Dinesh kumarAssistant Professor

Department of ZoologyMultanimal Modi College

Modinagar

TYPES OF JAW SUSPENSION IN FISHES

INTRODUCTION OF JAW

● Jaw, either of a pair of bones that formthe framework of the mouth of vertebrateanimals, usually containing teeth andincluding a lower jaw and upper jaw .Jaws function by moving in opposition toeach other and are used for biting,chewing, and the handling of food.

EXPLANATION OF JAW SUSPENSION

● Jaw suspension means the methodby which the upper and lower jawsare suspended or attached from theskull ( chondrochranium) for efficientbiting and chewing.

● There are different ways in whichthese attachments are attaineddepending upon the modification inthe visceral arches.

EVOLUTION OF JAW● The prevertebrates had a ciliary pump therefore

they depended on the suspended matter in thesea water.

● In larger fish ( agnathans) ciliary pump becameless effective and was replaced by muscularpharynx pump as agnathans were depositfeeders and mud grabbers that pushed theirmouth into loose organic or siltmud and drewsediment rich organic particles.

● Then transition from agnathans to gnathostomesinvolved switch in feeding methods, thereforethey became raptorial feeders, so suddenexpansion of pharynx developed to close themouth to prevent escape of capture and itsingestion, so the jaws powered by muscle actionwere developed. This could shut mouth quickly.

Autostylic jaw suspension is divided into three subtypes :- (a)Holostylic (b) monimostylic and (c) streptostylic.Out of theseholostylic type developed in the ancient placoderms and is still seenin Holocephali i.e.,Chimaeras. In this type the upper jaw is firmlyfused with the skull and lower jaw is suspended from the quadrateregion of the upper jaw. Hyoid arch is complete, independent andnot attached to skull ( chondrocranium).The other two types arefound in tetrapods.

CONCLUSION:-● Development of jaws represents the

transition in the feeding methodsduring the course of evolution.

● With the help of jaw mouth could shutquickly with a strong bite, securing theingested prey.

● Prey size limits were also removed.● Active predation became a common

lifestyle in subsequent vertebrates.

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