Intertidal invertebrates

Sea anemones and corals belong to a fascinating group of animals called cnidarians. Despite looking like plants they are animals, related to jellyfish. These creatures are found along Devon’s rocky shores and in its underwater habitats, where they play an important role in marine ecosystems.

Anemones and corals are soft-bodied animals with a simple structure. They have a central mouth surrounded by tentacles armed with stinging cells called nematocysts, which help them catch food and defend themselves. Most are attached to rocks or other surfaces and rely on currents or their tentacles to capture tiny prey like plankton. Some UK corals are soft-bodied and some secrete a calcium carbonate skeleton that forms a protective base and helps anchor them to the seabed.

Sea anemones are often described as “flowers of the sea” because of their bright colours and petal-like tentacles. In Devon, you might spot the Snakelocks Anemone, which has long green tentacles tipped with purple. These anemones thrive in sunny rock pools and shallow waters, where they stay attached to rocks or seaweed. They’re solitary animals, feeding by stunning small fish and invertebrates with their stinging tentacles before drawing them into their central mouth.

Stalked jellyfish are a rare and unusual type of jellyfish that live in shallow coastal waters. Unlike their free-floating relatives, they use a stalk to attach themselves to seaweed, seagrass, or rocks. They’re small (usually under 5 cm), often beautifully patterned, and can be hard to spot due to their camouflage and preference for sheltered habitats like rockpools and estuarine lagoons.

There are ten species recorded in the UK, with four more commonly found in Devon. Each species has a central bell-shaped body with eight arms, each ending in clusters of tentacles. These tentacles are often tipped with stinging cells the jellyfish use to catch tiny prey such as plankton. Their presence is a strong indicator of clean, undisturbed intertidal habitats.

The Tentacled Lagoon Worm belongs to a family of bristle worms that includes ragworms, tube worms and fan worms. These species share key features, including segmented bodies with bristles and feeding tentacles.

This particular worm is very small, just 3 to 5 mm long, and barely visible to the human eye. It lives in shallow mudflats in brackishWater that's a mix of fresh and salt water, often found where rivers meet the sea. water or lagoons, either on the surface or partially buried in sediment, within tubes that it builds by gluing fine sediment particles together with mucus.

The Tentacled Lagoon Worm has a distinctive life cycle. Unlike most bristle worms, which typically have a planktonic larval stage (where larvae are released into the water column to grow and develop), this species does not disperse in that way. Instead, its larvae develop inside the mother and stay in her tube for around 12 days before emerging onto the surface of the mud. They feed by using the tentacles around their mouths to gather detritus from the surrounding sediment.

Because the larvae do not enter the water column, they are unable to disperse over long distances. This limited mobility makes the species particularly vulnerable to habitat degradation and changes in local environmental conditions.

Tentacled Lagoon Worms are protected under UK conservation legislation (Schedule 5 of the Wildlife and Countryside Act 1981) due to their rarity and vulnerability. Their specialised habitat is easily disturbed by activities such as dredging, pollution or changes in salinity. Because they do not disperse far, populations cannot easily recover if habitats are lost or degraded.

Spiny Cockle, Celtic Sea Slug and Native Oyster are listed as Devon Special Species. For more information on intertidal molluscs see the Molluscs page.