, *Porcellio scaber*

### Stock footage

* Green sea turtle, *Chelonia mydas*
* Christmas Island red crab, *Gecarcoidea natalis*
* Plains zebra, *Equus quagga*
* Common whelk, *Buccinum undatum*
* Garden snail, *Cornu asperum*
* White-lipped snail, *Cepaea hortensis*
* European flat oyster, *Ostrea edulis*
* Ballan wrasse, *Labrus bergylta*
* Blue mussel, *Mytilus edulis*
* Blue crab, *Callinectes sapidus*
* Eurasian oystercatcher, *Haematopus ostralegus*
* Portuguese man-o-war, *Physalia physalis*
* Violet raft snail, *Janthina janthina*
* Cone snail, *Conus sp*.
* Sea goldie, *Pseudanthias squamipinnis*
* Common cockle, *Cerastoderma edule*
* Queen scallop, *Aequipecten opercularis*
* Hawksbill sea turtle, *Eretmochelys imbricata*
* Common yellow scorpion, *Buthus occitanus*
* Desert locust, *Schistocerca gregaria*
* Common pill woodlouse, *Armadillidium vulgare*
* Florida spiny lobster, *Panulirus argus*
* Grey triggerfish, *Balistes capriscus*
* Palmetto tortoise beetle, *Hemisphaerota cyanea*
* Common spiny lobster, *Palinurus elephas*
* Common cuttlefish, *Sepia officinalis*
* Bigfin reef squid, *Sepioteuthis lessoniana*
* Domestic cattle, *Bos taurus*
* Domestic goat, *Capra hircus*
* Coconut crab, *Birgus latro*
* Goose barnacle, Thoracica
* Chambered nautilus, *Nautilus pompilius*
* Comb-jelly, Ctenophora
* Sea gooseberry, *Pleurobrachia pileus*
* Basking shark, *Cetorhinus maximus*
* Giant clam, *Tridacna gigas*
* Sea urchin, Echinoidea
* Ploughshare tortoise, *Astrochelys yniphora*

## Stock footage sources

* Wildlife on One: Scorpion (1979) – Scorpion killing locust
* Natural World: The Lost World of Medusa (1984) – Cone snail eating fish
* The First Eden: Wastes of War (1987) - Goose barnacles
* The Trials of Life: Finding the Way (1990) – Spiny lobsters migrating and being attacked by triggerfish, hawksbill sea turtle
* Land of the Eagle – The Great Encounter (1991) – Blue crabs

## Credits

* Director - Sam Hodgkin
* Producer - Richard Thomson
* Writer - David Stafford
* Music - Guy Dagul
* Graphics Director - Dean Stockton
* Graphics Design - Stan Peplinski
* Camera - Sean Bobbitt and Matthew Poynter
* Set Design - John Brace and Mark Dadswell
* Production Co-ordinator - Nicola Melluish
* Production Assistants - Tilly Colaco and Quin Jessop
* Researcher - Shaun Whiteside
* Archive Researchers - Rebecca Cody, Philippa Graves and Anuschka de Rohan
* Graphics - Simon Kilroe, Kim Aldis and Kate Hood
* Editors
	+ Offline - Mark Fox
	+ Online - Trevor Aylward
* Dubbing Mixer - Steve Cookman
* Music Engineer - Roger King

## Making this programme

The making-of documentary shows how the Eyewitness style of a pure white background is created, by simply painting the entire studio white. Over twenty gallons of paint is used in each repainting, with the crew members having different ways of avoiding getting their shoes covered in paint. In the studio, each crew member has their own role to play in making the programme come together – from the cameraman and his assistant, the makeup artist and the arts department, who are responsible for props and special effects. While each crew member is an expert in their field, they sometimes do a job outside their normal remit. In Shell, the studio spark or electrician was the only crew member who could fit inside the suit of armour. Once the armour was fitted, the knight was laid out in the position of a previously filmed lobster. The filming went perfectly but, just out of frame, the armour seized up which proved the point the episode was making – that shells can be heavy and inflexible.

## Home media releases

Shell has only ever been released on VHS. None of the three different DVD releases included this episode.

**Writing staff**: Anne MacLeod • Ben Southwell • Ben Steiner • Brian Meehl • David Hanson • David Stafford • David Helton • George Bloom • Lynette Singer • Mike Tomlinson • Paul Thomas • Stan Cullimore
**Directors**: Gavin Maxwell • Justine Kershaw • David Hutt • Andrew Jackson • Justin Hardy • Ludo Graham • Jerry Foulkes • Derek Hall • Sanjida O'Connell • Caius Julyan • Bonni Cohen • Leanne Pooley • Edwina Vardey • Alexandra Beazley • Sam Hodgkin • Karen Walsh • Jack Weber • Richard Simkin • Alex Hearle • Brian Cummins • Ben Southwell
**Composers**: Guy Michelmore (season one) • Guy Dagul (seasons two and three)

**Season One**: Cat • Fish • Horse • Dog • Jungle • Bird • Amphibian • Insect • Shark • Elephant • Reptile • Dinosaur • Skeleton
**Season Two**: Desert • Tree • Ape • Mammal • Butterfly and Moth • Volcano • Rock and Mineral • Seashore • Pond and River • Weather • Arctic and Antarctic • Prehistoric Life • **Shell**
**Season Three**: Flight • Bear • Sight • Island • Survival • Mountain • Monster • Human Machine - Plant • Ocean • Planets • Life • Natural Disasters