Sea hare

If you go to the beach at low tide and search a weedy rockpool, you just might find a slug-like creature munching on the seaweed. But watch out! This peaceful-looking animal has a surprising defence.

Fast Facts

Latin name: Aplysia punctata

Notable feature: ‘Bunny ear’ tentacles, a pair of fleshy ridges on the back.

Rarity in the UK: Rare / Common

Where in the UK: Widespread in shallow coastal waters.

Slug or snail?

Sea hares are a type of Sea snail found in weedy coastal waters around the UK. They are named for their ‘bunny ear’ tentacles, known as Rhinophores which are used to detect scents in the water. Though they look more like slugs, they have a small shell embedded in their back with fleshy frills either side called parapodia, used for breathing.

Sea hares range from green or brown to red or purple. Their colour depends on the type of seaweed they feed on, which also helps keep them camouflaged amongst it.

A Sticky defence

Despite being soft and slow-moving, sea hares have an explosive defence. If one is pestered by a predator, it can eject a cloud of ink and a milky chemical called opaline. The ink helps to surprise and distract the predator, whilst the opaline coats it in a sticky mess which can clog up the antennae of crustaceans such as Lobsters. With the predator left surprised and senseless the sea hare can make a getaway.

Start a love chain

Like many other snails, sea hares are hermaphrodites (each is both male and female) but they must come together to breed. A sea hare which is ready to mate releases a powerful hormone which attracts others.

When other Sea hares arrive they join onto the back of the party to make a mating chain. The front sea hare acts as a female, the back one as a male and the middle as both, fertilising the eggs of those in front. This amorous conga line can go on for hours, whilst the acting females lay spaghetti-like clumps of egg strings.