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Beachcombing for shells
Rob Arnhem does what any resident of Oman should in the summer – hit the beach and study

Oman's 1,300km of beaches offer a ready opportunity to indulge in one of our earliest ancestors' favourite activities – beachcombing. The Gulf is home to at least 1,200 species of mollusc, the term given to the huge family we usually just call snails or shellfish. Some are found on land but most live in watery habitats, both fresh and salty. The vast majority of molluscs have an external skeleton or shell protecting the soft and often juicily edible body. There are 80,000 to 10,0000 species worldwide, divided into six classes, but the two producing 'shells' as we know them are the gastropods (univalves) and bivalves. These are also the most widespread, attractive, varied and collectible.

As their name suggests, bivalves have two usually matching shells that fit together tightly to protect the soft inner body. They live buried in sand or crevices or attach themselves permanently to rocks. A univalve has one shell, generally spiral, pointed and closed at one end and flared at the other to allow it to move on its flattened fleshy 'foot'. Most bivalves are filter feeders or herbivorous algae eaters, but many gastropods (literally 'stomach foot') are carnivorous and need to move around in search of their prey – often bivalves. The most valuable edible mollusc is the abalone, Haliotis species. In Oman it occurs only offshore in Dhofar. The big fleshy foot is cut off and dried, canned or frozen. It's an expensive, and for Oman, lucrative delicacy, exported mainly to the Far East. All along the coast of Oman, heaps of accumulated shells prove that we've been enjoying shellfish for millennia.

So what makes the shell itself so remarkable and attractive?
The soft body of a mollusc, its mantle, can often extend to cover the entire shell. It extracts calcium carbonate, or 'lime' from seawater and deposits it around itself. Lime bonds with conchiolin, a natural substance similar to our nails, which the creature secretes. As the shell grows, the mollusc covers more of its outer surface with more layers, writing its own genetic signature into the surface in a programmed pattern of colours, lines and textures. It also cleverly makes more room inside for its growing soft
body by dissolving some of the inner layer and re-depositing it externally. Oysters and mussels line their shells with satiny iridescent layers of nacre, or mother-of-pearl, which may produce a natural pearl.

The all-time attractions of the shell world are probably the cowries. They're mostly algae grazers which hide under stones during the day, or are camouflaged by their often cryptic mantle, which covers the entire shell and gives it an incomparable glossy finish. The best known and oddly named tiger cowrie is actually spotted, not striped. The most common in Oman is the lovely understated thrush cowrie, pale blue with a sprinkling of brown spots like a thrush's egg.

Like clams, which are often called 'Venus' shells because of their heart-shaped forms. Cowries are called Cypraea and some clams Paphia in honour of Aphrodite, the Greek goddess of love.

Other shells are not quite so blessed and beneficial. The Conus genus is equipped with a poisonous harpoon-like sting, which can be fatal. They almost all look stunning too, with beautiful bold designs as their specific names suggest: Conus textile, geographicus, striatus, tesselatus. Although only four of them here are dangerous, but be very careful when picking any species of cone shell up, as they can extend the proboscis backwards and penetrate even a cloth bag. A somewhat similar-looking type, but harmless, is Strombus, with a pointed tip and a bright pink lip. A feature of many gastropods is a hard horny trapdoor attached to the 'foot', which can be closed to seal the animal in safely in event of attack. In Salalah, these Opercula, to give them their scientific name, are gathered and ground as part of the ingredients of bakhoor, the traditional incense mixtures).

The shallow sandy flats of the Batinah can be strewn with millions of dead shells, like the tiny button shell Umbonium. This attractive little shell comes in a huge range of colours and patterns, from bright pink to deep maroon. It's easy to collect them by the handful at Sawadi, and turns whole beaches pink further south near Khaluf. Often found with them are the little curved white shells shaped like miniature elephant tusks, called Dentalium. One of the most amazingly varied shells is Oliva bulbosa, common in the soft muddy sand where it leaves its signpost tracks. It can range from delicately speckled pale grey to almost coffee, but the zigzag op-art doodlings on many of its shells are its best feature. Slender extended spiral cones are the trademark of Turritella or auger shells. Similar but plainer and smaller glossy ones, the scavengers of the beach can be seen homing in on any dead creature which they will rasp away at with their file-like 'tongues', or radulas. These so-called plough shells are useful indicators of a beach safe for swimming (to seek their food they live in shallow safe water with little backwash – conditions making for safe swimming for us too). When they do get washed away by a wave, they rapidly dig in their sail-like 'foot' to stabilise themselves. Moon shells are also quite common, especially the pure white porcelain-like one, and a larger pinkish-grey one sometimes called 'shark's eye'. These carnivorous snails attack other shells and drill an incredibly neat round hole through their shell with their radulas, aided by a strong acid. Then, like spiders, they simply suck the pre-digested contents out at leisure.

In Oman, you need a license to collect live shellfish. Carefully replace any rocks you've lifted after checking what's under them. Inspect any apparently empty shells for signs of life – you might be abducting a hermit crab, which has prior right of occupation. Wash the shells to flush out any remaining dead contents, or the smell will soon notify you. Once dry, you can buff them up with a little olive oil if they look dull. If you become a serious collector, you'll have to keep them away from light, as they will fade in time. Please try hard to avoid buying those wonderfully attractive tropical shells displayed for sale in places like the Seychelles and Caribbean, and recently, at Bandar Jissa beach. Beautiful they are, but they're generally gathered alive, seldom eaten and boiled before being deodorised for the tourist market. Need and greed drive poorer countries to resort to this, but the ecological damage and sheer waste is immense. It's best to resist owning shell artefacts. Just collecting washed up empty shells on relaxing beachcombing walks and arranging them artfully in a bowl on a coffee table should satisfy most normal urges.