[2013] Megan Hanlin (7th AC Life): The World Below The Water: Cartiliginous Fish

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[2013] Megan Hanlin (7th AC Life): The World Below The Water: Cartiliginous Fish

Cartilaginous fish are a special type of fish. They do not have bones like humans and many other mammals. This is because the cartilage they have as a baby never transforms into solid bone, so they have cartilage. Cartilage is a tough, flexible material that makes up the flexible parts of a human ears and nose.

The World Below The Water: Cartilaginous Fish

Scientific Name:Chondrichthyes

The Advantages - Fully functional jaws - Strong swimmers - Expert Predators - Excellent senses of sight and smell

The Disadvantages- must keep moving to stay afloat- stop swimming and they slowly sink- fish are denser than the water

Cartilaginous Fish:These fish are divided into two subclasses on the basis of gill slits and other characteristics. The first subclass is the Elsamobranchs, which have at least five gill slits and gills on each side. There is also one spiracle behind each eye, dermal teeth on the upper body surface, a tooth jaw, and an upper jaw not firmly attached to the skull. Animals such as sharks, rays, and skates belong to this group. The second group are the Holocephalis, which includes the chimeras. This group is a taxon of cartilaginous fish. Chimaeriformes is the only known surviving group of this subclass, which includes rat fish, rabbit fish, and elephant fish.Cartilaginous fish do not have swim bladders, so a swimming motion must be maintained continuously, even when sleeping, or they will sink to the bottom and die because their body can't handle the pressure that is put on them when the sink. The caudal fin of the shark provides the propellant force in swimming, the dorsal fin provides balance, and the pectoral fins are used for upward force and depth rudders.The flattened body and the rear spine of the rays makes their swimming motion unique and completely different than any other fish. The large flattened body of the rays has become fused with pectoral fins, which produces vertical waves from front to rear, similar to a bird in flight.The chimeras utilize their pectoral fins when swimming, beating these fins simltaneously for propulsion, or alternately, to change direction. This method is highly effective for this group of cartilaginous fish, but it is most often seen in bony fish.The pectoral fins in the male cartilaginous fish are also used for mating. The rear part of the pectoral fin is modified as a copulatory (sperm) organ. All cartiliginous fish have internal fertilization. Internal fertilization is when the male deposits sperm inside the female, and then the female lays fertilized eggs with embryos inside. Only true rays, species of sharks whichlive near the sea bed, and the chimeras lay eggs. The eggs are often encased in a leathery shell with twisted tendrils which anchor the egg case to rocks or weeds. These leathery shells are known as the "mermaid's purse." Cartilaginous fish are predatory, which means that they feed on other animals. They are sought after by humans as a food source. For example, shark meat, which used to be marketed under the name "steakfish," is now popular worldwide. Sharkfins have also been popular in the Orient. Rays are considered delicacies in Great Britain and France, and thornback rays and flapper skates are often sold as sea trout.There are many things to learn about these boneless creatures. They are part of the unknown world below the surface. They are cartilaginous fish.



Name: Megan HanlinDate: April 28thClass: 7th Period

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