Nemertea

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Nemertea

Nemertea is a phylum

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
of invertebrate

Invertebrate

An invertebrate is an animal lacking a vertebral column. The group includes 98% of all animal species ? all animals except those in the Chordate subphylum vertebrate ....
animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the Kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life....
s also known as ribbon worms or proboscis worms. Most of the 1,400 or so 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....
are marine, with a few living in fresh water

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve....
and a small number of terrestrial forms

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land, as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats ....
; they are found in all marine habits, and throughout the world's oceans. Nemerteans are named for Nemertes, one of the Nereids

Nereids

In Greek mythology, the Nereids are sea nymphs, the fifty daughters of Nereus and Doris . They often accompany Poseidon and are always friendly and helpful towards sailors fighting perilous storms....
of Greek mythology

Greek mythology

Greek mythology is the body of myths and legends belonging to the Ancient Greece concerning their List of Greek mythological figures#Immortals and Greek hero cult, Cosmology#Metaphysical cosmology, and the origins and significance of their own cult and ritual practices....
, and alternative spellings for the phylum have included Nemertini and Nemertinea. Libbie Hyman

Libbie Hyman

Libby Henrietta Hyman , was an American zoologist.Born in Des Moines, Iowa, she was the daughter of Joseph Hyman and Sabina Neumann. Hyman's father, a Polish/Russian Jew, adopted the surname when he immigrated to the United States as a youth....
named them Rhynchocoela, a name used primarily in North America but gradually abandoned since the 1980s.

majority of nemertean worms live on or in the sea floor, with many species extending into brackish water

Brackish water

Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuary, or it may occur in brackish fossil aquifers....
in estuaries, and some freshwater

Fresh Water

Terrestrial animal

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Encyclopedia

Nemertea is a phylum

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
of invertebrate

Invertebrate

An invertebrate is an animal lacking a vertebral column. The group includes 98% of all animal species ? all animals except those in the Chordate subphylum vertebrate ....
animal

Animal

Species

Fresh Water

Terrestrial animal

Nereids

Greek mythology

Libbie Hyman

Ecology and distribution

The majority of nemertean worms live on or in the sea floor, with many species extending into brackish water

Brackish water

Fresh Water

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land, as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats ....
species. Freshwater genera include the large genus Prostoma, while the terrestrial forms are best represented by Geonemertes, a genus mostly found in Australasia

Australasia

Australasia is a region of Oceania: New Zealand, Australia, Papua New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes ....
, but with one species in the Seychelles

Seychelles

Seychelles , officially the Republic of Seychelles , is an archipelago Country of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....
, one found widely across the Indo-Pacific

Indo-Pacific

The Indo-Pacific is a biogeography region of the earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia....
, one from Tristan da Cunha

Tristan da Cunha

Tristan da Cunha is a remote volcanic group of islands in the south Atlantic Ocean, 2,816 km from South Africa and 3,360 km from South America....
in the South Atlantic, and one, G. chalicophora, first found in the Palmengarten
Palmengarten

The Palmengarten is one of two botanical gardens in Frankfurt and is located in the city district Westend-S?d .Like many Frankfurt public sites, it was privately financed and implemented by the architect Heinrich Siesmayer....
in Frankfurt

Frankfurt

is the largest city in the German States of Germany of Hesse and the List of cities in Germany with more than 100,000 inhabitants in Germany, with a 2008 population of 670,000....
, but since discovered in the Canary Islands

Canary Islands

The Canary Islands are a Spain archipelago which, in turn, forms one of the Spanish Autonomous Communities and an Outermost Region of the European Union....
, Madeira

Madeira

Madeira is a Portugal archipelago in the north Atlantic Ocean that lies between and . It is one of the Autonomous regions of Portugal, with Madeira Island and Porto Santo Island being the only inhabited islands....
and the Azores

Azores

The Azores is a Portugal archipelago in the Atlantic Ocean, about 1,500 km from Lisbon and about 3,900 km from the east coast of North America....
.

They are often found in and among seaweed

Seaweed

Seaweed is a loose colloquial term encompassing macroscopic, multicellular, benthos ocean algae. The term includes some members of the rhodophyta, phycophyta and green algae....
s, rock

Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
s, mussel

Mussel

The common name mussel is used for members of several different families of clams or bivalve molluscs, from both saltwater and freshwater habitats....
and barnacle

Barnacle

A barnacle is a type of arthropod belonging to infraclass Cirripedia in the Subphylum Crustacean, and is hence distantly related to crabs and lobsters....
beds, or buried in mud, sand, or gravel substrates.

Most nemerteans are carnivorous and predatory, catching prey with their proboscis

Proboscis

In general, a proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate..The correct Greek plural is proboscides, but in English it is more common to simply add -es, forming proboscises....
, although some are scavenger

Scavenger

Scavenging, or necrophagy, is a carnivorous feeding behaviour in which a predator consumes corpses or carrion that were not killed to be eaten by the predator or others of its species....
s and some are herbivore

Herbivore

Herbivory is a form of predation in which an organism, known as an herbivore, heterotrophs principally autotrophs such as plants, algae and photosynthesizing bacteria....
s. In some families, it is armed with a sharp stylet which may be poisonous, while those that lack the stylet often use a sticky secretion on the proboscis to entrap their prey. The proboscis is wrapped around the prey, which is normally other invertebrates such as crustacean

Crustacean

Crustaceans are a large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles....
s and annelid

Annelid

The annelids, collectively called Annelida , are a large Scientific classification of animals comprising the segmented worms, with about 15,000 modern species including the well-known earthworms and leeches....
s and can be many times larger than the nemertean itself, and the prey is then stabbed repeatedly with the stylet until dead.. A few, such as Malacobdella, live parasitically in the mantle cavity

Mantle (mollusc)

The mantle is a significant part of the anatomy of molluscs: it is the dorsum body wall which covers the visceral mass.In many, but by no means all, species of molluscs, the Epidermis of the mantle secretes calcium carbonate and conchiolin, and creates a mollusc shell....
of molluscs and live on the food filtered by their hosts

Anatomy

Nemertean worms are long, thin, unsegmented animals. They are distinguished by the presence of an eversible proboscis which is used for catching prey. Although generally considered acoelomate, the cavity which contains the proboscis includes a true coelom

Coelom

The coelom is a fluid filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsequently lost in several lineages....
. The circulatory system

Circulatory system

The circulatory system is an organ that moves nutrients, gases, and wastes to and from cells to help fight diseases and help stabilize body temperature and pH to maintain homeostasis....
of nemerteans is closed, as is the digestive system, which includes separate mouth

Mouth

The mouth, buccal cavity, or oral cavity is the first portion of the alimentary canal that receives food and begins digestion by mechanically breaking up the solid food particles into smaller pieces and mixing them with saliva....
and anus

Anus

The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to expel feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest, such as coprolite ; food material after all the nutrients have b...
(unlike flatworm

Flatworm

The flatworms, known in scientific literature as Platyhelminthes are a Phylum of relatively simple bilaterian, Segmentation , soft-bodied invertebrate animals....
s, which have a single opening). The nervous system

Nervous system

The nervous system is a Neural network of specialized cells that communicate information about an animal's surroundings and itself. It processes this information and causes reactions in other parts of the body....
includes a brain

Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
and several nerve cords; respiration

Respiration (physiology)

In animal physiology, respiration is the transport of Oxygen from the outside air to the cells within Tissue s and the transport of carbon dioxide in the opposite direction....
is entirely by diffusion

Diffusion

Molecular diffusion, often called simply diffusion, is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion....
.

Nemertean worms are unique in possessing a "cerebral organ" — a sensory and regulatory organ closely associated with the brain.

Nemerteans often have numerous gonad

Gonad

The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells....
s, and most species have separate sexes, although all the freshwater forms are hermaphroditic

Hermaphrodite

A hermaphrodite is an organism having both male and female reproductive organs. In many species, hermaphroditism is a common part of the life-cycle, enabling a form of sexual reproduction in which partners are not separated into distinct male and female types of individual....
. Fertilization is usually external

External fertilization

External fertilization is a form of fertilization in which a sperm cell is united with an egg cell external to the body of the female. Thus, the fertilization is said to occur "externally"....
, although some species have both internal fertilization

Internal fertilization

Internal Fertilization is a form of fertilization of an egg by within the body of an animal, whether female or hermaphrodite. This is distinct from external fertilization, where the union of the ova and spermatozoa occur outside of the organism....
and live birth

Live birth

A live birth occurs when a fetus, whatever its gestational age, exits the maternal body and subsequently shows any sign of life, such as voluntary muscle, heartbeat, or pulsation of the umbilical cord, for however brief a time and regardless of whether the umbilical cord or placenta are intact....
.

Length

Nemerteans range in size from 5 mm to over 30 metres long in the case of the European Lineus longissimus
Lineus longissimus

The bootlace worm is in the phylum Nemertea or ribbon worms. It is one of the longest animals known, with specimens up to 30 metre long being reported and some speculation that they may grow as long as 60 m, which would make it the largest organism in the world....
. There are also reports of specimens up to 50 m or 60 m long, which would make it the longest animal in the world; the longest vertebrate on record is a female blue whale

Blue Whale

The Blue Whale is a marine mammal belonging to the suborder of baleen whales . At up to 32.9 metres in length and 172 metric tonnes or more in weight, it is the largest whale and the largest living animal and is believed to be the largest organism ever to have existed....
, 29.9 m long.

Classification

The earliest record of a nemertean worm is probably an account by Olaus Magnus

Olaus Magnus

Olaus Magnus was a Sweden ecclesiastic and writer, who did pioneering work for the interest of Nordic countries people. He was reported as born in October 1490 in ?sterg?tland, and died on August 1, 1557....
in 1555 of a long, greyish-blue marine worm, which is probably Lineus longissimus
Lineus longissimus

The bootlace worm is in the phylum Nemertea or ribbon worms. It is one of the longest animals known, with specimens up to 30 metre long being reported and some speculation that they may grow as long as 60 m, which would make it the largest organism in the world....
, but the first species was not formally described until Gunnerus

Johan Ernst Gunnerus

Johan Ernst Gunnerus was a Norway bishop and botanist.Gunnerus was born at Christiania. He was bishop of Trondheim from 1758, and professor of theology at the university of Copenhagen....
described the same species (as Ascaris longissima) in 1770. In 1995, a total of 1,149 species had been described, and grouped into 250 genera.

The fossil record of the phylum is sparse, as expected for a group of soft-bodied animals, but even the hard stylets are not found. The only possible nemertean fossil is Archisymplectes from the Mazon Creek biota of the Pennsylvanian

Pennsylvanian

The Pennsylvanian is an epoch in the geologic timescale or a series in the stratigraphic column. It is a subdivision of the Carboniferous period lasting from roughly to Ma ....
of Illinois

Illinois

The State of Illinois is a U.S. state of the United States, the 21st to be admitted to the United States. Illinois is the most populous and demographically diverse Midwestern United States state and the fifth most populous state in the nation....
.

Once classified as "degenerate" flatworm

Flatworm

Lophotrochozoa

The Lophotrochozoa are one of three major groupings of protostome animals. The taxon was introduced in 1995 in a paper by Kenneth M Halanych et al based on molecular data....
, such as Annelida and Mollusca

Mollusca

MolluscsSpelled mollusk in the USA; the spelling "mollusc" is preferred by some authors, see the reasons given by . are animals belonging to the Phylum Mollusca....
.

The traditional classes of Enopla

Enopla

Enopla is one of the Class of the worm phylum Nemertea, characterized by the presence of a peculiar armature of spines or plates in the proboscis....
for nemerteans armed with one or more stylets and Anopla

Anopla

Anopla are a Class of marine worms of the phylum Nemertea, characterized by the absence of stylets on the proboscis, the mouth being below or behind the brain, and by having separate openings for the mouth and proboscis....
for those without are not monophyletic

Monophyly

In common cladistic usage, a monophyletic group is a clade, consisting of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly....
is not supported by molecular data. Similarly, the subclass Bdellonemertea, erected for nemerteans which live as parasites on molluscs, is nested within Hoplonemertea, and probably represents a specialised offshoot from that group rather than an independent lineage . Recent molecular phylogenetic

Molecular phylogeny

Molecular phylogenetics, also known as molecular systematics, is the use of the structure of molecules to gain information on an organism's evolutionary relationships....
study has, however, confirmed the monophyly

Monophyly

In common cladistic usage, a monophyletic group is a clade, consisting of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly....
of each of Heteronemertea

Heteronemertea

Heteronemertea is a Monophyly order of about 500 species, containing genus such as Lineus and Cerebratulus and including the largest and most muscular nemerteans....
and Hoplonemertea, as well as the expected paraphyly

Paraphyly

In phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor Common descent but does not contain all the descendants of that ancestor....
of Palaeonemertea

Palaeonemertea

Palaeonemertea may be a para- or Polyphyly order , consisting of 3 to 5 clades and totalling about 100 species. These worms have several apparently simple features and, as their name suggests, they are often considered to be the most primitive nemerteans....
.