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Limpets

Common limpet
Patella vulgata

Limpets are a familiar feature of rocky shores. They can be found clinging to hard surfaces, forming characteristic indentations known as scars. They are keystone species are important in keeping algal levels under control.

Life span
Limpets living on bare rock grow slowly, but may live for around 15 years. If food is abundant, they grow faster but may only survive 2-3 years.

Statistics
They are up to 6cm in diameter and 3cm high.

Distribution
The common limpet is a temperate species, found from Norway, through Europe to Portugal.

Habitat
Limpets are abundant on rocky shores, where they attach to rocks or other hard substrates.

Diet
Limpets are herbivores, grazing on the thin form of algae that forms on rocks and weed. They will also graze on settling larvae if small enough to eat.

Behaviour
Adult limpets usually return to the same area of rock after feeding. They form a small depression, known as a scar, by rubbing against the rock. This scar ensures a tighter fit for the shell, helping the limpet avoid desiccation.

Limpets are active foragers and wander around the rocks when the tide is in. They use chemical cues to follow their own mucus track back to their home point. They sometimes use the edge of the shell like a bulldozer to scrape away at rocks and algae.

Reproduction
Limpets are hermaphrodites (producing both male and female reproductive cells) and undergo sex change during life. They mature as males at about 9 months of age, but after a couple of years they change sex to become female.

Spawning occurs once a year, usually during winter, and is triggered by rough seas which disperse the eggs and sperm. Larvae are pelagic for a couple of weeks before settling onto a hard substrate.

Conservation status
Limpets are considered to be a keystone species of rocky shores because they keep algal levels in check. They are not considered to be endangered.

 

 
 

Marine Ecology


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Upper Eulittoral Zone

High Tide Zone: Also called the Upper Mid-littoral Zone (Upper Eulittoral) and the high intertidal zone. This area is flooded only during high tide. Organisms in this area include anemones, barnacles, brittle stars, chitons, crabs, green algae, isopods, limpets, mussels, sea stars, snails, whelks and some marine vegetation.

This is where the confusion lies bewteen the barnacles belt & this zone the upper Uelittoral zone where actually a lot of barnacles like to live. Pictured here are the small white dots of Semibalanus balanoides shown above the algae.

The midlittoral zone is covered and uncovered twice a day by the tides. Animals in this zone have adapted to being immersed in air and sea water.

Anemones close when the tide is out, keeping in the moisture necessary for survival. Mussels close their shells tightly "clam up" for the same purpose, and open to feed as the tide brings in their food.

This zones upper level - mean high low water - is approximately +2.5 feet. The lower level - mean low low water is approximately 0 feet. It is frequented by a host of organisms and animals.

Species Found in Upper Eulittoral Exposed Sandy Shore

Exposed Sandy Shore tend to be dominated by crustaceans. A sandy beach is made up of minute grains of sand or crushed shells and rock. Because it is grainy, wind and water reshape a beach every day. Sandy shores are exciting places with life in and underneath the sand and water.

The intertidal zone is the area exposed between high and low tides. In the intertidal zone, part of the day is spent in open air and the rest of the day is spent covered in ocean water. High tide brings with it nutrients and food. When it goes out, the tide takes with it waste products and disperses eggs and larvae. Because of the shifting sands, organisms living in the intertidal zone on a beach have adapted to these changing conditions. Without the cover of water, many animals simply shut down during low tide. Some of the animals spend most of their life buried under the sand. Others burrow into the sand when the tide is low or when the crashing waves hit the shore. Some of the animals feed on materials that washes ashore. Others filter food from the water. Still others feed on tiny algae and bacteria among the sand grains.

Eurydice pulchra: Speckled sea louse (Isopod)

Phylum: Crustacea
Class: Malacostraca 
Order: Amphipodidae 
Family: Talitridae

Widespread on open coast and estuarine sandy beaches, with reduced abundance in south-east England

Found in the intertidal zone, on fine to medium grained sandy shores. Eurydice pulchra occupies a middle shore zone, but its distribution shifts up shore on spring tides and down shore on neap tides.

A small and distinctive 'louse-like' isopod. The body is flattened with an oval outline. It has large eyes, positioned laterally and a long second pair of antennae. It may be pale grey to brown in colour, with black spots covering all surfaces of the body.


Bathyporeia sp: Sand Digger Shrimp (Amphipod)

Found on sandy coasts of Britain and Ireland. Found in wet, clean, fine to medium sand, from slightly above the mean tide level into the shallow sublittoral; often abundant above mean tide level

Description: A small crustacean that grows to approximately 6-8 mm in length. Its body is laterally compressed with two pairs of antennae and seven pairs of thoracic limbs. Antenna 1 is shorter than antenna 2, and holds an accessory flagellum. The basal segment of antenna 1 is very large, and rectangular in shape. The remaining segments of antenna 1 are smaller and arise at right angles to the basal segment, a feature known as geniculate, and characteristic of the genus. The body appears semi-transparent to white, with varying degrees of red pigment associated with the abdomen. The eyes are red in colour and easily visible.


Phylum: Crustacea (Arthropods) 
Class: Malacostraca
Order: Amphipoda 
Family: Haustoriidae (Plump amphipod)

Scolelepis squamata: Bristleworm. (Nerine cirratulis) (Polychaete)

Scolelepis squamata is found in the mid to lower shore of exposed beaches. Found mainly in sand or sometimes muddy-sand in vertical burrows lined with mucus.

Well-draining beaches of coarse to medium grained mobile sand, generally on exposed coasts, support populations of burrowing amphipods and the isopod Eurydice pulchra . The degree of drainage appears to be a critical factor in determining the presence of polychaetes; only Scolelepis squamata appears to be capable of tolerating the well-drained sediments of this biotope.

DescriptionScolelepis squamata is a slender medium length worm 5-8 cm long and 2-3 mm wide. There are up to 200 segments and from the 2nd segment there are dorsal gills and chaetae almost to the tail end. The worm is a bluish green colour with distinct red vessels in gills and palps (paired projections from head). Head is elongated and conical in front and pointed behind. Swims in spirals when disturbed. It is listed as a Red List Species - categorized as Critically Endangered, Endangered, or Vulnerable.


Phylum: Annelida (Segmented) 
Class: Polychaeta (bristleworms)
Order: Spionida
Family: Spionidae

Species Found on Sheltered Muddy, Sandy Shore

Cerastoderma edule: Common Cockle (Bi-valve)

Widely distributed in estuaries and sandy bays around the coasts of Britain and Ireland. Inhabits the surface of sediments, burrowing to a depth of no more than 5 cm. Found on clean sand, muddy sand, mud or muddy gravel from the middle to lower intertidal, sometimes subtidally.

Description: The familiar edible cockle. The shell is solid, thick, equivalve, globular and broadly oval in outline; up to 5 cm long but usually less. Shell with 22-28 radiating ribs, crossed by conspicuous concentric ridges and may bear short, flat spines. Outer surface off-white, yellowish or brownish. Growth lines are prominent.


Phylum: Mollusca
Class: Pelecypoda (Bi-valve molluscs - lamellibranchs)
Order: Veneroida 
Family: Cardiidae (Cockles) 

Macoma balthica : Baltic Tellin

Common in estuarine environments around the British Isles, with the exception of the south coast. Macoma balthica lives a few centimetres below the surface of sand, mud and muddy sand. It is found from the upper regions of the intertidal into the sublittoral, particularly in estuaries and on tidal flats. Can tolerate very low salinities.

Macoma balthica is widely distributed throughout north-west Europe and Britain. It has a plump almost circular shell, up to 25 mm in length, with umbones close to the midline. The posterior of the shell may be very slightly tapered. The colour of Macoma balthica varies between pink, purple, yellow, white and may be blackened in sulphide-rich sediments. The colour is either uniform throughout the shell or in concentric bands.

This picture of brightly coloured shells was a collection of shells found onRampside beach, Morecambe Bay, Cumbria, UK.

Macomas are mud-dwelling clams which differ from most other bivalves in their mode of feeding. Most clams are filter-feeders. They draw water into a siphon, filter out nutrients and exhale the filtered water through another siphon. Macomas are deposit feeders. The inhalent siphon is very long and and sweeps over the mud, acting like a vacuum cleaner.


Phylum: Mollusca
Class: Pelecypoda (Bi-valve molluscs - lamellibranchs)
Order: Veneroida 
Family: Tellinidae

Scrobicularia plana: Peppery furrow shell

A bivalve (mollusc) which can be identified when buried by the star-shaped markings made on the surface

The peppery furrow shell is found in estuarine and intertidal conditions and is able to tolerate low salinities in thick mud or muddy sand. It burrows up to 20 cm deep in sediments and can be identified when buried by the characteristic star-shaped markings made at the surface by its inhalant siphon.

This bivalve has a thin, rounded and flattened shell and grows up to 6.5 cm in length. Internal features for identification are the hinge of the valves (the right valve has two teeth and the left valve one tooth) and the broad and almost circular pallial sinus. Externally, the shell is sculptured with fine concentric lines, the outer surface white, pale grey or yellow and the inner surface is white.


Phylum: Mollusca
Class: Pelecypoda (Bi-valve molluscs - lamellibranchs)
Order: Veneroida 
Family: Scrobiculariidae

Species Found on Rocky Shore

Barnacles :

Although barnacles may look like mollusks with their shell-like covering, they are actually crustaceans, related to lobsters, crabs and shrimp. The barnacle secretes the calcium-hard plates which totally encase them. In larvae stage they swim and look like tiny shrimp. Upon maturing they swim the waters until they find the right place to stop. They then attached them self to this selected area head first.

The barnacle uses a brown glue like substance to attach itself firmly. The barnacle attached itself so strongly to a surface that the its cone base is still around long after the animal has died. Dentists have studied this glue like substance to learn more about its adhesive values.

Semibalanus balanoides : Acorn barnacle

Semibalanus balanoides is a dominant member of the eulittoral fauna of British rocky shores. It can be found on shores of all exposure. It may extend into the lower reaches of estuaries as it can tolerate salinities down to 20 psu.

Semibalanus balanoides is the most widespread intertidal barnacle in the British Isles. It may grow up to 15 mm in diameter and has 6 calcified grey-white shell plates. It may be distinguished from other barnacles by the presence of a diamond shaped opercular aperture and a membranous shell base. The barnacle feeds on zooplankton when immersed, by extending the thoracic appendages (cirri). It is a cross fertilizing hermaphrodite and may live for up to 8 years, depending on its position on the shore.

In fact S balanoides is one of the most widespread barnacles on the northern hemisphere. Along the Norwegian coast it can be found as far north as the western parts of Finnmark. It is most common in the intertidal zone (occasionally below) on exposed locations.

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Phylum: Crustacea
Class: Cirripedia 
Order: Thoracica 
Family: Balanidae 

 
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