''Scutellastra cochlear'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Patellidae Patellidae is a taxonomic family of true limpets, marine gastropod molluscs in the superfamily Patelloidea. (The superfamily Patelloidea should not be confused with the similar-sounding genus of true limpets '' Patelloida'' which is in the ...

, one of the families of

true limpets 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 ...

. It is commonly known as the snail patella, the pear limpet or the spoon limpet and is native to South Africa. It often grows in association with the crustose coralline alga ''

Spongites yendoi ''Spongites yendoi'' is a species of crustose red seaweed with a hard, calcareous skeleton in the Family (biology), family Corallinaceae. It is found on the lower shore as part of a diverse community in the southeastern Atlantic and the Indo-Paci ...

'' and a filamentous red alga which it cultivates in a garden. It was first described by the

malacologist Malacology, from Ancient Greek μαλακός (''malakós''), meaning "soft", and λόγος (''lógos''), meaning "study", is the branch of invertebrate zoology that deals with the study of the Mollusca (molluscs or mollusks), the second-largest ...

Ignaz von Born Ignaz Edler von Born, also known as Ignatius von Born (, , ) (26 December 1742 in Alba Iulia, Grand Principality of Transylvania, Habsburg monarchy – 24 July 1791 in Vienna), was a mineralogist and metallurgist. He was a prominent freemason ...

in 1778 as ''Patella cochlear''.

Description

''Scutellastra cochlear'' has a distinctive pear-shaped shell. It is a slow-growing species and may live for 25 years, attaining a length of . The outer surface is often encrusted with coralline algae. The inner surface is white with a bluish tinge, sometimes speckled with black patches, and with a black, U-shaped muscle scar.

Distribution and habitat

''Scutellastra cochlear'' is native to exposed coasts of South Africa where it forms dense colonies on rocks on the lower shore. Its range extends southwards from the mouth of the

Orange River The Orange River (from Afrikaans/Dutch language, Dutch: ''Oranjerivier'') is a river in Southern Africa. It is the longest river in South Africa. With a total length of , the Orange River Basin extends from Lesotho into South Africa and Namibi ...

in the west of South Africa, round the three

Cape Province The Province of the Cape of Good Hope (), commonly referred to as the Cape Province () and colloquially as The Cape (), was a province in the Union of South Africa and subsequently the Republic of South Africa. It encompassed the old Cape Co ...

s and northwards to

Durban Durban ( ; , from meaning "bay, lagoon") is the third-most populous city in South Africa, after Johannesburg and Cape Town, and the largest city in the Provinces of South Africa, province of KwaZulu-Natal. Situated on the east coast of South ...

on the east coast.

Biology

''Scutellastra cochlear'' is an important part of the lower tidal community in what is sometimes known as the "cochlear zone". Each adult establishes a scar on the underlying rock and occupies this for the rest of its life. This limpet occurs at greater densities than most other species of limpet but that is partly because juveniles often establish themselves on the shell of larger individuals, feeding on the algae and lichen which grow there, until the juveniles are large enough to establish their own scars on the rock. Densities have been found to vary between 90 and about 1,700 limpets per square metre, with greater densities being present in areas with the greatest wave motion. This limpet has a strong influence on the structure of the community as it excludes most species of algae and limits the

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

in its vicinity to the coralline alga ''

'' and the strips of filamentous red algae gardens that fringe each limpet. The limpets do not need to move out of their scars to feed as they can reach enough edible material by rotating themselves in their scar. At low tide, when the limpet is exposed to the air,

urea Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...

accumulates on the underside of the rim of its shell and diffuses out into the surrounding algae. Here it boosts the supply of nitrogen available to the algae and this increases the algal productivity. ''Scutellastra cochlear'' is

territorial A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...

and defends its garden against other limpets. A marine

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

'' Pyrenocollema'' spp. often grows on this limpet's shell, and ''Spongites yendoi'' frequently grows on top of this and on the surrounding rocks. The relationship between the limpet and this coralline alga could be considered a form of mutualism. The limpet gets 85% of its nutritional needs by grazing on the coralline alga and leaves it in thin sheets with a damaged surface. The limpet is not present in the north of the alga's range and in these areas the algal sheets are much thicker and flabbier, and develop protuberances. It has been observed that the thin form of the alga grows laterally five times as fast as the thick form and is less likely to be attacked by burrowing organisms, so the association between the two organisms may be mutually beneficial.

References

{{DEFAULTSORT:Scutellastra Cochlear Patellidae Marine molluscs of Africa Molluscs of the Atlantic Ocean Molluscs of the Indian Ocean Gastropods described in 1778 Taxa named by Ignaz von Born