Lottia digitalis
Encyclopedia
Lottia digitalis or the ribbed limpet is a species
of sea snail
, a true limpet, a marine gastropod mollusk in the family
Lottiidae
. These limpets are usually found on the surface of rocks in the high intertidal region on the coastal fringes of the north east Pacific Ocean
.
to northern Mexico
. 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
, young limpets, up to ten millimetres in diameter, often live on the opercular plates of gooseneck barnacles, Pollicipes polymerus and on mussel
shells. In both cases, the colouring varies from that of the rock-based form and provides camouflage
.
, 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 dessicating habitats.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of sea snail
Sea snail
Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....
, a true limpet, a marine gastropod mollusk in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Lottiidae
Lottiidae
Lottiidae is a family of sea snails, specifically true limpets, marine gastropod mollusks in the superfamily Lottioidea and the clade Patellogastropoda .- 2005 taxonomy :...
. These limpets are usually found on the surface of rocks in the high intertidal region on the coastal fringes of the north east Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
.
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 with the colour usually being brown or dark olive with white patches.Distribution and habitat
The range of L. digitalis extends from northern AlaskaAlaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
to northern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. It is a common species and is found among acorn barnacles
Sessilia
Sessilia is an order of barnacles, comprising the barnacles without stalks, or acorn barnacles. They form a monophyletic group and are probably derived from stalked barnacles. The order is divided into three suborders. Brachylepadomorpha contains a single family, Neobrachylepadidae, while...
on vertical rock faces in high to mid-intertidal zones, on both exposed and sheltered coasts. In California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, young limpets, up to ten millimetres in diameter, often live on the opercular plates of gooseneck barnacles, Pollicipes polymerus and on mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
shells. In both cases, the colouring varies from that of the rock-based form and provides camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
.
Behaviour
At Mission Point on the California coast, L. digitalis coexists with the similar species, Lottia scabraLottia scabra
Lottia scabra or the rough limpet is a species of sea snail, a true limpet, a marine gastropod mollusk in the family Lottiidae. It is found on the Pacific coast of the United States.-Description:...
, 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 dessicating habitats.