Radiole: Difference between revisions

Add links
From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Line 37: Line 37:
|day=27
|day=27
|url=http://www.jstor.org/stable/82713
|url=http://www.jstor.org/stable/82713
|accessdate=03 May 2010}}</ref><ref name=memorial>Department of Biology, Memorial University of Newfoundland: [http://www.mun.ca/osc/oscedu/sabella.php Eudistylia_vancouveri ''Eudistylia vancouveri''], Ocean Sciences Centre. Accessed 03 May 2010.</ref> It is because of this role in gas exchange that the structures are commonly referred to as "gills".
|accessdate=03 May 2010}}</ref><ref name=memorial>Department of Biology, Memorial University of Newfoundland: [http://www.mun.ca/osc/oscedu/sabella.php Eudistylia_vancouveri ''Eudistylia vancouveri''], Ocean Sciences Centre. Accessed 03 May 2010.</ref><ref name=Kennedy>{{cite journal
|author=Bill Kennedy, Harald Kryvi
|title=Autotomy in a polychaete: Abscission zone at the base of the tentacular crown of Sabella penicillus
|journal=Zoomorphology
|volume=96
|issue=1-2
|pages=33-43
|year=1980
|month=October
|day=
|pmid=
|doi=10.1007/BF00310075
|url=http://www.springerlink.com/content/v592528142g89312/
|accessdate=03 May 2010}}</ref> It is because of this role in gas exchange that the structures are commonly referred to as "gills".


==Pigmentation of radioles==
==Pigmentation of radioles==

Revision as of 04:57, 3 May 2010

radioles extending from the branchial stalk of a Spirographis feather duster worm

A radiole is a heavily ciliated feather-like tentacle found in highly organized clusters on the crowns of Canalipalpata. Canalipalpata is an order of sessile marine polychaete worms consisting of 31 families (including the Sabellidae, Serpulidae, Terebellidae, and Alvinellidae, a family of deep-sea worms associated with hydrothermal vents). These benthic annelid tube worms employ radioles primarily for alimentation. While they are primarily feeding structures, the radioles also serve as respiratory organs. Because of their role in gas exchange, radioles are often referred to as "gills".

Anatomical location of radioles

Canalipalpata have a head located at the anterior end of the body. The head is formed by the fusion of a funnel-shaped, symmetrical peristomium with the prostomium.[1][2][3] The prostomium bears a specialized mouth appendage which is referred to as a branchial crown. The crown functions as both a sieve and a gill. The animal can extend the crown from its calcareous tube for feeding and gas exchange, and rapidly retract it when disturbed or threatened.[4]

The crown consists of two bundles (one right and one left) of featherlike tentacles known as branchiae, or radioles. Each of these bundles consists of a single row of radioles attached to a branchial stalk and curved into a semicircle. These two semicircles form the funnel-shaped branchial crown. The mouth is located at the apex of the funnel, between the two branchial stalks.[4]

An adult worm typically has about forty radioles in its crown. The radioles themselves are covered by tiny hair-like branches called cilia. This arrangement gives the crown the appearance of a small fan or feather duster (for which the animals are often referred to as fanworms, or feather duster worms). When extended, these heavily ciliated radioles trap particles of organic matter and transport them towards the mouth.

Use of radioles in filter feeding

The ventral surface of each radiole is covered by cilia that rhythmically move in such a way as to create a current in the surrounding water column. This current carries planktonic particles from the underside of the crown upwards through the net of radioles to the dorsal surface.[4]

The dorsal or upper side of each radiole has a ciliated longitudinal radiolar food groove running down its center, extending along its longitudinal axis from the tip to the center of the crown.[4] Planktonic food particles are swept into these grooves, where they become trapped in a coating of mucus. At this point, the animal subjects the particles to an examination and selection process, whereby any particles that are determined to be unsuitable due to size or chemical composition are rejected by the animal and discarded back into the water column. Once the selection process is complete, the cilia transport the particles towards the mouth of the animal, from where they enter the digestive tract.[4]

Use of radioles in respiration

While they are primarily feeding structures, the radioles also serve as respiratory organs.[4][5][6][7][8][9] It is because of this role in gas exchange that the structures are commonly referred to as "gills".

Pigmentation of radioles

The radioles of different species of canalipalpata vary widely in color. Those of the serpulid tubeworms are typically red, pink, or orange in color, with white transverse bands. Astaxanthin, a carotenoid pigment, is responsible for the bright red color of the crown of Serpula vermicularis.[10]

Growth and regeneration of radioles

Juvenile and other worms of small size have small crowns and radioles and therefore prefer to capture and eat very small particles, like bacterioplankton and single-celled phytoplankton and zooplankton. As a worm matures and grows in size, so does its crown. The larger crown allows the animal to feed on larger multicellular plankton. The preferred food size depends on the maximum size achieved by the adult worm.

Canalipalpata worms can sometimes lose one or more radioles, or even the entire crown as a result of predation by other animals or other types of trauma. However, the animals have the ability to regenerate new radioles to replace those that have been amputated.[11][12] Any would-be predators that pass by after a worm has lost its crown will get the impression that the worm has died; this protects the animal from further attack. The crown typically reappears after about two weeks. When it does reappear, it is initially smaller in size, but it eventually grows back to its former size and color.

Specialized radioles

In addition to having ordinary radioles, some canalipalpata possess one or more highly modified radioles located on the dorsal part of the head. This specialized structure is called an operculum. The operculum is a cone-shaped cartilaginous structure located at the distal end of a long cartilaginous stalk. When threatened or disturbed, the animal withdraws rapidly into its protective calcareous tube and employs the operculum as a plug to occlude the entrance to the tube.[13] The operculum, which is usually similar in color to the other radioles, secretes a mucus which seems to possess antibiotic properties. It is not unusual for the animal to have two crowns, and hence two opercula.

Serpulids and sabellids are two families of the Sabellida suborder of canalipalpata tubeworms that are similar in nearly every respect, but they can be readily distinguished by the fact that while both have radioles, the sabellids (such as Sabella pavonina) lack an operculum.[14]

Gallery

References

  1. ^ Department of Biology, Walla Walla University: Serpula vermicularis, Rosario Beach Marine Laboratory. Accessed 03 May 2010.
  2. ^ Colin G. Moore; Graham R. Saunders; Dan B. Harries (1998). "The status and ecology of reefs of Serpula vermicularis (Polychaeta: Serpulidae) in Scotland". Aquatic Conservation: Marine and Freshwater Ecosystems. 8 (5): 645–656. Retrieved 03 May 2010. {{cite journal}}: Check date values in: |accessdate= (help)
  3. ^ Fan Worms & Feather Dusters (Annelids). Accessed 03 May 2010.
  4. ^ a b c d e f Richard S. Fox, Invertebrate Anatomy OnLine: Eudistylia vancouveri. Lander University, 4 July 2006. Accessed 03 May 2010.
  5. ^ Richard S. Fox, Invertebrate Anatomy OnLine: Serpula vermicularis. Lander University, 4 July 2006. Accessed 03 May 2010.
  6. ^ An Underwater Field Guide to Point Lobos: Invertebrates: Worms. Accessed 03 May 2010.
  7. ^ G. P. Wells (1952). "The Respiratory Significance of the Crown in the Polychaete Worms Sabella and Myxicola". Proceedings of the Royal Society of London (Series B, Biological Sciences). 140 (898): 70–82. Retrieved 03 May 2010. {{cite journal}}: Check date values in: |accessdate= (help); Unknown parameter |day= ignored (help); Unknown parameter |month= ignored (help)
  8. ^ Department of Biology, Memorial University of Newfoundland: Eudistylia_vancouveri Eudistylia vancouveri, Ocean Sciences Centre. Accessed 03 May 2010.
  9. ^ Bill Kennedy, Harald Kryvi (1980). "Autotomy in a polychaete: Abscission zone at the base of the tentacular crown of Sabella penicillus". Zoomorphology. 96 (1–2): 33–43. doi:10.1007/BF00310075. Retrieved 03 May 2010. {{cite journal}}: Check date values in: |accessdate= (help); Cite has empty unknown parameter: |day= (help); Unknown parameter |month= ignored (help)
  10. ^ Pamela L. Beesley, Graham J. B. Ross, Christopher J. Glasby (eds) (2000). "Gregory W. Rouse (2000). Family Serpulidae.". Polychaetes & allies: the southern synthesis, Volume 4, Part 1. Melbourne, Australia: CSIRO Publishing Australia. p. 187. Retrieved 03 May 2010. {{cite book}}: |author= has generic name (help); Check date values in: |accessdate= (help)CS1 maint: multiple names: authors list (link)
  11. ^ Timothy P. Fitzharris (1976). "Regeneration in Sabellid Annelids". American Zoologist. 16 (3): 593–616. doi:10.1093/icb/16.3.593. Retrieved 03 May 2010. {{cite journal}}: Check date values in: |accessdate= (help); Cite has empty unknown parameters: |day= and |month= (help)
  12. ^ Department of Biology, Walla Walla University: Eudistylia_vancouveri, Rosario Beach Marine Laboratory. Accessed 03 May 2010.
  13. ^ Jean Hanson (1949). "Observations on the Branchial Crown of the Serpulidae (Annelida, Polychaeta)". Quarterly Journal of Microscopical Science. 90 (s3): 221–233. Retrieved 03 May 2010. {{cite journal}}: Check date values in: |accessdate= (help); Cite has empty unknown parameter: |month= (help)
  14. ^ Edward E. Ruppert; Richard S. Fox (1988). "Annelida: Segmented Worms". Seashore animals of the Southeast: a guide to common shallow-water invertebrates of the southeastern Atlantic Coast. Columbia, South Carolina: University of South Carolina Press. p. 219. ISBN 0-87249-535-3. Retrieved 03 May 2010. {{cite book}}: Check date values in: |accessdate= (help)
Retrieved from "https://en.wikipedia.org/w/index.php?title=Radiole&oldid=359784180"