Jawless Fish Cartilaginous Fish Boney Fish

Jawless Fish Agnatha (means “without jaws”) are fish covered with a bony plate. They were quite abundant, but only 81 species exist today. These living fish are known as hagfishes and lampreys. They are eel-like creatures with scaleless, slimy skin, and lack paired fins. Their skeleton is mostly composed of cartilage and there is no well-developed vertebral column. The gills of agnathans lie within pouches that branch from the pharynx.

Lampreys – means stone licker Most kinds of lampreys spend their entire lives in fresh water. A few live in sea water as adults, but all return to fresh water to breed. Some lampreys are external parasites that feed on other fishes. A parasitic lamprey’s mouth is recessed in a funnel-like structure. Sharp, tooth-like hooks in the funnel help the lamprey to attach to the host. The rim of the funnel acts as a suction cup.

A rough tongue scrapes off small particles of the host’s skin and flesh. The lamprey sucks in these particles along with the host’s blood. The lamprey secretes a substance that prevents the host’s blood from clotting. The size ranges from 5 in to 40 in. They will not normally attack humans unless they are starved. They do not like high water temperatures so they are not usually found in the Tropic regions.

Lamprey mouth-no jaw

Catch in Alaska in the Yukon River

Fish with parasitic lampreys

Once the lamprey is fed, it drops off the host Once the lamprey is fed, it drops off the host. Damage to the host can be severe due to infections or death due to blood loss. Large populations of lampreys can cause great damage to the fish populations. Lampreys caused serious decline in commercial and sports fishing in the Great Lakes. The population was eventually reduced by treating the Great Lakes with poisons toxic to lamprey larvae.

Hagfishes Hagfishes are scavengers that generally feed on dead or dying animals. The hagfish enters the body through the gill openings, the mouth or the anus. Once inside, it feeds on the internal organs of the animal. Hagfish become a nuisance to fisherman as they attack the catch and devour them before they can get them to the surface. An adult hagfish can secrete enough slime to turn a large bucket of water into gel in a matter of minutes. Hagfishes are about 18 inches long.

Pacific Hagfish

1 in single hagfish egg