digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Business

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

This article is about the biological structure. For the medical condition, see Polyp (medicine). For the cartoonist, see P. J. Polyp.
Gorgonian polyps in a reef aquarium

A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the vase-shaped body. In solitary polyps, the aboral end is attached to the substrate by means of a disc-like holdfast called the pedal disc, while in colonies of polyps it is connected to other polyps, either directly or indirectly. The oral end contains the mouth, and is surrounded by a circlet of tentacles.

Classes[edit]

In the class Anthozoa, comprising the sea anemones and corals, the individual is always a polyp; in the class Hydrozoa, however, the individual may be either a polyp or a medusa, with most species undergoing a life cycle with both a polyp stage and a medusa stage. In class Scyphozoa, the medusa stage is dominant, and the polyp stage may or may not be present, depending on the family. In those scyphozoans that have the larval planula metamorphose into a polyp, the polyp, also called a "scyphistoma," grows until it develops a stack of plate-like medusae that pinch off and swim away in a process known as strobilation. Once strobilation is complete, the polyp may die, or regenerate itself to repeat the process again later. With Cubozoans, the planula settles onto a suitable surface, and develops into a polyp. The cubozoan polyp then eventually metamorphoses directly into a Medusa.

Anatomy[edit]

Anatomy of a coral polyp.

The body of the polyp may be roughly compared in a structure to a sac, the wall of which is composed of two layers of cells. The outer layer is known technically as the ectoderm, the inner layer as the endoderm (or gastroderm). Between ectoderm and endoderm is a supporting layer of structureless gelatinous substance termed mesogloea, secreted by the cell layers of the body wall. The mesogloea may be a very thin layer, or may reach a fair thickness, and then sometimes contains skeletal elements formed by cells which have migrated into it from the ectoderm.

The sac-like body built up in this way is attached usually to some firm object by its blind end, and bears at the upper end the mouth which is surrounded by a circle of tentacles which resemble glove fingers. The tentacles are organs which serve both for the tactile sense and for the capture of food. Polyps extend their tentacles, particularly at night, containing coiled stinging nettle-like cells or nematocysts which pierce and poison and firmly hold living prey paralysing or killing them. Polyp prey includes copepods and fish larvae.[1] Longitudinal muscular fibrils formed from the cells of the ectoderm allow tentacles to contract when conveying the food to the mouth. Similarly, circularly disposed muscular fibrils formed from the endoderm permit tentacles to be protract or thrust out once they are contracted. These muscle fibres belong to the same two systems, thus allows the whole body to retract or protrude outwards.

We can distinguish therefore in the body of a polyp the column, circular or oval in section, forming the trunk, resting on a base or foot and surmounted by the crown of tentacles, which enclose an area termed the peristome, in the centre of which again is the mouth. As a rule there is no other opening to the body except the mouth, but in some cases excretory pores are known to occur in the foot, and pores may occur at the tips of the tentacles. Thus it is seen that a polyp is an animal of very simple structure, a living fossil that has not changed significantly for about half a billion years (per generally accepted dating of Cambrian sedimentary rock).

The external form of the polyp varies greatly in different cases. The column may be long and slender, or may be so short in the vertical direction that the body becomes disk-like. The tentacles may number many hundreds or may be very few, in rare cases only one or two. They may be long and filamentous, or short and reduced to mere knobs or warts. They may be simple and unbranched, or they may be feathery in pattern. The mouth may be level with the surface of the peristome, or may be projecting and trumpet-shaped. As regards internal structure, polyps exhibit two well-marked types of organization, each characteristic of one of the two classes, Hydrozoa and Anthozoa.

In the class Hydrozoa, the polyps are indeed often very simple, like the common little fresh water species of the genus Hydra. Anthozoan polyps, including the corals and sea anemones, are much more complex due to the development of a tubular stomodaeum leading inward from the mouth and a series of radial partitions called mesenteries. Many of the mesenteries project into the enteric cavity but some extend from the body wall to the central stomodaeum.

Reproduction[edit]

It is an almost universal attribute of polyps to reproduce asexually by the method of budding. This mode of reproduction may be combined with sexual reproduction, or may be the sole method by which the polyp produces offspring, in which case the polyp is entirely without sexual organs.

Asexual reproduction[edit]

In many cases the buds formed do not separate from the parent but remain in continuity with it, thus forming colonies or stocks, which may reach a great size and contain a vast number of individuals. Slight differences in the method of budding produce great variations in the form of the colonies. The reef-building corals are polyp-colonies, strengthened by the formation of a firm skeleton.

Sexual reproduction[edit]

Among sea anemones, sexual plasticity may occur. That is, asexually produced clones derived from a single founder individual can contain both male and female individuals (ramets).[2] When eggs and sperm (gametes) are formed, they can produce zygotes derived from “selfing” (within the founding clone) or out-crossing, that then develop into swimming planula larvae.

The overwhelming majority of stony coral (Scleractinia) taxa are hermaphroditic in their adult colonies.[3] In these species, there is ordinarily synchronized release of eggs and sperm into the water during brief spawning events.[4] Although some species are capable of self-fertilization to varying extents, cross-fertilization appears to be the dominant mating pattern.[3]

Etymology[edit]

The name polyp was given by René Antoine Ferchault de Réaumur[5] to these organisms from their superficial resemblance to an octopus (Fr. poulpe, ultimately from Greek adverb πολύ (poly, "much") + noun πούς (pous, "foot")), with its circle of writhing arms round the mouth. This comparison contrasts to the common name "coral-insects" applied to the polyps which form coral.

Threats[edit]

75% of the world's corals are threatened[6] due to overfishing, destructive fishing, coastal development, pollution, thermal stress, ocean acidification, and introduced invasive species.[7]

See also[edit]

Notes[edit]

  1. ^ Chang, T.D. and Sullivan, J.M. "Temporal associations of coral and zooplankton activity on a Caribbean reef" Dartmouth Studies in Tropical Ecology. 2008. Accessed 2009-06-21.
  2. ^ Schlesinger A, Kramarsky-Winter E, Rosenfeld H, Armoza-Zvoloni R, Loya Y (2010). "Sexual plasticity and self-fertilization in the sea anemone Aiptasia diaphana". PLoS ONE 5 (7): e11874. doi:10.1371/journal.pone.0011874. PMC 2912375. PMID 20686700. 
  3. ^ a b Heyward AJ, Babcock, RC (1986). Self- and cross-fertilization in scleractinian corals. Marine Biology 90, 191-195
  4. ^ Harrison PL, Babcock RC, Bull GD, Oliver JK, Wallace CC, Willis BL (March 1984). "Mass spawning in tropical reef corals". Science 223 (4641): 1186–9. doi:10.1126/science.223.4641.1186. PMID 17742935. 
  5. ^ Stott, Rebecca. "Darwin's ghosts: the secret history of evolution" New York, Spiegel & Grau (2012). ISBN 9781400069378
  6. ^ "NOAA's Coral Reef Conservation Program: New Analysis: 75% of Coral Reefs Under Threat". coralreef.noaa.gov. Retrieved 2015-06-08. 
  7. ^ Burke, Reytar (2011). "Reefs at Risk Revisted". World Resources Institute. 

References[edit]

External links[edit]


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Polyp — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
64815 videos foundNext > 

Endoscopic Nasal Polyp Removal

Endoscopic Nasal Polyp Removal.

Endoscopy Polypectomy of Polyp of Descending Colon

Endoscopy Polypectomy of Polyp of Descending Colon This is a 21 year old lady that presented with Gi bleeding a colonoscopy was performed finding this ...

What is a Colon Polyp? | Los Angeles Colonoscopy

http://www.laendo.net/ Colon polyp is an extermely common condition found during colonoscopy. It can eventually grow to become colon cancer. One or more ...

Hysteroscopic removal of endometrial polyp with scissors A015.wmv

Hysteroscopy for abnormal menstrual bleeding, showing the presence of an endometrial polyp and the removal with scissors.

Colonoscopy Video Tour: Removal of a Colon Polyp (Polypectomy)

ACG Trustee Mark B. Pochapin, MD, FACG, Director, Division of Gastroenterology New York University Langone Medical Center (former Director of The Jay ...

Nasal Polyp Surgery 1

Recent Nasal Polyp Surgery removal.

Antrochoanal Polyp

This type of polyp originates in the maxillary antrum and comes to nasopharynx via the nasal cavity. The polyp can cause post nasal drip, nasal obstruction ...

Huge Antrochoanal Polyp

The importance of appropriate nasal endoscopy and ENT evaluation is illustrated here. A 37 year old man was being treated with antibiotics and allergy ...

Polyp Stummer Bremervörde Frühjahrsmark 2013

Removal of a Cervical Polyp

How to Remove of a Cervical Polyp Vale of York CCG.

64815 videos foundNext > 

7300 news items

The Frisky

The Frisky
Thu, 13 Aug 2015 10:26:15 -0700

One IV, five mega-absorbent gauze pads, and four hours later, the doctor arrived, did an exam and found the cause of my problem: a giant uterine polyp. For those who are unfamiliar with what a polyp is — consider yourself lucky! Polyps are typically ...
 
Healio
Thu, 20 Aug 2015 11:45:00 -0700

A randomized controlled trial demonstrated that during colonoscope withdrawal, examining patients in the left lateral position increased polyp detection in the right side of the colon compared with examining patients in the supine position.

JAMA: The Journal of the American Medical Association

JAMA: The Journal of the American Medical Association
Tue, 01 Sep 2015 08:11:15 -0700

Systemic corticosteroids and oral doxycycline (both for 3 weeks) reduced polyp size compared with placebo for 3 months after treatment (P < .001). Leukotriene antagonists improved nasal symptoms compared with placebo in patients with nasal polyps (P ...

fox13now.com

fox13now.com
Fri, 28 Aug 2015 15:41:15 -0700

Colorectal cancer usually starts with a polyp, which is simply a tiny mass of tissue that grows and grows, and at some point, turns into cancer, Pickron explained. Genetics along with environmental conditions and diet are risk factors for the disease ...
 
Taipei Times
Wed, 02 Sep 2015 08:56:15 -0700

The poached coral include staghorn, star, finger and polyp stony coral, which took decades to grow to their current sizes, the park administration said. The theft devastated a whole colony of coral in the area, as coral cannot survive more than two ...

People Magazine

People Magazine
Wed, 12 Aug 2015 13:15:44 -0700

Osmond, 57, underwent surgery on Tuesday in Boston to treat a hemorrhagic polyp (otherwise known as a bleeding lesion) on his right vocal cord. The operation was performed by Harvard Medical School's Dr. Steven M. Zeitels, who recently treated Grammy ...

Albuquerque Journal

Albuquerque Journal
Sun, 30 Aug 2015 23:11:15 -0700

But if a polyp is found and removed during a colonoscopy, the patient can be stuck paying a large bill, depending on their coverage. That financial risk discourages some people from getting the test, an important tool in detecting potential problems ...

Entertainment Weekly

Entertainment Weekly
Thu, 27 Aug 2015 19:26:15 -0700

It turns out that the wedding is a sham on a handful of levels: Elizabeth is in fine health (she had a polyp removed by ex-husband Ted, who notes, “If that polyp was a tumor, then I'm Clarence f—ing Clemons”), new husband Jeremy is gay, and she was ...
Loading

Oops, we seem to be having trouble contacting Twitter

Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!

Searchlight Group

Digplanet also receives support from Searchlight Group. Visit Searchlight