''Serpula'' (also known as calcareous tubeworm, serpulid tubeworm, fanworm, or plume worm) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

, marine

annelid The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to vario ...

tube worm A tubeworm is any worm-like sessile invertebrate that anchors its tail to an underwater surface and secretes around its body a mineral tube, into which it can withdraw its entire body. Tubeworms are found among the following taxa: * Annelida, the ...

s that belongs to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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 ...

. Serpulid worms are very similar to tube worms of the closely related sabellid family, except that the former possess a

cartilaginous Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

'' operculum'' that occludes the entrance to their protective tube after the animal has withdrawn into it. The most distinctive feature of worms of the genus ''Serpula'' is their colorful fan-shaped "crown". The crown, used by these animals for

respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...

and alimentation, is the structure that is most commonly seen by scuba divers and other casual observers.

Taxonomy

Following is a brief description of the

cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...

and

taxonomic classification In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given ...

of ''Serpula'': ;Higher taxonomic ranks * The

''Serpula'' belongs to the

, also known as serpulid worms or tubeworms. * Family Serpulidae is one of 31 described families of the

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Canalipalpata Canalipalpata, also known as bristle-footed annelids or fan-head worms, is an order of polychaete worms, with 31 families in it including the suborder Sabellida (families Serpulidae (tubeworms) and Sabellidae (fanworms and feather duster worm ...

, also known as bristle-footed annelids or fan-head worms. In addition to the Serpulidae, the Canalipalpata also includes the fanworms (

Sabellidae Sabellidae, or feather duster worms, are a family of marine polychaete tube worms characterized by protruding feathery branchiae. Sabellids build tubes out of a tough, parchment-like exudate, strengthened with sand and bits of shell. Unlike th ...

) and a family of deep-sea worms associated with hydrothermal vents (

Alvinellidae The Alvinellidae are a family of small, deep-sea polychaete worms endemic to hydrothermal vents in the Pacific Ocean. Belonging to the order Terebellida, the family contains two genera, '' Alvinella'' and '' Paralvinella''; the former genus con ...

). * Order Canalipalpata belongs to the

class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...

Polychaeta, also known as bristle worms. There are more than 10,000 described species of polychaetes; they can be found in nearly every marine environment. Some species live in the coldest ocean temperatures of the

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They ...

, while others can be found in the extremely hot waters adjacent to

hydrothermal vent Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hot ...

s. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

near the surface, to a 2–3 cm specimen (still unclassified) observed by the robot ocean probe

Nereus In Greek mythology, Nereus ( ; ) was the eldest son of Pontus (the Sea) and Gaia ( the Earth), with Pontus himself being a son of Gaia. Nereus and Doris became the parents of 50 daughters (the Nereids) and a son ( Nerites), with whom Nereus ...

at the bottom of the

Challenger Deep The Challenger Deep is the List of submarine topographical features#List of oceanic trenches, deepest known point of the seabed of Earth, located in the western Pacific Ocean at the southern end of the Mariana Trench, in the ocean territory o ...

, the deepest spot in the Earth's oceans. * Class Polychaeta belongs to the

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

Annelida The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to variou ...

, also called ringed worms. There are over 17,000 living annelid species, ranging in size from microscopic to the Australian

giant Gippsland earthworm The giant Gippsland earthworm (''Megascolides australis'') is one of Australia's 1,000 native earthworm species. Description These giant earthworms average long and in diameter and can reach in length; however, their body is able to expand an ...

, which can grow up to long.

Species of ''Serpula''

While the higher taxonomy is fairly well understood, the lower taxonomy within the genus ''Serpula'' is somewhat confusing, and not yet thoroughly worked out. Earlier sources have described as many as 77 different species and subspecies.Appeltans W, Bouchet P, Boxshall GA, Fauchald K, Gordon DP, Hoeksema BW, Poore GCB, van Soest RWM, Stöhr S, Walter TC, Costello MJ. (eds) (2010)
World Register of Marine SpeciesWoRMS Taxon list for Genus ''Serpula''
Accessed 1 May 2010. However, there are currently only 29 recognized species in the genus ''Serpula''. The number and names of these species may soon change as a result of an ongoing revision of the genus by taxonomists. *'' Serpula cavernicola'' (Fassari & Mollica, 1991),

Messina Messina ( , ; ; ; ) is a harbour city and the capital city, capital of the Italian Metropolitan City of Messina. It is the third largest city on the island of Sicily, and the 13th largest city in Italy, with a population of 216,918 inhabitants ...

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

*'' Serpula columbiana'' (Johnson, 1901),

Puget Sound Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

*'' Serpula concharum'' (Langerhans, 1880),

Madeira Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...

, Mediterranean-Atlantic *'' Serpula crenata'' (Ehlers, 1908),

Zanzibar Zanzibar is a Tanzanian archipelago off the coast of East Africa. It is located in the Indian Ocean, and consists of many small Island, islands and two large ones: Unguja (the main island, referred to informally as Zanzibar) and Pemba Island. ...

Indo-West Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the s ...

;

bathyal The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypelag ...

*'' Serpula granulosa'' ,

Kagoshima , is the capital Cities of Japan, city of Kagoshima Prefecture, Japan. , the city had an estimated population of 583,966 in 285,992 households, and a population density of 1100 persons per km2. The total area of the city is . Etymology While the ...

and Enoshima, Japan, Indo-West Pacific *'' Serpula hartmanae'' (Reish, 1968),

Bikini A bikini is a two-piece swimsuit primarily worn by women that features one piece on top that covers the breasts, and a second piece on the bottom: the front covering the pelvis but usually exposing the navel, and the back generally covering ...

, Indo-West Pacific *'' Serpula indica'' (Parab & Gaikwad, 1989),

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

*''

Serpula israelitica ''Serpula'' (also known as calcareous tubeworm, serpulid tubeworm, fanworm, or plume worm) is a genus of sessile, marine annelid tube worms that belongs to the family Serpulidae. Serpulid worms are very similar to tube worms of the closely r ...

'' (Amoureux, 1976),

Haifa Haifa ( ; , ; ) is the List of cities in Israel, third-largest city in Israel—after Jerusalem and Tel Aviv—with a population of in . The city of Haifa forms part of the Haifa metropolitan area, the third-most populous metropolitan area i ...

, Levant Basin,

Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...

*'' Serpula japonica'' (Imajima, 1979),

Honshu , historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the list of islands by area, seventh-largest island in the world, and the list of islands by ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

; possibly

Seychelles Seychelles (, ; ), officially the Republic of Seychelles (; Seychellois Creole: ), is an island country and archipelagic state consisting of 155 islands (as per the Constitution) in the Indian Ocean. Its capital and largest city, Victoria, ...

*'' Serpula jukesii'' , Indo-West Pacific *'' Serpula lobiancoi'' (Rioja, 1917), Mediterranean-Atlantic *'' Serpula longituba'' (Imajima, 1979), Honshu, Japan *'' Serpula maorica'' ,

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

*'' Serpula nanhaiensis'' (Sun & Yang, 2001),

South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by South China, in the west by the Indochinese Peninsula, in the east by the islands of Taiwan island, Taiwan and northwestern Philippines (mainly Luz ...

*'' Serpula narconensis'' , Narcon Island, Antarctica, subantarctic *'' Serpula oshimae'' (Imajima & ten Hove, 1984), Indo-West Pacific *'' Serpula pacifica'' (Uchida, 1978), Sabiura, Japan *'' Serpula philippensis'' (McIntosh, 1885),

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

; bathyal *'' Serpula planorbis'' (Southward, 1963),

Irish Sea The Irish Sea is a body of water that separates the islands of Ireland and Great Britain. It is linked to the Celtic Sea in the south by St George's Channel and to the Inner Seas off the West Coast of Scotland in the north by the North Ch ...

; bathyal *'' Serpula rubens'' (Straughan, 1967),

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

*'' Serpula sinica'' (Wu & Chen, 1979), South China Sea *'' Serpula tetratropia'' (Imajima & ten Hove, 1984),

Palau Palau, officially the Republic of Palau, is an island country in the Micronesia subregion of Oceania in the western Pacific Ocean. The Republic of Palau consists of approximately 340 islands and is the western part of the Caroline Islands ...

and

Caroline Island Caroline Island (also known as Caroline Atoll or Millennium Island) is the easternmost of several uninhabited coral atolls comprising the southern Line Islands in the central Pacific Ocean nation of Kiribati. The atoll was first sighted by Eu ...

*'' Serpula uschakovi'' (Kupriyanova, 1999), Gilderbrandt Island,

Sea of Japan The Sea of Japan is the marginal sea between the Japanese archipelago, Sakhalin, the Korean Peninsula, and the mainland of the Russian Far East. The Japanese archipelago separates the sea from the Pacific Ocean. Like the Mediterranean Sea, it ...

*'' Serpula vasifera'' (Haswell, 1885),

Port Jackson Port Jackson, commonly known as Sydney Harbour, is a natural harbour on the east coast of Australia, around which Sydney was built. It consists of the waters of Sydney Harbour, Middle Harbour, North Harbour and the Lane Cove and Parramatta ...

, New South Wales, Australia *'' Serpula vermicularis'' , Western Europe *'' Serpula vittata'' (Augener, 1914),

Shark Bay Shark Bay () is a World Heritage Site in the Gascoyne region of Western Australia. The area is located approximately north of Perth, on the westernmost point of the Australian continent. UNESCO's listing of Shark Bay as a World Heritage S ...

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

; Indo-West Pacific *'' Serpula watsoni'' ,

Trincomalee Trincomalee (; , ; , ), historically known as Gokanna and Gokarna, is the administrative headquarters of the Trincomalee District and major resort port city of Eastern Province, Sri Lanka, Eastern Province, Sri Lanka. Located on the east coast o ...

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

; Indo-West Pacific *'' Serpula willeyi'' , Sri Lanka *'' Serpula zelandica'' , New Zealand

Geographic distribution, evolution, and habitat

Worldwide, very common.

Pacific 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 the definition, to Antarctica in the south, and is bounded by the cont ...

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

, and

Indian Indian or Indians may refer to: Associated with India * of or related to India ** Indian people ** Indian diaspora ** Languages of India ** Indian English, a dialect of the English language ** Indian cuisine Associated with indigenous peoples o ...

oceans,

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

. Species of the genus ''Serpula'' are common on the west coast of North America from

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

, but are rarely if ever found on the east coast of the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. They are common in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

.Department of Biology, Walla Walla University
Serpula vermicularis
, Rosario Beach Marine Laboratory. Accessed 1 May 2010. Like most tube-building polychaetes, worms of the genus ''Serpula'' are

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...

, sedentary suspension feeders. They secrete and inhabit a permanent

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

tube attached to hard substrata. As they do not travel outside their tubes, these worms do not have any specialized appendages for swimming. Worms of the genus ''Serpula'' are commonly found attached to submerged rocks, shells, and even boats in many coastal areas around the world. They are found at depths ranging from

intertidal The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various sp ...

to at least 800 meters. Predators include predatory starfish such as the

Ochre Sea Star ''Pisaster ochraceus'', generally known as the purple sea star, ochre sea star, or ochre starfish, is a common seastar found among the waters of the Pacific Ocean. Identified as a keystone species, ''P. ochraceus'' is considered an important indi ...

(''Pisaster ochraceous''). ''Serpula'' has lived since the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

period, according to fossils found in the Cretaceous

Black Creek Formation The Black Creek Group is a Late Cretaceous (early to middle Campanian)-aged geologic group in the southeastern United States, where it is known from the coastal plain of North Carolina and South Carolina. Deposited in brackish or nearshore marine ...

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

Anatomy

Head

The funnel-shaped, symmetrical

peristomium The peristomium is the first true body segment in an annelid worm's body in the anterior end. It is directly behind the prostomium and contains the mouth, tentacular cirri, and sometimes feeding palps, which may instead occur on the prostomium. If ...

is fused with the

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; : prostomia; sometimes also called the "acron") is the Cephalization, cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not in ...

to form the head, at the

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

end of the body. Worms of the genus ''Serpula'' have two photoreceptors or "eyespots" on the peristomium. The prostomium bears a branchial "crown", a specialized mouth appendage which resembles a fan (for which the animals are given the name ''fanworms''). This crown, which can be extended for feeding and gas exchange, and rapidly retracted when threatened, consists of two bundles (one right and one left) of featherlike '

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

s', known as ''branchiae'' or ''

radiole A radiole is a heavily ciliated feather-like tentacle found in highly organized clusters on the crowns of Canalipalpata. Canalipalpata is an order of sessile marine polychaete worms consisting of 31 families (including the Sabellidae, Serpulida ...

s''. Each of these bundles consists of a single row of radioles attached to a branchial stalk and curved into a semicircle. These two semicircles form the funnel-shaped branchial crown. The mouth is at the apex of the funnel between the two branchial stalks. When extended, these heavily

ciliated The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike pr ...

radioles trap particles of organic matter and transport it towards the mouth. While they are primarily feeding structures, the radioles also serve as respiratory organs. The radioles of different ''Serpula'' species are typically red, pink, or orange in color, with white transverse bands.

Astaxanthin Astaxanthin is a keto- carotenoid within a group of chemical compounds known as carotenoids or terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups. It is a lipid-solu ...

, a

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

pigment, is responsible for the bright red color of the crown of ''S. vermicularis''. There are usually about 40 radioles in an adult. One of these radioles, called an ''operculum'', is a highly specialized structure located on the dorsal part of the head. The operculum consists of a long, thick stalk with a

, cone-shaped plug at the distal end. This plug can be used to seal the opening of the tube after the animal has retreated inside. The operculum, which is usually red in color, secretes a mucus which seems to possess

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

properties. It is not unusual for the animal to have two opercula. Both serpulid and sabellid worms have radioles, but sabellids (such as ''

Sabella pavonina ''Sabella pavonina'', commonly known as the peacock worm, is a marine polychaete worm belonging to the family Sabellidae. They can be found along the coasts of Western Europe and the Mediterranean. It is found in shallow, tidal waters with a be ...

'') lack an operculum. A single median

nephridiopore A nephridiopore is part of the nephridium, an excretory organ found in many organisms, such as flatworms and annelids. Polychaetes typically release their gametes into the water column using nephridiopores. Nephridia are homologous to nephrons ...

is located

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

ly on the head, between the upper lip and a median dorsal papilla. The anterior end of the fecal groove passes over it and urine is released from it into the waste current. Like all serpulids and sabellids, they have only a single pair of

metanephridia The nephridium (: nephridia) is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Nephridia co ...

, which empty via this nephridiopore.

Thorax

The thoracic region of the body consists of seven chaetigers (segments bearing chaetae).

Chaeta A chaeta or cheta (; ) is a chitinous bristle or seta found on annelid worms, although the term is also frequently used to describe similar structures in other invertebrates such as arthropods. Polychaete annelids (''polychaeta'' literally me ...

e are small appendages that aid the worm with mobility. The first of these segments is the collar segment (peristomium), to which the prostomium is attached. The peristomium bears an elaborate, delicate, membranous collar that overlaps the margins of the aperture of the tube and covers the opening of the tube when the head is extended. There is a pair of calcium-secreting

gland A gland is a Cell (biology), cell or an Organ (biology), organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also funct ...

s located near the midventral line on the posterior end of the peristomium. These glands open onto the "ventral shields", which are wide glandular pads on the

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

side of the anterior thoracic segments. The ventral shields secrete

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

material and use this, combined with the calcium secreted by the glands, to form a paste from which the tube is made. These white

tubes are made of both

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

and

aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...

. They are usually smooth with faint longitudinal ridges, curved but not strongly coiled, and are rarely more than 12 cm in length. The tube appears to be shaped by the ventral shields and by a collar which is just behind the head. There is a median, longitudinal, ciliated, thoracic fecal groove on the dorsal midline of the thorax. It is a broad, shallow, relatively indistinct trough running the length of the thorax and ending at the head.

Abdomen

Worms of the genus ''Serpula'' have a distinct abdominal region, composed of up to 190 very short, wide segments. The terminal body region is the tiny

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

, on which the

anus In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facil ...

is located. A fecal groove extends the length of the ventral midline of the abdomen. The fecal groove spirals across to the dorsal position as it reaches the thoracic region. Vertical ciliary tracts in the grooves between adjacent abdominal segments move particles toward the abdominal fecal groove. Once in the abdominal fecal groove, further ciliary currents transport particulate matter (feces, gametes, etc.) from the depths of the tube, through the thoracic segment to the aperture where it can be released to the sea.

Physiology

Circulatory system

Vasculature

Worms of the genus ''Serpula'' have a very unusual dual circulatory system, consisting of a central system of large vessels through which a continuous true circulation of blood is maintained, and also a peripheral system of small, predominantly blind-ending vessels which alternately empty and fill in a tidal fashion. In the central circulatory system, the blood moves anteriorly from the tip of the abdomen to the front of the thorax through a

sinus Sinus may refer to: History * a sac in front of body worn into a toga, in the typical style of wearing it Anatomy * Sinus (anatomy), a sac or cavity in any organ or tissue ** Paranasal sinuses, air cavities in the cranial bones, especially those ...

enveloping the

alimentary canal The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascular system. ...

, and posteriorly through a ventral blood vessel. The ventral vessel and the sinus communicate with each other by segmentally arranged ring vessels, and by a dorsal vessel, a

transverse Transverse may refer to: *Transverse engine, an engine in which the crankshaft is oriented side-to-side relative to the wheels of the vehicle *Transverse flute, a flute that is held horizontally * Transverse force (or ''Euler force''), the tangen ...

vessel, and a pair of circum esophageal vessels situated at the anterior end of the thorax. The dorsal vessel in some of the larger serpulids, like ''Serpula'', possesses a valve and a muscular

sphincter A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the human bo ...

, probably to prevent backflow of blood from the transverse vessel. The blood circulation in the periphery, especially the radiole, is especially unusual. Instead of

venous Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal c ...

and

arterial An artery () is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in ...

blood flowing through afferent and efferent vessels within the radiole, there is a single branchial sinus through which blood flows in both directions, in a tidal fashion. The vessels of the peripheral system receive their blood from the central system, returning it back along the same channels (i.e., these channels serve in both afferent and efferent directions). The peripheral circulatory system has the following components: the two branchial vessels and their branches in the crown; the periesophageal vascular

plexus In anatomy, a plexus (from the Latin term for 'braid') is a branching network of blood vessels, lymphatic vessels, or nerves. The nerves are typically axons outside the central nervous system. The standard plural form in English is plexuses. Al ...

es; the vessels of the collar and lips; the vessels supplying the body wall, thoracic membrane, and

parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; : parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed late ...

. The single vessels in each radiole of the branchial crown, and the vessels of opercula, are all branches of the two branchial vessels. When the crown is retracted inside the tube, the radioles and operculum cease to function as a respiratory organ. The movement of blood in the capillaries of the thoracic membrane and body wall continues, however. Under these circumstances, respiratory exchange is probably carried out between the blood in these vessels and the surrounding water, which is kept moving through the tube by vigorous pumping movements of the abdomen and also by the activity of the ciliary tracts.

Oxygen transport mechanisms

The well-developed

longitudinal Longitudinal is a geometric term of location which may refer to: * Longitude ** Line of longitude, also called a meridian * Longitudinal engine, an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, ...

muscles of the body wall of serpulids lack a special blood supply. The body surface in the larger serpulids, like ''Serpula'', has a rich blood supply, and the water in contact with this surface is constantly renewed. It seems probable that the outer body surface of serpulids serves as a respiratory

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Bi ...

, supplying oxygen to the underlying muscles by

diffusion Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

The biochemistry of the blood of ''Serpula'' is especially unusual in that the blood contains not only hemoglobin, but also chlorocruorin. While all sabellids and serpulids employ chlorocruorin as an oxygen transport macromolecule, ''Serpula'' is the only genus that appears to possess both hemoglobin as well as chlorocruorin. Chlorocruorin is an oxygen-binding

hemeprotein A hemeprotein (or haemprotein; also hemoprotein or haemoprotein), or heme protein, is a protein that contains a heme prosthetic group. They are a very large class of metalloproteins. The heme group confers functionality, which can include oxyge ...

whose affinity for oxygen is weaker than that of most

hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

s. A dichromatic compound, chlorocruorin is noted for appearing green in dilute solutions, though it appears light red when found in concentrated solutions. Its structure is very similar to

erythrocruorin Erythrocruorin (from Greek ''eruthros'' "red" + Latin ''cruor'' "blood"), and the similar chlorocruorin (from Greek ''khlōros'' "green" + Latin ''cruor'' "blood"), are large oxygen-carrying hemeprotein protein complex, complexes, which have a mo ...

, each molecule being composed of more than a hundred interlinked 16-17

kDa The dalton or unified atomic mass unit (symbols: Da or u, respectively) is a unit of mass defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest. It is a non-SI unit accepted f ...

myoglobin-like subunits arranged in a giant complex with a total weight exceeding 3600

. This enormous

macromolecule A macromolecule is a "molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass." Polymers are physi ...

is free floating in the plasma, and not contained within red blood cells. The ratio of plasma hemoglobin to chlorocruorin is high in younger individuals, but this ratio reverses as the animal matures. Presumably this reflects a lower oxygen consumption in the adult worm, relative to the juveniles.

Nervous system

Like other annelids, these worms possess well-developed nervous systems. The nervous system consists of a central brain in the upper part of the head, which is relatively large compared with that of other annelids. Extending from the brain is a large ventral nerve cord running the length of the body. There are many supporting

ganglia A ganglion (: ganglia) is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system, this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system, there a ...

along the length of this cord (including pleural, pedal and cerebral ganglia), and a series of small nerves in each body segment. Signals transmitted through the pedal ganglia allow the worms to retract rapidly into their tube if threatened.

Reproductive system

Sexes are separate. Like other annelids, the

coelom The coelom (or celom) is the main body cavity in many animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, i ...

stores and provides nutrients for gametes.. When they reproduce, they simply shed their gametes straight into the water where the ova and spermatozoa become part of the

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

and are carried by the currents to new sites, where the juvenile worms settle into the substrate. Length of the planktonic stage is unknown but comparison with other serpulids suggests it may be between six days and two months, although in other species the period has been shown to vary with season, salinity or food availability, and delayed settling may cause reduced discrimination of substrata during settling (see ten Hove, 1979 for additional references).

Digestive system

Worms of the genus ''Serpula'' are

filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...

s, and possess a complete digestive system. Like other polychaetes, ''Serpula'' excrete with fully developed

nephridia The nephridium (: nephridia) is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Nephridia co ...

Gallery

File:Serpulavermicularis.jpg, '' Serpula vermicularis'' (Calcareous tubeworm) File:Serpula vermicularis.jpg, '' Serpula vermicularis'' (Calcareous tubeworm) File:Serpula vermicularis 1.jpg, '' Serpula vermicularis'' (Calcareous tubeworm) Clic
here
to see more photographs of various specimens of the genus ''Serpula''.

References

External links

* Raffles Museum of Biodiversity Research
Polychaete Families of Singapore: Serpulidae
* Annelida.net

Accessed 1 May 2010. * Chamberlin, Ralph V. 1920. The Polychaetes Collected by the Canadian Arctic Expedition, 1913–18. Report of the Canadian Arctic Expedition 9. Annelids, parasitic worms, Protozoans, etc. (B. Polychaeta): 1-41. Pl.1-6. Thomas Mulvey. Ottawa. * Hartmann-Schröder, G. (1996). Annelida, Borstenwürmer, Polychaeta nnelida, bristleworms, Polychaeta 2nd revised ed. The fauna of Germany and adjacent seas with their characteristics and ecology, 58. Gustav Fischer: Jena, Germany. . 648 pp. (look up in IMIS) {{Taxonbar, from=Q2153566 Serpulidae Annelid genera Taxa named by Carl Linnaeus