(Above) By-the-wind-sailor, (below) Shipworm wood, (bottom) Sea beans © J Hatcher (below middle) Goose barnacles © M Raper
By-the-wind-sailor, Velella velella, is a species that sometimes strands in such high numbers that it forms a purple tide line on the beach.
Although they look like a jellyfish each individual is actually a colony of animals called Hydrozoa that all work together and perform different roles to make up one functioning body. They get their name from the sail attached to their disc shaped float that means they get blown around by the wind as they bob on the surface of the ocean. With a strong South-Westerly behind them they have no choice but to visit our beaches!
Ship Worm Wood
Ship worms are sometimes known as “termites of the sea” because they bore through wood including piers and ships, riddling them with so many holes that they are sometimes completely destroyed. Despite their name, ship worms are actually bivalve molluscs, more closely related to mussels and clams than any type of worm. They have a long body with 2 small shells at one end that they use to rasp away at the wood to drill holes, feeding on the fine particles of wood created. Look for evidence of their voracious hunger in pieces of driftwood on the beach.
Goose barnacles spend their lives attached to floating objects like wood and in more recent years; plastic. They settle onto it as larvae and attach themselves with a strong stalk. As they grow they develop a hard white shell with 2 halves (each half is made up of 5 plates) which protect their feathery legs that are used for feeding, sieving out tasty morsels as they travel the open oceans, going wherever the current takes them. Their lack of ability to steer against the flow of water means some of them are doomed to end their lives washed up on beaches where we can find them, often attached to objects in huge numbers. Several species of goose barnacle are found in Dorset. The most frequently seen is the Common Goose Barnacle (Lepas anatifera) but another interesting one is the Buoy Barnacle (Dosima fascicularis). It can attach to flotsam or create its own float by secreting a kind of cement that has the texture of expanded polystyrene foam- it is the only species of goose barnacle able to do this.
It’s not just animals you find along the strandline when you go out beachcombing, there are also sea beans. These are the seeds of tropical plants that are designed to disperse long distances via rivers and the sea. Many of those found in the UK were probably washed a bit too far from the coast by a tropical deluge of rain. Keep your eyes peeled for the pearly Grey Nickernut, aptly named Hamburger Bean or the heart-shaped seeds of the Monkey Ladder Vine that grows amongst the canopy of tropical forests. Although rarely found in Dorset there have been records, proving that whatever the weather, there can be exciting things to see at the beach!