Cartilaginous Fishes

Define a cartilaginous species with examples.

A fish class that has cartilage instead of bone (ex: great white shark, spiny dogfish, nurse shark)

What is a nictitating membrane?

A layer that goes over the shark's eye when it attacks. All sharks have this.

What is a mermaid's purse?

An egg case of a skate

What are the major differences between cartilaginous and bony fishes?

Cartilaginous fishes have a liver filled with oil for buoyancy, and cartilage. Bony fishes have a swim bladder for buoyancy, they also have scales and a skeletal structure.

Fin types

Caudal, anal, pelvic, dorsal, pectoral, and males have claspers near the pelvic fins

What are the male reproductive organs?

Claspers

Lateral Line

Detects the velocity of surrounding water currents

Ovoviviparous

Eggs absorbed within the mother in uterus with no direct connection (ex: sand tiger shark)

Smell

Excellent sense of smell; can smell blood from far distances

Oviparous

External egg cases (ex: horn sharks)

Eyesight

Have colored sight and see well in dim lighting

Viviparous

Placental development with direct connection to mother (ex: spiny dogfish)

Why/how are sharks hydrodynamic?

Sharks are hydrodynamic because their smooth skin brings no drag. Also, some of their fins act as stabilizers (pelvic & dorsal) while other fins (pectoral) control lift and drag.

How do sharks maintain buoyancy?

Sharks maintain buoyancy because of their oil filled liver.

What are differences between skates and rays?

Skates are oviparous, small proportions, fleshy tails, and lack spines. Rays are viviparous, absent or reduced dorsal fin, kite-shaped/whip-like tail with stinging barbs.

Taste

Taste buds in their mouth but no tongue; after the first bite, they can tell if it is worth it

How are the scales and teeth related?

The placoid scales are believed to have turned into the shark teeth.

How are the ratfish and ghost shark related to sharks?

They are in class Chonrichhyes but ratfishes are in sub-class Holocephalii while sharks are in sub-class Elasmobranchii.

Describe the respiration of sharks.

They have two ventral nostrils which lead to olfactory sacs equipped with folds of skin that allow continual movement of water. There are 5-7 gill slits.

Ampullae of Lorenzini

Used as an electroreceptor; senses electrical currents at short ranges

Describe the skin of a shark.

Very rough with sandpaper like texture

Hearing

Very sensitive to low frequency sound and good directional hearing

Can sharks stop moving and still breathe?

While most sharks cannot stop moving and still breath, the nurse shark is an exception. They can do his through spiracles which supply oxygen directly to the eyes and brain of the shark.