Nemertea - Knowledge

1307: 1070: 827: 1089: 140: 1295: 969: 1868:). In the specimens preserving the anterior end of the body, this end is pointed or rounded, bearing a rhynchocoel with the proboscis, which is characteristic for nemerteans. The authors attributed these fossils to nemerteans and interpreted them as the oldest record of the group reported so far. However, Knaust & Desrochers cautioned that partly preserved putative nemertean fossils might ultimately turn out to be fossils of 803: 127: 1071: 1073: 1074: 334:, consisting of about 1300 known species. Most ribbon worms are very slim, usually only a few millimeters wide, although a few have relatively short but wide bodies. Many have patterns of yellow, orange, red and green coloration. The foregut, stomach and intestine run a little below the midline of the body, the 2256:

of nemertea are usually in the walls of the fluid vessels and are served by "drains" from which the wastes exit by a small number of tubes through the skin, while the flame cells of flatworms are scattered throughout the body. Rigorous comparisons show no synapomorphies of nemertean and platyhelminth

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Larger species often break up when stimulated, and the fragments often grow into full individuals. Some species fragment routinely and even parts near the tail can grow full bodies. But this kind of extreme regeneration is restricted to only a few types of nemerteans, and is assumed to be a derived

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exits from an orifice which is separate from the mouth, coils around the prey and immobilizes it by sticky, toxic secretions. The Anopla can attack as soon as the prey moves into the range of the proboscis. Some Anopla have branched proboscises which can be described as "a mass of sticky spaghetti".

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In the simplest type of circulatory system, two lateral vessels are joined at the ends to form a loop. However, many species have additional long-wise and cross-wise vessels. There is no heart nor pumping vessels, and the flow of fluid depends on contraction of both the vessels and the body wall's

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is an infolding of the body wall, and sits in the rhynchocoel when inactive. When muscles in the wall of the rhynchocoel compress the fluid inside, the pressure makes the proboscis jump inside-out along a canal called the rhynchodeum and through an orifice, the proboscis pore. The proboscis has a

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organs, sacs whose only openings are to the outside. Others species have unpaired evertible organs on the front of their heads. Some have slits along the side of the head or grooves obliquely across the head, and these may be associated with paired cerebral organs. All of these are thought to be

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invertebrates encircle the foregut. Most nemertean species have just one pair of nerve cords, many species have additional paired cords, and some species also have a dorsal cord. In some species the cords lie within the skin, but in most they are deeper, inside the muscle layers. The central

692:, however, is usually only a few millimeters wide. The bodies of most nemerteans can stretch a lot, up to 10 times their resting length in some species, but reduce their length to 50% and increase their width to 300% when disturbed. A few have relatively short but wide bodies, for example 633:

The typical nemertean body is very thin in proportion to its length. The smallest are a few millimeters long, most are less than 20 centimetres (7.9 in), and several exceed 1 metre (3.3 ft). The longest animal ever found, at 54 metres (177 ft) long, may be a specimen of

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believe the Bdellonemertea are a part of the Monostilifera (with one active stylet), which are within the Hoplonemertea – which implies that "Enopla" and "Hoplonemertea" are synonyms for the same branch of the tree. The Polystilifera (with many tiny stylets) are monophyletic.

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barb, with which the animal stabs the prey many times to inject toxins and digestive secretions. The prey is then swallowed whole or, after partial digestion, its tissues are sucked into the mouth. The stylet is attached about one-third of the distance from the end of the

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undulations. A few live in the open ocean while the rest find or make hiding places on the bottom. About a dozen species inhabit freshwater, mainly in the tropics and subtropics, and another dozen species live on land in cool, damp places. Most nemerteans are

1589:. Comprises about 400 species. The majority are marine, but three are freshwater. Their body-wall muscles are disposed in four layers, alternately circular and length-wise starting from the outermost layer. The order includes the strongest swimmers. Two 388:

vessels which are joined at the ends to form a loop, and these and the rhynchocoel are filled with fluid. There is no heart, and the flow of fluid depends on contraction of muscles in the vessels and the body wall. To filter out soluble waste products,

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muscles. In some species, circulation is intermittent, and fluid ebbs and flows in the long-wise vessels. The fluid in the vessels is usually colorless, but in some species it contains cells that are yellow, orange, green or red. The red type contain

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They are unsegmented, but at least one species, Annulonemertes minusculus, is segmented. But this is assumed to be a derived trait. The segmentation does not include the coelom and body wall, and is therefore referred to as pseudosegmentation.

2264:(outer part of the mesoderm, which is the layer in which most of the internal organs are built) is derived from cells labelled 3a and 3b, and endomesoderm (inner part of the mesoderm) is derived from the 4d cell. Some of the ectomesoderm in 1837:

has been classed as a nemertean, based on a resemblance to some unusual deep-sea swimming nemerteans, but few paleontologists accept this classification as the Burgess Shale fossils show no evidence of rhynchocoel nor intestinal caeca.

2248:. The rhabdites of nemertea have a different structure from those of flatworms at the microscopic scale. The frontal glands or organs of flatworms vary a lot in structure, and similar structures appear in small marine annelids and 1072: 924: 855:

proboscis, which extends only enough to expose the stylet. On either side of the active stylet are sacs containing back-up stylets to replace the active one as the animal grows or an active one is lost. Instead of one stylet, the

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are emitted), one per gonad, are built when the ova and sperm are ready. The eggs are generally fertilised externally. Some species shed them into the water, some lay them in a burrow or tube, and some protect them by

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R. Gibson (1995). "Nemertean genera and species of the world: an annotated checklist of original names and description citations, synonyms, current taxonomic status, habitats and recorded zoogeographic distribution".

743:, but these are not associated with differences in movement. Nemerteans also have dorso-ventral muscles, which flatten the animals, especially in the larger species. Inside the concentric tubes of these layers is 464:, one per gonad, when the ova and sperm are ready. The eggs are generally fertilised externally. Some species shed them into the water, and others protect their eggs in various ways. The fertilized egg divides by 696:

is up to 3.5 centimetres (1.4 in) long and 1 centimetre (0.39 in) wide, and some of these are much less stretchy. Smaller nemerteans are approximately cylindrical, but larger species are flattened

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to emerge just above the mouth to capture the animal's prey with venom. A highly extensible muscle in the back of the rhynchocoel pulls the proboscis in when an attack ends. A few species with stubby bodies

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which filter out the wastes are embedded in the front part of the two lateral fluid vessels. The flame cells remove the wastes into two collecting ducts, one on either side, and each duct has one or more

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Nemerteans generally move slowly, though they have occasionally been documented to successfully prey on spiders or insects. Most nemerteans use their external cilia to glide on surfaces on a trail of

2849:. While analyses by molecular phylogeny are confident that members of Lophotrochozoa are more closely related to each other than of non-members, the relationships between members are mostly unclear. 907:

in everting the proboscis and in burrowing. The vessels circulate fluid round the whole body and the rhynchocoel provides its own local circulation. The circulatory vessels are a system of coeloms.

1106:, some of which is produced by glands in the head. Larger species use muscular waves to crawl, and some aquatic species swim by dorso-ventral undulations. Some species burrow by means of muscular 860:

have a pad that bears many tiny stylets, and these animals have separate orifices for the proboscis and mouth, unlike other Enopla. The Enopla can only attack after contacting the prey.

4417: 4381: 1897:, may be a nemertean. This fossil, however, only preserves the outline of the "worm", and there is no evidence of a proboscis, so there is no certainty that it represents a nemertean. 1347:-like tubes. Mainly in the tropics and subtropics, about 12 species appear in freshwater, and about a dozen species live on land in cool, damp places, for example under rotting logs. 5191: 2224:

analyses emphasised as shared features: multiciliated (with multiple cilia per cell), glandular epidermis; rod-shaped secretory bodies or rhabdites; frontal glands or organs;

1049:, which can detect light but not form an image. Most nemerteans have two to six ocelli, although some have hundreds. A few tiny species that live between grains of sand have 1804:

As nemerteans are mostly soft-bodied, one would expect fossils of them to be extremely rare. One might expect the stylet of a nemertean to be preserved, since it is made of

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larva, in which the developing juvenile has a gut which lies across the larva's body, and usually eats the remains of the larva when it emerges. The bodies of some species

6966: 4288: 4232: 4077: 3949: 3839: 3326: 1523:, and other nemerteans. Nemerteans' skins secrete toxins that deter many predators, but some crabs may clean nemerteans with one claw before eating them. The American 7597: 1269:(developing gut) and coalesce to form the juvenile. When it is fully formed, the juvenile bursts out of the larva body and usually eats it during this catastrophic 2220:

English-language writings have conventionally treated nemerteans as acoelomate bilaterians that are most closely related to flatworms (Platyhelminthes). These pre-

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wrote of a marine worm which was apparently 17.76 metres (58.3 ft) long ("40 cubits"), about the width of a child's arm, and whose touch made a hand swell.

7623: 4590:"Hox genes pattern the anterior-posterior axis of the juvenile but not the larva in a maximally indirect developing invertebrate, Micrura alaskensis (Nemertea)" 2287:

flatworms produce no ectomesoderm. In nemerteans the space between the epidermis and the gut is mainly filled by well-developed muscles embedded in noncellular

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larvae (for example Annelida and Mollusca); and some other phyla (such as Platyhelminthes, Sipuncula, Gastrotricha, Gnathostomulida, Micrognathozoa, Nemertea,

1386:. It can build a cocoon, which allows it to avoid desiccation while being transported, and it may be able to build populations quickly in new areas as it is a 956:

through which the wastes exit. Semiterrestrial and freshwater nemerteans have many more flame cells than marines, sometimes thousands. The reason may be that

7710: 739:. Next to the dermis are at least three layers of muscles, some circular and some longitudinal. The combinations of muscle types vary between the different 4640: 4888:

Knaust, Dirk; Desrochers, André (2019). "Exceptionally preserved soft-bodied assemblage in Ordovician carbonates of Anticosti Island, eastern Canada".

891:, and respiration occurs over the surface of the body, which is long and sometimes flattened. Like other animals with thick body walls, they use fluid 762:

The mouth is ventral and a little behind the front of the body. The foregut, stomach and intestine run a little below the midline of the body and the

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in Scotland. Other estimates are about 30 metres (98 ft). Zoologists find it extremely difficult to measure this species. For comparison:

2195:("armed") are monophyletic, but find that Palaeonemertea is doubly paraphyletic, having given rise to both the Heteronemertea and the Enopla. 1117:, whose proboscis have one active stylet, move by extending the proboscis, sticking it to an object and pulling the animal toward the object. 5024: 4973: 4865: 4539: 4429: 4393: 4364: 4272: 4216: 4185: 4061: 4010: 3974: 3933: 3823: 3781: 3661: 3627: 3580: 3497: 3463: 3397: 3372: 3310: 3139: 2969: 1261:

cap with the ear flaps pulled down. It has a gut which lies across the body, a mouth between the "ear flaps", but no anus. A small number of

3522:"Determining the largest known land animal: A critical comparison of differing methods for restoring the volume and mass of extinct animals" 2160:(trait shared by an ancestor and all its descendants, but not by other groups) include the eversible proboscis located in the rhynchocoel. 5208: 5113: 4313: 903:

is contained in the main body cavity. The fluid in the rhynchocoel moves substances to and from the proboscis, and functions as a fluid

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muscle which attaches to the back of the rhynchocoel, can stretch up to 30 times its inactive length and acts to retract the proboscis.

5349: 3417: 1061:, which feeds on polychaetes, can follow the prey's trails of mucus, and find its burrow by backtracking along its own trail of mucus. 5386: 5247: 5055: 4758: 4119: 3168: 4754: 393:

are embedded in the front part of the two lateral fluid vessels, and remove the wastes through a network of pipes to the outside.

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to move substances through their bodies. The circulatory system consists of the rhynchocoel and peripheral vessels, while their

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Knaust, Dirk (2010). "Remarkably preserved benthic organisms and their traces from a middle Triassic (Muschelkalk) mud flat".

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Walker, J.C.; Anderson, D.T. (1998). "The Platyhelminthes, Nemertea, Entoprocta and Gnathostomulida". In D.T. Anderson (ed.).

1209:, in which the fate of a cell can usually be predicted from its predecessors in the process of division. The embryos of most 472:, in which the fate of a cell can usually be predicted from its predecessors in the process of division. The embryos of most 519:, as one order of Anopla is more closely related to Enopla than to the other order of Anopla. The phylum Nemertea itself is 7615: 3615: 2985: 1512:

is considered a significant factor in the collapse of the dungeness crab fishery. Other coastal nemerteans have devastated

5502: 5492: 5475: 4102: 255: 3451: 770:, a cavity which mostly runs above the midline and ends a little short of the rear of the body. The rhynchocoel of class 2897: 1633:

and all the hosts steal food from them. These nemerteans have short, wide bodies and have no stylets but have a sucking

698: 489: 405: 3651: 2228:; and acoelomate body organization. However, multiciliated epidermal cells and epidermal gland cells are also found in 1339:

animals. Some live deep in the open oceans, and have gelatinous bodies. Others build semi-permanent burrows lined with

585:, was first used in 1806 by Sowerby. In 1995, a total of 1,149 species had been described and grouped into 250 genera. 7519: 7506: 6665: 3570: 3058: 2156:(meaning that the phylum includes all and only descendants of one ancestor that was also a member of the phylum). The 3552: 4961: 7550: 3487: 3099: 344:, a cavity which mostly runs above the midline and ends a little short of the rear of the body. All species have a 3998: 3964: 1302:. The animal is 1.5 centimetres (0.59 in) long, of which the anterior 1 centimetre (0.39 in) is visible. 7705: 7628: 7563: 6809: 2299:, but a similar structure of body-wall muscles embedded in noncellular connective tissue is widespread among the 1610:. Their mouth is located underneath and ahead of the brain. Their main nerve cords run inside body-wall muscles. 139: 1690:

Recent molecular phylogenetic studies divided the group into two superclasses, three classes, and eight orders:

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being the rhynchocoel and eversible proboscis. Traditional taxonomy says that nemerteans are closely related to

4661: 3127: 2805:, which include about half of the extant animal phyla. Lophotrochozoa groups: those animals that feed using a 1566:. Comprises 100 marine species. Their body wall has outer circular and inner length-wise muscles. In addition, 1232:, swimming for some time and eating prey larger than microscopic particles. However, many members of the order 842:, the proboscis exits from a common orifice of the rhynchocoel and mouth. A typical member of this class has a 681: 381: 774:

has an orifice a little to the front of the mouth, but still under the front of the body. In the other class,

1464:, and may kill annelids of about their own size. They sometimes take fish, both living and dead. Insects and 1206: 1045:. Small pits in the epidermis appear to be sensors. On their head, some species have a number of pigment-cup 469: 6894: 5507: 5354: 4933: 1886: 1327:

Most nemerteans are marine animals that burrow in sediments, lurk in crevices between shells, stones or the

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Schram, Frederick R. (September 1973). "Pseudocoelomates and a Nemertine from the Illinois Pennsylvanian".

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Cedhagen, Tomas; Per Sundberg (1986). "A previously unrecognized report of a nemertean in the literature".

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The few predators on nemerteans include bottom-feeding fish, some sea birds, a few invertebrates including

7446: 6658: 5379: 4566: 2924: 1557:("unarmed"). Includes animals with proboscis without stylet, and a mouth underneath and behind the brain. 1497: 1282: 1183: 1057: 981: 867:, absorb organic food in solution through their skins, which may make the long, slim bodies an advantage. 807: 7524: 7659: 7122: 6772: 5470: 3164:"Lophotrochozoa internal phylogeny: new insights from an up-to-date analysis of nuclear ribosomal genes" 2176: 1433: 1247: 1080: 1004:, masses of nerve cells, positioned round the rhynchocoel near its front end – while the brains of most 485: 2252:

larvae. The protonephridia of nemertea and flatworms are different in structure, and in position – the

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Roe, Pamela; Norenburg, Jon L.; Maslakova, Svetlana (2007). Sol Felty Light; James T. Carlton (eds.).

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Cannon, J.T.; Vellutini, B.C.; Smith, J.; Ronquist, F.; Jondelius, U.; Hejnol, A. (4 February 2016).

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develop either directly to form juveniles (like the adult but smaller) or larvae that resemble the

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involved during development, which are only found in the juveniles developing inside the larvae.

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are estimated at approximately 35 metres (115 ft) and 31 metres (102 ft) respectively.

5183: 7646: 6909: 6357: 6277: 5627: 5497: 5460: 5448: 5438: 5372: 5321: 5274: 5140: 5132: 5082: 5020: 4969: 4861: 4724: 4621: 4535: 4491: 4425: 4389: 4360: 4332: 4309:"The invention of the pilidium larva in an otherwise perfectly good spiralian phylum Nemertea" 4268: 4212: 4181: 4158: 4115: 4057: 4006: 3970: 3929: 3819: 3777: 3752: 3657: 3623: 3576: 3493: 3459: 3393: 3368: 3306: 3238: 3195: 3135: 3075: 2965: 2961: 2953: 2288: 1861: 1805: 1438: 1294: 1158: 1018: 748: 732: 597: 460:), and build temporary gonoducts (ducts from which the ova or sperm are emitted) opening to a 385: 5204: 3684:

Martin, Gary G. (1978). "A new function of rhabdites: mucus production for ciliary gliding".

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Traditional taxonomic classification has divided the group into two classes and four orders:

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is at the tip of the tail, and the mouth is under the front. A little above the gut is the

7602: 7358: 7263: 7225: 7180: 7112: 6869: 6829: 6814: 6707: 6638: 6544: 6395: 6298: 6155: 5688: 5016: 5010: 4652: 4531: 4525: 4264: 4258: 4208: 4202: 4053: 4047: 3925: 3919: 3815: 3809: 3302: 3296: 2668: 1824: 1813: 1560: 1551: 1383: 1202: 1111: 816: 740: 666: 568: 515:("armed" with a dagger) also with two orders. However, it is now accepted that Anopla are 508: 500: 465: 766:

is at the tip of the tail. Above the gut and separated from the gut by mesenchyme is the

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A phylum-wide survey reveals multiple independent gains of head regeneration in Nemertea

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connect to the brain and run along the length of the body. Most nemerteans have various

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The Marine Biological Laboratory: Phylum Nemertea (Nemertinea, Nemertini, Rhynchocoela)

5269: 5242: 5077: 5050: 4719: 4686: 4616: 4589: 4486: 4453: 3747: 3722: 3190: 3163: 2802: 2798: 2478: 2225: 2188: 2018: 1964: 1931: 1744: 1710: 1698: 1682:. Includes about 100 pelagic and 50 benthic species. Their pads bear many tiny stylets. 1630: 1614: 1607: 1586: 1563: 1520: 1502: 1477: 1424: 1237: 1233: 1229: 1225: 1135: 1042: 957: 936: 872: 802: 701:. Many have visible patterns in various combinations of yellow, orange, red and green. 532: 445: 373: 358: 354: 271: 240: 4452:

Shinobe, Shotaro; Uchida, Shota; Mori, Hideaki; Okochi, Isamu; Chiba, Satoshi (2017).

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The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon

7694: 7142: 7127: 7089: 7014: 6950: 6936: 6884: 6879: 6793: 6782: 6777: 6757: 6752: 6727: 6448: 6352: 5851: 5333: 4917: 4838: 4811: 3707: 3686: 3548: 3425: 3042: 3010: 2885: 2881: 2410: 2204: 2070: 2055: 2048: 1834: 1765: 1759: 1752: 1679: 1668: 1645: 1638: 1492: 1390: 1359: 1270: 1262: 1243: 1114: 1038: 953: 857: 281: 81: 778:, the mouth and the front of the rhynchocoel share an orifice. The rhynchocoel is a 368:, positioned around the rhynchocoel near the animal's front end. At least a pair of 7338: 7333: 7308: 7283: 7273: 7200: 7069: 6943: 6904: 6889: 6864: 6859: 6804: 6737: 6554: 6549: 6437: 6293: 6179: 6065: 5968: 5947: 5817: 5768: 5724: 5705: 2893: 2794: 2683: 2342: 2172: 2157: 2144: 1732: 1412: 1371: 1179: 752: 564: 524: 520: 516: 276: 126: 7498: 5159: 4137:"Building the vertebrate heart - an evolutionary approach to cardiac development" 1533:, both called "tapeworms" in their respective localities, are sold as fish bait. 7584: 7511: 7478: 7393: 7368: 7313: 7288: 7210: 7205: 7170: 7160: 6854: 6767: 6515: 6486: 6472: 6462: 6047: 5863: 5776: 5558: 4802: 4785: 4201:

Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). "Introduction to Bilateria".

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According to more recent analyses, in the development of nemertean embryos, ecto

1890: 1869: 1579: 1399: 1387: 1321: 1312: 1266: 1258: 1251: 1107: 1096: 875:, which have a proboscis but no stylet, and use suckers to attach themselves to 767: 672: 184: 56: 35: 4710: 4477: 3034: 7426: 7388: 7318: 7298: 7293: 7278: 7248: 7220: 7175: 7165: 7137: 7132: 7074: 7049: 6742: 6717: 6612: 6597: 6592: 6573: 6568: 6496: 6443: 6413: 6405: 6347: 6221: 6213: 6196: 5976: 5888: 5841: 5781: 5743: 5717: 5563: 5548: 5359: 4606: 3421: 3112: 2877: 2873: 2853: 2822: 2806: 2418: 2253: 2229: 2221: 1853: 1657: 1461: 1408: 1344: 1187: 1175: 1154: 1131: 1010: 1005: 997: 948: 944: 928: 912: 847: 783: 744: 728: 716: 655: 647: 552: 544: 422: 410: 390: 220: 101: 66: 17: 7469: 5136: 4909: 3079: 7343: 7323: 7215: 7094: 7029: 7019: 7004: 6999: 6980: 6732: 6578: 6525: 6520: 6491: 6480: 6429: 6424: 6376: 6288: 6281: 6075: 6070: 6032: 5881: 5873: 5802: 5754: 5675: 5662: 5643: 5638: 5597: 4687:"Declining soil Crustacea in a World Heritage Site caused by land nemertean" 4454:"Declining soil Crustacea in a World Heritage Site caused by land nemertean" 4111: 3071: 2865: 2857: 2830: 2818: 2785: 2611: 2557: 2464: 2456: 2448: 2323: 2304: 2249: 2237: 2153: 1845: 1618: 1575: 1481: 1473: 1449: 1420: 1375: 1355: 1050: 1022: 896: 852: 795: 528: 430: 426: 349: 345: 210: 197: 171: 151: 106: 5325: 5278: 5260: 5144: 5127: 5108: 5086: 5068: 4728: 4625: 4495: 4336: 4162: 4135:

Pérez-Pomares, José M.; Juan M. González-Rosa; Ramón Muñoz-Chápuli (2009).

3884: 3865: 3756: 3738: 3521: 3242: 3199: 3181: 535:, a very large clade, sometimes viewed as a superphylum that also includes 444:

In most species the sexes are separate, but all the freshwater species are

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Russell, Peter J.; Wolfe, Stephen L.; Hertz, Paul E.; Cecie Starr (2008).

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Russell, Peter J.; Wolfe, Stephen L.; Hertz, Paul E.; Cecie Starr (2008).

4153: 4136: 3233: 3214: 2303:(animals in which the early cell divisions make a spiral pattern) such as 7463: 7398: 7378: 7348: 7328: 7303: 7268: 7258: 7253: 7084: 7059: 7039: 6699: 6602: 6586: 6509: 6501: 6456: 6419: 6400: 6389: 6371: 6365: 6226: 6143: 6040: 5921: 5810: 5694: 5585: 5576: 5482: 4327: 4308: 4176:

Anderson, D.T. (1998). "The invertebrate phyla". In D.T. Anderson (ed.).

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cavity of molluscs and feed on micro-organisms filtered out by the host.

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and have suckers at the front and back ends, with which they attach to a

230: 96: 91: 76: 71: 61: 31: 5317: 811:, a species within class Anopla, discharges a sticky branched proboscis. 7403: 7383: 7079: 7054: 7044: 7034: 6990: 6927: 6562: 6538: 6530: 6467: 6381: 6201: 6188: 6121: 6112: 6057: 5982: 4946: 3699: 2861: 2814: 2494: 2308: 2296: 2273: 2233: 1873: 1817: 1653: 1649: 1634: 1453: 1428: 1218: 1146: 1001: 876: 705: 548: 540: 536: 477: 438: 414: 365: 111: 86: 5364: 2291:. This structure is similar to that found in larger flatworms such as 1437:

has been implicated in the decline of native arthropod species on the

923: 7589: 7243: 7235: 7104: 6607: 6341: 5631: 5541: 5528: 5399: 5396: 3215:"Hox and ParaHox genes in Nemertodermatida, a basal bilaterian clade" 2801:

and perhaps Sipuncula) and Mollusca make the ribbon-worms members of

2357: 2192: 2180: 1995: 1865: 1857: 1599: 1554: 1480:("smell") and are not selective about their prey. A few species live 1367: 1198: 1191: 1150: 1046: 1014: 915:

and carry oxygen, but the function of the other pigments is unknown.

839: 819: 779: 775: 771: 736: 617: 593: 512: 507:("unarmed" – their proboscises do not have a little dagger) with two 504: 457: 404:, while larger species use muscular waves to crawl, and some swim by 377: 323: 319: 285: 161: 7440: 1656:

sea water, in freshwater and on land. They feed by commensalism and

1501:

has consumed about 55% of the total egg production of its host, the

992:

that connect to the brain and run along the length of the body. The

492:

readily, and even parts cut off near the tail can grow full bodies.

4359:. Philadelphia, PA: Holt-Saunders International. pp. 252–262. 2896:, which are neither protostomes nor deuterostomes, are regarded as 1675:. Some use the stylet for locomotion as well as for capturing prey. 7576: 7152: 7024: 2284: 2245: 2200: 1590: 1394: 1340: 1332: 1305: 1293: 1254: 1221: 1166: 1142: 1103: 1087: 1068: 993: 985: 922: 900: 888: 825: 801: 724: 713: 709: 589: 473: 453: 449: 401: 397: 4645:(Dakin) in Hawaii (Nemertinea: Hoplonemertinea: Prosorhochmidae)" 3367:(1 ed.). Oxford University Press Australia. pp. 79–85. 7190: 6682: 1626: 1513: 1457: 1299: 1210: 1171: 1162: 763: 727:

in which the cilia glide. Each ciliated cell has many cilia and

616:

are a separate phylum, whose closest relatives appear to be the

418: 335: 7444: 6654: 5660: 5368: 5051:"Ribbon worm relationships: A phylogeny of the phylum Nemertea" 4519: 4517: 4515: 4513: 4511: 4509: 4507: 4505: 4257: