Taxonomy of Finfish

2.1.5.5 Jaws

As already stated the pre-maxillaries,maxillaries and mandiblebones fonn the upper and lowerjaws. They are united by a symphysis Ooint) which enables them to open and close the mouth. Thejaws bear the teeth described above and act as the frame for the shape of the mouth.The palate teeth are borne by the vomer bone,which is not a part of thejaw. Thejaws are essentiallymeantto capture,hold andswallow the prey and the teeth help in munching, grinding andmaking it fit for passage through the gullet. In most fishes thejaws aremore or less of equal length, but in somethe upperjaw is longer than the lower (Fig. 16 A). In Clupeidae the lower jaw is longer than the upper (Fig. 16B). In Engraulidae the upper jaw is projecting. In Ctenops species both the jaws are elongated to form a some what pipe-shaped mouth. In Hyporhamphus species (Hemiramphidae) the lower jaw in the adult is elongated as a long beak (Fig. 16 C). In Pipefishes (Ichthyocampus species) both the jaws are produced as a beak. In puffer fishes both jaws are divided by a median suture with a cutting edge and covered by ivory like substance. In some the lower jaw may be having a horny covering as in Labeo fisheri (Fig. 16D).

Fig.16. Jaws. A. Upper jaw longer than lower jaw (Engraulidae). B. Lower jaw longer than upper jaw (Clupeidae. C. Lower jaw elongated (Hemiramphidae). D. Jaw ridge horny (Labeo fisheri).