Spirorbis spirorbis
Encyclopedia
Spirorbis spirorbis is a small (3-4 mm) coiled polychaete
that lives attached to seaweed
s and eel grass
in shallow saltwater.
They have a smooth, white, sinistral
(left-handed) coiled shell encasing an orange body about 3 mm in length. The tube has a peripheral flange
where it attaches to the substrate.
The worm has a short abdominal region and a slightly broader thorax
terminating in ten stiff tentacles, used to filter food from the water. One of the tentacles is slightly larger than the rest and shaped like a saucer, which is used as an operculum
. This seals the opening of the shell and serves to protect the worm from predators and desiccation
when out of water.
It lives primarily on toothed wrack
(Fucus serratus) and bladder wrack
(Fucus vesiculosus), but is also found on the basal part of thongweed (Himanthalia elongata). Numerous individuals can be found on any one surface.
Spirorbis spirorbis are cross fertilising hermaphrodites, who brood their young in a tube attached to the worm inside the shell. The larva
e are released at an advanced stage of development and spend just a few hours as free-living organisms before attaching themselves to the nearest suitable surface, often the same seaweed as the parent.
and Ireland
; North Norway
to the English Channel
.
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
that lives attached to seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
s and eel grass
Zostera
Zostera is a small genus of widely distributed seagrass, commonly called marine eelgrass or simply eelgrass . The genus Zostera contains sixteen species.-Ecology:Zostera is found on sandy substrates or in estuaries submerged or partially floating...
in shallow saltwater.
They have a smooth, white, sinistral
Sinistral
Sinistral and dextral are scientific terms that describe chirality or relative direction in a number of disciplines.The terms are derived from the Latin words for “left” and “right” ....
(left-handed) coiled shell encasing an orange body about 3 mm in length. The tube has a peripheral flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
where it attaches to the substrate.
The worm has a short abdominal region and a slightly broader thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
terminating in ten stiff tentacles, used to filter food from the water. One of the tentacles is slightly larger than the rest and shaped like a saucer, which is used as an operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
. This seals the opening of the shell and serves to protect the worm from predators and desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...
when out of water.
It lives primarily on toothed wrack
Toothed wrack
Fucus serratus is a seaweed of the north Atlantic Ocean, known as toothed wrack or serrated wrack. It is olive–brown in colour and similar to F. vesiculosus and Fucus spiralis. It grows from a discoid holdfast. The fronds are flat, about 2 cm wide, bifurcating, and up to 1 m long...
(Fucus serratus) and bladder wrack
Bladder wrack
Fucus vesiculosus, known by the common name bladder wrack or bladderwrack, is a seaweed found on the coasts of the North Sea, the western Baltic Sea, and the Atlantic and Pacific Oceans, also known by the common names black tang, rockweed, bladder fucus, sea oak, black tany, cut weed, dyers fucus,...
(Fucus vesiculosus), but is also found on the basal part of thongweed (Himanthalia elongata). Numerous individuals can be found on any one surface.
Spirorbis spirorbis are cross fertilising hermaphrodites, who brood their young in a tube attached to the worm inside the shell. The larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e are released at an advanced stage of development and spend just a few hours as free-living organisms before attaching themselves to the nearest suitable surface, often the same seaweed as the parent.
Distribution
All around BritainGreat Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
and Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
; North Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
to the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
.