''Lutraria lutraria'' 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 ...

of large marine bivalve mollusc 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 ...

Mactridae Mactridae, common name the trough shells or duck clams, is a family of saltwater clams, marine bivalve mollusks in the order Venerida. Description These clams have two short siphons, each with a horny sheath. The shell is shaped like a rounded- ...

. Its common names include the otter shell and the common otter shell. It occurs in coastal regions of the north east Atlantic Ocean where it lives buried in the sand.

Taxonomy

''Lutraria lutraria'' is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

'' Lutraria'', the name ''Mya lutraria'' being the basionym used by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...

when he described the species in 1758. It was later determined that there were sufficient differences between it and other '' Mya'' species for the otter shell to be placed in its own genus. The similarity between '' Mya'' and '' Lutraria'' is due to

convergence Convergence may refer to: Arts and media Literature *''Convergence'' (book series), edited by Ruth Nanda Anshen *Convergence (comics), "Convergence" (comics), two separate story lines published by DC Comics: **A four-part crossover storyline that ...

due to exploitation of the same habitat rather than a close

phylogenetic relationship In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

.Cleansing mechanisms and the function of the fourth pallial aperture in ''Spirula subtruncata'' and ''Lutraria lutraria
/ref>

Description

''L. lutraria'' has a pair of large, elongated oval valves up to long. They are smooth, glossy and fairly thin. They are a creamy colour and the periostracum is olive brown. This layer gets worn away over time and is often completely missing in shells found on the beach. There are concentric sculptured lines showing periods of growth and a few faint radial lines near the hinge. The left valve has two cardinal teeth with a third small one behind. The right valve has two small cardinal teeth and a small lateral one. The flesh of the animal is white. The foot is thick and protrudes through the pedal gape at the posterior end. The mantle edges are fringed with white and are fused together. The massive siphons can be extended to two or three times the length of the shell and are joined together for their entire length. They are streaked with brown and purple and are housed in a transparent, gelatinous sheath composed of protein and chitin. The siphons are outgrowths of the mantle while the sheath is a continuation of the periostracum. There are two rings of tiny tentacles round the orifice of the inhalant siphon and a single ring and a membrane round the exhalant one.The British species of ''Lutraria'' (Lamellibranchia), with a description of ''L. angustior''
/ref> The mantle has a fourth pallial opening near the base of the siphon.

Right and left valve of the same specimen: File:Lutraria lutraria 01.jpg, Right valve File:Lutraria lutraria 02.jpg, Left valve

Distribution

''L. lutraria'' is found off the coasts of north west Europe from Norway south to the Mediterranean Sea and also in West Africa. It is found in soft substrates from the low tide mark down to about one hundred metres. The largest individuals with the longest siphons bury themselves at the greatest depths.

Biology

''L. lutraria'' is a filter feeder. It draws in water through one siphon and expels it through the other. Respiration takes place as the water current passes over the gills. Waste is periodically expelled through the fourth pallial opening which can also be used for expulsion of water from the mantle cavity. Trawling may damage or remove the tips of the siphons and bottom feeding fish may nip them off but the animal can regenerate the inner layers over the course of a few days. Hydraulic blade dredge fishing takes place for razor clams, ''

Ensis ''Ensis'' is a genus of medium-sized edible saltwater clams, littoral bivalve molluscs in the family Pharidae. ''Ensis'', or razor clams, are known in much of Scotland as spoots, for the spouts of water they eject while burrowing into the sa ...

spp.'', in Scotland and the process was studied to examine its impact. Bottom trawling of the seabed is often preceded by a sand fluidation process designed to loosen the sediment. Dredging damages a considerable portion of the benthic megafauna including ''L. lutraria'', however this species tends to live at greater depths than is reached by the process. Nevertheless, between 20% and 100% are damaged in a single dredge haul. Some individuals are undamaged but left lying on the surface and it has been found that their ability to rebury themselves is limited. Unlike razor clams, they normally spend their lives in one spot and the foot is relatively small and mainly used for anchorage rather than digging. Any animal unable to rebury itself rapidly is likely to fall prey to the scavengers that move in after a trawl has passed. Such studies are of importance in assessing the ecological consequence and sustainability of fisheries.

References

{{Taxonbar, from=Q2472974 Mactridae Molluscs of the Atlantic Ocean Molluscs described in 1758 Taxa named by Carl Linnaeus