''Lacuna vincta'', commonly known as the northern lacuna, the wide lacuna, the northern chink shell, or the banded chink shell, 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 sea snail, a marine gastropod

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 ...

Littorinidae The Littorinidae are a Taxonomy (biology), taxonomic family (biology), family of over 200 species of sea snails, marine (ocean), marine gastropod molluscs in the clade Littorinimorpha, commonly known as periwinkles and found worldwide. Names In ...

, the winkles or periwinkles. It is found intertidally and in shallow waters in both the northern Atlantic Ocean and the northern Pacific Ocean. It is a herbivore, feeding on seaweed and diatoms with its toothed radula.

Description

The shell of ''Lacuna vincta'' is conical, with five to six smooth whorls and a pointed apex. The aperture is about half the height of the shell or slightly larger. The umbilicus has a prominent groove between two white ridges of

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...

. The exterior of the shell is pale brown with a broad spiral of white and a glossy periostracum. The interior of the shell is not white and pearly and the aperture can be closed by an operculum. The maximum recorded

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

length is .Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". '' PLOS One'' 5(1): e8776. .

Distribution and habitat

The distribution of ''L. vincta'' is circumboreal, extending as far south in the Atlantic Ocean as the British Isles and France, and the eastern coast of North America. In the northeastern Pacific its range extends from Alaska to California, but it is seldom found further south than Washington state. It is present on algae on rocky shores, intertidally and down to about . In the British Isles, the larvae settle preferentially on brown seaweed such as ''

Fucus serratus ''Fucus serratus'' is a seaweed of the north Atlantic Ocean, known as toothed wrack or serrated wrack. Description and reproduction ''Fucus serratus'' is a robust alga, olive-brown in colour and similar to '' Fucus vesiculosus'' and ''Fucus spi ...

'' and ''

Laminaria ''Laminaria'' is a genus of brown seaweed in the order Laminariales (kelp), comprising 31 species native to the north Atlantic and northern Pacific Oceans. This economically important genus is characterized by long, leathery laminae and relati ...

'' spp. and on short red seaweed such as '' Lomentaria articulata'', as well as on the seagrass ''

Zostera ''Zostera'' is a small genus of widely distributed seagrasses, commonly called marine eelgrass, or simply seagrass or eelgrass, and also known as seaweed by some fishermen and recreational boaters including yachtsmen. The genus ''Zostera'' co ...

'' spp. In the Pacific they settle mainly on

kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwa ...

, eelgrass and surfgrass.

Ecology

''L. vincta'' is a herbivore, grazing on seaweed and on diatoms living on the surface of

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the or ...

es. The radula has 45 to 95 rows of tiny teeth, with about three new rows being formed each day. Two separate types of teeth are produced; if the snail is grazing on seaweed, these newly formed teeth are sharply pointed and are used to tear deeply into the algal frond; if on the other hand, the snail is currently feeding on diatoms growing on seagrass, the new teeth are much blunter and are used to scrape diatoms off the leaves. The new teeth are formed at the back of the radula and work their way forward as the older teeth wear away and are discarded, so it takes some time for the snail's teeth to adjust to a change in diet. This snail favors sheltered positions and in exposed areas seeks the shelter of crevices or dense patches of seaweed. In unsuitable conditions, such as at times of food shortage or when there are excessive numbers of predators, it can produce a string of

mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...

which it uses as a "parachute" to help it to drift to a more favorable location. The sexes are separate in this snail with eggs being laid in a ring on seaweed or seagrasses. They may be laid throughout the year but in some locations, such as the British Isles, they are laid in the spring and early summer after which the adults die. The eggs hatch in about six days and the veliger larvae 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 crucia ...

ic for up to six months before settling on the shallow seabed at a shell-length of about . In eastern Canada these juvenile snails have been recorded at a density of 1500 per square meter.

References

{{DEFAULTSORT:Lacuna Vincta Littorinidae Molluscs of the Atlantic Ocean Molluscs of the Pacific Ocean Gastropods described in 1803 Taxa named by George Montagu (naturalist)