''Scutellastra cochlear'' 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 appropriate s ...

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 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 ...

mollusc 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 esti ...

in the

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

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

, 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 ...

. 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 Corallinaceae. It is found on the lower shore as part of a diverse community in the southeastern Atlantic Ocean and the Indo-Pacific Ocean. ...

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

malacologist Malacology is the branch of invertebrate zoology that deals with the study of the Mollusca (mollusks or molluscs), the second-largest phylum of animals in terms of described species after the arthropods. Mollusks include snails and slugs, clams, ...

Ignaz von Born Ignaz Edler von Born, also known as Ignatius von Born ( hu, Born Ignác, ro, Ignațiu von Born, cs, Ignác Born) (26 December 1742 in Alba Iulia, Grand Principality of Transylvania, Habsburg monarchy – 24 July 1791 in Vienna), was a mineral ...

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: ''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 Namibia to the north ...

in the west of South Africa, round

Cape Province The Province of the Cape of Good Hope ( af, Provinsie Kaap die Goeie Hoop), commonly referred to as the Cape Province ( af, Kaapprovinsie) and colloquially as The Cape ( af, Die Kaap), was a province in the Union of South Africa and subsequen ...

and northwards to

Durban Durban ( ) ( zu, eThekwini, from meaning 'the port' also called zu, eZibubulungwini for the mountain range that terminates in the area), nicknamed ''Durbs'',Ishani ChettyCity nicknames in SA and across the worldArticle on ''news24.com'' from ...

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 about 1,700 limpets per square metre and 90 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 or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

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 known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

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, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or a ...

and defends its garden against other limpets. A marine

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.Pyrenocollema ''Pyrenocollema'' is a genus of lichenized fungi in the biological division Ascomycota. Its relationship to other genera is unclear, and it has not been assigned to any family Family (from la, familia) is a group of people related eithe ...

'' 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 Gastropods described in 1778 Taxa named by Ignaz von Born