Irish Seashore Life
Walking along the shore at the high tide mark you can often encounter debris that was left behind by the tide. On this strandline you can sometimes find some interesting or unusual objects. Some of these may have come from the deeper waters of the ocean, attached to a ship wreck or freely floating to arrive upon the shore.
The ocean covers an immense area and is inhabited by countless forms of plant and animal life. Here is a selection of the creatures you are likely to meet in the rock-pools around Ireland’s shores.
Sparrán na caillí mairbhe
This is an egg case laid by the dogfish in deeper waters. Long twisted tendtils are to be found on each corner which once were used to attach the egg case to seaweed or other floating structures. Light brown in colour, the “mermaid’s purse” is only seen when it is washed upon the shore. By this time it is usually quite dry and hard. The mermaid’s purse is normally found empty as the young fish will have hatched out by the time it has washed ashore.
(skeleton) Cudal (Cnámh)
Belonging to the same family as the Octopus and Squid, the Cuttlefish lives usually in bays and estuaries. When alive, the bone inside its body has many tiny holes which fill with gas halping it to float. You may find such a Cuttlefish bone on the shore as it floats about in the water for a long tiem after the uttlefish dies. If you have a pet budgie, you may give it such a bone to help it keep its beak trim!
Starfish and Sea Urchins
Starfish and sea urchins are part of a group of animals known as echinoderms –the spiny-skinned animals. They all carry spiny skins as their name suggests however in some, the spines are soft and not so obvious. Apart from their spines, echinoderms share another feature –they have bodies divided into equal sections arranged around a central point. The starfish is a case in point.
The sea urchin
If you examine it closely you will find that it too is divided into segments, not unlike an orange. Starfish have five arms, which may be rough and spiny or quite smooth to touch. Many small tube-feet with suckers line the underside of their bodies. These are used for moving about and feeding. Some of these suckers are strong enough to prise open shellfish. Once open, a starfish can stick its stomach out of its mouth and into a shellfish. Using digestive juices it then proceeds to soften the animal that is to be dinner, and absorbs it.
Sea Potato also known as a Heart Urchin
If you are lucky enough to chance upon a Sea Potato, be careful to handle with care – their shells tend to be extremely fragile and brittle – much to the dismay of small children! This sea creature gets its name from the potato-like appearance of its empty white shell. The Sea Potato usually lives where it can burrow into clean sand in deeper waters. Covered with a thick layer of yellow-brown spines, the Sea Potato can grow up to 9cm but is usually smaller. When alive it uses rows of tube-feet to collect particles from within its burrow.
You are bound to encounter many sandhoppers if you decide to venture onto one of Ireland’s beaches. By day they care to be found under the debris or seaweed of the high tide mark. These little creatures come out at night from their hiding places to feast on seaweed. There are numerous different kinds of sandhopper. By flexing its tail this small creature can hop quite long distances.
The red-brown crab with its “pie-crust” edging is easy to recognise, its small green eyes, black tips on its large pincers. Claws used for defence and feeding tend to be bigger in the male crab than on the female. To hide, the edible crab may tuck its legs under its body and partly bury itself among stones making itself difficult to see. You may find big specimens in the deeper waters but on the shore smaller edible crabs may be found.
Common or Curved Razon Shell
Scian Mhara Chuar
This shellfish has a long, thick and slightly curved and rectangular shaped shell. You may be lucky enough to encounter one empty on the shore. The two halves of this shell or valves are held together by a strong ligament along one side. When the shell is closed, the ends remain open, creating a tube-like effect. A filter feeder, this bivalve must remain close to the surface of the water as its siphon is very short. If it feels threatened it can pull itself deep into the sand by extending a strong, muscular foot to pull its shell downwards.
Common or Edible Cockle
Ruacan Cerastoderma edule (Cardium edule)
The Common Cockle is a bivalve that lives buried in sand or mud by the shore. Often its empty shell is all that you may see on the surface. The shell is thick and greyish white in colour having broad rounded ribs running from the top to the edge of the shell. You can tell the animals’ age by looking at the growth rings running across these ribs. Each year a heavy ring is added. The cockle lives 2-3 cm below the surface of the water anchored by its foot. It pushes its two tube-like siphons up to the surface of the sand to feed and breath when the tide is in.
Excerpts from A Beginners Guide to Ireland’s Seashore.
Common or Blue Mussel
This mollusc prefers to attach to a hard structure, rocks or a shipwreck. Its slightly oval shaped shell may be blue, black or brown in colour. Inside it is pearly white with a darker boarder. You will find mussels living together in huge colonies on rocky shores. They will choose areas where there is plenty of water in movement, such as a tidal zone. Water carries tiny animals and plants that the mussel filters out as food using its gills. Using its strong hair-like byssus threads the mussel attaches itself to rocks, stones or other mussels.
This is one of the most common and familiar sea snails on the Irish seashore and is the largest of the winkle family. Edible Periwinkles bear a thick coiled shell dark grey brown in colour and often with darker lines. This colouring is a camouflage helping the Periwinkle to blend in with the seaweeds under which it lives. Out of water the Edible Periwinkle closes its shell with a horny disc called the operculum sealing the creature inside. This type of Periwinkle can be found on all types of shore of the Irish coast.
The common limpet is a common sight on rocky Irish shores, easily recognised by its cone shaped shell. One strong sucker foot allows it to cling onto the rock surface. The watertight grip allows the limpet to keep water within its’ shell also protecting it from predators and strong waves. Look closer and you will see how each Limpet has its own “home base” on a rock. This is an oval scar which is the exact shape of the shell. The limpet likes to wander when covered by water grazing lazily on tiny seaweeds and encrusting animals. It then returns to the scar once the tide goes out once again.
Walk upon a beach and you may notice some spaghetti like casts in the sand. These, more than likely are a type of bristly worm, the Lugworm. This sea worm spends its life inside its U-shaped burrow feeding on the sand and extracting any nourishment it can. A pit is formed above its head as it eats while the undigested sand is removed and this forms the cast. The body, as in all bristle worms, is segmented and looks similar to an earthworm.
Smugairle an chompáis
Bluish white in colour and bearing brown V-shaped markings on the top of its bell-shaped body and a ‘frill’ of brown markings around the edge – the Compass Jellyfish is quite a pretty sight. The anatomy of this Jellyfish is made up of 24 tentacles arranged in groups as well as four very long and “frilly” mouth arms and eight sense organs. You may find Adult Compass Jelly fish in Ireland’s coastal waters from July to September often to a size of 30cm in diameter. Also, they may be seen washed up on a beach. The Compass Jellyfish feeds on worms and small jellyfish.
A free floating animal, the Common Jellyfish feeds on a wide range of plankton and small fish. It has a body shaped like a saucer and can grow up to 25 cm in diameter with four mouth arms purple in colour hanging below it. It has four purple horseshoe shaped rings on the top of its body which are its reproductive organs. This Jellyfish is most commonly seen as a blob of transparent jelly washed up on the shore. It may be found in large numbers in the summer around coastal waters.
Excerpts from A Beginners Guide to Ireland’s Seashore.