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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. Fishes
A. General Info
1. Well developed sensesexcellent 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.
o
7. exothermic – body T 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 mouth
c. skin is like sandpaper; placoids
-> cover entire body; Tooth
scales
d. males easy to identify by a set
of claspers by anal fins; for
copulation
e. has internal fertilization
f. 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
Class Agnatha
Gill holes
Mouth
No jaw
Single
long fin
Skeleton made
of cartilage
No
scales
Placoid
scales
Dorsal fin
Uneven
nd
2 dorsal caudal
fin
Lateral lines fin
mouth Gill slits
Pelvic
fin
Pectoral
fin
Class
Chondrichthyes
Anal fin
Cartilage
skeleton
Skeleton boneDorsal
Pectoral
Caudal
fin
fin
fin
Lateral line
Overlapping
scales
Class
mouth
Osteichthyes
operculum Pelvic fin anal fin