''Spirorbis spirorbis'' or ''Spirorbis borealis'' is a small (3–4 mm) coiled sedentary marine

polychaete Polychaeta () is a paraphyletic class of generally marine Annelid, annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called c ...

worm in the

Serpulidae The Serpulidae are a family of sessile, tube-building annelid worms in the class Polychaeta. The members of this family differ from other sabellid tube worms in that they have a specialized operculum that blocks the entrance of their tubes w ...

family that lives attached to

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

s and

eel grass Eelgrass is a common name for several plants and may refer to: * ''Zostera'', marine eelgrass * ''Vallisneria ''Vallisneria'' (named in honor of Antonio Vallisneri) is a genus of freshwater aquatic plant, commonly called eelgrass, tape grass or ...

in shallow saltwater. It is commonly called the sinistral spiral tubeworm and is the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of the genus ''Spirorbis''. ''S. spirorbis'' is a cross-fertilising

hermaphrodite A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many ...

that broods its young in a tube attached to the worm inside the shell. The

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

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.

Description

''S. spirorbis'' secretes a very small, unridged, off-white, calcareous tube. This is about five millimetres in diameter and forms a flat, clockwise spiral coil as seen from above. The worm retreats into its tube when above water but under water can be seen to have green tentacles.John Barrett and C M Young, Collins Pocket Guide to the Sea Shore (1958) p.76 The species has a smooth, white,

sinistral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

(left-handed) coiled shell encasing an orange body about 3 mm in length. The tube has a

peripheral A peripheral device, or simply peripheral, is an auxiliary hardware device that a computer uses to transfer information externally. A peripheral is a hardware component that is accessible to and controlled by a computer but is not a core compo ...

flange A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of a steel beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer o ...

where it attaches to the substrate. The worm has a short

abdominal The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

region and a slightly broader

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

terminating in ten stiff

tentacles In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

, 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

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s and

desiccation Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...

when out of water.

Distribution and habitat

''S. spirorbis'' is found on either side of the north Atlantic Ocean. This includes the coasts of

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

and

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

Prince Edward Island Prince Edward Island is an island Provinces and territories of Canada, province of Canada. While it is the smallest province by land area and population, it is the most densely populated. The island has several nicknames: "Garden of the Gulf", ...

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

, the

Gulf of St Lawrence The Gulf of St. Lawrence is a gulf that fringes the shores of the provinces of Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, in Canada, plus the islands Saint Pierre and Miquelon, Saint-Pierre and Miquelon, ...

and the St Lawrence estuary,Read, G.; Fauchald, K. (Ed.) (2024). World Polychaeta Database
''Spirorbis borealis'' Daudin, 1800.
Accessed through: World Register of Marine Species on 2024-12-06 perhaps even

North Norway Northern Norway (, , ; ) is a geographical region of Norway, consisting of the three northernmost counties Nordland, Troms and Finnmark, in total about 35% of the Norwegian mainland. Some of the largest towns in Northern Norway (from south to no ...

to the

English Channel The English Channel, also known as the Channel, is an arm of the Atlantic Ocean that separates Southern England from northern France. It links to the southern part of the North Sea by the Strait of Dover at its northeastern end. It is the busi ...

and

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer months. The ...

. It is typically found growing on ''

Fucus ''Fucus'' is a genus of brown algae found in the intertidal zones of rocky seashores almost throughout the world. Description and life cycle The thallus is perennial with an irregular or disc-shaped holdfast or with haptera. The erect portion ...

'', ''

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

'' and other seaweeds as well as on rocks and stones. It is widely distributed and abundant on the middle and lower shore, down to a depth of about thirty metres.

Biology

''S. spirorbis'' is a

. The segments at the front of the abdomen are female while those at the back are male. The male and female

gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...

s mature at much the same time but the sperm is usually released first. Fertilisation is external to the body but inside the tube. The

e are free swimming member of the plankton for a short time. They then settle out. In a study, where fronds of ''Fucus serratus'' already colonised by adults were available for settling, the larvae avoided the most densely populated areas and favoured the concave grooves on either side of the midribs. When prevented from settling out for eight hours, they were much less selective and settled on any ''Fucus'' surface regardless of the presence of adults.

References

External links

General spirorbid morphology and ecology
from the Indian River Lagoon Species Inventory by the Smithsonian Marine Station at Fort Pierce {{Taxonbar, from=Q1986934, from2=Q2765832 Serpulidae Animals described in 1758 Taxa named by Carl Linnaeus