''Lottia digitalis'', the fingered limpet or ribbed 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 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

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 ...

, 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 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 ...

Lottiidae Lottiidae is a family of sea snails, specifically true limpets, marine gastropod mollusks in the superfamily Lottioidea and the clade Patellogastropoda (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). Subfamilies 20 ...

. These limpets are usually found on the surface of rocks in the high intertidal region on the coastal fringes of the northeast

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

.Marine Biodiversity of British Columbia

Description

This limpet grows up to thirty millimetres long and is shaped like a low cone with the apex close to the anterior edge. The anterior slope is concave and sometimes overhanging. The posterior slope is convex and has heavy radial ribbing and the margin is somewhat lobed and irregular. The shell characteristics are very variable. The color is usually brown or dark olive with white patches.Eogastropoda: Rocky Shore Limpets
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Distribution and habitat

The range of ''L. digitalis'' extends from northern

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

to northern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. It is a common species and is found among acorn barnacles on vertical rock faces in high to mid-intertidal zones, on both exposed and sheltered coasts. In

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

, young limpets, up to ten millimetres in diameter, often live on the opercular plates of gooseneck barnacles, '' Pollicipes polymerus'' and on

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

shells. In both cases, the colouring varies from that of the rock-based form and provides

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...

Behavior

On the coast of central California, ''L. digitalis'' coexists with the similar species, '' Lottia scabra'', but each occupies a slightly different habitat. ''L. digitalis'' tends to occupy vertical rock faces or overhangs and certain horizontal ones clothed by algae and barnacles. ''L. digitalis'' clump together more often, prefer wave-exposed areas, occupy sites further up the shore and are seldom found in rock pools. Both species move about freely when the tide is up but ''L. digitalis'' settles in a different location at each low tide whereas ''L. scabra'' tends to home to the same spot. ''L. scabra'' has a more rugged outline and grows to fit the rock surface of its home base. The differences in micro-habitat may be explained by its greater tolerance of exposure to desiccation during low tides in less protected sites because it is able to retain water better. If transplanted to unfamiliar territory, each species soon reselects its typical base habitat. In an experiment, when these two species were caged together with only vertical surfaces available, it was found that ''L. scabra'' grew at a much slower rate and achieved a much smaller maximum size than similar limpets in control plots. It seems that the ability of ''L. digitalis'' to respond to seasonal changes by moving up and down the shore and utilising resources better give it an edge over the more static species which remains for life in its restricted home range. ''L. scabra'' is less able to compete under optimal conditions and is therefore restricted to horizontal desiccating habitats.Haven, S. B. 1973. Competition for food between the intertidal gastropods ''Acmaea scabra'' and ''Acmaea digitalis''. Ecology 54: 143-151.

References

{{DEFAULTSORT:Lottia Digitalis Lottiidae Molluscs of the Pacific Ocean Taxa named by Martin Rathke Gastropods described in 1833