View source for Gill raker

{{Short description|Bony or cartilaginous processes that project from the branchial arch}}
[[File:Gills2.jpg|thumb|300px|Top left: Gill-rakers attached to the branchial arch, showing the projecting rows of hooks (×50)<br/>
Top right: Hooks attached to the gill-raker (×180)<br/>
Bottom: Gill-rakers in cross section, showing angle at which hooks project from their point of attachment (water flow is downwards)]]
'''Gill rakers''' in fish are [[bone|bony]] or [[cartilaginous]] processes that project from the [[branchial arch]] (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the [[gill filament]]s that compose the fleshy part of the gill used for gas exchange. Rakers are usually present in two rows, projecting from both the anterior and posterior side of each gill arch. Rakers are widely varied in number, spacing, and form. By preventing food particles from exiting the spaces between the gill arches, they enable the retention of food particles in filter feeders.<ref>{{cite web|url=http://203.250.122.194/lecture/anatomy/htmanat2/anat14.htm|title=Respiratory system|website=203.250.122.194}}</ref>
The structure and spacing of gill rakers in fish determines the size of food particles trapped, and correlates with feeding behavior. Fish with densely spaced, elongated, comb-like gill rakers are efficient at filtering tiny prey, whereas carnivores and omnivores often have more widely spaced gill rakers with secondary projections. Because gill raker characters often vary between closely related taxa, they are commonly used in the classification and identification of fish species. Much of the variation in gill raker morphology is thought to be due to adaptation to optimize the consumption of different diets.
To prevent the potentially damaging passage of solid material through the gill slits and over the gill filaments, early gill rakers strained large particles from the water and diverted them to the [[esophagus]]. Since an appreciable fraction of this material was nutritious, rakers subsequently evolved as food-trapping mechanisms in filter feeders. Gill rakers, when long and closely set, play the same role in suspension-feeding fish such as [[herring]], [[Mullet (fish)|mullet]], [[megamouth shark|megamouth]], [[Basking shark|basking]] and [[whale shark]]s, as [[baleen]] in the [[baleen whales|filter-feeding whales]].<ref name=Salman_Morphometry>{{cite journal|last=Salman |first=Nadir A. |author2=Al-Mahdawi, Ghaith J. and Hassan |author3=Heba, M.A. |title=Gill Rakers Morphometry and Filtering Mechanism in some Marine Teleosts from Red Sea Coasts of Yemen |journal=Egyptian Journal of Aquatic Research |date=2005 |volume=31 |issue=Special Issue |pages=286–296 |url=http://www.nodc-egypt.org/contacts_files/Egyptian%20Journal%20of%20Aquatic%20Special%20Issue%202005/Egyptian%20Journal%20of%20Aquatic%20Research-Conferance%20Volume_files/21/Text.pdf |access-date=2 March 2013 |url-status=dead |archive-url=https://web.archive.org/web/20120320134145/http://www.nodc-egypt.org/contacts_files/Egyptian%20Journal%20of%20Aquatic%20Special%20Issue%202005/Egyptian%20Journal%20of%20Aquatic%20Research-Conferance%20Volume_files/21/Text.pdf |archive-date=March 20, 2012 }}</ref>
[[File:Pharynx and Gill raker of Epinephelus coioides.jpg|thumb|250px|center|Gill rakers of an [[orange-spotted grouper]], ''Epinephelus coioides'']]
==References==
{{Reflist}}
{{diversity of fish}}
[[Category:Fish anatomy]]