Gill raker

Top left: Gill-rakers attached to the branchial arch, showing the projecting rows of hooks (x50)
Top right: Hooks attached to the gill-raker, (x180)
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 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 filaments 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.^[1]

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 mullet, herring, megamouth, basking and whale sharks, as baleen in the filter-feeding whales.^[2]

• 

  Gill rakers

References

Fish
About fish	Diversity Ethnoichthyology Evolution Diseases and parasites Fisheries Fishing Fish as food Fear of fish FishBase Fish kill Hypoxia in fish Ichthyology
Anatomy and physiology	Fish anatomy Fish physiology Estimating age Anguilliformity Bone dermal intramembranous ossification Cleithrum Chromatophore Fins dorsal fin Gill branchial arch gill raker gill slit pharyngeal arch pharyngeal slit pseudobranch Glossohyal Jaw hyomandibula pharyngeal jaw Leydig's organ Mauthner cell Meristics Operculum papillare Papilla Photophore Root effect Shark cartilage Scales ganoine Spiral valve Suckermouth Swim bladder physoclisti physostome Teeth pharyngeal teeth shark teeth Teleost leptins Digital Library
Sensory systems	Sensory systems in fish Ampullae of Lorenzini Barbel Hydrodynamic reception Electrocommunication Electroreception Jamming avoidance response Lateral line Otolith Passive electrolocation Capacity for pain Schreckstoff Surface wave detection Vision Weberian apparatus
Reproduction	Fish reproduction Bubble nest Clasper Egg case Fish development Ichthyoplankton Juvenile fish Life history theory Milt Mouthbrooder Polyandry in fish Pregnancy Roe Sequential hermaphroditism Spawning triggers
Locomotion	Fish locomotion Fin and flipper locomotion Amphibious fish Walking fish Flying fish Undulatory locomotion Tradeoffs for locomotion in air and water RoboTuna
Other behaviour	Aquatic predation Aquatic respiration Bait ball Bottom feeders Cleaner fish Diel vertical migration Electric fish Filter feeders Forage fish Migrating fish Paedophagy Predatory fish Salmon run Sardine run Scale eaters Schooling fish Sleep in fish Venomous fish Fish intelligence
By habitat	Cave Coastal Coldwater Coral reef Deep sea Demersal Euryhaline Freshwater Groundfish Pelagic Tropical
Other types	Bait Coarse Diversity Game Genetically modified Hallucinogenic Oily Poisonous Rough Whitefish
Commercial	Fish farming Carp Salmonids Tilapia Wild fisheries Predatory fish billfish mackerel salmon tuna Forage fish anchovy herring sardine sprats Demersal fish cod flatfish pollock
Major groups	Jawless fish hagfish lampreys Cartilaginous fish chimaeras sharks rays Bony fish spiny-finned fleshy-finned
Lists	Aquarium life Blind fish Fish common names Fish families Fish on stamps Glossary of ichthyology Large fish Threatened rays sharks Prehistoric fish more lists...
Category Portal WikiProject