3 classes of FISH 5 th Grade

There are 3 main classes of fishes  Can you guess the 3?

1) Bony Fish 2) Cartilaginous Fish 3) Jawless Fish 3 Classes of Fishes

What is a Bony fish?

Bony Fish:  Has a skeleton made from bone  Have scales  Single pair of gill openings  Swim bladder  Over 20,000 species

Bony Fish:

What is a cartilaginous fish?

Cartilaginous Fish  Have skeletons made of cartilage instead of bone  Do not have typical fish scales  Their skin is tough and abrasive  Have between 5 and 7 gills

What types of fish are Cartilaginous Fish?  Sharks  Rays  Skates  Chimaeras

Cartilaginous Fish

Jawless Fish  “Agnatha” = means “no jaw” in Ancient Greek  Have long bodies and look like eels  Skeletons are made of cartilage, not bone  They have no scales  Only 50 species left worldwide  This group is made of lampreys and hagfish

Jawless Fish

Jawless Fish (Agnatha)  Lampreys:  Parasitic  Instead of a jaw they have a sucking disc that they attach to their fish host and rasp away at the flesh

Hagfish:

What can the SHAPE of a fish’s body tell us about the fish?

The body shape can tell us:  Where it lives  How it feeds  How it moves through the water

Demersal Fish “bottom-dwelling” fish  Flat in shape  Do not swim continuously so do not need to be streamlined  A flat, pancake-like shape means that the fish is able to stay very close to the sea floor where they feed  Ex. Flounder or Wobbegong

Other slow-moving fish have rounded bodies (often have poisonous flesh since they cannot move quickly)  Blowfish  White-barred boxfish

Fish with elongated bodies are able to swim very fast for a long time so do not have any special body protection (ex. sea mullet)

How do FINS work?  Pectoral Fins –used to maneuver the fish up, down, and sideways –act as brakes and the fish can use them to swim backwards  Pelvic Fins –used for braking and steering  Dorsal fin –stabilizer so that that fish does not roll on its side  Caudal Fin –speed and strength

Parts of a bony fish

Lateral Line Lateral Line: a sensory organ that runs along the sides of the fish’s body under the skin A series of tiny, sensitive cells called “neuromasts” Tiny vibrations in the water pass through the lateral line to help the fish detect differences in pressure and movement in the water Nerves connect the lateral line to the ears and the brain

What is special about a fish’s Swim Bladder?

Swim Bladder:  Swim Bladder: an oval-shaped sac found in the fish’s abdominal cavity  Neutral Buoyancy: the ability of an organism to use little or no energy to stay at particular levels of water, and is achieved through the expanding and shrinking of the swim bladder due to varying gas pressure  At different times it can be filled with varying amounts and composition of gases

Swim Bladder:  Fish can have more control over their movements while expending minimal amounts of energy  Helps fish stay floating all day long without using up too much energy

Do freshwater or salt water fish require a larger swimbladder?

Freshwater!  Freshwater fishes require a larger swimbladder than those in salt water because freshwater is less buoyant than salt water  Buoyant: ability to float  Objects float better on SALT water than freshwater