Onchidoris bilamellata
Encyclopedia
Onchidoris bilamellata, common name
the rough-mantled doris, is a species
of sea slug
, a dorid nudibranch
, a shell-less marine
gastropod mollusk in the family Onchidorididae
.
to a depth of about 20 m. It has been found in the North Atlantic and the North Sea
from Britain
and France
to the Norwegian Sea
, Iceland
and Greenland
; along the North America
n coast as far south as Connecticut
. It has also been recorded in the North Pacific in the Bering Sea
, and from Alaska
south to northern California
.
These sea slugs sometimes occur in abundant numbers during breeding time, swarming
with over 1,000 individuals per square metre, as has been observed on numerous occasions. These swarms are all oriented in the same direction, determined by the flow of the tide. They follow each other at the same speed, forming columns, in different close-knitted rows.
. But some individuals display a mixed pattern of colours, from a lighter brown colour to dark brown. Even fewer individuals are white, with brown color only in the rhinophore
s and the gills. A rare few are completely white, and yet they are not albinos, as their eyes are pigmented.
Onchidoris bilamellata has a broadly oval shape with its back covered with short, knobby papillae. Their antennae are comblike. The gills are arranged in two half rings on the back at the rear end and consist of 16 to 32 simple featherlike plumes.
The branchial ganglia are fused in Onchidoris bilamellata.
s in the genera Elminius
and Balanus
. It uses its rachidian tooth to chew away at the top plates of the barnacles and then sucks out the soft body.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
the rough-mantled doris, is a species
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 slug
Slug
Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
, a dorid nudibranch
Nudibranch
A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...
, a shell-less marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
gastropod mollusk in the family Onchidorididae
Onchidorididae
Onchidorididae are a taxonomic family of dorid nudibranchs or sea slugs, marine gastropod molluscs.-Genera:Genera in the family Onchodorididae include:* Acanthodoris Gray, 1850, see Orange-peel doris* Adalaria Bergh, 1879...
.
Distribution
This nudibranch has a wide distribution, mostly in colder intertidal watersIntertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
to a depth of about 20 m. It has been found in the North Atlantic and the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
from Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
to the Norwegian Sea
Norwegian Sea
The Norwegian Sea is a marginal sea in the North Atlantic Ocean, northwest of Norway. It is located between the North Sea and the Greenland Sea and adjoins the North Atlantic Ocean to the west and the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a...
, Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
and Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
; along the North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n coast as far south as Connecticut
Connecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...
. It has also been recorded in the North Pacific in the Bering Sea
Bering Sea
The Bering Sea is a marginal sea of the Pacific Ocean. It comprises a deep water basin, which then rises through a narrow slope into the shallower water above the continental shelves....
, and from Alaska
Alaska
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...
south to northern 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...
.
These sea slugs sometimes occur in abundant numbers during breeding time, swarming
Population density
Population density is a measurement of population per unit area or unit volume. It is frequently applied to living organisms, and particularly to humans...
with over 1,000 individuals per square metre, as has been observed on numerous occasions. These swarms are all oriented in the same direction, determined by the flow of the tide. They follow each other at the same speed, forming columns, in different close-knitted rows.
Description
This is a small species, no longer than 4 cm. They mostly show an abundant rusty brown pigmentPigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
. But some individuals display a mixed pattern of colours, from a lighter brown colour to dark brown. Even fewer individuals are white, with brown color only in the rhinophore
Rhinophore
A rhinophore is one of a pair of club-shaped structures which are the most prominent part of the external head anatomy of a group of sea slugs, marine gastropod opisthobranch mollusks in the order Nudibranchia, the nudibranchs, specifically the dorid nudibranchs.- Etymology :The name relates to the...
s and the gills. A rare few are completely white, and yet they are not albinos, as their eyes are pigmented.
Onchidoris bilamellata has a broadly oval shape with its back covered with short, knobby papillae. Their antennae are comblike. The gills are arranged in two half rings on the back at the rear end and consist of 16 to 32 simple featherlike plumes.
The branchial ganglia are fused in Onchidoris bilamellata.
Feeding habits
Onchidoris bilamellata feeds mainly on acorn barnacleBarnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s in the genera Elminius
Elminius
Elminius is a genus of barnacles in the family Archaeobalanidae, containing the following species:* Elminius kingii King, 1831 * Elminius modestus Darwin, 1854...
and Balanus
Balanus
Balanus is a genus of barnacles in the family Balanidae of the subphylum Crustacea, containing the following species:*Balanus albicostatus*Balanus amaryllis Darwin*Balanus amphitrite Darwin, 1854*Balanus aquila Pilsbry, 1907...
. It uses its rachidian tooth to chew away at the top plates of the barnacles and then sucks out the soft body.