''Patella ferruginea'', commonly known as the ribbed Mediterranean limpet, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the a ...

, a

true limpet The Patellogastropoda, common name true limpets and historically called the Docoglossa, are members of a major phylogenetic group of marine gastropods, treated by experts either as a clade or as a taxonomic order. The clade Patellogastropoda is ...

, a marine

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Patellidae, one of the families of true limpets. It is a large limpet, native to the western

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on ...

, and although common in the past, it is now rare and restricted to only a few locations.

Description

''Patella ferruginea'' is a distinctive large limpet with a thick heavy shell. It can exceed in diameter, but most individuals are rather smaller than this. The robust, cone-shaped shell has thirty to fifty broad ridges and a wavy margin. The ribs are irregular and sometimes nodular; the shell is often worn smooth or covered with

epibiotic An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An e ...

organisms such as

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...

and

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...

s. The external surface is cream-coloured or rusty brown, while the inside is marbled white with a dark muscle scar. The muscular foot is yellowish-orange with dark grey sides, and the

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s are black. Juveniles have flattened shells which are whitish with dark concentric bands and a small number of broad ribs, giving them star-shaped outlines.

Distribution and habitat

This limpet is restricted to the Mediterranean Sea. In the past it had a wide range in the western Mediterranean, as evidenced by large shell

midden A midden (also kitchen midden or shell heap) is an old dump for domestic waste which may consist of animal bone, human excrement, botanical material, mollusc shells, potsherds, lithics (especially debitage), and other artifacts and eco ...

s formed by

Paleolithic The Paleolithic or Palaeolithic (), also called the Old Stone Age (from Greek: παλαιός '' palaios'', "old" and λίθος ''lithos'', "stone"), is a period in human prehistory that is distinguished by the original development of stone too ...

and

Neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several pa ...

hunter gatherers. It is now limited to a few locations in northwestern Africa, one of which is the Al Hoceima National Park, as well as a few scattered locations in southern Spain, Gibraltar, Sardinia and Corsica, and some islets in the central Mediterranean. It lives on rocky surfaces in the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...

. It is classified as an "

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

" by Spain, and is the first invertebrate, as well as the first marine species, for which Spain has developed a national conservation strategy.

Ecology

This limpet is found in the mid-littoral zone, at the lower end of the zone occupied by the barnacle '' Chthamalus stellatus'' and above that formed by red algae, where the gastropod mollusc ''

Dendropoma petraeum ''Dendropoma petraeum'' is a species of sea snail, a marine gastropod mollusk in the family Vermetidae The Vermetidae, the worm snails or worm shells, are a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in ...

'' is to be found. At night and when submerged, it travels to graze on the film of

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...

and young algae that forms on rocks, returning to the same homing site each time the tide recedes. This spot is discernible because a ring of

coralline algae Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of re ...

develops under the edge of the shell. The limpet faces

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

from the crabs ''

Eriphia verrucosa ''Eriphia verrucosa'', sometimes called the ''warty crab'' or ''yellow crab'', is a species of crab found in the Black Sea, Mediterranean Sea and eastern Atlantic Ocean from Brittany to Mauritania and the Azores. Individual crabs have been caugh ...

'' and '' Pachygrapsus marmoratus'', and the dog winkle '' Stramonita haemastoma''. Breeding takes place in the autumn at about the time of year when the first storms occur, with

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

s being liberated into the sea. The

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

e are

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cruc ...

ic for a while before settling in similar habitats to those occupied by the adults. This limpet appears to be a protrandrous hermaphrodite, smaller individuals always being male and the proportion of females among larger individuals increasing with size. However, there is some indication that individuals can change sex in either direction.

Status

This limpet is on the verge of extinction in Spain, where fewer than a thousand individuals are thought to exist. More healthy populations are present in North Africa, with the largest being in

Melilla Melilla ( , ; ; rif, Mřič ; ar, مليلية ) is an autonomous city of Spain located in north Africa. It lies on the eastern side of the Cape Three Forks, bordering Morocco and facing the Mediterranean Sea. It has an area of . It was pa ...

Ceuta Ceuta (, , ; ar, سَبْتَة, Sabtah) is a Spanish autonomous city on the north coast of Africa. Bordered by Morocco, it lies along the boundary between the Mediterranean Sea and the Atlantic Ocean. It is one of several Spanish territori ...

and the Chafarinas Islands, as well as the

Habibas Islands The Habibas islands ( ar, جزر حبيبة) are located about 12 km off the Algerian coast, northwest of Oran. The islands consist of a principal island 1.3 km long surrounded by an archipelago covering a total area of about 40 h ...

off the coast of Algeria. Populations in Sardinia and Corsica seem to be declining.

References

{{DEFAULTSORT:Patella Ferruginea Patellidae Molluscs of the Mediterranean Sea Gastropods described in 1791 Taxa named by Johann Friedrich Gmelin