dcsimg
Image of Loxosoma Keferstein 1862
Creatures » » Animals »

Goblet Worms

Entoprocta

Brief Summary

provided by EOL staff

The phylum Entoprocta (=Kamptozoa) includes around 180 known species (Iseto and Hirose 2010) and the actual world fauna likely exceeds 500 species (Nielsen 1989). Entoprocts are small, transparent, sessile (i.e., fixed to the substrate), solitary or colonial animals that superficially resemble cnidarian hydroids and ectoprocts ( = bryozoans in some usage, see below). They are largely radially symmetrical. Entoprocts are found along the coasts of every continent, including Antarctica. All but two known species are marine, but one of the two freshwater species, Urnatella gracilis, is known from every continent except Antarctica and, in contrast to other entoprocts, forms massive growths that may be quite conspicuous to the naked eye (Nielsen 1989).

Colonial entoprocts (around a quarter of known species, Nielsen 2010) may live attached to algae, shells, rocks, or other living or non-living substrates. Solitary species may be commensal on a variety of hosts, such as sponges, ectoprocts, polychaetes, sipunculans, and ascidians and are typically associated with just one or a few host species. Some solitary entoprocts are found on non-living substrates. Although entoprocts are found mainly in shallow water such as in the intertidal zone, some species may occur to depths as great as 500 meters.

(Brusca and Brusca 2003; Fuchs et al. 2010; Margulis and Chapman 2010)

Entoprocts are suspension feeders, extracting food particles (mainly phytoplankton) from currents produced by the lateral cilia on their tentacles. The dorsal suface of these animals is attached to the stalk and the ventral side faces upward. Water currents pass from dorsal to ventral, flowing between the tentacles. Food is trapped by the lateral cilia and moved in a sheet of mucus to the frontal cilia, which move the mucus and food to food grooves at the base of the ring of tentacles. (Brusca and Brusca 2003)

Colony growth occurs by budding. Solitary forms also reproduce by budding. Sexual reproduction occurs as well. Colonial forms may have hermaphroditic or (more commonly) dioecious (i.e., separate sex) zooids, and a colony may contain just one or both sexes. Larvae are typically free-swimming and planktotrophic (i.e., feeding in the water column), although a few species produce lecithotrophic (non-feeding) or benthic crawling larvae. Following a brief swimming phase, larvae of most species settle, affix to a substrate, and metamorphose into adults (larvae of a few species do not metamorphose but bud instead). (Brusca and Brusca 2003; Fuchs et al. 2010)

During most of the 18th and 19th centuries, entoprocts and ectoprocts were included together in the phylum Bryozoa. For most of the 20th century, however, the Entoprocta have been treated as a distinct phylum that may not even be closely related to the ectoprocts (with the ectoprocts being referred to as either Ectoprocta or Bryozoa). Beginning in the 1970s, some authors have been arguing that the entoprocts and ectoprocts may indeed be very closely related (Nielsen 2001 and references therein). Recently, some molecular data have supported this position (Hausdorf et al. 2007; Hejnol et al. 2009), although it appears that the sister group to Ectoprocta may be (Entoprocta + Cycliophora), as was originally suggested by Funch and Kristensen (1995). However, some other analyses have suggested that Ectoprocta may not be very close to (Entoprocta + Cycliophora) (Passamaneck & Halanych 2006; Hejnol et al. 2009; Fuchs et al. 2010; Mallatt et al. 2010).

license
cc-by-nc-sa-3.0
copyright
Shapiro, Leo
author
Shapiro, Leo
original
visit source
partner site
EOL staff

Comprehensive Description

provided by EOL staff

The phylum Entoprocta (=Kamptozoa) includes around 180 known species (Iseto and Hirose 2010) and the actual world fauna likely exceeds 500 species (Nielsen 1989). Entoprocts are small, transparent, sessile (i.e., fixed to the substrate), solitary or colonial animals that superficially resemble cnidarian hydroids and ectoprocts ( = bryozoans in some usage, see below). They are largely radially symmetrical. All but two known species of entoprocts are marine. Marine entoprocts are found along the coasts of every continent, including Antarctica. One of the two freshwater species, Urnatella gracilis, is known from every continent except Antarctica and, in contrast to other entoprocts, forms massive growths that may be quite conspicuous to the naked eye (Nielsen 1989).

Colonial entoprocts (around a quarter of known species, Nielsen 2010) may live attached to algae, shells, rocks, or other living or non-living substrates. Solitary species may be commensal on a variety of hosts, such as sponges, ectoprocts, polychaetes, sipunculans, and ascidians and are typically associated with just one or a few host species. They are often found inside the burrows or tubes of hosts that produce ventilating currents. Nearly all members of the genus Loxosoma live in association with polychaetes (Nielsen 1996). Some solitary entoprocts are found on non-living substrates.

Entoprocts are found mainly in shallow water such as in the intertidal zone, but some species may occur to depths as great as 500 meters. Individual entoproct zooids consist of a cuplike "calyx" supported by a stalk. A whorl of 6 to 36 ciliated tentacles (depending on age and species) surrounds the calyx (unlike either ectoprocts or cnidarians, entoprocts fold their tentacles when disturbed; they do not withdraw them into their bodies). The calyx has a circular sphincter that controls its size and small bundles of muscle fibers along the stalk cause a characteristic "nodding" behavior. Both the mouth and anus are located on the surface of the calyx and are surrounded by tentacles. The anus is elevated on a distinct structure called the anal cone. The entire animal, including tentacles, calyx, and stalk, may extend to 10 mm.

(Brusca and Brusca 2003; Fuchs et al. 2010; Margulis and Chapman 2010)

Entoprocts are suspension feeders, extracting food particles (mainly phytoplankton) from currents produced by the lateral cilia on the tentacles. The dorsal suface of these animals is attached to the stalk and the ventral side faces upward. Water currents pass from dorsal to ventral, flowing between the tentacles. Food is trapped by the lateral cilia and moved in a sheet of mucus to the frontal cilia, which move the mucus and food to food grooves at the base of the ring of tentacles. (Brusca and Brusca 2003)

Colony growth occurs by budding. Solitary forms also reproduce by budding. Sexual reproduction occurs as well. Colonial forms may have hermaphroditic or (more commonly) dioecious (i.e., separate sex) zooids, and a colony may contain just one or both sexes. Sperm apparently are released into the water and enter the female reproductive tract, with fertilization occurring in the ovaries or oviducts. In most species, embryos develop within a brood chamber, though in others the embryos are retained within the ovary. Larvae are typically free-swimming and planktotrophic (i.e., feeding in the water column), although a few species produce lecithotrophic (non-feeding) or benthic crawling larvae. Following a brief swimming phase, larvae of most species settle, affix to a substrate, and metamorphose into adults (larvae of a few species do not metamorphose but bud instead). (Brusca and Brusca 2003; Fuchs et al. 2010)

During most of the 18th and 19th centuries, entoprocts and ectoprocts were included together in the phylum Bryozoa. For most of the 20th century, however, the Entoprocta have been treated as a distinct phylum that may not even be closely related to the ectoprocts (with the ectoprocts being referred to as either Ectoprocta or Bryozoa). The main anatomical and developmental differences between entoprocts and ectoprocts are the position of the anus (inside vs. outside the tentacle crown), the cleavage pattern during development (spiral vs. radial), and the body cavities (acoelomate vs. coelomate) (Fuchs et al. 2010). Beginning in the 1970s, some authors have been arguing that the entoprocts and ectoprocts may indeed be very closely related (Nielsen 2001 and references therein). Recently, some molecular data have supported this position (Hausdorf et al. 2007; Hejnol et al. 2009), although it appears that the sister group to Ectoprocta may be (Entoprocta + Cycliophora), as was originally suggested by Funch and Kristensen (1995). However, some other analyses have suggested that Ectoprocta may not be very close to (Entoprocta + Cycliophora) (Passamaneck & Halanych 2006; Hejnol et al. 2009; Fuchs et al. 2010; Mallatt et al. 2010). The putative clade consisting of Ectoprocta, Entoprocta, and Cycliophora has been termed Polyzoa (Cavalier-Smith 1998).

The biology of the Entoprocta was reviewed by Wasson (2002). Nielsen (1989) also reviewed entoproct biology and provided a dichotomous key to all species known from northwestern Europe, with the caveat that the possibility of encountering undescribed species is not unlikely in many areas. Wasson (1997) reviewed and revised the systematics of the colonial entoprocts of the Pacific coast of North America.

license
cc-by-nc-sa-3.0
copyright
Shapiro, Leo
author
Shapiro, Leo
original
visit source
partner site
EOL staff

Entoprocta

provided by wikipedia EN

Entoprocta /ɛntˈprɒktə/ (lit.'inside rectum/anus'), or Kamptozoa /kæm(p)təˈzə/, is a phylum of mostly sessile aquatic animals, ranging from 0.1 to 7 millimetres (0.004 to 0.3 in) long. Mature individuals are goblet-shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles towards the mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly.

Some species eject unfertilized ova into the water, while others keep their ova in brood chambers until they hatch, and some of these species use placenta-like organs to nourish the developing eggs. After hatching, the larvae swim for a short time and then settle on a surface. There they metamorphose, and the larval gut rotates by up to 180°, so that the mouth and anus face upwards. Both colonial and solitary species also reproduce by cloning — solitary species grow clones in the space between the tentacles and then release them when developed, while colonial ones produce new members from the stalks or from corridor-like stolons.

Fossils of entoprocts are very rare, and the earliest specimens that have been identified with confidence date from the Late Jurassic. Most studies from 1996 onwards have regarded entoprocts as members of the Trochozoa, which also includes molluscs and annelids. However, a study in 2008 concluded that entoprocts are closely related to bryozoans.

Names

"Entoprocta", coined in 1870,[3] means "anus inside".[4] The alternative name "Kamptozoa", meaning "bent" or "curved" animals,[5] was assigned in 1929.[3] Some authors use "Entoprocta",[6][7] while others prefer "Kamptozoa".[4][8]

Description

Most species are colonial, and their members are known as "zooids",[9] since they are not fully independent animals.[10] Zooids are typically 1 millimetre (0.039 in) long but range from 0.1 to 7 millimetres (0.004 to 0.3 in) long.[4]

Distinguishing features

Entoprocts are superficially like bryozoans (ectoprocts), as both groups have a "crown" of tentacles whose cilia generate water currents that draw food particles towards the mouth. However, they have different feeding mechanisms and internal anatomy, and ectoprocts undergo a metamorphosis from larva to adult that destroys most of the larval tissues; their colonies also have a founder zooid which is different from its "daughters".[4]

Zooids

 src=
Barentsia discreta

The body of a mature entoproct zooid has a goblet-like structure with a calyx mounted on a relatively long stalk that attaches to a surface. The rim of the calyx bears a "crown" of 8 to 30 solid tentacles, which are extensions of the body wall. The base of the "crown" of tentacles is surrounded by a membrane that partially covers the tentacles when they retract. The mouth and anus lie on opposite sides of the atrium (space enclosed by the "crown" of tentacles), and both can be closed by sphincter muscles. The gut is U-shaped, curving down towards the base of the calyx, where it broadens to form the stomach. This is lined with a membrane consisting of a single layer of cells, each of which has multiple cilia.[4]

 src=
Pedicellina cernua (magnified x 27)

The stalks of colonial species arise from shared attachment plates or from a network of stolons, tubes that run across a surface.[4] In solitary species, the stalk ends in a muscular sucker, or a flexible foot, or is cemented to a surface.[7] The stalk is muscular and produces a characteristic nodding motion. In some species it is segmented. Some solitary species can move, either by creeping on the muscular foot or by somersaulting.[4]

The body wall consists of the epidermis and an external cuticle,[4] which consists mainly of criss-cross collagen fibers. The epidermis contains only a single layer of cells, each of which bears multiple cilia ("hairs") and microvilli (tiny "pleats") that penetrate through the cuticle.[4] The stolons and stalks of colonial species have thicker cuticles, stiffened with chitin.[7]

There is no coelom (internal fluid-filled cavity lined with peritoneum) and the other internal organs are embedded in connective tissue that lies between the stomach and the base of the "crown" of tentacles. The nervous system runs through the connective tissue and just below the epidermis, and is controlled by a pair of ganglia. Nerves run from these to the calyx, tentacles and stalk, and to sense organs in all these areas.[4]

Feeding, digestion, excretion, circulation and respiration

A band of cells, each with multiple cilia, runs along the sides of the tentacles, connecting each tentacle to its neighbors, except that there is a gap in the band nearest the anus. A separate band of cilia grows along a groove that runs close to the inner side of the base of the "crown", with a narrow extension up the inner surface of each tentacle.[7] The cilia on the sides of the tentacles create a current that flows into the "crown" at the bases of the tentacles and exits above the center of the "crown".[4] These cilia pass food particles to the cilia on the inner surface of the tentacles, and the inner cilia produce a downward current that drives particles into and around the groove, and then to the mouth.[7]

Entoprocts generally use one or both of: ciliary sieving, in which one band of cilia creates the feeding current and another traps food particles (the "sieve"); and downstream collecting, in which food particles are trapped as they are about to exit past them. In entoprocts, downstream collecting is carried out by the same bands of cilia that generate the current; trochozoan larvae also use downstream collecting, but use a separate set of cilia to trap food particles.[12]

In addition, glands in the tentacles secrete sticky threads that capture large particles.[4] A non-colonial species reported from around the Antarctic Peninsula in 1993 has cells that superficially resemble the cnidocytes of cnidaria, and fire sticky threads. These unusual cells lie around the mouth, and may provide an additional means of capturing prey.[13]

The stomach and intestine are lined with microvilli, which are thought to absorb nutrients. The anus, which opens inside the "crown", ejects solid wastes into the outgoing current after the tentacles have filtered food out of the water; in some families it is raised on a cone above the level of the groove that conducts food to the mouth.[4][14] Most species have a pair of protonephridia which extract soluble wastes from the internal fluids and eliminate them through pores near the mouth. However, the freshwater species Urnatella gracilis has multiple nephridia in the calyx and stalk.[4]

The zooids absorb oxygen and emit carbon dioxide by diffusion,[4] which works well for small animals.[15]

Reproduction and life cycle

 src=
Apical tuft (cilia)
Prototroch (cilia)
Stomach
Mouth
Metatroch (cilia)
Mesoderm
Anus
/// = cilia
 src=
Trochophore larva[16]

Most species are simultaneous hermaphrodites, but some switch from male to female as they mature, while individuals of some species remain of the same sex all their lives. Individuals have one or two pairs of gonads, placed between the atrium and stomach, and opening into a single gonopore in the atrium.[7] The eggs are thought to be fertilized in the ovaries. Most species release eggs that hatch into planktonic larvae, but a few brood their eggs in the gonopore. Those that brood small eggs nourish them by a placenta-like organ, while larvae of species with larger eggs live on stored yolk.[4] The development of the fertilized egg into a larva follows a typical spiralian pattern: the cells divide by spiral cleavage, and mesoderm develops from a specific cell labelled "4d" in the early embryo.[17] There is no coelom at any stage.[4]

In some species the larva is a trochophore which is planktonic and feeds on floating food particles by using the two bands of cilia round its "equator" to sweep food into the mouth, which uses more cilia to drive them into the stomach, which uses further cilia to expel undigested remains through the anus.[18] In some species of the genera Loxosomella and Loxosoma, the larva produces one or two buds that separate and form new individuals, while the trochophore disintegrates. However, most produce a larva with sensory tufts at the top and front, a pair of pigment-cup ocelli ("little eyes"), a pair of protonephridia, and a large, cilia-bearing foot at the bottom.[7] After settling, the foot and frontal tuft attach to the surface. Larvae of most species undergo a complex metamorphosis, and the internal organs may rotate by up to 180°, so that the mouth and anus both point upwards.[4]

All species can produce clones by budding. Colonial species produce new zooids from the stolon or from the stalks, and can form large colonies in this way.[4] In solitary species, clones form on the floor of the atrium, and are released when their organs are developed.[7]

Taxonomy

The phylum consists of about 150 recognized species, grouped into 4 families:[4][6]

Evolutionary history

Fossil record

 src=
The Mid-Cambrian Dinomischus was once hailed as the earliest fossil entoproct,[23] but the classification is uncertain[24]

Since entoprocts are small and soft-bodied, fossils have been extremely rare.[24] In 1977, Simon Conway Morris provided the first description of Dinomischus, a sessile animal with calyx, stalk and holdfast, found in Canada's Burgess Shale, which was formed about 505 million years ago. Morris regarded this animal as the earliest known entoproct, since its mouth and anus lay inside a ring of structures above the calyx, but noted that these structures were flat and rather stiff, while the tentacles of modern entoprocts are flexible and have a round cross-section.[23]

In 1992 J.A. Todd and P.D. Taylor concluded that Dinomischus was not an entoproct, because it did not have the typical rounded, flexible tentacles, and the fossils showed no other features that clearly resembled those of entoprocts. In their opinion, the earliest fossil entoprocts were specimens they found from Late Jurassic rocks in England. These resemble the modern colonial genus Barentsia in many ways, including: upright zooids linked by a network of stolons encrusting the surface to which the colony is attached; straight stalks joined to the stolons by bulky sockets with transverse bands of wrinkles; overall size and proportions similar to that of modern species of Barentsia.[24]

Another species, Cotyledion tylodes, first described in 1999, was larger than extant entoprocts, reaching 8–56 mm in height, and unlike modern species, was "armored" with sclerites, scale-like structures. C. tylodes did have a similar sessile lifestyle to modern entoprocts. The identified fossils of C. tylodes were found in 520-million-year-old rocks from southern China. This places early entoprocts in the period of the Cambrian explosion.[25]

The Maotianshan Shales fossil, Cotyledion tylodes, has been reevaluated as being an ancient, sclerite-bearing entoproct (originally having been identified as a putative carpoid echinoderm).[1] This entoproct interpretation of Cotyledion, however, has been questioned by Mark McMenamin, who considers it best interpreted as a stem group echinoderm based on the morphology of its stem sclerites.[26]

Family tree

When entoprocts were discovered in the nineteenth century, they and bryozoans (ectoprocts) were regarded as classes within the phylum Bryozoa, because both groups were sessile animals that filter-fed by means of a "crown" of tentacles that bore cilia. However, from 1869 onwards, increasing awareness of differences, including the position of the entoproct anus inside the feeding structure and the difference in the early pattern of division of cells in their embryos, caused scientists to regard the two groups as separate phyla.[27] "Bryozoa" then became just an alternative name for ectoprocts, in which the anus is outside the feeding organ.[28] However, studies by one team in 2007 and 2008 argue for sinking Entoprocta into Bryozoa as a class, and resurrecting Ectoprocta as a name for the currently identified bryozoans.[27][29]

The consensus of studies from 1996 onwards has been that entoprocts are part of the Trochozoa, a protostome "superphylum" whose members are united in having as their most basic larval form the trochophore type. The trochozoa also include molluscs, annelids, flatworms, nemertines and others. However, scientists disagree about which phylum is mostly closely related to enctoprocts within the trochozoans.[30] An analysis in 2008 re-introduced the pre-1869 meaning of the term "Bryozoa", for a group in which entoprocts and ectoprocts are each other's closest relatives.[27]

Ecology

Distribution and habitats

All species are sessile.[4] While the great majority are marine, two species live in freshwater: Loxosomatoides sirindhornae, reported in 2004 in central Thailand, and Urnatella gracilis, found in all the continents except Antarctica.[3] Colonial species are found in all the oceans, living on rocks, shells, algae and underwater buildings.[4] The solitary species, which are marine,[3] live on other animals that feed by producing water currents, such as sponges, ectoprocts and sessile annelids.[7] The majority of species live no deeper than 50 meters, but a few species are found in the deep ocean.[31]

Interaction with other organisms

Some species of nudibranchs ("sea slugs"), particularly those of the genus Trapania, as well as turbellarian flatworms, prey on entoprocts.[32]

Small colonies of the freshwater entoproct Urnatella gracilis have been found living on the aquatic larvae of the dobsonfly Corydalus cornutus. The ectoprocts gain a means of dispersal, protection from predators and possibly a source of water that is rich in oxygen and nutrients, as colonies often live next to the gills of the larval flies.[33] In the White Sea, the non-colonial entoproct Loxosomella nordgaardi prefers to live attached to bryozoan (ectoproct) colonies, mainly on the edges of colonies or in the "chimneys", gaps by which large bryozoan colonies expel water from which they have sieved food. Observation suggests that both the entoprocts and the bryozoans benefit from the association: each enhances the water flow that the other needs for feeding; and the longer cilia of the entoprocts may help them to capture different food from that caught by the bryozoans, so that the animals do not compete for the same food.[34]

Entoprocts are small and have been little studied by zoologists. Hence it is difficult to determine whether a specimen belongs to a species that already occurs in the same area or is an invader, possibly as a result of human activities.[35]

References

  1. ^ a b Zhang, Zhifei; et al. (January 2013). "A sclerite-bearing stem group entoproct from the early Cambrian and its implications". Scientific Reports. 3: 1066. Bibcode:2013NatSR...3E1066Z. doi:10.1038/srep01066. PMC 3548229. PMID 23336066.
  2. ^ Todd, J. A.; Taylor, P. D. (1992). "The first fossil entoproct". Naturwissenschaften. 79 (7): 311–314. Bibcode:1992NW.....79..311T. doi:10.1007/BF01138708. S2CID 44229586.
  3. ^ a b c d Wood, T.S. (2005). "Loxosomatoides sirindhornae, new species, a freshwater kamptozoan from Thailand (Entoprocta)". Hydrobiologia. 544: 27–31. doi:10.1007/s10750-004-7909-x. S2CID 23481992.
  4. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Kamptozoa and Cycliophora". Invertebrate Zoology (7th ed.). Brooks/Cole. pp. 808–812. ISBN 0-03-025982-7.
  5. ^ The prefix "campto-" is explained at:
  6. ^ a b "ITIS Standard Report Page: Entoprocta". Integrated Taxonomic Information System. 2006. Retrieved 2009-08-26.
  7. ^ a b c d e f g h i Nielsen, C. (2002). "Entoprocta". Encyclopedia of Life Sciences. John Wiley & Sons, Ltd. doi:10.1038/npg.els.0001596. ISBN 0-470-01617-5.
  8. ^ a b c d e f Wasson, K. (1997). "Systematic revision of colonial kamptozoans (entoprocts) of the Pacific coast of North America". Zoological Journal of the Linnean Society. 121 (1): 1–63. doi:10.1111/j.1096-3642.1997.tb00146.x.
  9. ^ Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Lophoporata". Invertebrate Zoology (7th ed.). Brooks / Cole. pp. 829–845. ISBN 0-03-025982-7.
  10. ^ Little, W.; Fowler, H.W.; Coulson, J. & Onions, C.T. (1964). "Zooid". Shorter Oxford English Dictionary. Oxford University Press. ISBN 0-19-860613-3.
  11. ^ Rich, T.H.; Fenton, M.A.; Fenton, C.L. (1997). ""Moss Animals", or Bryozoans". The fossil book. Dover Publications. pp. 142–152. ISBN 978-0-486-29371-4. Retrieved 2009-08-07.
  12. ^ Riisgård, H.U.; Nielsen, C.; Larsen, P.S. (2000). "Downstream collecting in ciliary suspension feeders: the catch-up principle" (PDF). Marine Ecology Progress Series. 207: 33–51. Bibcode:2000MEPS..207...33R. doi:10.3354/meps207033. Retrieved 12 Sep 2009.
  13. ^ Emschermann, P. (April 1993). "On Antarctic Entoprocta" (PDF). Biological Bulletin. 184 (2): 153–185. doi:10.2307/1542225. JSTOR 1542225. PMID 29300524. Retrieved 12 Sep 2009.
  14. ^ Barnes, R.S.K. (2001). "The Lophophorates". The invertebrates: a synthesis (3rd ed.). Wiley-Blackwell. pp. 142–143. ISBN 0-632-04761-5.
  15. ^ Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Introduction to Metazoa". Invertebrate Zoology (7th ed.). Brooks / Cole. p. 65. ISBN 0-03-025982-7.
  16. ^ Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Mollusca". Invertebrate Zoology (7th ed.). Brooks / Cole. pp. 290–291. ISBN 0030259827.
  17. ^ Lambert, J.D. (2008). "Mesoderm in spiralians: the organizer and the 4d cell". Journal of Experimental Zoology. Wiley InterScience. 310B (1): 15–23. doi:10.1002/jez.b.21176. PMID 17577229.
  18. ^ Ruppert, E.E.; Fox, R.S. & Barnes, R.D. (2004). "Mollusca". Invertebrate Zoology (7th ed.). Brooks / Cole. pp. 290–291. ISBN 0-03-025982-7.
  19. ^ "ITIS Standard Report Page: Barentsiidae". 2006. Retrieved 2009-09-14.
  20. ^ "ITIS Standard Report Page: Pedicellinidae". 2006. Retrieved 2009-09-14.
  21. ^ "ITIS Standard Report Page: Loxokalypodidae". 2006. Retrieved 2009-09-14.
  22. ^ "ITIS Standard Report Page: Loxosomatidae". 2006. Retrieved 2009-09-14.
  23. ^ a b Morris, S.C. (1977). "A new entoproct-like organism from the Burgess Shale of British Columbia" (PDF). Palaeontology. 20 (4): 833–845. Retrieved 13 Sep 2009.
  24. ^ a b c Todd, J.A.; Taylor, P.D. (July 1992). "The first fossil entoproct". Naturwissenschaften. 79 (7): 311–314. Bibcode:1992NW.....79..311T. doi:10.1007/BF01138708. S2CID 44229586.
  25. ^ Sid Perkins, "ScienceShot: Fossils of Enigmatic Sea Creature Emerge", ScienceNOW, January 17, 2013
  26. ^ McMenamin, M. A. S. (2013). "Breakthrough on the Cambrian Explosion". BioScience. 63 (10): 834–835. doi:10.1525/bio.2013.63.10.14.
  27. ^ a b c Hausdorf, B.; Helmkampf, M.; Meyer, A.; et al. (December 2007). "Spiralian phylogenomics supports the resurrection of Bryozoa comprising Ectoprocta and Entoprocta". Molecular Biology and Evolution. 24 (12): 2723–2729. doi:10.1093/molbev/msm214. PMID 17921486.
  28. ^ Halanych, K.M.. (2004). "The new view of animal phylogeny" (PDF). Annual Review of Ecology, Evolution, and Systematics. 35: 229–256. doi:10.1146/annurev.ecolsys.35.112202.130124.
  29. ^ Helmkampf, M.; Bruchhaus, I.; Hausdorf, B. (22 August 2008). "Phylogenomic analyses of lophophorates (brachiopods, phoronids and bryozoans) confirm the Lophotrochozoa concept". Proceedings of the Royal Society B. 275 (1645): 1927–1933. doi:10.1098/rspb.2008.0372. PMC 2593926. PMID 18495619.
  30. ^ Haszprunar, G.; Schander, C.; Halanych, K.M. (2008). "Relationships of Higher Molluscan Taxa". In Ponder, W.F.; Lindberg, D.R. (eds.). Phylogeny and evolution of the Mollusca. University of California Press. pp. 19–22. ISBN 978-0-520-25092-5. Retrieved 13 Sep 2009.
  31. ^ A New Inside Anus Found Very Deep
  32. ^ Canning, M.H.; Carlton, J.T. (11 May 2005). "Predation on kamptozoans (Entoprocta)". Invertebrate Biology. 119 (4): 386–387. doi:10.1111/j.1744-7410.2000.tb00107.x.
  33. ^ Tracy, B.H.; Hazelwood, D.H. (November 1983). "The phoretic association of Urnatella gracilis (Entoprocta: Urnatellidae) and Nanocladius downesi (Diptera: Chironomidae) on Corydalus cornutus (Megaloptera: Corydalidae)". Freshwater Invertebrate Biology. The North American Benthological Society. 2 (4): 186–191. doi:10.2307/1467150. JSTOR 1467150. S2CID 87592771.
  34. ^ Yakovis, E.L. (December 2002). "Substrate preferences of a non-colonial kamptozoan, and its interactions with bryozoan hosts". Marine Biology. 141 (6): 1109–1115. doi:10.1007/s00227-002-0902-x. S2CID 85767673.
  35. ^ Wasson, K.; Von Holle, B.; Toft, J.; Ruiz, G. (March 2000). "Detecting invasions of marine organisms: kamptozoan case histories". Biological Invasions. 2 (1): 59–74. doi:10.1023/A:1010049907067. S2CID 38120150.
license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN

Entoprocta: Brief Summary

provided by wikipedia EN

Entoprocta /ɛntoʊˈprɒktə/ (lit. 'inside rectum/anus'), or Kamptozoa /kæm(p)təˈzoʊə/, is a phylum of mostly sessile aquatic animals, ranging from 0.1 to 7 millimetres (0.004 to 0.3 in) long. Mature individuals are goblet-shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles towards the mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly.

Some species eject unfertilized ova into the water, while others keep their ova in brood chambers until they hatch, and some of these species use placenta-like organs to nourish the developing eggs. After hatching, the larvae swim for a short time and then settle on a surface. There they metamorphose, and the larval gut rotates by up to 180°, so that the mouth and anus face upwards. Both colonial and solitary species also reproduce by cloning — solitary species grow clones in the space between the tentacles and then release them when developed, while colonial ones produce new members from the stalks or from corridor-like stolons.

Fossils of entoprocts are very rare, and the earliest specimens that have been identified with confidence date from the Late Jurassic. Most studies from 1996 onwards have regarded entoprocts as members of the Trochozoa, which also includes molluscs and annelids. However, a study in 2008 concluded that entoprocts are closely related to bryozoans.

license
cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
partner site
wikipedia EN