Pharyngeal jaws
Encyclopedia
Pharyngeal jaws are a "second set" of jaw
s contained within an animal's throat, or pharynx
, distinct from the primary (oral) jaws. They are believed to have originated as modified gill arches, in much the same way as oral jaws.
Although approximately 30,000 species of fish
es are known to have pharyngeal jaws, in many species having their own teeth, the most notable example of animals possessing them is the moray eels of the family Muraenidae. Unlike those in other fishes known to have them, those of the moray are highly mobile. This is possibly a response to their inability to swallow as do other fishes by creating a negative pressure
in the mouth, perhaps induced by their restricted environmental niche (burrows). Instead, when the moray bites prey, it first bites normally with its oral jaws, capturing the prey. Immediately thereafter, the pharyngeal jaws are brought forward and bite down on the prey to grip it; they then retract, pulling the prey down the moray eel's gullet, allowing it to be swallowed.
inside of the throat, in place of a tongue. This proboscis is shown to rapidly shoot forward with force to attack prey.
Jaw
The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
s contained within an animal's throat, or pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
, distinct from the primary (oral) jaws. They are believed to have originated as modified gill arches, in much the same way as oral jaws.
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
es are known to have pharyngeal jaws, in many species having their own teeth, the most notable example of animals possessing them is the moray eels of the family Muraenidae. Unlike those in other fishes known to have them, those of the moray are highly mobile. This is possibly a response to their inability to swallow as do other fishes by creating a negative pressure
Negative pressure
Negative pressure may refer to:*negative pressure as opposed to positive pressure*stretched liquid*vacuum*negative gauge pressure, a way of expressing pressure measurements below atmospheric pressure*suction*transpirational pull...
in the mouth, perhaps induced by their restricted environmental niche (burrows). Instead, when the moray bites prey, it first bites normally with its oral jaws, capturing the prey. Immediately thereafter, the pharyngeal jaws are brought forward and bite down on the prey to grip it; they then retract, pulling the prey down the moray eel's gullet, allowing it to be swallowed.
In fiction
Probably the most famous example of pharyngeal jaws is the fictional extraterrestrial creature from the Alien film series called the "Xenomorph". In the films, Xenomorphs are depicted with a secondary, inner set of jaws mounted onto a proboscisProboscis
A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...
inside of the throat, in place of a tongue. This proboscis is shown to rapidly shoot forward with force to attack prey.