Patella Vulgata

– Common Limpet –

Description

The limpet is a gastropod with an approximately conical shell with an almost circular base . The diameter of this base reaches a maximum of 6 centimeters (up to 8 cm in Ireland).

The blue limpet is the most common in the Mediterranean. Its cone-shaped shell is flat, thin, sculpted with strong radial ribs, with little marked intermediate ribs. This cone is often asymmetrical , with an apex shifted from the anterior side: “the front”, housing the animal’s head and tentacles, is narrower than the “rear”. It is dirty gray-brown in color and measures 2 to 4 cm in diameter, growing to 6 cm, and about 1 cm high. Its outline can be oval or very irregular .

The edge of the mantle, made up of the palleal gills, is embedded in a continuous groove of the shell.
The interior is strongly iridescent , with white or bluish reflections , with dark rays. It can also be dark blue, although this coloration fades in old shells.

She wears rather regular ribs not very prominent .
The height of the shell depends on the surrounding hydrodynamic conditions: convex in beaten mode and more flattened in calm mode or in depth.
The body has a head with a muzzle and two gray cephalic tentacles, a very powerful muscular foot orange-yellow to gray-brown in color, and a distinct visceral mass. A coat fringed with tiny white tentacles lines the shell between the inner rim and the foot.
The dominant exterior color of the shell is gray but may be tinged with yellowish or greenish. The inside of the shell, smooth, has the same hues, and brown bands are visible on the edge of the opening.
Inside, halfway between the top and the edge of the opening, there is a narrow and dull band in the shape of a horseshoe open towards the front: it is the muscular imprint, the trace of the insertion of the muscle that connects the soft parts of the animal to its shell.
The latter is the mostoften covered with algae but also other organisms such as barnacles, worms, etc …

Similar Species

Patella intermedia Murray in Knapp, 1857 = Patella depressa Pennant, 1777: the inside of the shell shows brown bands. Its opening is oval and irregular. It has a diameter of 3 to 4 cm. Its top is more anterior than that of P. vulgata . Its distribution is identical.

Patella ulyssiponensis Gmelin, 1791 = Patella aspera Röding, 1798 = Patella tarentina : more often submerged, very flat with brown bands on the top of the shell also visible from the inside. The ribs are more flattened and give the shell an approximately geometric shape with 10 sides.

Patella rustica = Patella lusitanica : around the coasts of Spain and Portugal as well as in the western Mediterranean basin. It wears thin black bands on its oval shell with dashes and dots on a gray background.

Patella caerulea : very flat with a bluish iridescent interior, at very shallow depth, abundant in the Mediterranean, penetrates a little in the Atlantic.

Patella ferruginea : large Mediterranean limpet about 8 to 9 cm in diameter. It is found very high on the rocks at the limit of the spray. Large rust-colored ribs giving the animal its name. Protected species.

Biotope

Limpets are fond of hard substrates (or soft such as limestone rock from the Normandy coast) of the foreshore to which they attach very firmly like a very powerful suction cup. They can be found in calm or beaten mode from the upper mediolittoral up to a few meters deep. These mollusks are part of the procession of marine organisms capable of attaching themselves very high on the foreshore and of resisting emersion for a long time, even in full sun.

Alimentation

A herbivorous grazer, the limpet consumes (preferably at night and at high tide for 4 to 5 hours), micro-algae that it scrapes on the stones with its radula *, then returns to its place to digest. It then finds the same location in the same orientation because the contours of the shell perfectly match its imprint left in the rock. This can be moved a few tens of cm away with a maximum of one meter. It is probably thanks to a very developed sense of smell that she finds her way back. This particular behavior of limpet is called homing *.
It also happens to attack brown algae such as wrack and ascophylls which it is seriously endangering,
It is not uncommon to see one or more limpets moving as the tide has receded. It is in no way in danger because it has a great capacity to resist emersion.
Choose a quiet spot on the foreshore, stop moving, listen, and you will hear the creaks and friction generated by the movement of an army of limpets!

Reproduction

Reproduction is sexual. Limpets are hermaphodites * protandrous *: they are male at the beginning of their life, then become female. The emission of gametes * in water takes place in autumn / winter.
Large limpets produce eggs and small ones produce sperm. Fertilization generates a veliger larva * which leads a planktonic life of 10 to 15 days. The larva eventually falls onto bedrock, undergoes metamorphosis, and turns into a tiny limpet.
Any single individual quickly becomes a female.

Associated Life

It is very common to observe limpets whose shell is colonized by algae, barnacles, spirorbs , bryozoans, etc …

Various Biology

By adhering strongly to the rocks the limpets constitute a water reserve. This allows them to breathe so to survive during the emersion protected from desiccation until the next high tide.
In soft substrates such as limestone, thanks to an acid secretion, they dig cavities called cupules in which they are embedded: this allows them to better resist the onslaught of waves.
Depending on their location on the foreshore and the quality of their environment, limpets can live from 5 to 15 years.

By turning over a limpet, we can observe a slight asymmetry of the shell in the front back direction. Because this animal, an archeogasteropod, has lost its right gill during its evolution, the movement of water goes from left to right inside the palleal cavity and not from front to back as for neogasteropods. .

Further Information

Contrary to a very widespread idea it is not only the suction effect which strongly maintains the limpet on its support but also the structure of the cells of the foot which clings to the rock. This is verified by unhooking a limpet from a limestone support: a hard layer covers the foot. A few moments later, the foot relaxes and the lime can be removed easily.

They are the prey of sea birds, such as gulls, and purples ( Nucella lapillus ).

They can be eaten (only the foot) raw or cooked.