Phylum Chordata

Fish

I. Phylum Chordata

Includes Fish, Reptiles, Birds and Mammals

A. Characteristics of Chordates

1. All have bilateral symmetry

2. All have internal skeleton

3. Notochord – Flexible internal, supporting structure; “backbone”

4. all have paired gill slits; at some point in life (even mammals)

5. Have 2 layer body covering – scales, feathers, hairs, skin,

6. Closed circulatory system

7. Highly developed nervous system

8. Chambered heart – 2, 3, or 4

9. Dorsal nerve cord – spinal cord; protected by the notochord

II. FishesA. General Info

1. Well developed senses- excellent smell, sight (for most)

2. Most have scales covering body

3. All secrete mucous to protect from bacterial and fungal infections

4. Have gills for entire life

5. Most have fins; used for moving

6. Vary in size; 12mm to 40ft.

7. exothermic – body To changes with surrounding To = “cold blooded”

8. 3 classes of fish

B. Class Agnatha

1. “Jawless” fish; has no jaw

2. Circular mouth

3. Eel shaped body; long and slender

4. Most primitive living fish

5. Very smooth skin; no scales

6. Skeleton made of cartilage

7. Two types of Agnathas

a. lamprey

1) found both freshwater and saltwater

2) has become a big problem in the Great Lakes

3) lampreys are considered parasites

4) has a sucker like mouth with sharp teeth

5) “drill” into their prey; sucks out blood and fluids; “vampire fish”

6) lives up to 9 years

7) averages 2ft feet in body length

8) gray in color

9) very strong suction ability

b. Hagfish

1) only found in saltwater

2) very slimy -> “slime-eel”

3) secretes so much mucus;

noses get clog; has to sneeze to clear nose

4) feed only on dead fish

5) no eyes;

instead uses barbels -> very sensitive extensions can smell up to 2ft away

6) grayish/purplish in color

7) lives on the ocean bottom

8) coils up when resting

9) basically no skeleton except for spine

10) gnaws on food with rough tongue

C. Class Chondrichthyes

Includes sharks and rays

1. General information

a. no true bones -> skeleton made of cartilage

b. very strong jaws, moveable

b. mouth on underside; can’t really see what goes into mouthc. skin is like sandpaper; placoids

-> cover entire body; Tooth scalesd. males easy to identify by a set

of claspers by anal fins; for copulatione. has internal fertilizationf. has 5, 6 or 7 open gill slits

2. Sharks

a. General information

1) over 350 species

2) only 50 are known to attack man

3) Most feared sea creature; thanks to movies like “Jaws”

4) More humans are killed and attacked by dogs than sharks

5) sizes vary from 6 inches- > cigar shark to 40 ft -> whale shark

b. Body of shark

1) streamlined for fast speeds -> hydrodynamic

2) Very muscular body, tail moves from side to side;

tail fin is called the caudal;

has two parts: upper part much longer than bottom part

3) very pointy nose; increases hydrodynamics ability;

nose is very sensitive

4) has lateral lines -> enhances smell ability, run from nose down the sides

5) tiny holes found within the lateral lines

6) most sharks must keep moving or will suffocate

7) teeth are very sharp and in rows; like a conveyor belt,

teeth replace every 2-3 wks

8) Very large liver; weigh about 1/4 the body weight; contains oil that humans use for vitamin A

9) Intestine is spiraled on the inside for storing food

10) fins do not bend;

used for braking and steering;

dorsal fin most noticeable -> keeps shark from spinning

c. Feeding of sharks

1) Carnivores -> will eat just about anything ->seals,

fish bumpers, tin cans

2) filter feeders -> eat plankton & small marine life;

two largest sharks are plankton feeders: whale

and basking shark

d. Types of sharks

1) Great White-> most feared, but rare; largest carnivore

2) Bull -> fastest shark and very aggressive; 45 m/h

3) whale shark -> largest of all fish; very shy; 6ft wide mouth

4) Megamouth-> deep sea shark; only 8 discovered;

first found in 1978, 2nd in 1984 off the coast of CA

5) Hammerhead -> unusual head = very broad and flat; aggressive

6) And many more very interesting ones

e. Importance of sharks

1) Top of the food chain; keeps nature balanced

2) Used in cancer research

3) Used as food; shark fin soup; shark stakes

4) Clothing -> boots, etc.

5) Skin for burn victims, meshes really good

6) Source of vitamins and oils

3. Rays and Skates

a. General information

1) body is flattened

2) have “wings” to swim

3) most have a whip -like tail

4) Most live on the bottom in the sand

5) very peaceful and shy animals, attack only when

provoked

6) Feed mostly on squid, fish

7) Has spiracles to breathe while resting on the bottom

b. Protection

1) barb -> located on tail; whip it right into leg, very painful

2) “battery-packed sting” -> can knock a man out, stun prey

3) can swim very fast to avoid danger

c. Types of rays

1) Manta ray -> largest of all rays; 24ft “wing span”;

plankton feeder;

very, very peaceful;

no barbed spine

2) Blue - spotted ->very poisonous; be careful

3) Common sting ray -> shuffle feet when entering water to avoid being hit by tail;

4) live mostly in shallow waters

D. Class Osteichthyes

Includes all bony fish

1. General information

a) largest class of vertebrates

b) skeleton made of bone (calcium carbonate)

Heaviest bony fish 5000 lbs

c) have protective, overlapping scales

d) swim using pectoral fins and tail ( sharks only use tails)

e) Most have external fertilization

f) Most have a air bladder -> allows them to “hover” or suspend

2. Body plan

a. tail fins are even ->

sharks ->

b. most have large eyes

c. Mouth in front of body; sharks underneath

d. have nostrils; used only for smelling NOT respiration

e. 4 pairs of gills; protected by an operculum

f. have retractable fins; sharks cannot retract fins

g. mostly made of muscle; makes for very fast fish

h. variety of shapes and sizes

MouthNo jaw

No scales

Gill holes

Single long fin

Class Agnatha

Skeleton made of cartilage

Dorsal fin

2nd dorsal fin

Uneven caudal fin

Anal finPelvic finPectoral

fin

mouth Gill slits

Placoid scales

Lateral lines

Class Chondrichthyes

Cartilage skeleton

mouth

operculum

Pectoral fin

Dorsal fin

Lateral line

Caudal fin

anal finPelvic fin

Overlapping scales

Class Osteichthyes

Skeleton bone