Molluscs

Molluscs are among some of the most successful of all marine animals. They display great diversity and a remarkable range of body forms which allow them to live anywhere in the marine from the deep ocean to the splash zone. Some species lack eyes and shells and live passively in sediment or on the seabed. Others are intelligent, active hunters with complex nervous systems and large eyes. 

Cuttlefish - Sepia officinalis

These animals are related to octopus and squid. They have ten arms which are all armed with tiny suckers. These are used to capture their favourite prey, crabs and prawns. At the centre of the tentacles lies the mouth which is an armoured horny beak. This is used to inject a fast acting poison into the prey, limiting damage that can be caused by a defensive crab’s pincers. This poison acts on the prey's nervous system, stopping its functioning, which results in the internal organs shutting down. The poison will not hurt us, but cuttlefish can still give a nasty bite if handled too roughly!

Cuttlefish can move about very quickly. They use a siphon lying below the mouth which squirts out water, jet propelling the animal through the water.

Marine biologists have discovered that cuttlefish are very intelligent and have a complex social behaviour. Experiments show that cuttlefish are able to communicate with each other using flashes of colour produced by special cells in the skin. The timing of these flashes and patterns appear to be used during social activity such as mating and fighting. For example a male is able to flash warning messages to a competitor, swimming close by on one side, whilst at the same time courting a female, with different patterns, swimming by on the other side.

 

Common Limpet - Patella vulgata

Abundant on rocks from the high to the low water mark, limpets are superbly adapted for life on the rocky shore. A strong conical shell protects it from predators and its muscular foot grips to the rock regardless of the strength of wave.  Higher up the shore taller, wider limpet shells allow for greater water retention when exposed by the falling tide.  Limpets travel slowly, grazing rocks of microscopic algae with a rasp-like 'radula' or toothed tongue.  They follow a trail of mucus left and return to the same spot or ’home scar' after every excursion.  This scar is a ring which the limpet gradually grinds into their anchor spot on the rock, to aid their grip and help them retain water.

 

Polycera sp

Many different species of sea slug are found in the waters around Lundy. They are related to other sea-snails, and also garden snails, but have lost their large external shells. Instead protection is provided by poisonous stinging cells which are actually taken from their prey. When sea slugs feed on anemones and sea mats they consume the stinging cells, but do not eat them. Somehow the sea slugs can then internally transport these stinging cells and store them in special bumps on their backs. Here they provide a nasty concentrated stinging defence against any would be predators. Sea slugs have external gills which look like feathers gathered in a ring towards the back end. They come in a bewildering variety of bright colours warning predators that they are poisonous to eat!