Patella vulgata

The common patella ( Patella vulgata Linnaeus) is a mollusc Gastéropode Prosobranche, known also under the name of “bernic” (Brittany), " lampote" (Normandy) or, more commonly, of “Chinese hat”, very commun run on the rocks of the estran to which it adheres firmly. Its body is protected by a roughly conical shell.

Description

The shell

Its conical form is not perfect, its base is not exactly circular and its top, rather definitely excentré, is off-set side of the head of the animal. This shell is decorated scratches, more or less marked, radiant starting from its top. Concentric reliefs, corresponding to stops or disturbances of the growth, cross the radiant scratches, The edge of the shell applies narrowly to the support by marrying its possible irregularities The interior of the shell is smooth. One clearly distinguishes a horseshoe mark there which corresponds to the insertion of the muscle of the shell, very developed, which in particular makes it possible to firmly apply the edge of the shell against the surface at which the foot is fixed. The opening of the horseshoe is located at front, above the site of the head of the patella. The shell is secreted by a pad of the skin called coat or pallium.

The body

The body of the patella is made up: of a head, a cavity palléale, a foot, a visceral mass.

The head

It is equipped with two large tentacles with tactile function and which are perhaps also the seat of the chemical direction. These tentacles carry, close to their base, on the external side, two black spots: eyes. The head is prolonged by an extensible boor at the end of which the mouth is with which the floor is equipped with a body which makes it possible the patella to take its food: the radule or radula, equipped with very many teeth. This remarkably long body (approximately 1,5 times the length of the shell) is folded up on itself in a pocket independent of the digestive tract and extends until the part postpones right body where it can describe a loop.

The cavity palléale

If it is not strictly speaking a “part” of the body of the animal, the cavity palléale is a formation characteristic of the Molluscs which contains important bodies and its position, at Prosobranches, deserves explanation. The coat or pallium, is spread out above the head to the manner of a hood and thus delimits a cavity called cavity palléale, at the bottom of which opens, on the line, the anus, flanked, on its left of the opening of the left kidney and on its right-hand side of the opening of the right kidney which is also the genital opening. On each side of the cavity palléale one notices, on the floor, a spot orange red: the osphradie. Both osphradies are chimiorécepteurs, i.e. bodies which detect dissolved chemical substances in water (what corresponds to our direction of the taste and the sense of smell). All these elements are normally located at the back of the body and their position at the patella (and Prosobranches generally), almost above the head of the animal, is the consequence of a misadventure of its development called torsion, of which the effects are also very Nets on the level of the anatomy of the nervous system in particular. Contrary to many Prosobranches (term which means “with gills located ahead”, insinuation, of the heart), the patella does not have gills (primary gills) in its cavity palléale: its respiratory bodies are represented by very many layers (secondary gills) laid out transversely in a furrow located around the foot and in front of the head.

The foot

With contour rounded, it is musculeux. It is used with the snaking and fixing of the animal on its support. The extremely close contact of this body with the rock is made perfectly tight thanks to a layer of mucus which takes part in the remarkable solidity of adherence.

Visceral mass

It is primarily made up by:

the very long and circumvented digestive tract, placed in its appendix, digestive gland, of yellow color, brown or greenish. The unit constitutes a dark mass located above the foot, behind of the head.
the gonade, male (testicle) or female (ovary), is located below digestive gland (generally) and develops especially left side of the animal. The sexes are separate but part of male patellas transforms into females into growing old (hermaphrodism protandre)
the kidneys: the left kidney of reduced size, is located on the left anus, the right, thin but very wide kidney, is spread out over all the right-sided, until the back of digestive gland.
the heart (1 auricle with front, 1 ventricle with the back) is placed in a pericardial pocket located between the left kidney and the left former pillar of the muscle of the shell, at the bottom of the cavity palléale.
the nervous system comprises mainly three pairs of ganglia (cerebroid, pleural and pedal) located on both sides former area of the digestive tract.

Food

Using their radule the patellas scrape the surface of the rocks on which they are installed and of this fact they consume the film of microscopic algae or small size which develop to with it as well as the small animal organizations (Crustacé S, Annélide S, Mollusque S etc) placed in this “grass”. But it is able to them also to attack the large algae (Ascophylle S and Fucus) of which they take pieces and which they are likely to cross and to eliminate. Each patella exploits during the period of immersion, a territory a few decimetres in diameter and returns, before the sea is withdrawn on its site of origin. However, on the smooth rocks, or when food is done rare, certain patellas have a behavior much more wandering and can traverse distances of several meters even of several decametres without returning on their site.

Reproduction

The gonades of the common patellas are wall at the end of the summer and autumn. The laying takes place in autumn and winter. The gamètes (spermatozoa and ovules) are released directly in sea water where fecundation occurs. The larvae, ciliées, live in the plankton approximately two weeks and metamorphose themselves on the bottom by giving the youthful ones which measure only 0.2 mm length. The youthful ones meet mainly in the low parts of the estran where the rocks remain always wet and in the puddle pools.

Lifespan

Generally about 5-7 years for the patellas of the mean level of the estran but that of the high parts, with slow growth, can live nearly 20 years!

The patellas, collected in zones considered salubrious, are edible, at the believed state, all the year. One can also cook them by adapting them in various ways: ragouts, pies, grills etc For consumption in a believed state it is preferable to select the animals of size small or average, collected with the bottom of the estran, because they have a more tender and more tasted flesh. Located at levels discovering with all the tides, the patellas constitute a source of proteins, glucids and lipids, easily accessible and free often scorned nowadays. They however constituted in a still recent past (at least until the Fifties) a considerable share of the food of the populations of the littoral and often allowed the most stripped to escape the famine.

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